Recent content by washburnbassman

Hey Garry, Hope you fixed your amp! Mine is still going strong, love these machines.

"slap two 2x4's together" Have had that done to me. terrifying. Also now working in IT, but unfortunately still finding ways to electrocute myself outside of my job. I can afford to buy these things new. I don't know what is wrong with me but I prefer buying them broken and fixing them.

Makes sense and thanks for clarifying, I have been fiddling with stuff for over 20 years and am pretty careful but this certainly isn't an amp to start messing around on.

Thank you and sorry that I snapped back at you.

@agedhorse I think I understand where you are coming from. I would never charge for my work. This is a hobbyist repair on my own amp, and I do not consider myself highly skilled or an EE. I don't think I am the target demographic here, I'm not service personnel, but i accept your point. This...

Can a mod add the text below to the top of the first post (if we're not deleting the post, which I'm also fine with). DISCLAIMER : You can electrocute yourself with mains voltage working on this amp. If you are not used to opening and working on radios or other mains voltage devices, then do...

extra credit for back to the future, and it certainly could have turned out like this, and almost did a couple of times. As Geri said, I probably got lucky, but I have fixed a lot of radios, so pre-amp/power amp work wasn't foreign to me. I did very specifically track down the Zener diode...

If me going through my fixes isn't useful content, and isn't even recommended, given the dangers involved, then I'm happy to remove it. agedhorse seemed to not recommend me trying to fix this myself from the get go, which is fair enough, and his posts kind of reflected that. I don't mind...

Pearls of wisdom from agedhorse here folks. Pearls of wisdom. If you are an SVT400T owner with an EQ board problem followed by a power board problem, I encourage you all to scroll up to some of the other helpful and informative posts he has submitted in relation to the SVT400T in this thread...

At a minimum you should replace the power caps below (about$20 for 6). Mine were the originals from the early 90s and while they tested fine for capacitance (i.e around 3381uF), they were no longer capable of keeping stable high power output (loudness) at their age and were the core problem...

This amps power section has been repaired it sounds like brand new driving a marshall 1960A cab. I replaced the power caps, but i also replaced pretty much every other cap aswell, i dont want to be goinng back into this unit for a long while. I also replaced 2 shorted transistors. I will list...

This amp's EQ section has been repaired. The (now blue) D11 Zener 1N746A diode was causing the EQ problem. With these units, you will need to ground the board when you are working on it to complete the circuit and be able to test components. I grounded it by soldering wires to the ground points...

Quick update. Removed Zener D11 from the board and tested it with Fluke 87 Diode mode again. It is shorted. Now that it is removed, the green LED lights when the EQ knob is pulled, but EQ is obviously still dead. Once the Zener is replaced, I'll update.

Thanks for the tip on the foot switch I’d forgotten I could engage it there. The patch cable trick didnt help but I like the idea of the power amp test, will try that out

Update. Had some time today and made some progress. Tested EQ board today using Fluke MM. D11 diode is blown. Pin 1 of JRC 4558 Op Amp tests @ 13.9 volts, but when the EQ switch is engaged it does not flip to -12v per schematic test points. It switches to - 0.2v. Will replace diode and recheck.