Tuac Amplifier modules

[Trevor]

Valve power no problem I will carry on on my own as apart from you no one has expressed any interest re new transformers
regards Trev

[crackersjv]

Hiya

I've done some measuring. the big blue capacitors say on them 63v DC - KA3132T HYA. One gives 39.2v (nearest transformer) and the other 38.6v.

The 4 black electrolytics, 2 smaller ones which say 25v 22uf, the outer one gives no reading at all and the inner one 1.95v The two bigger ones, the inner gives 29.1v and the outer 35v. They say on them 63v 47uf.

I guess if one gives no reading at all then that could be a bit of a problem haha. But what would you say of those results?

Many thanks once again

Anything else I can tell you about?

Jim

[Trevor]

can you point /circle the cap with no voltage
regards trev

[crackersjv]

Hi Trevor

Hopefully, here is the photo with the volt readings marked on for each cap, in yellow so I hope it's clear enough. Hope this helps?

Thanks.

Jim

[Trevor]

I would like you to measure the voltages on the caps using the chassis as the negative point
regards trev

[crackersjv]

Hi Trev

I've measured as requested. In the same order as I gave before, 2 small caps 0.0v and 1.95v and 2 bigger ones 28.0v and 34.7v. I might add that, when I measure the cap that gives 0 voltage it does cause a very noticeable buzz through the speaker, don't know whether that means anything?

Does this help?

Thanks

Jim

[Trevor]

Both the small caps should have a low voltage of bout 2 volts re the earth ref I would look there but as you are getting a buzzing sound I would try and inject a signal source at the cap to see if the power amp is working
regards trev

[crackersjv]

Hi Trev

Well, we know the power amp is working because it gives off the proper volume until something reaches a certain temperature (presumed) then cuts out. Both the small caps seem to feed (or feed from) one leg of the transistor that I think its getting way too hot, one through one resistor and one through two resistors (ok, one of the caps is thus connected through it's negative end and one through it's positive).

Now, having little understanding of how these circuits work, I'd conclude that if one cap is not registering any flow then one should replace the cap (and it should work), although I could accept that another component may not be feeding current through that cap, but does it seem likely to you that replacing the cap which is not showing current would solve the problem? Or is there an alternative?

Thanks for any further help.

Jim

[Trevor]

I would measure the voltage on the emitter resistor of the driver transistor under normal and fault condition
please advise asap

[crackersjv]

Hi Trev. I'd instantly oblige if I had any idea what the driver transistor or emitter resistor were or where to find them. And, I presume you wouldn't want me to measure the voltage drop across the transistor? You might have to tell me exactly where to stick the meter prongs in order to give the readings you need Sorry, I am a bit uneducated as regards electronic circuits :O

Many thanks

Jim

[Trevor]

The emiter resistor on the driver is the 22 ohm unit red/red/black/and maybe silver that is connected to driver transistor
Try to measure the voltage across it when the amp is working and when not
regards Trev

[crackersjv]

Hi Trev

I'm afraid I still don't know the terminology and don't know which the driver transistor is. There isn't a resistor red/red/black and maybe silver. The only resistor that may not be clear in the photo is the one between the two green barrels and next to the transformer. This is orange/orange/red/silver. I think it is connected to one leg of the black transistor, middle of the three in a row. It measures 6.4 volts when the amp is working and 4.4v when not. But I don't know if I've measured the correct thing. If I haven't then you'll need to give me directions by location to the one you want measured.

Did I get the right one and does it help?

Thanks

Jim

[Trevor]

i need to know the voltages on the pins of the hot transistor that is the driver!
regards trev

[crackersjv]

Hi Trev

From one arm of the transistor that gets hot, 2 resistors go off in parallel, that's a line of two (series) next to the bank of terminals at the bottom of the photo, and then the next line up (series). So;

for the resistor nearest both the hot transistor and the bank of terminals (red/purple/red/gold) reads 0.19, (0.15 on a second reading) when the amp works and 0.47v when it doesn't. The next in series, furthest from the hot transistor but nearest the terminal bank (red/red/orange/gold) 1.4v when working and 3.93v when not.

For the next line of resistors up, nearest the hot transistor (orange/white/black/gold) 2.24v when working and 5.28v when not and furthest from the hot transistor (brown/blue/orange/gold) 0.83v when working and 0.79v when not.

I hope one of those is the measurement you're looking for? By the way, the 2nd of the resistors nearest the bank of terminals connects to the cap with no reading as does the next line of resistors up, according to the pcb. However, only the furthest terminal of the 2nd in the line of resistors nearest the bank of terminals buzzes when I put the meter on it, the next line of resistors up does not.

Hope this all helps?

Jim

[Trevor]

Sorry re the delay I have had to spend a bit of time thinking about this
If you disconect the power amplifier board and send it to me I will repair it F,o,c,
you can send me a private message on the forum I will then give you my address
I promise to do it within 2 weeks
best regards Trev

[Trevor]

Jim has posted his faulty module so I will take photos etc as soon as it arrives
regards Trev

[Trevor]

The Tuac has arrived , I have located the problem I will post pictures, schematic and comments later
regards For now Trev

[Valvepower]

Hi Trevor,

It’ll be interesting to compare this module to that of the TP125 I posted the details of a while ago.

Regards
Terry.

[Trevor]

Yes Valvepower
Please find attached the schematic its quite a bit different
When given the correct voltage a min of +/- 40 volts its a nice sounding amplifier!
Tr3 is consisderably overworked at runs at over 100 deg c
I am trying to locate a heatsink for it I have fitted a pair of 2n3442 output devices as the 2N3055 fitted are being over run concerning VCe it would be about 90 volts in normal mode
Feedback is quite differant to the 125 in that it does not go to the emitter of tr1 but seams to be a series connection
I have to leave right now but will get back asap
regards\trev

[seymour32]

Hi, I too had a miss spent youth dabbling in the disco side of entertainment. I also built a couple of disco systems using TUAC amplifiers and lighting controllers. The thing is I still have some bits around. I have an original TP125 amplifier module as from factory complete with its RCA 2N6254 output transistors. I also have 2 TL100 amplifiers I can lay my hands on also with RCA 2N6254 output set. None of them have been used for years so may need so I may need to” gently bring them back to life”.
Chris.