F6 Illustrated Build Guide

From post #2338 and #2341 (meanie)

When I turn on with bulb tester,
PSU have + - 25V.
But 5-10seconds later, PSU down to +,- 10V.

The power supply hold full voltage (even with the bulb tester?) for 5 - 10 seconds then drops to 10 volts which seems to indicate a problem with the power supply (and/or that huge 2 x 75,000uF charge) - check the power supply with/without the "bulb tester" on two dummy loads ( 24v/(2x1.5A) = 24/3A = 8R)

The transformer primary thermistor/soft-start is working okay with this turn-on current surge? And, check the rectifier diodes too for failure or insulation breakdown.
 
Yes, it's rather frustrating and is why I think there's a hidden problem elsewhere - it's actually quite instructive too, and I appreciate your patience as I'm sure 'tamra' is too.

I tend to get the power supply organized first (with a variac, not a 'bulb tester) and full current load soaking before attaching the active amp circuits but this isn't not everyone's method
 
Member
Joined 2019
Paid Member
Excellent advise as always! :)

It's implied within Pico's post, but I add one teeny step between 1 and 2 (depending on build sequence) based on reading some other issues and having one of my own saved by the dim bulb tester before I had lab supplies and a variac.

1a) After mounting boards to heatsinks, but before hooking to PSU or lab supply - check for shorts between all output device pins to heatsink. Little holes in the Keratherm (or similar) material seem to pop up unexpectedly at the worst times in people's builds. I've switched over to ceramic pads for newer builds to minimize that failure mode, but this is still a key step for me.

I learn a tremendous amount about the circuits (and how to prevent issues) by reading the troubleshooting segments within the threads. Thanks to all!

Tamra - I hope you get yours working perfectly.
 
Official Court Jester
Joined 2003
Paid Member
remember, OCD, stop at LEDs, yours

:clown:

edit: me being taught by few members, hopping to help..... and they tried to make my nose bleed .......

not saying that this is the same case here, but just saying - that taught me that you can't help everyone, even if you're able

no judging, of course, except in case of these swaying at ya

just one caveat in that , I'm bloody bad with memory, stumbled on same ones not once :rofl:
 
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