Sansui 5000A 1040 mod, now no output

[smokinone]

I did the skippy mod to the original 1040 boards, and replaced all the electrolytic caps. Also did the 4 2200 caps, ripple board and protector board.
Here is what I've done pretty much
http://audiokarma.org/forums/index.php?threads/sansui-5000a-bulb-replacement.742707/

I also replaced all the output 118's with new transistors.



I get 80V at the fuse holders and was able to set the bias @23ma.
The problem now is I have no output from any input to the speakers it seems. If I touch the TR802 on either 1040 board I get the hum and noise from the speakers and it goes up or down with the volume. It also gets very warm to the touch.
I don't know if I'm just not getting the signal through the board all the way at the input of the boards or what. I'm not sure where to start to check. I do get a 38V reading at the base and emitter of TR803 on both boards with 80V on the collector. TR804 is about the same with 36V on the base and emitter. Those are the 2 transistors changed out with skippy mod.

It's not blowing any fuses so I assume there are no shorts. I did get a little arching at the fuse holders when setting the bias when attaching the leads, but I think that would be normal since I would be completing the circuit when inserting the meter.





Whatever the issue it seems to be equal on both boards.
I am getting the FM STEREO light lit up as well while testing. And I did hook up a turntable with the same results of no output to the speakers? or input to the amp boards?

Anyone with ideas? I'd sure appreciate it. I have limited knowledge, but have willingness to learn and try.

Thanks

 

[Bruno Primas]

First real post.....

I recently recapped a 4000, and I made the mistake of having the 1000uf ripple cap lead touching the heat shield on the transistor on the ripple block. In your 1st picture, it appears that transistor, it is turning brown. The symptoms that happened, is everything appears to work, but no sound. Luckily, I figured it out, and no harm was done. Hope this helps.

Bruno

 

[Bruno Primas]

Oops, on the 5000a, it appears the ripple block is not directly over the backside of the 1000uf cap like it is on a 4000. Egg on my face. But, the symtoms you describe still seem like something is shorting out, touching what it shouldn't.

Bruno

 

[smokinone]

First real post.....

I recently recapped a 4000, and I made the mistake of having the 1000uf ripple cap lead touching the heat shield on the transistor on the ripple block. In your 1st picture, it appears that transistor, it is turning brown. The symptoms that happened, is everything appears to work, but no sound. Luckily, I figured it out, and no harm was done. Hope this helps.

Bruno

Thanks,
Well, I figured out the...dumb mistake by putting the transistor replacement for the 2SC458 in the wrong way. That sorted out, I now have no amplified sound from the right channel. Left channel works perfect. I changed the speakers around with the same result so once again I'm at a loss. If I turn the balance all the way to the right channel, I get a very low output.

I pulled the new right side output transistors and checked them and they are good. Looks like it might be something else on the board.
I still can set the 23ma for the bias so I guess pulling the transistors was more of a piece of mind check than anything.


I just switched to MONO and now have both speakers working. When taken out of MONO, back to right side not working. Sounds very nice in MONO, but stereo would be nice...I am tuned to an FM station as well.

Just also found if the reverse button is pushed in the sound goes from one speaker to the other when out of MONO mode. With this happening I wouldn't think it is the 1040 boards at this point.

 

[Mr. Nick]

I think you may have a loose connection there, which you need to find.

I worked on the boards fitted in amp, but unhooked some wires and grounding braids to be able swing the bad board from side to side to get better angle at soldering.
I had a similar problem, faint audio signal after putting it all back together and the problem lied with the audio signal cable that was loose next to R801. You might want to check it out?
Good luck.

 

[Trnsfmr]

If you can get both channels with the mono switch and reverse them with the reverse switch, then your problem has nothing to do with the driver boards. Your problem has to be before the mono switch, reverse switch and the vol control. That's pretty far back up the chain towards the input.

We've restored a lot these units. I would first exercise all the switches on the front panel while listening at low volume.

I had one with a channel missing that was caused by the vol control on the rear panel which is there to equalize input levels. Try all the other inputs, like FM, AM, phono, Aux, whatever and see if any one of them works. It can be a clue. The 5000A has the inputs set up pretty weird, in comparison to other Sansuis. For example, some inputs go through the same preamp that is used for phono.

I've had one with a broken wire right behind the 4 buttons on the right side of the panel, very hard to find, as you can't see behind the pushbuttons very well at all.

Look at the circuit and search for clues. It's like a puzzle to figure out. These kind of problems can be the bigest PIA.

 

[smokinone]

If you can get both channels with the mono switch and reverse them with the reverse switch, then your problem has nothing to do with the driver boards. Your problem has to be before the mono switch, reverse switch and the vol control. That's pretty far back up the chain towards the input.

We've restored a lot these units. I would first exercise all the switches on the front panel while listening at low volume.

I had one with a channel missing that was caused by the vol control on the rear panel which is there to equalize input levels. Try all the other inputs, like FM, AM, phono, Aux, whatever and see if any one of them works. It can be a clue. The 5000A has the inputs set up pretty weird, in comparison to other Sansuis. For example, some inputs go through the same preamp that is used for phono.

I've had one with a broken wire right behind the 4 buttons on the right side of the panel, very hard to find, as you can't see behind the pushbuttons very well at all.

Look at the circuit and search for clues. It's like a puzzle to figure out. These kind of problems can be the bigest PIA.

BINGO!! The level adjust pot was the only pot I didn't de-ox, and it was the stinker. Thanks for responding, I was about to pull the last of what hair I have left out.

I sure like the way this Sansui sounds. I'm just listening to a local FM channel on some cheap KLH 3 way bookshelf indoor/outdoor speakers and it sounds outstanding.

Thanks again.
I sure appreciate the expertise from all the members here. Every time I get on here I gain knowledge, and I am in need of it for sure.

 

[Trnsfmr]

I you're using the 5000A with the Klipsch's, what a wonderful combination. Those Klispch's have a wonderful bottom end and presentation that only horns can give.

I met old man Klispch once, at an AES show. He was quite the guy. If you talked to him, and he liked you, he would give you a "Bullshit" button to wear around at the show. He liked me cause I told him I had cut out and built several pairs of Klipschorns from plans, he was impressed. When you had one of those buttons on your lapel, the Sales types at the show would definitely reel in the hype, and treat you much better.

Don't know what you did for the two output caps, but it sounds like you replaced them with ones of the same value.
I talk about these early amps a lot here on AK and always recommend changing those two for much larger ones. In my opinion it's worth while to up them to at least 10,000uf. The last one of these I did, I put in 15,000uf caps. That's the two big caps next to the preamp cage near the inputs. These caps have the amp output going through them to the speakers. Low end and transparency is improved by going bigger. If you use Snap Ins, from Mouser, they don't cost very much. 2200uf was a very big, and expensive electrolytic in 1969.

 

[smokinone]

I you're using the 5000A with the Klipsch's, what a wonderful combination. Those Klispch's have a wonderful bottom end and presentation that only horns can give.

I met old man Klispch once, at an AES show. He was quite the guy. If you talked to him, and he liked you, he would give you a "Bullshit" button to wear around at the show. He liked me cause I told him I had cut out and built several pairs of Klipschorns from plans, he was impressed. When you had one of those buttons on your lapel, the Sales types at the show would definitely reel in the hype, and treat you much better.

Don't know what you did for the two output caps, but it sounds like you replaced them with ones of the same value.
I talk about these early amps a lot here on AK and always recommend changing those two for much larger ones. In my opinion it's worth while to up them to at least 10,000uf. The last one of these I did, I put in 15,000uf caps. That's the two big caps next to the preamp cage near the inputs. These caps have the amp output going through them to the speakers. Low end and transparency is improved by going bigger. If you use Snap Ins, from Mouser, they don't cost very much. 2200uf was a very big, and expensive electrolytic in 1969.

I'm off to Home Depot to get some foam tape (insulation) to replace the foam tape that has disintegrated from over the years. You can see in my other thread on the bulb replacement I did, so I need to get the front end put back together. I cleaned up all the plastic with NOVUS clean and shine or what ever it is. Then put it back together for now and give it a test run on the Klipsch playing some vinyl on the JVC.

I did put 3300uf caps back in for the large caps. All the others I replaced were same value of a higher voltage when they would fit.

These units are a pain to work on as all the leads are bent over across the traces and then soldered. Takes some patience and a variety of solder wick and de-soldering gun (HAKO 808 in my case).

Thanks again.

 

[Bruno Primas]

Glad to read that all is well....