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Old 19th November 2012, 08:02 PM   #8541
Salas is offline Salas  Greece
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Do you have an RC before the reg? Why it sags so much, across where it drops down? Is R1 10 Ohm, and does it have 1.6-2V DC across?
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Old 19th November 2012, 08:04 PM   #8542
Salas is offline Salas  Greece
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OK you wrote that R1Vdrop already I see now. So that is 220mA i.e. CCS in spec. Lets get rid of the input voltage sag now.
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Old 19th November 2012, 08:16 PM   #8543
Doug R is offline Doug R  United States
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OK, checked out the raw supply. raw AC Volts before bridge = 42

Replaced the reg with dummy load (350 ohms.)
Read 39 volts into dummy load. 39 V in/350 ohms = 111 mA load.
So, that looks good.
Removed the dummy load and put reg back in (now with a 500 ohm dummy load.)
Still get 21 volts at input of reg, and 3.5 volts at output.
So it looks like it is specific to the regulator, and not the raw power supply.
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Old 19th November 2012, 08:18 PM   #8544
Salas is offline Salas  Greece
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Are there long wires from raw to reg? What is the raw made of? Just bridge and caps? No series R element there?
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Old 19th November 2012, 08:24 PM   #8545
Doug R is offline Doug R  United States
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Since I used a 36 V transformer, I had to drop some volts to get it down to 39-40 volts (with a 350 ohm load.)

My PS looks like (with the following voltages with a 350 ohm dummy load):

FWV Schottky bridge(56 V)----22 ohm R(46 V)----100 uF C(46 V)---2H choke (53 ohms DCR)(40 V)----4700 uF C----10 ohm R(39 V)------4700 uF C(39 V)-------4 ohm R(39 V)-------4 ohm R(38 V)-----output
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Old 19th November 2012, 08:26 PM   #8546
Doug R is offline Doug R  United States
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The wires from the PS are about 10 inches long with another 10 inches of clip leads.
The reg was getting 40 V before I replaced Q2.
Don't know what happened.

I can certainly get rid of some resistors in the PS, but something else seems awfully wrong.
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Old 19th November 2012, 08:31 PM   #8547
Doug R is offline Doug R  United States
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I think I should set down again and make sure my wiring is OK in the reg.
I must have done something (else) wrong.
I become dyslexic with SS. WIth tubes, I am usually fine.
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Old 19th November 2012, 08:38 PM   #8548
Salas is offline Salas  Greece
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Thoughts at this point of the debugging effort.

A. 56-38=18V drop for 111mA load. You measured 2.2V across the 10R R1 in CCS. That is adding 220mA. I.e. 331mA total. That is 3 times. Or 2 times with just the reg. Sure it will hold?

B. I was looking the top side photo now, where are R2 and R9 gate stoppers? Maybe in heat shrink under? (Those are doing what grid stoppers do and should be used as grid stoppers for proximity or big instability risks occur as you know from tube builds.)

C. If the input cables from raw are long decouple with 0.1uF right at reg's input.
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Old 19th November 2012, 08:40 PM   #8549
Salas is offline Salas  Greece
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Quote:
Originally Posted by Doug R View Post
The reg was getting 40 V before I replaced Q2.
Don't know what happened.
Now you got a warm Q1 and proper drop across R1. Seems like working after Q2. At least partially for current draw.
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Old 19th November 2012, 08:47 PM   #8550
Salas is offline Salas  Greece
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So 220mA is 2 times what your test dummy brings to the raw without the reg. Shouldn't it drop another 18V for the reg?...Doug, 39-18=20. Rings a bell?
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