Static! Noise! Simple Fix for a Vintage Receiver: Pioneer SX-440 Transistors
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- เผยแพร่เมื่อ 23 ส.ค. 2024
- This problem is common with early-70's Pioneer receivers. One day it was working fine, and the next it was making awful static-like noises! Knock wood, I have fixed the problem by replacing several small transistors, and this beautiful old Pioneer is making beautiful music once again. Bad transistors commonly cause problems with Pioneer receivers from the early 70's. Symptoms include static and pops. The noises may start off relatively quiet but can quickly progress to being very loud. With this receiver, the problem started as moderately noisy static in one channel and progressed to loud static from both channels. I previously encountered this sort of problem with a Pioneer SX-828. In that receiver, bad transistors were causing loud pops in both channels. Transistors failing in this way may not appear as faulty in simple transistor testers, and the transistors needing replacement are typically inexpensive, so rather than tracking down the source of the fault, replacement of several or many transistors is often the most simple way to address the problem. That method worked for the SX-828 and appears to have worked for this SX-440.
The SX-440 is so good for near field applications. I use it with my desktop computer and it has a beautiful sound. It has a vintage tube like echoey resonance that really shines with certain songs and the bass is surprisingly tasty(I like a lot of electronic house music). I love the look of it and the wood case is beautiful! It’s nice to see real wood on an entry level piece. This is my favorite piece I have sound-wise but it’s not powerful enough for large rooms. I’m looking for a SX-1500td or SX2500 to get the same sound signature for a larger room.
I'll keep this in mind if I run across any similar problems. I have a 1974 SX-434 that was handed down to me in 1979.
That’s good that I know how to solder and I know a bit about everything
A very interesting video, this little Receiver is a loverly little unit. I will be trying to get an intermintant tuner in this sorted very soon parts on order, pretty much just changing caps and transitors bit of a shotgun approach but be interesting to see if it solves the problem. Great videos on your channel.
Sometimes the shotgun approach is the most efficient. Address common failure modes, see if that works, and move on if it does. And thanks!
besten dank from switzerland......best regards
Hello, thank you very much for this video. Could you share that Excel table with replacements?
Greetings!
Old capacitors often read high in capacitance, when in reality the capacitance may not be high. This is due to the capacitor’s high leakage current which can fool the capacitor tester. The tester measures, in effect, the total admittance, but that can be a combination of capacitive susceptance plus leakage conductance. It takes a lab grade instrument like an HP to separate these factors. In any case, any old cap measuring that high should be replaced.
That's pretty much exactly what I learned through a FB forum recently. I had generally made it my practice to replace caps that were out of spec, whether over or under, but I hadn't known that the high value was erroneous or what the underlying issue was. From your comment, it sounds like I need to refresh my memory regarding this SX-440 and its need for a new filter cap.
Ok, I just re-watched, so now I know it's the output caps you were referring to. Could those bad caps have been the problem after all?
Tracking down intermittent noise such as you experienced can be tough, and even humiliating. Capacitors (esp. electrolytics and old paper caps, resistors and semiconductors can all make noise. Certainly if your output caps were leaking DC into the speakers intermittently it could make a sputtering sound. If those caps fail completely they could essentially short the power supply to your speakers. Even if they measured perfectly I would replace them as insurance, after so many decades. If you still have “static” you won’t have wasted your money on new output coupling caps, IMO. The black lead disease for the semiconductors is due to the leads being silver plated. They corrode to black silver oxide, which can break the tight seal of the plastic enclosure around the lead and allow atmospheric moisture and pollution in inside to the die. But generally I do not replace transistors without good cause. Old electrolytics are different, being time bombs.
BTW, I came to your video because I recently acquired the very similar SX-770. It needs some caps and a new FM demultiplexer chip (talk about unobtainium!). Bulbs too, of course. My very first stereo back in 1970 as a kid was centered around the SX-770. Despite having a high-end system today I wanted a 770 for nostalgic reasons and for a system for my home office. Mine is cosmetically near perfect, after I washed off lots of grime. I noticed some of your knobs have a copper color to them. I suspect they were originally black (which the 440’s brochure shows). They were probably exposed to sunlight for years and the UV bleached the black coating on the decorative cap on the knobs.
Agreement all around. I went ten rounds with a Nikko TRM-750. Replaced a couple of transistors that had bad reputations, replaced all the el-caps, and still had intermittent noise issues. Finally, I treated all of the front-panel switches with DeoxIT, and the problem was solved. That'll now be a routine thing for these old units. Here's another: Microswitches on old turntables! I have a LAB-400 that had a speed fluctuation issue. I treated the speed adjustment pots (probably twice) to no effect. Replaced one of the microswitches and deassembled and cleaned the other, and problem solved completely.
another saved receiver
Great pioneer
They are a pip, a restored 440 are awesome.
Hello. I have a boombox which does not play any radio station clearly. Every station has static noise. My car radio plays them all good so the signal is good. The boombox is very clean inside and has a new fm antenna. Where should I check? TY
I don't know. I don't know much about radios. Sorry!
I have a Sherwood s-9400 in mint condition however when you turn it on there's a very loud pop snap that comes out of the speakers not like a constant static but like a loud popping sound like very loud is there any way I could send you a video of this and get your opinion of what you think is wrong because I have no idea what to do the rest of the unit is in such great shape I don't want to get rid of it and it's kind of a hand-me-down from my father so I'd really like to hold on to it. Let me know if there is like an email or somewhere I could send you a video of this noise
Does it pop repeatedly or just once when you turn it on?
It's like a loud static pop and it happens when I turn the volume knob sometimes one of the speakers will cut out but it's so loud it sounds like it's going to blow the speaker almost
Treating the pot with Faderlube F5 might fix it.
So which part of this is the simple fix. Or is it all of it
just had the same thing happen to my Harman Kardon hk505 ,left channel is up to over 115mv on both A B speakers ...
that unit was re capped (I was told) couple years ago ... I wonder I was running a couple sets of speakers for a bit before I learned that it's not a good idea...could that be the problem ?
I don't know. I don't know for sure how low impedance damages amps, but I suppose the effect is similar to that of shorting the outputs, and I'm again supposing that shorting the outputs would overload the output transistors and/or other components in the output stage. The damage might result in noise. I'm speculating, though.
My one is currently being repaired new transistors etc £300
Ouch
But a great looking and sounding machine
Yeah, ouch! Transistors are cheap. Bench time isn't.
Interesting to hear how much they charge these days for repairs. This is a very under rated little receiver.
Yeah, if I had to pay someone else to fix stuff, I would not be into vintage gear!
So... the spreadsheet... Is that something you put together or is it available online somewhere? Thanks!
That's my own "cheat sheet" of transistor substitutes.
This is the model I have 😁. Fortunately, I don't have this problem right now.
However, I was wondering why I receive so much feedback when I'm using an aux cord plugged into a PC monitor for sound? Is it cause the stereo's source is so old and it's plugged into a new system? Like is it bad to use the aux output on this stereo?
Hmm. It should be fine. That's how my son uses it. What kind of feedback? Amps can pick up cellular noise.
I'm having the same issue with my sx525
Yeah... changed many of those small xistors before. You should really change out all those electrolytic's, it don't look like there is that many..the 70's was a long time ago and they were at end of life many years ago .. there all probably out of spec reading higher than they are as they are pretty dried out. Then she should be good for the long haul.
That's on the to-do list for sure!
I have the same reciver problem with it is when I power on popping noise in speakers nothing after that sounds good.
Did you email me?
You cannot judge output DC voltage without proper few ohm speaker connected to output terminals because capacitors must have way to charge themself to 17 Volts. If they stay not charged all voltage has to stay at free terminals When charged through volt meter with resistance of many MOhms the time constant of charging may be even half an hour - never will reach zero
. Up to my experience such cracks may appear also from faulty resistors in which the metal connection is to loose on the coal trace and when resistance works it produces heat thermal expansion which moves both surfaces agains themself. When replacing transistors may happen that such resistor will be apparently bend and it will fix by self No transistor in my life produced cracking noise
My initial tests were naive and mistaken. That was kind of the point of showing them! And if I'm following your post, you're saying that an old transistor will never produce crackling, static-like noise? I don't have any testing data to refute you, but I would point to long threads on Audiokarma about bad transistors and their failure modes. Pops and static are among the most common cited. I'm not saying that all those people couldn't be mistakenly attributing the effects of cracked solder joints to transistors, but surely some of them tried reflowing joints before replacing transistors. But maybe not.
@@Lancaster_Hi-Fi I've said that in my life it never happened. Realy you cannot refute my private observations - nobody can. You may not worry if you like not
I do not also dispute bad solderings - this is of course probably case but with resoldering easy to get away from
. I mentoned about time wear of resistors - it is something that people rarely suspect and are puting attention to replacement of active elements which as original type sometime are after 50 years hardly available. Unnecessary replacements may lead to distortions or not equal amplification .
Yeah, changing transistors is tricky. And, I've actually replaced all the resistors in an SX-828. It was so much work! After replacing all the resistors and electrolytic caps and resoldering every joint on every board, that receiver still had serious problems that only disappeared after I replaced all the "bad-reputation" transistors. And I know that the hypothesis is still unproven, but it's not disproven, and that's how the scientific method works. Hypothesis: bad transistor(s). Prediction: If "problem" transistors are replaced, the problem will go away. Test: Problem transistors were replaced, and the problem went away. It's only a failure to disprove the hypothesis, but that's how we eventually establish knowledge in science. Sorry, not preaching or arguing; just trying to be clear.
@@Lancaster_Hi-Fi Up to my knowledge transistor is assembled using inside soldered connections with golden wires and it is small and mechanicaly fixed thus resistant for vibrations . But as you say w- never say never. I met in my life tiny ceramic capasitor, beautifull and expensine production, inside FM filter which did the same totaly good in no voltage, when few volts were present. it was irregulary making cracks. So difficult to rectify that radio (tube and marvelous) was never repaired until I got iot in horrible dirty condition after some 60 years of laying in basement
More schematics.
Great video.
Hm. Duly noted.