I don’t know electronics, but I’ve learned a lot watching your channel. It would be great if you can add a future segment on how you use the oscilloscope and whether an analog or digital scope is better.
Hello. Your videos are awesome. I hope I can find an answer here. Does a faulty part (diode, caps, resistors or whatever goes in the phono board) can degrade the sound of the channel? Like weak or low treble or low sound output in general, intermittently? Both channels of my pioneer sx 1980 drops treble especially the right channel..i dont know if faulty parts can make that happen. A couple of techs cant find the problem or just dont want to work on a complex unit like this…thank you…
In a nice spacious unit like that, you could easily upgrade your phone preamp to a Jfet unit with high end capacitors, one good circuit is the lepacific which uses lsk170s
I love vintage audio and do quite a bit of repairs myself. But still lives channels like this. And this video as the first of yours that I've seen seems fine. I would suggest a tripod and a better microphone so you don't need to talk so loud. I get a bit seasick by watching the shaky videos. This is just my personal opinion though.
Thanks for sharing and for watching. That was one of my earlier videos. I've gotten better over time( I think). Check out this video that I've recently done. Not so much of the shakes. th-cam.com/video/q0XYkMeaSyc/w-d-xo.html
salve. volevo sapere il 2sa798 ha diverse sigle .sono tutti uguali o sono specifici servono solo per i canali audio o possono anche regolare la velocita' del motore di un giradischi grazie
You *CANNOT* always find replacement parts at a reasonable price. The SONY TA-2000f Preamp (1975) is good example. It uses 2SK43 and 2SK23 FETS developed by SONY in the mid-70's. Only recently have they popped up on ebay between $11-19.00 a piece ! ($97.00 for an 8-pack!) Nor can one use common J-FETS to replace them. There is NO "NTE" Equivalent part like there is for most bi-polar devices. What I ended up doing is drawing the original circuit into circuit simulator software and then trying out common audio-grade low-noise FETS and bi-polars in the "virtual circuit". I ended up using NPN-MPSA18's (low noise high beta devices) but I had to re-design the entire bias and feedback network around the bi-polar devices. Lucky for me it was just a 3 stage "textbook" circuit. The new bi-polars have a much better transient and square wave response than the original SONY-FETS and are just as quiet. From what I understand..the reason SONY used FETS (in the gain stages) was for their low-noise characteristics. However I DID change the "sound" of the unit...for the better (IMHO). The THD was within the original spec also..but this was more a function of the simple circuit design than the parts used. Purchasing and learning how to use good a circuit simulator program is highly recommended if you cannot find an exact part match. (IMHO) The built-in libraries contain thousands of parts...(even more if you use a web-based sim tool) You can replace parts and measure gain, noise, transient response and even THD (!) all "virtually". The only drawback with most "end-user/hobbyist" circuit-simulator software is that they *CANNOT* discriminate among various capacitor types. A cap is just a cap. (There probably are circuit-sims out there for cap-modeling but they cost over $1000 to purchase and many are subscription based..)
Hi , you have a great channel, and I have a question that I hope you can answer. I’m nearly finished with my first repair and recap on my pioneer sx-450. The last replacements I made were on 2 of the faulty transistors in the phono preamp, replacing them with ksa992s. On one of them, I accidentally heated my desoldering gun too hot and the solder pag came straight off and I lost it...☹️. Is there a potential fix for this, and if not will one missing transistor in just the phono eq section affect playback on other inputs?
Hi, thank you for the kind words. No, big deal. I've damaged many myself for one reason or the other. Yes, you should fix it and it can be fixed. Search here on TH-cam "repairing solder pads". There are many videos on that subject as it happens often. Watching someone in a video will help you fix it better then me trying to tell you in words.
What's your opinion on power transistors from 1970s? I just removed mine (Toshiba 2SD428+2SB558) for cleaning and changing mica, they worked OK but are they really worth keeping? would a new complementary pair, say, MJ15024+MJ15025 be safer in the long run?
I think that they should stay. There are some transistors that are known troublemakers but I don't think those are on the bad list. Also you are a person that can do his own work so if something happened to them in the future you could take care of it.
@@vintageaudioaddict Seems like they have to go, anyway. I suppose I damaged one in the process, or perhaps it's deeeper than this. After putting it all together, one channel is fine, the other appears to be working, but I cannot set idle current and it distorts. At the widest bias spreader setting, the voltage across output transistor bases is only 0.9 volts, with 0.6 V across PNP base-emitter but only 0.3 V across NPN. Seems like it's hogging current from the driver, so the bias spreader is always starved (it's good, the current source feeding it is good, yet all that current flows into the NPN leg). I'm out of ideas except replacing driver and output transistors altogether.
I would like to know how you know what modern equivilant transistor is appropriate for a vintage replacement transistor? This question has always stumped me.
This is not an easy answer. You have to look at the parameters of each. It can take a lot of time and research to find the correct choice but a equivalent modern replacement can usually be found.
@@vintageaudioaddict Yes, but WHICH parameters are the most important, is the question. Always stumping me because there's such an myriad of parameters
@@vintageaudioaddict Thanks I appreciate the answer. I have flipped a Marantz a while back and a few cheaper stereos. Now I have 2 vintage pioneers to flip. They are both in great condition. It gives me hope that you learned on your own. That way I can learn how to fix them so I can buy for a better price. Flip most of them and keep a few.
@@moodyga40 thanks for the reply. I need to ask one more if you dont mind. Does a faulty transistor or cap on the phono amp can make an intermittent problem? Distortion, treble drop?
I always replace those low value ceramics in the signal path with silver micas because ceramics always drift and dull the sound. The sound difference is night and day
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Thank you for showing this repair. That said, I wish you'd spend a little more time on how you bonded the two emitter leads from the 2SA992s
Thank you, Thank you! Dealing with this exact problem in a Protect circuit.
Thank you for watching.
I don’t know electronics, but I’ve learned a lot watching your channel. It would be great if you can add a future segment on how you use the oscilloscope and whether an analog or digital scope is better.
Bravo pour cette réparations, très interressant comme d'habitude.
Hello. Your videos are awesome. I hope I can find an answer here. Does a faulty part (diode, caps, resistors or whatever goes in the phono board) can degrade the sound of the channel? Like weak or low treble or low sound output in general, intermittently? Both channels of my pioneer sx 1980 drops treble especially the right channel..i dont know if faulty parts can make that happen. A couple of techs cant find the problem or just dont want to work on a complex unit like this…thank you…
In a nice spacious unit like that, you could easily upgrade your phone preamp to a Jfet unit with high end capacitors, one good circuit is the lepacific which uses lsk170s
I love vintage audio and do quite a bit of repairs myself. But still lives channels like this.
And this video as the first of yours that I've seen seems fine. I would suggest a tripod and a better microphone so you don't need to talk so loud. I get a bit seasick by watching the shaky videos.
This is just my personal opinion though.
Thanks for sharing and for watching. That was one of my earlier videos. I've gotten better over time( I think). Check out this video that I've recently done. Not so much of the shakes. th-cam.com/video/q0XYkMeaSyc/w-d-xo.html
salve. volevo sapere il 2sa798 ha diverse sigle .sono tutti uguali o sono specifici servono solo per i canali audio o possono anche regolare la velocita' del motore di un giradischi grazie
You *CANNOT* always find replacement parts at a reasonable price. The SONY TA-2000f Preamp (1975) is good example. It uses 2SK43 and 2SK23 FETS developed by SONY in the mid-70's. Only recently have they popped up on ebay between $11-19.00 a piece ! ($97.00 for an 8-pack!) Nor can one use common J-FETS to replace them. There is NO "NTE" Equivalent part like there is for most bi-polar devices. What I ended up doing is drawing the original circuit into circuit simulator software and then trying out common audio-grade low-noise FETS and bi-polars in the "virtual circuit". I ended up using NPN-MPSA18's (low noise high beta devices) but I had to re-design the entire bias and feedback network around the bi-polar devices. Lucky for me it was just a 3 stage "textbook" circuit. The new bi-polars have a much better transient and square wave response than the original SONY-FETS and are just as quiet. From what I understand..the reason SONY used FETS (in the gain stages) was for their low-noise characteristics. However I DID change the "sound" of the unit...for the better (IMHO). The THD was within the original spec also..but this was more a function of the simple circuit design than the parts used. Purchasing and learning how to use good a circuit simulator program is highly recommended if you cannot find an exact part match. (IMHO) The built-in libraries contain thousands of parts...(even more if you use a web-based sim tool) You can replace parts and measure gain, noise, transient response and even THD (!) all "virtually". The only drawback with most "end-user/hobbyist" circuit-simulator software is that they *CANNOT* discriminate among various capacitor types. A cap is just a cap. (There probably are circuit-sims out there for cap-modeling but they cost over $1000 to purchase and many are subscription based..)
Hi , you have a great channel, and I have a question that I hope you can answer. I’m nearly finished with my first repair and recap on my pioneer sx-450. The last replacements I made were on 2 of the faulty transistors in the phono preamp, replacing them with ksa992s. On one of them, I accidentally heated my desoldering gun too hot and the solder pag came straight off and I lost it...☹️. Is there a potential fix for this, and if not will one missing transistor in just the phono eq section affect playback on other inputs?
Hi, thank you for the kind words. No, big deal. I've damaged many myself for one reason or the other. Yes, you should fix it and it can be fixed. Search here on TH-cam "repairing solder pads". There are many videos on that subject as it happens often. Watching someone in a video will help you fix it better then me trying to tell you in words.
What's your opinion on power transistors from 1970s? I just removed mine (Toshiba 2SD428+2SB558) for cleaning and changing mica, they worked OK but are they really worth keeping? would a new complementary pair, say, MJ15024+MJ15025 be safer in the long run?
I think that they should stay. There are some transistors that are known troublemakers but I don't think those are on the bad list. Also you are a person that can do his own work so if something happened to them in the future you could take care of it.
@@vintageaudioaddict Seems like they have to go, anyway. I suppose I damaged one in the process, or perhaps it's deeeper than this. After putting it all together, one channel is fine, the other appears to be working, but I cannot set idle current and it distorts. At the widest bias spreader setting, the voltage across output transistor bases is only 0.9 volts, with 0.6 V across PNP base-emitter but only 0.3 V across NPN. Seems like it's hogging current from the driver, so the bias spreader is always starved (it's good, the current source feeding it is good, yet all that current flows into the NPN leg). I'm out of ideas except replacing driver and output transistors altogether.
I would like to know how you know what modern equivilant transistor is appropriate for a vintage replacement transistor? This question has always stumped me.
This is not an easy answer. You have to look at the parameters of each. It can take a lot of time and research to find the correct choice but a equivalent modern replacement can usually be found.
@@vintageaudioaddict Yes, but WHICH parameters are the most important, is the question. Always stumping me because there's such an myriad of parameters
Can u mail me some photo's how u put them together with the pins connected together? I cannot see what u have connected together of the pins
Great video. I am considering getting into this. Is there any books you or your subscribers recommend?
Thanks for watching. I'm a self taught hobbyist so most of what I learned was from working on the equipment. So, I can't recommend any certain books.
@@vintageaudioaddict Thanks I appreciate the answer. I have flipped a Marantz a while back and a few cheaper stereos. Now I have 2 vintage pioneers to flip. They are both in great condition. It gives me hope that you learned on your own. That way I can learn how to fix them so I can buy for a better price. Flip most of them and keep a few.
phono amp also corrects the bass and treb as well the RIAA
Hello, what do you mean corrects bass and treble?
@@cheng96818 puts the bass back on the record
@@moodyga40 thanks for the reply. I need to ask one more if you dont mind. Does a faulty transistor or cap on the phono amp can make an intermittent problem? Distortion, treble drop?
@@cheng96818 it can
@@moodyga40 ok thank you, now at least i know what to tell these techs….
Very well
Thanks
Where did you get the grabber type test leads? All I can find is for logic level. They have the 2mm jacks. Do you use those and replace with a 4mm?
👍👍
Thank You!
Sir ml120 transistor equivalent plzz 5pin transistor
Please go slows when soldering fast stuff just drives me crazy. I am doing my best to learn
Noted!
I always replace those low value ceramics in the signal path with silver micas because ceramics always drift and dull the sound. The sound difference is night and day
Thanks a lot for sharing your experience with the ceramic capacitors.
Where is the best place to purchase them?
@@vincef.8261 purchase what?