Pioneer SX-1250 Keeps blowing speakers right channel, Ideas Help?

I will only tell you this once!!! CAUTION CAUTION CAUTION!!!!

These are STV3 diodes. They are very very difficult to obtain these days as they have not been manufactured for a good many years.
You must unscrew those, and whatever you do, do NOT grab them and move them around the place, be very very careful, hold them by the legs near the circuit board to move them out of the way, do not bend them by holding the diode, they will break off.
If you are unlucky enough to have one that is broken and have not noticed, the amplifier will destroy itself, blown output transistors, burned out emitter resistors....you do not want to go there!!

Extreme caution required!!
Are we talking about the same diodes? The horseshoe shaped ones that are screwed to heat sinks have white insulated wires running to them.
 
Are we talking about the same diodes? The horseshoe shaped ones that are screwed to heat sinks have white insulated wires running to them.
Yes these are the STV3 Diodes as stated above, yes they have the white insulators on them but they are single strand wires and break off the diode very easy.....
 
Yes these are the STV3 Diodes as stated above, yes they have the white insulators on them but they are single strand wires and break off the diode very easy.....
ok thanks for that tip. Sounds like I'm going to be working on a glass project with eggshell parts.
 
I always apply a little bit of glue (epoxy) to secure the fragile STV wires. push the sleeving back a bit to get glue on the leads where they enter the horseshoe pkg, then let the sleeving go back to it normal position so all gets glue & secured, done deal.
 
I always apply a little bit of glue (epoxy) to secure the fragile STV wires. push the sleeving back a bit to get glue on the leads where they enter the horseshoe pkg, then let the sleeving go back to it normal position so all gets glue & secured, done deal.
I like that tip!!! Sounds like a great idea, Thanks
 
I tried something once and was pleased with how it turned out. I layed the diode out flat and used silicon rubber gasket maker and formed it about 1/2 to 3/4 inch from the "horseshoe" It is now completely encased in rubber for that !/2 inch or so. Now if the wire for some reason was to break, I can remove some of the silicon rubber and repair the wire.

It's a good idea to check these diodes with your DVOM on diode test. Keep in mind I've discovered that the cheap/free/throw away DVOM's sometimes don't have enuff output to check these. Same as the "give away free" meters you see advertised. The reason is they are basically three diodes in series so it takes the better meters to read them.

As Kev mentioned above, you can't be careful enuff.

The reason I asked above if they were there is some people don't realize how critical they are and also what they are.

Bob
 
I tried something once and was pleased with how it turned out. I layed the diode out flat and used silicon rubber gasket maker and formed it about 1/2 to 3/4 inch from the "horseshoe" It is now completely encased in rubber for that !/2 inch or so. Now if the wire for some reason was to break, I can remove some of the silicon rubber and repair the wire.

It's a good idea to check these diodes with your DVOM on diode test. Keep in mind I've discovered that the cheap/free/throw away DVOM's sometimes don't have enuff output to check these. Same as the "give away free" meters you see advertised. The reason is they are basically three diodes in series so it takes the better meters to read them.

As Kev mentioned above, you can't be careful enuff.

The reason I asked above if they were there is some people don't realize how critical they are and also what they are.

Bob
I think I need to clarify one thing... the diode itself is not encased in the silicon rubber, only the wires up to it so the diode itself still can make solid contact with the heat sink.

Bob
 
Yes, the Nichicon's they have used are all 85˚C caps, which is not the end of the world but would have more durability if they used the higher temp grade and used caps designed for the application.

Pretty sure you are wrong here.

Those leaded blue radial caps with black stripe are probably Nichicon KT series which are rated to 105c.
 
Pretty sure you are wrong here.

Those leaded blue radial caps with black stripe are probably Nichicon KT series which are rated to 105c.
I know, I didn't see the KT caps in the first pictures. I use the KT for audio path myself in my own restorations.
Odd choice of caps in my opinion as they have 85˚C caps in the power supply where they should be using Nichi PW series, but they use FG series...
The selection of caps is not the route I would take and many others.
 
Just read the thread and it appears the OP's offset readings were 2 and 5 mV which I would have thought would be fantastic, did everyone agree that's not the problem and I just missed it?
 
Just read the thread and it appears the OP's offset readings were 2 and 5 mV which I would have thought would be fantastic, did everyone agree that's not the problem and I just missed it?
I think there was some random "popping" from one channel IIRC.....the offset is not the issue, it could be 50mV and not be the problem...
 
I know, I didn't see the KT caps in the first pictures. I use the KT for audio path myself in my own restorations.
Odd choice of caps in my opinion as they have 85˚C caps in the power supply where they should be using Nichi PW series, but they use FG series...
The selection of caps is not the route I would take and many others.
Out of curiosity, what is wrong with UFG in the power supply?
 
Out of curiosity, what is wrong with UFG in the power supply?

They wont last as long. PW is a better design for power supply applications where there is a lot of ambient temperature.

Use whatever, makes no difference to me, I am saying what I use when I am restoring Pioneers. Its a free world and if you think fine gold is the way to go, then knock yourself out.....
 
I want to thank everyone who helped me by providing all your information and technical knowledge. I finally figured it out.
I sent amp to a very decent tech I met online and had a complete recap and problem transistors/relays....in other words a complete restoration electrically. So I get it back all fresh and played it for a while and sounded great using CDs. The next day I let it play at the lowest volume setting for about 8 hrs with my mp3 player. Then I turned up volume to about 10 o'clock position....BLOWN left woofer coil. I'm pissed WTF?. I wrap it up and take it to another local guy and he goes through it and calls me after a week say "we cannot find a thing wrong with this unit"

Ok long story short IT WAS ME all along. I had been feeding it with my mp3 player with compressed shit music files and compensating more volume for better sound and driving it into clipping thus cooking voice coils. Yes I learned something valuable and while I am glad I sent it out for a total rebuild before it went up in smoke on its own I still never knew all this new computer file technology, I grew up with LPs, FM radio and 8 tracks.

But anyway this thing sounds INCREDIBLE when fed with clean music.
Again thanks all,
Mike

P.S. by the way after burning up enough nice speakers I did learn how to completely rebuild speakers from the frames/magnets out....lol its a cool skill that I always thought was super secret and hard to do. Not so much now.

upload_2021-8-22_15-32-51.png CV D3s, CV VS 150s and HPM 100s
 
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I can't say on here my opinion on mp3's!

Just in case it hasn't been mentioned before,
Google "why tweeters blow" choose the web site "ESP" You'll have to search that site for the article but you'll find it. Very good article.
Bob
 
One thing people overlook is that many digital to analog systems can output much much higher signal that is the norm for "line level". If you are driving the AUX input, designed for 150 mV max or so, with 500mV, you will quickly drive your amp into clipping. The pre-amp, normally exposed to a maxium of 150mV is suddenly starting with 500 mV and will drive the power amp into clipping to shooting the voltage up much higher than normal. Pays to use a defined out put DAC, or at least measure the output voltage ato keep with close the expected line input level.

If you have the output turned way up on a CD player or DAC of some sort, you will reach clipping level sin your power amp quite quickly.
 
Very interesting article and leaves the big question of where to get the cleanest music source these days??? Who do we trust!
Looks like you read the article. When listening to music, pictures those graphs from the article in your mind. You'll be able to tell. I'm sure you've noticed some CD's are much louder than others. This is mentioned in that article.
Glad you read it.
Bob
 
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