[TrollDragon]

Hmm yes, that doesn't suit me either, I couldn't do it any better.
I will try to fix it again.
If the conductor path is broken, how can I fix it?

You would probably need to unsolder that headphone jack to see what damage has been done, which in turn might cause more damage to the board unless you have good experience unsoldering multi leg components.

With the amplifier unplugged from the AC you can use your ohm meter to check the continuity between both tubes sockets. Pin #3 of each socket should be connected together and have 0 ohms resistance, the same for Pin #4. These are the heater pins and they would be in parallel with each other.

 

[TrollDragon]

Take the tubes out if they are not already removed. Set your meter to resistance, put one probe on Pin #3 of the first socket and your other probe on Pin #3 of the second socket and you should get a reading of ~0 ohms. If you don't then that tube socket closest to the headphone jack is most likely the problem. Check Pin#4 on each socket the same way to see if there is 0 ohms resistance between them, hopefully they are fine.


Without having to remove the headphone jack, you could solder a piece of wire from Pin #3 on one socket to Pin #3 on the other to fix that issue. It probably won't fix the LED problem though. Also this addition of a wire between the tube sockets might induce noise as well, but it is a quick check to see if that is actually the problem.

To properly repair it you will need to remove the headphone jack, remove the existing solder around that pad and see where the trace is broken. Then it could be repaired by scraping off some of the enamel and soldering a small wire bridge over the break. Solder Wick works well for repairing some breaks too.


Hopefully that was the only pin with a problem.

 

[Deleeh]

Take the tubes out if they are not already removed. Set your meter to resistance, put one probe on Pin #3 of the first socket and your other probe on Pin #3 of the second socket and you should get a reading of ~0 ohms. If you don't then that tube socket closest to the headphone jack is most likely the problem. Check Pin#4 on each socket the same way to see if there is 0 ohms resistance between them, hopefully they are fine.


Without having to remove the headphone jack, you could solder a piece of wire from Pin #3 on one socket to Pin #3 on the other to fix that issue. It probably won't fix the LED problem though. Also this addition of a wire between the tube sockets might induce noise as well, but it is a quick check to see if that is actually the problem.

To properly repair it you will need to remove the headphone jack, remove the existing solder around that pad and see where the trace is broken. Then it could be repaired by scraping off some of the enamel and soldering a small wire bridge over the break. Solder Wick works well for repairing some breaks too.


Hopefully that was the only pin with a problem.

Okay,
You were right here.
I desoldered the cables from the transformer to the circuit board, extracted them and soldered them on again.
It works, the LED lights up again and the left channel is heated.
But there is no sound so it seems to have something to do with what you said Dragon
I will have another look at it.

Thanks for the helpful tips and support.

 

[TrollDragon]

Awesome, it's a step in the right direction. As for no sound I'd have a look at the input wires you changed and check the soldering on the board for them as well as on the RCA end.

 

[Deleeh]

Yes, I think so too.
They were all helpful tips.
I still had that in mind and thought it was enough.
I didn't expect the effects to be so great.
My soldering skills are certainly in need of improvement.

I don't suspect the Rca connection so much.
I paid more attention to it, but I can lay a cable to test it.
I soldered the cable to the opposite side because it doesn't have to pass through the tube socket.
See the picture of the black cable.

I suspect that there is something wrong with the left-hand tube socket.
Something is bothering me somehow.

 

[TrollDragon]

When you do put it back together make sure you get all the insulators in place under those transistors. Also there should be two of the white plastic screw insulators for the bigger transistors on the outside edges. I see one still in the hole on the lower transistor in that picture, remember to put one in the hole for the upper transistor as well.

 

[tomchr]

I'd go back and measure the AC input and DC output of the rectifier bridges.

I wouldn't be too worried about the melted corner on the headphone jack. Just don't make it a habit.

Tom

 

[Deleeh]

When you do put it back together make sure you get all the insulators in place under those transistors. Also there should be two of the white plastic screw insulators for the bigger transistors on the outside edges. I see one still in the hole on the lower transistor in that picture, remember to put one in the hole for the upper transistor as well.

I'd go back and measure the AC input and DC output of the rectifier bridges.

I wouldn't be too worried about the melted corner on the headphone jack. Just don't make it a habit.

Tom

Hello again,

@TrollDragon I listened to your tips with the Rca connection.
And what can I say, you were right!

Both channels are working now.
I sucked out the solder and soldered it again with less material at the end and pressed the ground connection together better.

So it was mainly due to my "soldering skills" that it didn't work. @tomchr you are right!
It's been running for a good 30 minutes now without any problems.

Without your help I would have been stranded and probably wouldn't have thought of it.
The tube socket on the left side was exactly the same: I just warmed it up and vacuumed it, then brushed off the dried soldering grease with a toothbrush.
Instead of silver solder, I used the normal solder for the Rca connection.

The sound with the Nichicon Fg capacitors compared to the others is a bit better as described, a bit better bass and more lowends in the treble.
So it fits quite well and I like it better.
I assume the capacitors still need a little time to break in.

Overall, it is now also less warm than usual or before.
Even though it was a bit of work, I'm still satisfied and happy that it's running again.

Many thanks again to both of you, without you it would probably have ended up in the bin.

Ps:I have to look where the white insulators are.when I tighten the screws it doesn't run.I took the screws out first and there are little mats stuck in the housing.

 

[tomchr]

So it was mainly due to my "soldering skills" that it didn't work. @tomchr you are right!
It's been running for a good 30 minutes now without any problems.

Sweet! You're welcome.

[...] then brushed off the dried soldering grease with a toothbrush.

Soldering grease? Are you using pipe solder or that greasy flux used for soldering copper pipe?

For future reference: I have a longer article on how to choose solder for electronics here: https://neurochrome.com/pages/choosing-solder

If you use solder intended for electronics there's no need to add more flux. The solder already has flux in it.

Tom

 

[Deleeh]

Sweet! You're welcome.

Soldering grease? Are you using pipe solder or that greasy flux used for soldering copper pipe?

For future reference: I have a longer article on how to choose solder for electronics here: https://neurochrome.com/pages/choosing-solder

If you use solder intended for electronics there's no need to add more flux. The solder already has flux in it.

Tom

No, it was the normal solder that I used afterwards, which you can get at the hardware store.
Before that I used the silver solder from Inakustik which is a bit more difficult to solder with.

The normal solder leaves a bit of residue, which I removed by brushing it off.

I'll read the article, thanks for the tip.

 

[TrollDragon]

Ps:I have to look where the white insulators are.when I tighten the screws it doesn't run.I took the screws out first and there are little mats stuck in the housing.

Those little mats and insulators are crucial to the running of the amp. The mats keep the transistor tab from shorting out to the case and the insulator keeps the screw from shorting out the transistor. That is why it stops working when you tighten down the screw without the insulator.

The transistors must be tightened down to the chassis, it acts as a heat sink to draw away the excess heat from them and they will eventually fail without being tightened down.

So you need to make sure all the pads are under the transistors that had them.
Locate the other white insulator for the screw hole or use a nylon screw instead of the metal one.
Make sure all of those transistors are snugged down tight before running the amp otherwise you will be replacing those transistors.

If you can't find the other white insulator or a nylon screw stop using the amp and order a package of insulators from Amazon or a local electronics supplier where you live.
https://www.amazon.de/Silicone-Heatsink-Insulator-Insulating-Particles/dp/B00KV6P828

 

[TrollDragon]

Really glad that you got the amp up and running, but don't run the amp without the transistors properly attached.

It was my pleasure to help.

 

[Deleeh]

Really glad that you got the amp up and running, but don't run the amp without the transistors properly attached.

It was my pleasure to help.

Hello,
Thank you for the link, I will order it and put it in so that it works properly after all the work.

I just let it run for 2 hours to test if everything is ok before I finally put everything together and disconnected it from the mains again.
It ran completely trouble-free.

The sound has increased again a little bit, in the short time of listening it became softer instead of hard.
So there's a bit more to come, I'm looking forward to it.

Wouldn't have been possible without your trained eyes.
I am of course very happy that it works again and probably better than before and hopefully for a very long time.

If we lived nearby, I'd be due a nice crate of beer.

 

[TrollDragon]

If we lived nearby, I'd be due a nice crate of beer.

I would gladly have a beer or three with you anytime.

 

[tomchr]

The normal solder leaves a bit of residue, which I removed by brushing it off.

Interesting. I've never heard of flux that just brushed off. Learn something new every day, I guess.

Locate the other white insulator for the screw hole or use a nylon screw instead of the metal one.

Nylon tends to stretch over time and gets brittle. So it's not a good choice for a mounting screw.

All the transistors need thermal pads between them and the chassis or the metal of the transistor (which is electrically connected to the middle pin of the transistor) will short to the chassis and make bad things happen.
The two TO-220 package devices need a shoulder washer (that white insulator) in addition to the thermal pad or the mounting screw will cause the transistor to be connected to the chassis.
The four TO-126 package devices don't need a shoulder washer as the mounting screw never touches the metal in the device. I'm usually kind and put a flat washer between the nut and the transistor just to put the pressure on a larger area.
It requires surprisingly little torque to get a good amount of pressure on the thermal pads. The recommendation is generally 0.5 Nm which is maybe a quarter to half a turn beyond finger tight.

Tom