Thanks for the shout out and the kind words! I have a few of these in several cabinet versions. You're right these things true to the Zenith name are made very well. I've found problems with static on FM that sounds like SMD Actually is a defect in the slug tuner. Thanks for a glance at the schematic these are strictly thru SAMS. Great sound mod to!
I've heard a lot of table radios where the loudness compensation really improved the sound. Nice sound at normal and quiet levels, and loosing the bass boost at higher levels allowed the radio to fill a large room with clear sound without clipping. But Zenith sure did it wrong on these. Killed the treble along with the dip in midrange.
Very interesting about the tone mod, I'll have to remember that. About electrolytics; the old ones had a healthy surge rating, the new ones don't...and I've measured as high as 190v surge on a 160v cap. I use 250v nowadays, just for a little added safety margin.
Hello Shango I have a Crosley E15SL and its the best sounding table radio I have in my collection. You repaired a white model that was missing knobs. That Crosley had a tone tap like this Zenith but Crosley used different values and attenuated midrange and passes treble and bass. You're a great entertainer to watch you on Radio and TV repair and I have this game I play and guess what I think might be wrong during your diagnosis thanks again Ace 👍
Love the old radio's, they were my escape when I was a kid, we were dirt poor, my aunt gave me an old tube radio when I was at their farm working cattle one year, I put that beside my bed and late at night, I would play that radio loud enough so I didn't have to listen to my parents fight, man I can still recall listening to KOMA where the "good guy's" played all the latest rock and roll! Bismarck had Padre's Platters another rock played by a Catholic Priest. I still have that first transistor radio, mom saved it for me, and returned it about ten years ago, an old Jade 10 transistor...
Dude - you're a hero. I have an X316 and the muddy sound was driving me nuts trying to listen to it, so I boxed it up and put in in the garage. Just got it back out and I'm gonna fix the sound tomorrow! Thanks for getting to the bottom of this!
Power enters the output transformer at Y. Some current flows to the plate of the 35C5 and the rest of the current out to Z in opposing direction on the winding. This would help kill hum and remove some of the DC bias on the transformer core.
When I found one of these radios a few years back,I was curious about the dot on the dial around the 100 Mhz mark. It's not a CONELRAD mark but marks the Zenith owned Classical FM station WEFM 99.5. Thanks for the fidelity mod, FM should never sound that muddy.. Stations these days have over processed and compressed audio as it is in the loudness wars, that cap makes it worse.
just got done fixing an old radio i have had when i was 10or 11 a model 628 1145 jcpenney radio ..cleaned up the batt compartment no go ,,get out the cap tester well i replace all caps plays great ..an it played last time i used it ..easy fix ..love your vids you are one sharp kid keep it up
The capacitor values are both 24pF for “L10,” it’s identical “L8” according to my similar schematic of an X334 Zenith. I know this video has been out for years but I along with many other reference your videos for new repairs/restores that come along. I am now going to make the fidelity upgrade on my X334 as the values are identical.
Zenith in my opinion built the best AM-FM table radios in the tube era. My favorite is the 845C with a 7 inch round speaker and a tweeter. It has a true tone control not just a treble cut. I've had one beside my chair for over 30 years. I have one that looks like your plastic set but it's FM only, be interesting to see if it has that capacitor.
I subscribe to Radio Rescue and he is a good guy to watch. Another very talented and very detailed restorer is Restore Old Radios. This fellow does multi-part videos of his restorations that goes into chassis de-rusting, period specific wiring, and cabinet restoration as well.
Looking at that makes one feel that the original workers must've taken great pride in their work. That is, long before Zenith was forced to move production to Mexico & the Far East. And incidentally, I have a sealed Zenith-branded 9v alkaline battery in front of me (brother found it somewhere). It's dated 2016 & has the old "Z" logo on both the battery & the package, and old, "the quality goes in before the name goes on" phrase printed across the latter. But turn it around back & one sees, "Made in PRC." Ironic, yes?
LG (Lucky Goldstar) is the company that did in Zenith. They didn't want to build electronics in the USA. They got all the Zenith technology along with the huge dealer network, which is really what they craved.
All Zenith FM sets are slug tuned. The later AM/FM tube sets like yours had no tone control. The earlier sets have tone control, and some even have a small tweeter with a crossover! I enjoy watching "Radio Rescue" vids as well! Good stuff! Alexa, can you test the tubes in my Zenith! lol
If you or your viewers ever wondered what that dot is just to the left of the 100 megahertz marking on the FM tuning dial it signifies 99.5 megahertz the frequency of wefm, the nation's oldest FM stations at the time and it was owned by Zenith radio Corporation in Chicago. In its heyday, it was a classical music station in Chicago. I don't know what is on that frequency now as my information is dated as I left Chicago over 40 years ago. That dot was on every Zenith FM radio or radio tuner from 1948 up until the time they started having radios imported from the Orient.
So I got the X318 and I'm very pleased with the heavy bass. I have a longwire FM antenna hooked up to it, and I am pulling in stations 60 to 70 miles away with amazing clarity. (I am picking up 92.9 in Summersville, 105.1 in Saint Albans, 105.9 in Huntington, 103.7 in Beckley, and WKAZ-AM's low-powered FM repeater on 95.7.) AM reception is okay, but I mainly bought this for FM.
My father had that same radio on his kitchen table until he moved in 1976. He would listen to country western music on it. Not the kind of well produced country you hear these days but the real classics. Willie Nelson when he was clean shaven with short hair. Merle Haggard. Tammy Wynette. George Jones. Buck Owens.
It's wild how that cap being removed doesn't hurt the bass at all, it only makes the treble come back. I have no idea why they would design that in there, I wonder if that's how it was meant to sound or if something (on all of them?) has changed over the years?
The bass/low end was a gimmick of sorts, gave the radio a higher quality sound over the Japanese sets showing up around that time. Zeniths were always noted for plenty of low end on many of their mid-upper end radios. And as another commenter eluded to, it lessened listener fatigue over longer periods. Now as for AM sounding different, you have to remember that AM stations were putting out 10khz audio bandwidth when this rig was built. Today, most AM's are outputting 6khz audio bandwidth on non-HD stations, 4.5khz analog bandwidth for stations running HD. Big difference.
The low high end reminds me of something retrochad (I think) demonstrated with a jukebox he had where it was designed to cut down the high end as the volume control was turned down. I think it was probably so the music could be present, let's say in a diner, and so people could understand the conversations the where having with each other, since the high end in their voice could be heard over the music. This is just my guess.
That with the output transformer is not a filter choke ruther it's against core saturation. In this way you can use a smaller iron core for the output transformer and you have better base response.
FM stations in the USA use a pre-emphasis circuit with 75 microsecond time constant. The idea is to boost the high frequencies prior to transmission to improve the signal to noise ratio. At the receiver, a 75 microsecond time constant de-emphasis circuit is used to compensate and flatten the end to end frequency response. R29 and C28 appear to be that de-emphasis circuit. I think the problem is the relatively large speaker with good bass response but the lack of a tweeter. The high end frequency response is poor. Removing the de-emphasis circuit increases the amplitude of the high frequency content at the speaker and improves the overall frequency response.
To me, it is pure magic.. still I got a radio to play with, it has a cats eye like a end of 40's to 50's radio and a newer plywood box. As it is semi wrecked, I love a clear acrylic cover on it. It was restored at amateur level as part of the capacitors were replaced but some paper ones did stay behind... the cord was cut off and given to me. Where to start I think...
Arjan Wilbie I’m in the same position as well with a old 1955 radio with 5 tubes. Cord is missing as it’s been cut or chewed off, have no equipment to test the caps or tubes! Mine looks all original too with a lot of those wax caps.
There are some of us who love the bass. Guess I am among those, well I was until the VA gave me a set of hearing aides and I could hear all the highs that I had before going on my all expense paid 13 month vacation in The Republic of Vietnam.
The green capacitor is the "balancing capacitor" in the FM ratio detector circuit. [I stand corrected; the detector is a Foster-Seeley design here.] These radios remind me a lot of a Japanese-built Lloyd's radio I have. The dial design is almost identical. However, mine has two 12DT8s (dual triode, very similar to 12AT7) in the FM front end, whereas yours seems to only have one. The Lloyd's radio also uses conventional variable capacitor tuning on FM, rather than slugs. I suspect that the slug tuner would be less susceptible to microphonics than a variable capacitor.
Ratio detector vs discriminator - Eugene McDonald (head of Zenith) refused to use the ratio detector because it was RCA's answer to keep from having to pay royalties to Edwin Armstrong, the inventor of wide-band FM broadcasting. IIRC earlier Zenith FM radios advertised using the 'Armstrong circuit'. David Sarnoff was particularly vicious to Armstrong who ended up committing suicide over it.
Omg just pulled one similar to these and found that cap that muffles this thing and man does it sound so much better crazy what a lil cap can do for it
I concur with your view on the working voltage of replacement electrolytic capacitors. I have 'rebuilt' switch mode TV power supplies using a 240V AC (Australia) mains supply, then rectified to say, 345V DC as the 'hot' side, where the critical regulating components contain 25 WV electrolytics, generally coupled to the 'chopper' transistor. I made it a habit to match the manufacturer's working voltage, as well as the extra (small) expense in fitting low ESR types, and not too close to the heat sink.. The (original) main problem is loss of voltage regulation when the electrolytic goes low in capacitance (also at a low temperature) causing the chopper transistor to short.. ..followed by fusible resistors/fuses...
Same, said it before and will again. Whether it's a 5 minute update or a 2 hour epic it'll get watched by me multiple times now and into the future. Apart from the entertainment, it's a useful resource to pick up little titbits of knowledge along the way.
I removed a capacitor from my Philco 48-482 that shunted hf audio from the plate of the output tube directly to ground, had a similar effect and sounds great now
Why the audio output transformer has a tapped primary: That transformer has DC flowing in its primary, which produces static magnetic flux in its core. To keep the core from saturating, the transformer has a larger core and air gap than it would need if there were no DC. By tapping the primary and having DC flow in the opposite direction in that second section of the primary (31:55), some of the static flux is cancelled, so a smaller transformer can be used. (Some power supply hum is also cancelled.) However, to this arrangement's disadvantage, some of the audio signal is delivered to R40, diverting audio power that could be delivered to the speaker. Some AA5 radios also have the tapped audio output transformer, but, probably, most of them don't. You should be able to substitute an audio output transformer with two wires to its primary, connecting the Y (red) and Z (blue) wires together to one terminal on the primary and brown wire to the other terminal. If the replacement transformer's impedances properly match those of the output tube and speaker, the volume control should produce the same audio loudness at a lower setting.
I'm working on a similar Zenith AM-FM radio, model 7N07, which has a tweeter. It has the same sequence of 14GT8 -> 100K resistor -> .001 capacitor -> ground. I haven't gotten mine working yet, but when I get it working I'll see how it performs with and without deleting the .001 capacitor. Possibly Zenith optimized for the tweeter and not for radios without it. Maybe so that people doing a side comparison in a store would buy the more expensive radio?
you're quite right about cap voltage, if using one with voltage rating way above what it would be subjected to, it may well not stay formed long term, but too high a capacitance will result in high surge currents, valve/tube rectifiers may be damaged, but others should be ok..
it's just like the marantz 70's units. the early models had caps rated just above the operating voltage, and the later B models had caps rated just under the operating voltage.
22:50 That reminds me of the crossovers Magnavox put in some late 1960s Astro-Sonic consoles; they had a resistor in series with the horn tweeters that made them almost impossible to hear, especially the way they were mounted; shorting it out improved the sound a lot. In this case, I wonder if Zenith was worried about the discriminator distorting the high end when the signal got weak, or just the hiss being loud relative to the signal and just figured they'd get less grief with the treble cut out altogether.
It'd be interesting to see a video on an older "Roberts" radio, these are top notch English made portable radio's, they've been made over here for a good 70 plus year's, no idea if they were exported across the pond or not, but I'd bet there are plenty over in the states
RCAs shunt the high frequency audio too, especially on shortwave bands. I believe my RCA 16X13 has a 4 position switch for source; A is SW with high freq shunted, B is Broadcast with high freq shunted, C is Broadcast not shunted, and D is line in not shunted. I was wondering why my dad drilled a hole in the side of the case to mount a switch (the case was already REALLY rough) turns out it was to cut out that crossover cap. If I ever get to restoring the case I'll relocate the switch to the back.
Both radios are cute & so basic like my one. It sounds like your cat must of got a hair ball & needed to barf it up. LOL BTW I do prefer your videos nice & long too, even movie length is good as watching You is far better then a movie anyday! :)
There's probably a reason Zenith played around with the tone of these radios and why it's a little bass heavy. When they were originally manufactured, the FM dial was mostly middle-of-the road pop and "beautiful music" sourced from lp records. The source material didn't have the frequency range of what's on FM today - they were really making them sound good for the type of material that was on FM at the time.
These were commonly seen in homes back in the 60s and early 70s in the kitchen, living room, den, etc. Offices and waiting rooms, even in the small town I grew up in, had Muzak systems. The only businesses where you regularly saw a tabletop radio would be in like a mom and pop garage, cafe, or gas station.
that was fun, thanks man. what you said about buddy's channel,is how i feel about yours.. thanks for the recommendation tho... Have you ever heard of Rosie Okelly's channel. every now and then she works on vintage audio.
I think I know why they have that capacitor in there to take off some of the high end. If you think about it, most music back in the day when that radio was made did not have as much bass, so therefore they probably added that capacitor to make it have more low end.
I know this video is old now, but I bet Zenith did that little modification to intentionally make the radio sound flat, and not crisp because at the same time this was on the market, Hi-Fidelity radios and gear was the hot item to have and they wanted to SELL SELL SELL Hi-Fi. Couldn't have the cheap table top radios sounding almost as good as the expensive stuff, so make it sound flat.
every radio of that vintage seems like the high freq was a problem. I wonder if broadcast standards or even the kind of music or pre emphasis have changed? or maybe they were worried about stereo noise.
That's what I'm wondering, I've seen loads of recommendations to lift certain caps in these radios in order to open up the frequency range, the standard of the time must have been for bass heavy and treble light audio... as Shango066 would say... "who knows, who knows."
Greetings: Capacitor values: as capacitance value increases, so does initial rectifier current draw. Using an inrush current limiter such as the CL90A may help save tube rectifier life when cap value doubles.
With the filter capacitors, do you think the working voltage should exceed that of the old capacitors by a small amount? How true is it that older capacitors had a lot more of a working voltage tolerance window than new capacitors? So if it's a 150V cap you should replace it with a 200V ? Isn't the initial surge voltage somewhat higher than the "settled" working voltage?
Tone cap.: Best guess, when played very low (think sleeping baby or someone disturbed when it is "too quiet") limited highs make for a more soothing sound when fidelity is secondary .
The muffled sound is because people liked that sort of sound back then. Now the broadcasts have so much more compression. I had an English FM only radio that only offered degrees of muffled. It also had a totally dried out Dubilier filter can that left 70 V of ripple on the 230V B+ line. The radio was on a PCB that was toasted badly around the o/p stage. It was at this point I also saw the o/p tube was gassy (pink glow). That turd got EOL'd. Sometimes it just isn't worh wasting your time.
another common problem on these Zeniths is the plate load resistors to the 12DT8 often go out of spec & cause the FM to stop working or do other strange things.
I've always thought, with nothing to back it up, that putting in a super high voltage cap was a bad idea. Technically it ought to work fine but like you said you're way out of spec with that, just the inefficiency of putting in three times the part you need never really set right with me. I'm going to start telling people in my videos the same thing, if it's 160 try to keep it at 250 or so no need to crazy on these things. it just seems right and the form explanation makes sense.
I'd have to take the old filter caps out if they no longer worked myself. I like the look of new ones better. Plus maybe the radio would get better reception and might even run cooler with less stuff taking up space.
Hi I purchased a Zenith X323 On eBay and when It arrived the volume knob was broke off so to bad packaging so I need a new Volume Potentiometer with switch, do you know the make/model number of the Volume Potentiometer, I would rather order it and just take the radio apart once. Thanks Jeff
I got a zenith am fm radio I was looking at last night it's it's very similar but it's got 8 tubes and a couple other different things but it's about the same it's even got that slug tuner with the 2 red things that move in and out
I wish I had taken up repairing televisions and radios. Oh well too late now, but as it is now I can't even use a sell phone and some tv remotes in my old age.
31:57 Is that negative feedback through R38? I wonder if the use of the second primary winding is also intended to cancel load induced power supply ripple, though whatever its benefits, I'd also expect it to magnetize the core and make it saturate earlier. Either way, these sets were not intended for waking up the neighbors; FM cuts the normal 50C5 AA5 output in half.
AlexM answered my curiosity about core saturation; seems the DC through the extra winding was intended to cancel the DC through the audio primary (I'd forgotten about that), actually improving the headroom and preventing saturation.
In regards to the SMD noise, i found that the problem can go away just by playing the radio for a long period of time & putting it into daily use. i have several of these Zeniths & i use them on a weekly basis. the SMD problem went away after a day of use & has not appeared again.
I have a Zenith model N730 (very similar to with same chassis as the one in shango's video above), it initially suffered from SMD like effects which eventually went away with use. AM would cut in and out, and FM performance would come and go. All that cleared up after a few days of use. In the end it needed new filter caps and that was pretty much it. Decent tuning performance on both AM and FM, but it too suffers from the muddy FM sound. It is currently one of my most used tube sets.
Thanks for the shout out and the kind words! I have a few of these in several cabinet versions. You're right these things true to the Zenith name are made very well. I've found problems with static on FM that sounds like SMD Actually is a defect in the slug tuner. Thanks for a glance at the schematic these are strictly thru SAMS. Great sound mod to!
Radio Rescue you Shango and Radiotvphononut are the most entertaining electronics tinkers on the net!
I'm glad Shango gave you the shout out, I think I've missed your channel until he did. Watching a GE repair vid now, good stuff!
I subbed to your channel. If Shango says you are good, you are good ! :-)
Zachary : I would add Xraytony too, very long vids, but i learned from him a lot.
Radio Rescue Hi, hope you didn’t mind but I subscribed to your channel hoping your videos might help me with my 1955, 5 tube radio. :)
10:34 . . . "The cat is now barfing... that's attractive... maybe I should get some video of that."
My stomach is hurting from laughing so hard.
LakeNipissing Poor cat.
Maybe not. Often cats eat grass to deal with ingested hair.
LakeNipissing dogs do it as well to help with a upset tummy.
The level of humour using another level just lovely luckily I was not eating my lunch
They didn't play 10 commercials in a row back when those radios were new.
Adding the capacitor even improved the taste in music. Amazing.
I've heard a lot of table radios where the loudness compensation really improved the sound. Nice sound at normal and quiet levels, and loosing the bass boost at higher levels allowed the radio to fill a large room with clear sound without clipping. But Zenith sure did it wrong on these. Killed the treble along with the dip in midrange.
Very interesting about the tone mod, I'll have to remember that. About electrolytics; the old ones had a healthy surge rating, the new ones don't...and I've measured as high as 190v surge on a 160v cap. I use 250v nowadays, just for a little added safety margin.
I remember that in the Zenith model X334, it incorporated a piezoelectric tweeter to improve the quality of the sound.
Hello Shango I have a Crosley E15SL and its the best sounding table radio I have in my collection. You repaired a white model that was missing knobs. That Crosley had a tone tap like this Zenith but Crosley used different values and attenuated midrange and passes treble and bass. You're a great entertainer to watch you on Radio and TV repair and I have this game I play and guess what I think might be wrong during your diagnosis thanks again Ace 👍
Love the old radio's, they were my escape when I was a kid, we were dirt poor, my aunt gave me an old tube radio when I was at their farm working cattle one year, I put that beside my bed and late at night, I would play that radio loud enough so I didn't have to listen to my parents fight, man I can still recall listening to KOMA where the "good guy's" played all the latest rock and roll! Bismarck had Padre's Platters another rock played by a Catholic Priest. I still have that first transistor radio, mom saved it for me, and returned it about ten years ago, an old Jade 10 transistor...
I've been watching your channel for a month now and I've learned a lot about fixing these old tube radios. Thanks & Cheers!!
I really enjoy your videos. You're knowledge about electronics is immense.
Dude - you're a hero. I have an X316 and the muddy sound was driving me nuts trying to listen to it, so I boxed it up and put in in the garage. Just got it back out and I'm gonna fix the sound tomorrow! Thanks for getting to the bottom of this!
Power enters the output transformer at Y. Some current flows to the plate of the 35C5 and the rest of the current out to Z in opposing direction on the winding. This would help kill hum and remove some of the DC bias on the transformer core.
When I found one of these radios a few years back,I was curious about the dot on the dial around the 100 Mhz mark. It's not a CONELRAD mark but marks the Zenith owned Classical FM station WEFM 99.5. Thanks for the fidelity mod, FM should never sound that muddy.. Stations these days have over processed and compressed audio as it is in the loudness wars, that cap makes it worse.
just got done fixing an old radio i have had when i was 10or 11 a model 628 1145 jcpenney radio ..cleaned up the batt compartment no go ,,get out the cap tester well i replace all caps plays great ..an it played last time i used it ..easy fix ..love your vids you are one sharp kid keep it up
The capacitor values are both 24pF for “L10,” it’s identical “L8” according to my similar schematic of an X334 Zenith. I know this video has been out for years but I along with many other reference your videos for new repairs/restores that come along. I am now going to make the fidelity upgrade on my X334 as the values are identical.
barfing cats and lifting caps.
Zenith in my opinion built the best AM-FM table radios in the tube era. My favorite is the 845C with a 7 inch round speaker and a tweeter. It has a true tone control not just a treble cut. I've had one beside my chair for over 30 years. I have one that looks like your plastic set but it's FM only, be interesting to see if it has that capacitor.
I subscribe to Radio Rescue and he is a good guy to watch. Another very talented and very detailed restorer is Restore Old Radios. This fellow does multi-part videos of his restorations that goes into chassis de-rusting, period specific wiring, and cabinet restoration as well.
Yeah, I like the radio repair videos like this. I have watched Radio Rescue, he's pretty good too.
Looking at that makes one feel that the original workers must've taken great pride in their work. That is, long before Zenith was forced to move production to Mexico & the Far East.
And incidentally, I have a sealed Zenith-branded 9v alkaline battery in front of me (brother found it somewhere). It's dated 2016 & has the old "Z" logo on both the battery & the package, and old, "the quality goes in before the name goes on" phrase printed across the latter. But turn it around back & one sees, "Made in PRC." Ironic, yes?
LG (Lucky Goldstar) is the company that did in Zenith. They didn't want to build electronics in the USA. They got all the Zenith technology along with the huge dealer network, which is really what they craved.
Definitely a nicely made radio... plus, I like how they mounted the AM bar-antenna way up in the clear above the chassis.
That capacitor really made a difference!!! Thank you!!
I love this channel. I could watch this all day.
All Zenith FM sets are slug tuned. The later AM/FM tube sets like yours had no tone control. The earlier sets have tone control, and some even have a small tweeter with a crossover! I enjoy watching "Radio Rescue" vids as well! Good stuff! Alexa, can you test the tubes in my Zenith! lol
If you or your viewers ever wondered what that dot is just to the left of the 100 megahertz marking on the FM tuning dial it signifies 99.5 megahertz the frequency of wefm, the nation's oldest FM stations at the time and it was owned by Zenith radio Corporation in Chicago. In its heyday, it was a classical music station in Chicago. I don't know what is on that frequency now as my information is dated as I left Chicago over 40 years ago. That dot was on every Zenith FM radio or radio tuner from 1948 up until the time they started having radios imported from the Orient.
Your videos are always the best. Hope you never stop making them.
I love RR I am suprised you just found him. You, RR, and radiotvphononut are the best!
I have this radio in my garage. Thank you for posting this.
So I got the X318 and I'm very pleased with the heavy bass. I have a longwire FM antenna hooked up to it, and I am pulling in stations 60 to 70 miles away with amazing clarity. (I am picking up 92.9 in Summersville, 105.1 in Saint Albans, 105.9 in Huntington, 103.7 in Beckley, and WKAZ-AM's low-powered FM repeater on 95.7.) AM reception is okay, but I mainly bought this for FM.
Just got on ebay and had to buy this radio i like it im starting to like these
You are the the most enjoyable person to watch, like xraytony, Evblog and a few others but you are the best. 👍💕
As usual entertaining ,informative and useful.
My father had that same radio on his kitchen table until he moved in 1976. He would listen to country western music on it. Not the kind of well produced country you hear these days but the real classics. Willie Nelson when he was clean shaven with short hair. Merle Haggard. Tammy Wynette. George Jones. Buck Owens.
It's wild how that cap being removed doesn't hurt the bass at all, it only makes the treble come back. I have no idea why they would design that in there, I wonder if that's how it was meant to sound or if something (on all of them?) has changed over the years?
The bass/low end was a gimmick of sorts, gave the radio a higher quality sound over the Japanese sets showing up around that time. Zeniths were always noted for plenty of low end on many of their mid-upper end radios.
And as another commenter eluded to, it lessened listener fatigue over longer periods. Now as for AM sounding different, you have to remember that AM stations were putting out 10khz audio bandwidth when this rig was built. Today, most AM's are outputting 6khz audio bandwidth on non-HD stations, 4.5khz analog bandwidth for stations running HD. Big difference.
The low high end reminds me of something retrochad (I think) demonstrated with a jukebox he had where it was designed to cut down the high end as the volume control was turned down. I think it was probably so the music could be present, let's say in a diner, and so people could understand the conversations the where having with each other, since the high end in their voice could be heard over the music. This is just my guess.
This is my fav daily driver radio. I was wondering if there was a modification to improve the audio fidelity. Another great video, thank you so much!
LMFAO and the cat is now barfing.
That with the output transformer is not a filter choke ruther it's against core saturation. In this way you can use a smaller iron core for the output transformer and you have better base response.
FM stations in the USA use a pre-emphasis circuit with 75 microsecond time constant. The idea is to boost the high frequencies prior to transmission to improve the signal to noise ratio. At the receiver, a 75 microsecond time constant de-emphasis circuit is used to compensate and flatten the end to end frequency response. R29 and C28 appear to be that de-emphasis circuit.
I think the problem is the relatively large speaker with good bass response but the lack of a tweeter. The high end frequency response is poor. Removing the de-emphasis circuit increases the amplitude of the high frequency content at the speaker and improves the overall frequency response.
To me, it is pure magic.. still I got a radio to play with, it has a cats eye like a end of 40's to 50's radio and a newer plywood box. As it is semi wrecked, I love a clear acrylic cover on it. It was restored at amateur level as part of the capacitors were replaced but some paper ones did stay behind... the cord was cut off and given to me. Where to start I think...
Arjan Wilbie I’m in the same position as well with a old 1955 radio with 5 tubes. Cord is missing as it’s been cut or chewed off, have no equipment to test the caps or tubes! Mine looks all original too with a lot of those wax caps.
There are some of us who love the bass. Guess I am among those, well I was until the VA gave me a set of hearing aides and I could hear all the highs that I had before going on my all expense paid 13 month vacation in The Republic of Vietnam.
The Angry Radio Repairman - classic - great!
The green capacitor is the "balancing capacitor" in the FM ratio detector circuit. [I stand corrected; the detector is a Foster-Seeley design here.]
These radios remind me a lot of a Japanese-built Lloyd's radio I have. The dial design is almost identical. However, mine has two 12DT8s (dual triode, very similar to 12AT7) in the FM front end, whereas yours seems to only have one. The Lloyd's radio also uses conventional variable capacitor tuning on FM, rather than slugs. I suspect that the slug tuner would be less susceptible to microphonics than a variable capacitor.
Ratio detector vs discriminator - Eugene McDonald (head of Zenith) refused to use the ratio detector because it was RCA's answer to keep from having to pay royalties to Edwin Armstrong, the inventor of wide-band FM broadcasting. IIRC earlier Zenith FM radios advertised using the 'Armstrong circuit'. David Sarnoff was particularly vicious to Armstrong who ended up committing suicide over it.
I watch Radio Recuse's videos. Good stuff.
Omg just pulled one similar to these and found that cap that muffles this thing and man does it sound so much better crazy what a lil cap can do for it
I concur with your view on the working voltage of replacement electrolytic capacitors. I have 'rebuilt' switch mode TV power supplies using a 240V AC (Australia) mains supply, then rectified to say, 345V DC as the 'hot' side, where the critical regulating components contain 25 WV electrolytics, generally coupled to the 'chopper' transistor. I made it a habit to match the manufacturer's working voltage, as well as the extra (small) expense in fitting low ESR types, and not too close to the heat sink.. The (original) main problem is loss of voltage regulation when the electrolytic goes low in capacitance (also at a low temperature) causing the chopper transistor to short.. ..followed by fusible resistors/fuses...
Another great Shango066 video. Thanks.
Walt Anderson As always. *Thumbs Up*
Ooo, fidelity mod 🤩
Im sure there is other people like me that would'nt mind long videos...
Simon Østergaard I love his videos long.
Simon Østergaard yep I enjoy his videos no matter how long they might be never a dull moment 👍👍
Same, said it before and will again. Whether it's a 5 minute update or a 2 hour epic it'll get watched by me multiple times now and into the future. Apart from the entertainment, it's a useful resource to pick up little titbits of knowledge along the way.
I removed a capacitor from my Philco 48-482 that shunted hf audio from the plate of the output tube directly to ground, had a similar effect and sounds great now
Why the audio output transformer has a tapped primary: That transformer has DC flowing in its primary, which produces static magnetic flux in its core. To keep the core from saturating, the transformer has a larger core and air gap than it would need if there were no DC. By tapping the primary and having DC flow in the opposite direction in that second section of the primary (31:55), some of the static flux is cancelled, so a smaller transformer can be used. (Some power supply hum is also cancelled.) However, to this arrangement's disadvantage, some of the audio signal is delivered to R40, diverting audio power that could be delivered to the speaker.
Some AA5 radios also have the tapped audio output transformer, but, probably, most of them don't. You should be able to substitute an audio output transformer with two wires to its primary, connecting the Y (red) and Z (blue) wires together to one terminal on the primary and brown wire to the other terminal. If the replacement transformer's impedances properly match those of the output tube and speaker, the volume control should produce the same audio loudness at a lower setting.
An inline fuse on that OT choke circuit would be a good idea.
Good sound!
Top video !
The "Radio Whisperer" :)
I'm working on a similar Zenith AM-FM radio, model 7N07, which has a tweeter. It has the same sequence of 14GT8 -> 100K resistor -> .001 capacitor -> ground. I haven't gotten mine working yet, but when I get it working I'll see how it performs with and without deleting the .001 capacitor. Possibly Zenith optimized for the tweeter and not for radios without it. Maybe so that people doing a side comparison in a store would buy the more expensive radio?
You should have left the polka on! Polka is life! Everyone needs more Polka.
you're quite right about cap voltage, if using one with voltage rating way above what it would be subjected to, it may well not stay formed long term, but too high a capacitance will result in high surge currents, valve/tube rectifiers may be damaged, but others should be ok..
that cap you removed looks like a de emphasis cap, and should normally be needed, maybe they used too high a value?
The cat makes the funny meow sound, it looks like a bucking horse …
it's just like the marantz 70's units. the early models had caps rated just above the operating voltage, and the later B models had caps rated just under the operating voltage.
(@30:36) I just love those 100 volt triangles on pin 5! :)
22:50 That reminds me of the crossovers Magnavox put in some late 1960s Astro-Sonic consoles; they had a resistor in series with the horn tweeters that made them almost impossible to hear, especially the way they were mounted; shorting it out improved the sound a lot. In this case, I wonder if Zenith was worried about the discriminator distorting the high end when the signal got weak, or just the hiss being loud relative to the signal and just figured they'd get less grief with the treble cut out altogether.
It'd be interesting to see a video on an older "Roberts" radio, these are top notch English made portable radio's, they've been made over here for a good 70 plus year's, no idea if they were exported across the pond or not, but I'd bet there are plenty over in the states
RCAs shunt the high frequency audio too, especially on shortwave bands. I believe my RCA 16X13 has a 4 position switch for source; A is SW with high freq shunted, B is Broadcast with high freq shunted, C is Broadcast not shunted, and D is line in not shunted. I was wondering why my dad drilled a hole in the side of the case to mount a switch (the case was already REALLY rough) turns out it was to cut out that crossover cap. If I ever get to restoring the case I'll relocate the switch to the back.
"And the cat is now barfing"..
Ay, been there.
Like yer' vids. :-)
Both radios are cute & so basic like my one. It sounds like your cat must of got a hair ball & needed to barf it up. LOL
BTW I do prefer your videos nice & long too, even movie length is good as watching You is far better then a movie anyday! :)
Speaker Sex like carpet???? LOL 😂
Speaker Sex yeah it looks like someone just cut a piece of carpet out from their living room floor, slapped it on there & said “that will do”.
Cats go barf, dogs go woof.
There's probably a reason Zenith played around with the tone of these radios and why it's a little bass heavy. When they were originally manufactured, the FM dial was mostly middle-of-the road pop and "beautiful music" sourced from lp records. The source material didn't have the frequency range of what's on FM today - they were really making them sound good for the type of material that was on FM at the time.
These were commonly seen in homes back in the 60s and early 70s in the kitchen, living room, den, etc. Offices and waiting rooms, even in the small town I grew up in, had Muzak systems. The only businesses where you regularly saw a tabletop radio would be in like a mom and pop garage, cafe, or gas station.
that was fun, thanks man. what you said about buddy's channel,is how i feel about yours.. thanks for the recommendation tho... Have you ever heard of Rosie Okelly's channel. every now and then she works on vintage audio.
I think I know why they have that capacitor in there to take off some of the high end. If you think about it, most music back in the day when that radio was made did not have as much bass, so therefore they probably added that capacitor to make it have more low end.
I know this video is old now, but I bet Zenith did that little modification to intentionally make the radio sound flat, and not crisp because at the same time this was on the market, Hi-Fidelity radios and gear was the hot item to have and they wanted to SELL SELL SELL Hi-Fi. Couldn't have the cheap table top radios sounding almost as good as the expensive stuff, so make it sound flat.
I think the reason for lack high end. Zenith was going for a warmer sound,I don't know. But that makes sense!
"Smooth operator." - Sade. And she doesn't even know you!
Nice Sounding Old Radio. As Far As
The Cap You Removed Goes I can't
Tell Too Much Difference In The Sound.
It Still Sounds Almost The Same To Me.
every radio of that vintage seems like the high freq was a problem. I wonder if broadcast standards or even the kind of music or pre emphasis have changed? or maybe they were worried about stereo noise.
That's what I'm wondering, I've seen loads of recommendations to lift certain caps in these radios in order to open up the frequency range, the standard of the time must have been for bass heavy and treble light audio... as Shango066 would say... "who knows, who knows."
Greetings:
Capacitor values: as capacitance value increases, so does initial rectifier current draw. Using an inrush current limiter such as the CL90A may help save tube rectifier life when cap value doubles.
Shane go I think it was put there to probably keep the speaker on the phone but you're gonna crank that radio up that loud and it's life
With the filter capacitors, do you think the working voltage should exceed that of the old capacitors by a small amount? How true is it that older capacitors had a lot more of a working voltage tolerance window than new capacitors? So if it's a 150V cap you should replace it with a 200V ? Isn't the initial surge voltage somewhat higher than the "settled" working voltage?
Nice video! Your viewers might also like a channel called RestoreOldRadios
Tone cap.: Best guess, when played very low (think sleeping baby or someone disturbed when it is "too quiet") limited highs make for a more soothing sound when fidelity is secondary .
I have the X318 model on its way with the original box. I'm probably gonna sell one of my RCA 8X541 radios as well as my Sony ICF-9650W to make room.
The muffled sound is because people liked that sort of sound back then.
Now the broadcasts have so much more compression. I had an English FM only radio that only offered degrees of muffled.
It also had a totally dried out Dubilier filter can that left 70 V of ripple on the 230V B+ line.
The radio was on a PCB that was toasted badly around the o/p stage. It was at this point I also saw the o/p tube was gassy (pink glow). That turd got EOL'd. Sometimes it just isn't worh wasting your time.
That part of the curcuit deals with the 75 us de em
another common problem on these Zeniths is the plate load resistors to the 12DT8 often go out of spec & cause the FM to stop working or do other strange things.
I've always thought, with nothing to back it up, that putting in a super high voltage cap was a bad idea. Technically it ought to work fine but like you said you're way out of spec with that, just the inefficiency of putting in three times the part you need never really set right with me. I'm going to start telling people in my videos the same thing, if it's 160 try to keep it at 250 or so no need to crazy on these things. it just seems right and the form explanation makes sense.
I'd have to take the old filter caps out if they no longer worked myself. I like the look of new ones better. Plus maybe the radio would get better reception and might even run cooler with less stuff taking up space.
Hi I purchased a Zenith X323 On eBay and when It arrived the volume knob was broke off so to bad packaging so I need a new Volume Potentiometer with switch, do you know the make/model number of the Volume Potentiometer, I would rather order it and just take the radio apart once. Thanks Jeff
Actually, i was on Radio Rescue and your videos popped up. He's not very prolific lately.
I've watched Lots Of His Videod
& I Just Got Threw Talking
To Him About Taking One Radios
& Making A Bluetooth Speaker Out Of
It.
I got a zenith am fm radio I was looking at last night it's it's very similar but it's got 8 tubes and a couple other different things but it's about the same it's even got that slug tuner with the 2 red things that move in and out
I wish I had taken up repairing televisions and radios. Oh well too late now, but as it is now I can't even use a sell phone and some tv remotes in my old age.
What about using a W04G Bridge Rectifier and a voltage stabilizer based on a MJ3055 and a BD131 and a Zener Diode.
Id die to have a radio like that
31:57 Is that negative feedback through R38? I wonder if the use of the second primary winding is also intended to cancel load induced power supply ripple, though whatever its benefits, I'd also expect it to magnetize the core and make it saturate earlier. Either way, these sets were not intended for waking up the neighbors; FM cuts the normal 50C5 AA5 output in half.
AlexM answered my curiosity about core saturation; seems the DC through the extra winding was intended to cancel the DC through the audio primary (I'd forgotten about that), actually improving the headroom and preventing saturation.
In regards to the SMD noise, i found that the problem can go away just by playing the radio for a long period of time & putting it into daily use. i have several of these Zeniths & i use them on a weekly basis. the SMD problem went away after a day of use & has not appeared again.
I have a Zenith model N730 (very similar to with same chassis as the one in shango's video above), it initially suffered from SMD like effects which eventually went away with use. AM would cut in and out, and FM performance would come and go. All that cleared up after a few days of use. In the end it needed new filter caps and that was pretty much it. Decent tuning performance on both AM and FM, but it too suffers from the muddy FM sound. It is currently one of my most used tube sets.
Shango, have you ever worked on a Panasonic Quintrix tv set? theyre great tvs
Synthematix i got a few in my collection, great sets
My daughters use to have one in their bedroom. It lasted for years till the CRT went weak on it.
would the voltage drop be because it's pulsating DC without the cap instead of steady DC with the cap?