B100R pop on shutoff

[mtlbasslad]

The problem is asymetrical collapse of the positive and negative power supply rails. You can avoid one rail dropping quicker than the other by connecting the LED between the positive and negative power rails instead of just the positive rail as it is. It can be connected on the positive side just as it is, at J13 but connect the cathode of the LED instead of to ground, connect it to a 4.7k resistor and the other end of the resistor connected to the junction of C38 and R66.

Good day km6xz - some clarification please. This will be pushing my knowledge somewhat... if I continue on the path suggested by JM Fahey, that is replacing the 28V bulb with an LED, adding 2.2K to the existing 220 ohm resistor from the +40V rail, would it not be reasonable to have the same resistance to the neg rail? Also, how critical are the values (2.2K + 220) or 4.7K? Not sure if your idea of 4.7K to the neg rail was from the original layout or if it took into account adding the 2.2K to the pos rail...

Still haven't figured out how to remove the huge globs of silicone which would seem to be hiding that C38/R66 junction, tried pulling at it with needlenose pliers but it's slippery as, well, silicone!
Kinda nervous about damaging things. Sorry no pics yet, can't seem to find the cable - but there are pics of this amp somewhere on this forum, I'll try searching for them.

[mtlbasslad]

Yes, but have you tried the test.
A negative does not prove a positive.

Hi Jazz P, yep I've tried that

[mtlbasslad]

Finally found a (poor) pic of the B100R guts - it's on the Talkbass forum, post #355 of B100R rocket Aficianados...

[mtlbasslad]

Something seems wrong here, I can't see my last post?? I was asking km6xz for clarification... confused as usual...

[DrGonz78]

Perhaps you are viewing the thread in hybrid or threaded mode? This happens a lot if it is why your confused reading through the posts. If so then look at the top of thread page for Display and set it to linear mode, much less confusing.

[mtlbasslad]

Right you are DrGonz - these forums need a user manual LOL.

[mtlbasslad]

Hello Mr km6xz, patiently waiting for a response... JM Fahey, Enzo & all other gurus feel free to chime in...

[Enzo]

If I face a large glob of silicone that won't pull off readily, I slice it with a razor blade or my Xacto knife into smaller sections.

[mtlbasslad]

Thanks Enzo, I'll try the 'slicing & dicing' technique... any comments on km6xz's idea?

[The Dude]

... any comments on km6xz's idea?

Try it.

[mtlbasslad]

Yeah but the question was about the resistor value going to the neg supply rail...

[The Dude]

Yes. I got that. My point was to go ahead and try it. You don't necessarily have to shrink wrap, wire tie, fix anything in permanently. Tack the parts in and see what happens. It shouldn't take more than a few minutes. If you achieve your goal, wire it permanently. I have a set of clip leads I use for such "experimental" things.

[mtlbasslad]

Thanks Dude, the parts in there now are sure not 'finish install' in fact I only ripped the 28v bulb out, snipped the leads, soldered in the 2.2K & 'clip lead' to the neg.

Thing is, although I can 'talk the talk' a bit I've a bit more trouble 'walking the walk' LOL. That is, I'm slightly over my head here & don't want to mess up this (these) old amps out of ignorance. So I ask questions and wait. I asked km6xz for a clarification, but I guess he is busy. If you or any other 'wise men' could comment on my question to him I'd love it. See, at 67 my failing eyesight & shaky hands gotta be careful with a soldering iron on these 'modern' (read really close together) boards - I grew up on PT eyelet stuff which I can still see...

A great thing about being 'old' is that now I don't have to get up at 5AM, I can play music with with my Joanie and learn from her 60+ years of playing (the degree from the Royal Conservatory in classical piano kinda humbles me)

Damn I love this forum

[g1]

Wire it up as he said, keep the resistors that you have there, add 4.7K between neg. of led and negative voltage rail.
It doesn't matter about balance as the ground reference is now removed.
If brightness becomes a factor, then you can adjust resistor values.

[patlaw]

mtlbasslad, if g1's post above does not answer all of your questions, please repeat the remaining ones in your next post. This thread has gone on for a long time considering it's about wiring an LED. Let's get back to basics. It's not a complicated problem to solve, and km6xz's explanation sounds like a reasonable one.