T&L Publications

Well, here's another one I'm asking for help with. I've had this little amp for God knows how long now. I only use it on rare occasions in the bedroom, with tonight being one of those times. The left channel is dead. Absolutely 0 anything from it. I've pulled it and a cursory look reveals nothing amiss. Could have been the speaker itself, but I didn't check yet.

Anyway, my model is here:
https://www.radiomuseum.org/r/lafayette ... eo_10.html
And you can get a glimpse of the amp itself I'm this video: https://youtu.be/DQcu7F239DQ
The 10A has the same main amplifier section and volume volume controls, it just has more input options.

It won't be hard to trace, but i figured if I had a schematic, it'd be a bit easier to track down the issue.

Thanks.

First guess would be output transistor. Next, an aging volume potentiometer.

Let us know what you find!

The good thing is that I have 1 good working channel and it's so minimal that it'll be easy to check back and forth with a multimeter. I just need the elusive thing called time.

If you have a chance to look at that video I linked, you'll see how minimal it is.

jwax wrote: ↑Sat Feb 20, 2021 4:53 pm First guess would be output transistor. Next, an aging volume potentiometer.

Let us know what you find!

Do you have an actual model number on the amplifier?
I've been digging through Sams PhotoFacts and not finding it.

I agree with it possibly being fried output transistor(s).
But, I would think tracing the signal path from the Inputs,
all the way though to the last stage to the speakers shouldn't be that hard.

At the Left & Right Input Jacks, inject a 1Khz signal.
Then with a Signal Tracer, track the 1Khz signal through the circuit till you loose it.
Then at that point where you lose the signal, is where the problem lies.

I hope the output transistors are fine.
Some of those old transistors are getting hard to find, or even find a equivalent cross as a replacement.


Signed: Janitor Tzap

That is all that they have on the amp. I know there's a 10-A and a 10-B, not sure if there are any others. I'll look when I get back home.

Well, I put it on the bench and had a spare speaker hooked up. With the 1/8" stereo plug to RCA's plugged into the Phono stage, I did the finger noise test, switching the speaker positive back and forth. Both sides worked. So I cleaned the pots and switches, put it back together and hooked the regular speakers back up. That's when I found one of the ancient speaker wire splices was the culprit.

You'd be surprised at how good an old itty-bitty amp like this when paired with decent speakers (Fisher DS-153) can sound. And Bump. Was listening to this live: https://youtu.be/IGPiTuAVNQw and it was clean at full throttle. Kinda diggin it.

Cool.

Nice to know it was something simple.
Some of these early transistor designed amplifiers can be really well made.
Thus, they can out perform a lot of crappy cheap amps that die within a few years.

Just have to remember to give it a bit of a cleaning, once every few years.


Signed: Janitor Tzap

I had a radio kick my butt before.. everything checked out,,but sound never came out of the unit..headphones worked fine.. come to find out the headphone jack was the issue..there's 2 switches inside that thing. 5 connections.. one side wasn't making connections.. did some fiddling around and cleaning contacts, finally got it going..

Janitor Tzap wrote: ↑Sun Mar 07, 2021 7:13 am Cool.

Nice to know it was something simple.
Some of these early transistor designed amplifiers can be really well made.
Thus, they can out perform a lot of crappy cheap amps that die within a few years.

Just have to remember to give it a bit of a cleaning, once every few years.


Signed: Janitor Tzap

Well, the thing is over 50 years old and that was probably the first time it was cleaned. o_O