Awesome!

Excellent info and playing! 

Thanks very much for sharing!  <3) <3) <3)

:dbtu: :dbtu: :dbtu:

Nice work phatt! 

Never know when someone might need/want that info.

Thanks for documenting!

Pin 3 of the TDA2040 is connected to the heat sink tab.

If the supply is single ended, pin 3 can be grounded, according to the data sheet.

https://www.st.com/resource/en/datasheet/cd00000130.pdf

If using a split supply, pin 3 and the heat sink tab MUST NOT be grounded.

Looks like a CTS pot.

The number 137 is the EIA code for CTS.

The next 8929 is the date code. Probably 1989, 29th week.

The other numbers spec the pot.

Unsolder the pot and ohms measure from outside lug to outside lug to find the overall resistance.

Turn the shaft to center and measure ohms from middle lug to each outside lug.

Compare and if approx the same, it's a linear pot.

If one outside lug reads much higher (or lower) than the other, it's likely a log pot.

Got to DigiKey, Mouser, etc to find an equivalent.

DigiKey has the 450 Series of "Stock pots" that can be ordered/configured how you like.

Look in this pdf...

You might benefit from having the complete construction manual for that amp.

It is available here>>>  http://www.vintagemanuals.com/manual/Heathkit/TA-16

for a reasonable price.

Heathkit manuals are very well done (step by step) and have a trouble shooting section to help diagnose problems.
You will learn a lot just reading the manual.

If you decide to get the manual, be sure to go to their home page and read the ordering info and about their manuals.

http://www.vintagemanuals.com/mission.html

Quote from: phatt on February 19, 2019, 06:29:24 PM

Quote from: psafloyd on February 19, 2019, 08:55:57 AM


What an eejit. It so clearly has.

Just goes to show I need those readers or a magnifying glass. Age has not only caught up but overtaken me this last year... 

Thanks, again, Phil.

Yep I know the feeling, my eyes also struggle to see fine detail.
I don't even bother to try and fix anything that uses SMD's.  xP
I agree with *galaxiex* about replacing Electro's in old gear but I would add this;
Only replace the obvious first and get the amp working,,, then go back and replace the others.
If you shotgun the whole lot and it still does not work then you have no idea if you added yet another mistake.
Phil.

Yep, very good point. Fix the obvious first.

I have worked on quite a few SS amps from the 60's and 70's.

I've found in all cases those amps benefit from replacing ALL of the electrolytic caps.

I used to test them (caps) and leave them if they "seemed good" but the amp(s) would still have problems.

If that amp were mine I'd start by replacing ALL of those blue tubular electro caps.

Just my $0.02

Quote from: Dimi Pana on January 28, 2019, 06:54:32 PM
WOW galaxiex !!! Where on earth did you find this?! I love building little projects like that. Essentially I am making a step down transformer that is more portable than what I already have now and although I was looking for a more direct approach this workaround is certainly an option plus a bucking transformer is always a useful thingy to have on my bench. Thank you so much, where did this come from, do you have more projects you can share like that? I'd be very interested. Thank you!

You are very welcome. 

I got it from the Hoffman amp forum.
A member/moderator there by the name of "sluckey" is a pretty smart guy with amps.
That is his scrapbook of amp stuff.

Forum here.

https://el34world.com/Forum/index.php

Edit; Here's sluckey's web site...

http://sluckeyamps.com/

Well, you could make one of these bucking transformer things...

scroll to Page 2 of the pdf.

Do I have this backwards?
I thought fewer turns on the secondary (like a shorted winding would cause)
= higher voltage.

Ooops. Yes sorry I had it backwards.
Carry on...

Is it possible for the transformer heater winding to partially short a few winds and cause the higher AC heater voltage?

Is it possible that a damaged heater bridge rectifier could cause the high heater voltage?
Eg; one of the diodes shorted or open?

Or... maybe the transformer heater winding has a problem?

I use a laser printer and heat transfer method.

It can be tricky and sometimes takes me a couple tries to get a good transfer.

The trick seems to be using the right type of paper and the heating time/pressure. (old fashioned household clothes iron)

Some folks use glossy brochure paper, but you can buy special transfer paper.
I got some from ebay (China) that works ok.

I don't do enough one off boards to justify the more expensive options, such as the photo resist boards.
Might yield more consistent results tho....

Too cool enzo. 

I actually still have my R/S resistor calculator. I think I got it in the late 70's.

I also used to have a Heathkit Experimenter workshop somewhere around 1968.
It was exactly like this one.
I would have been about 10 years old then.

I've always been a "tinkerer" never took any formal training in electronics.

Sorry for the OT but the OP already got his question solved so I figured it wouldn't hurt. 

Quote from: Enzo on December 15, 2018, 10:39:05 PM
I see 1-0-x0.01, so 0.1 ohm then 5%, and the final black band is something I don't care about like temperature stability.  (250k ppm/K)


But then I am sitting on my couch drinking beer...

Sitting on your couch drinking beer...
you can probably diagnose circles around most of us...    :lmao: