Torque Bass T2001EB

[jondoe]

Hello all, further to my schematics request, here are some images of the internals. Someone has been in here before me as the speaker wire was cut, even though I was assured no one has ever tried to repair it

Fuses F5 and F3 are blowing, although the main fuse is good. I have 41v on both the big filter caps. The blown fuses connect directly to T5 and T7. I've removed both T5 and T7 and my transistor tester tells me they are just resistors, both are shorted Emitter to Collector. There was a track blown off under T7 (I bridged with a little used solder wick pictured). Googling the part numbers of those transistors didn't find anything. No DC on the speaker output.

One last thing, C5 on the far right of the top view is two (thick) metal legs sticking out the board, but no cap to be found. I see that there is pretty much an mirror image of both sides of the board so we are one capacitor less on the right side compared the left

Thanks!

[dmeek]

The two metal legs are test points: input and ground. I've never seen those output transistor numbers before. They're probably abbreviations The manufacturer was Semelab according to one forum post.
CR64 is PNP, CR65 is NPN. <edit:removed bad advice>
This is a bridge amplifier, here's the schematic:

https://music-electronics-forum.com/...1&d=1567789838

[jondoe]

Many thanks I'll order up some MJ15025's. I better take out the other two transistors and test those just to be on the safe side, at least they aren't blowing their individual fuses.

[dmeek]

Your burnt trace leads to the collector of T8. It's probably burnt too and check the 10 ohm emitter resistor R24.
<edit:removed bad advice>

[jondoe]

Your burnt trace leads to the collector of T8. It's probably burnt too and check the 10 ohm emitter resistor R24.
Just to be clear you will need 1 MJ15025 (PNP) and 1 MJ15024 (NPN) for each side.
It's better not to mix them with the old transistors.

Understood. I'll double check R24 and T8, I don't think it was shorted, but I'll pop it out and double check.

Would the 200v MJ15023/MJ15022 also be suitable?

Thanks

[J M Fahey]

WARNING: if that´s the schematic, MJ1502x will NOT work, Torque power transistors are Darlingtons.

In general metallic TO3 Darlingtons are rare and *expensive* , maybe even obsolete and out of production.

Maybe that´s why they resorted to a smallish factory such as Semelab, who would run a limited production batch.

As a side note, that´s a TERRIBLE PCB: wide tracks or whole copper areas where unneeded, skinny traces on ... power transistor collectors? ... REALLY?

[dmeek]

I thought they might be darlingtons but with only 3 diodes for biasing it didn't seem like it. Would be nice to have a datasheet.
Looks like Semelab is incorporated into TT Electronics now. I guess all the old data was trashed.

edit: I think Juan is right, they are darlingtons. A substitute would be MJ11015 (PNP) and MJ11016 (NPN) 120V/200W

[g1]

Worth a try: http://torque.ru/contacts/

[J M Fahey]

Wow
Torque is a longstanding British amp company, strange finding it in Russia.

In any case not sure they make their own, they may very well subcontract Chinese stuff.

As of the transistor type, 5 - 10mA Vas current must eventually turn into 5-10A through speakers.

That requires guaranteed Hfe around 1000X ... only Darlingtons can.

I also thought on the MJ11*** but last time I checked they were very expensive and hard to find.

If budget allows you may add a couple drivers on the underside of the board ... if you have space that is, OR use TIP42/147 but they would be just on the edge current and dissipation wise and only driving 8 ohm speaker, forget 4 ohm loads.

What speaker do you have in that Combo?

EDIT: these seem to be compatible and in theory still available:
2N6284/2N6287
https://www.st.com/resource/en/datasheet/cd00001223.pdf

And most comments mention an 8 ohm speaker.

[dmeek]

The MJ11015 and MJ11016 are available in-stock at Digi-Key for cdn$11 each. Not cheap but not too bad.

[The Dude]

Newark has them cheaper here:

https://www.newark.com/multicomp/mj1...C-GUSA-SKU-MDC

https://www.newark.com/multicomp/mj1...-to/dp/26M1593

[jondoe]

This escalated quickly after I went to bed, thank you all for the input guys

The speaker is a celestion truvox 1525, which I believe is 8ohm.

I can get four of those transistors for about £25 ($30), so not too expensive. You can pick up working examples of these combos for peanuts so I'm not sure my friend will want to shell out on the cost of parts and beer money for me to repair it I'll find out what he wants to do.

Cheers.

[jondoe]

Gentlemen, thank you once again for your assistance sourcing the correct parts, I've replaced the transistors with pairs of MJ11015/MJ11016 and she's alive and passing audio cleanly