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A/D/S power plate 80 and 100
A/D/S power plate 80 and 100
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Old 24th November 2020, 01:48 AM   #31
Rabbit 16v is offline Rabbit 16v
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so there is this odd spike that happens every second or so. Both transistor collectors report this. Pics are from only one transistor. I think scope resolution might be a little low at those settings to see anything, unless that tells you something?
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PS-106, 12v regulated power supply with crappy ammeter
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Old 24th November 2020, 01:53 AM   #32
Rabbit 16v is offline Rabbit 16v
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Ugh, doesnt look like the camera got the spike...
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PS-106, 12v regulated power supply with crappy ammeter
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Old 24th November 2020, 06:30 AM   #33
Perry Babin is offline Perry Babin  United States
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The power supply isn't operating. Are you sure that you have negative rail voltage?

The supply may simply be charging the capacitor on the pulses that you see but didn't capture.

Place a meter on the negative rail and see if it remains constant or changes slightly corresponding with the pulses.

Do the same with the positive rail.
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Old 25th November 2020, 01:55 AM   #34
Rabbit 16v is offline Rabbit 16v
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Unless I am testing it wrong. There is a cap on each leg that both join to one pad on the board. I am using this as reference. So, neg lead on the common pad where both caps are soldered and pos lead on one side and its a steady 33v. No fluctuation. Scope shows a little noise on it though. On the other side, its all over the place, but never goes about 8v or so.
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PS-106, 12v regulated power supply with crappy ammeter
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Old 25th November 2020, 02:58 AM   #35
Perry Babin is offline Perry Babin  United States
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Are you measuring on the terminals of C806 and C807 (referenced to the PS5 diagram) with the black scope probe on the circuit common to both of those capacitors (inverted triangle ground symbol)?

Do you have any spare electrolytic capacitors rated for 50v?
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Old 25th November 2020, 03:08 AM   #36
Rabbit 16v is offline Rabbit 16v
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Yes, those are the test points I am using and black lead on common connection for the caps.

I just looked and no spares. I would probably steal them out of the other amp, but I think if you are suggesting that I swap them out, I should just probably buy a few of them just to have in my stash of parts. Does that sound like a logical approach?
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PS-106, 12v regulated power supply with crappy ammeter
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Old 25th November 2020, 03:12 AM   #37
Perry Babin is offline Perry Babin  United States
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Do you have a 110v incandescent lamp (not LED, not CFL)? Lower wattage is better.
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Old 25th November 2020, 03:15 AM   #38
Rabbit 16v is offline Rabbit 16v
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Most likely, yes.
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PS-106, 12v regulated power supply with crappy ammeter
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Old 25th November 2020, 03:18 AM   #39
Perry Babin is offline Perry Babin  United States
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Try connecting it across the cap with 33v. Power up and watch the current draw from the 12v supply. Does it increase with the lamp connected?

What is the voltage across that cap with the lamp connected?

Do this with the PS transistors tightly clamped to the heatsink.

Switch the amp on only long enough to answer the questions.
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Old 25th November 2020, 03:20 AM   #40
Rabbit 16v is offline Rabbit 16v
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Ok, just so I am getting this right. Connect it in parallel across both sides of the cap that has -33vdc, observe action on meter on power supply, and check voltage on the same points I have been checking to obtain the -33vdc?
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