The Amp Garage

Interesting screen supply derived from secondary CT. Never seen this before.

I wonder if the diagram is wrong. I don't see how that would work.

Hi Guys, Thanks for your suggestions, they are greatly appreciated. I tend to agree that the OT may now be breaking down. There are no signs of carbon on the socket but I will replace it anyway. One of the faulty tubes has a measurable resistance between Plate and Heater which obviously explains the...

Hi guys, I have a fault which is causing me some serious headaches and I'm wondering if anyone has some suggestions. A customer brought me a Marshall DSL100H (New Vietnamese Model) which he said keeps blowing the mains fuse. After replacing the fuse I was treated to a light show inside one of the po...

V1 pins 3 and 8 should have the same voltage as they are tied to the
same cathode resistor.
The .01 caps are o.k. They should have high volts on one side and 0 volts
on the other. Find out why V1 pin 8 is 0V. Maybe bad joint/miswired.

Cheers,
Paddy

Hi there, I recently repaired a Teisco and had great difficulty finding schematics. I couldn't find one for the model I was working on but it seems a lot of them used similar topologies and I was able to use the schematic for the 100 Watt PA version (which I have attached) as a guide. Good luck. Che...

Is that 4K7 resistor on the bias board replacing the two 10K's as shown on the schematic? If so, I think you need to follow the schematic and use two separate resistors here. Also, I agree with Martin-No need for the isolation diodes as the grid circuit draws next to no current. The wiring on your b...

I'd stick with the 470 OHMs
Beware-that's OHMs Not KOHMs as you stated in your last post.

Just raise them off the board a little and add a little high temp silicone if you feel like it.

Cheers,
Paddy

The plate resistors for the PI are R57/58. I wouldn't be too concerned about the switching FET's at this stage.

Cheers,
Paddy

I just checked my repair database and I had a similar issue with one of these amps. The cause of the crackling turned out to be the PI plate resistors. I also agree that you should check out the tubes/sockets. I wouldn't worry too much about changing the 5 watters to 330 unless someone has come up w...

Hi there,

Can you tell if the noise is comming from the power transformer? Maybe loose laminations.
Also, these amps have a lot of trouble with dry joints on R78/79 which are the large white 5 Watt 470 Ohm resistors.

Cheers,
Paddy

Hi guys, Thanks for the replies. I have struggled on without the schematic and have pretty much sorted things out. I don't know where the so called 'electician' learned his trade but he even had the mains plug reverse wired! Sorry Ian, but the schematic I have is for the Checkmate 50 which has 12AX7...

Hi guys, I am in desperate need of a schematic for a Teisco Checkmate 60 schematic. A friend has asked me to repair the amp, which he bought from an electrician who "restored" it. The guy has hopelessley miswired things so badly that it is quite difficult to make sense of the original circuit. It is...

I've had trouble with both Sovtek and JJ's. I switched to Shuguang's
and I'm very happy with them.

Cheers,
Paddy

Hi gingertube,

thanks for the link. I have emailed them and will see
what comes of it.
If anyone else has an answer for me in the meantime
I would be grateful

Cheers,
Paddy

Hi guys,

I am currently trying to fix a Torque Bass Amp model T1200.
The output transistors are shorted but I can't find any reference
to them on the net.
The part numbers are CR64 and CR65.
If anyone can provide some info on these transistors or a substitute,
I would be most grateful.

Cheers,
Paddy