22rh550 problem with right channel

[jlc02]

vl448 is ok. This is what I tested first.

I probably didn't do the right thing to take the measurements. I touched the chassis, a chassis screw or where bd204 is screwed directly with the black lead.

When I put it on the headphone cable that is grounded it gives me different numbers.
If I touch the number 1,2 or 3 (A47) of the headphones, it's good?

[Regenpak]

When I put it on the headphone cable that is grounded it gives me different numbers.
If I touch the number 1,2 or 3 (A47) of the headphones, it's good?

I have no idea what you're doing. You say the fuse is OK yet you measure a supply voltage (+3) of half what it should be. Use alligator clips to keep your black lead firmly connected to ground (masse). Anything ground is OK. Headphone socket ground and collector of TS446b are both fine. Just keep it in one spot.

Remember, I don't have the unit on my workbench. It's on yours. I cannot see what you do.

Tjerk

[Will]

At this moment the measured values of the left channel make little sense... So it's quite difficult to figure out what's going on.

As a check and as an exercise do these measurements on the left channel (which is still ok). Publish the results here as you did for the right channel.

[jlc02]

I did as you advised, Will.
I took the measurements for left and right.

Left seems almost ok for the numbers (except ts435 which has a zero)

I took the measurements for right and put the black lead in the same place.

Ts438 seems cracked.

Sorry Tjerk, I don't have alligator clips. I have few electronic tools. if I succeed in repairing this amp I will invest a little in that.

[Regenpak]

Replace R716, TS436 and TS438 (use BC547B for both). Keep the output transistors out and measure again. R_Ch only because L_Ch is okay.

Tjerk

[jlc02]

Thank you very much.
I will order this online and do the measurements right away.

[Regenpak]

Did you test the output transistors? They are likely borked. Any TO-3 NPN/PNP pair (eg. 2N3055/MJ2955) will work in this location. This way you will only have to order once.

Tjerk

[jlc02]

I did not test the output transistors. I don't know the procedure to do that. On the internet, I find explanations that contradict each other.

I found replacement for R716, TS436 and TS438 but not for the output transistors.

The 2N3055/MJ2955 I found have a different shape than the ones in my amp.
Are there any alternatives?

[Regenpak]

I did not test the output transistors. I don't know the procedure to do that. On the internet, I find explanations that contradict each other.

Then try them all. Especially the ones with diode test. They are the easiest.

I found replacement for R716, TS436 and TS438 but not for the output transistors.

The 2N3055/MJ2955 I found have a different shape than the ones in my amp.
Are there any alternatives?

Oh wait, these transistors are TO-220. 60 V/8 A. There are many alternatives. MJE15028/9 is a nice pair. You could use parametric search. Most vendors offer that. Like Mr. Multisnort. Use this form for NPN and this one for PNP transistors. Put them side by side and choose a matching pair, like MJE2955/3055. Or MJE15030/1 because the 28/9 is not in stock there.

Tjerk

[jlc02]

Thank you very much.

Is using NOS transistors good or bad? Does it age badly?

I'll order what I need and come back to give results. Probably in a week or so.

[PatrickVB]

You can order the original ones here:
BD203
https://tessatronic.nl/index.php?keywor ... egory_id=0
BD204
https://tessatronic.nl/index.php?option ... gory_id=29

[jlc02]

Thank you Patrick. I'll have a look.

Should the output transistors be the same model/brand on the left and right channel?
Will it make any difference in sound or will it be insignificant?

[Regenpak]

Should the output transistors be the same model/brand on the left and right channel?
Will it make any difference in sound or will it be insignificant?

No.

Tjerk

[jlc02]

I received the parts. Unfortunately I can't install the transistors in a clean way. I haven't touched a soldering iron for a long time. I can't do anything right. It's too small for me. I don't have enough room and I don't have the right gestures to do the soldering. I prefer to stop here to avoid damaging the amp.

For this part, I will have to find someone to help me in real life. Internet can't help me. I will try to find a repair cafe or something.

Anyway, thanks a lot Tjerk for taking the time to share your knowledge ( I have learned a lot) and to help beginners to try to keep old material alive.

I'll try to come back and post as soon as I get some help for the soldering. I'll be able to fix it. I'm hopeful.

[Regenpak]

Hopefully you will find someone to help you out.

Tjerk