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April 06, 2020, 11:34:24 PM

Author Topic: blown resister  (Read 263 times)

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Offline pfontana

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blown resister
« on: March 15, 2020, 09:00:30 PM »
I built both the A and D socket boards for the 5670 tubes driver testing.  During testing the A board's voltages were incorrect.  The D board was perfect, but during the final testing, I accidently touched the positive mm probe to the 5731A transistor to OA.  See pictures for all the damage caused by this error!
Do I need to build another board?  Or just replace the blown resistor, leds, and transistor?
I may need to buy both boards/components too because the other one wasn't testing correctly.

Please let me know what I may need.  Thanks,
Philip

Offline Paul Birkeland

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Re: blown resister
« Reply #1 on: March 16, 2020, 05:54:58 AM »
I would start with a fresh board.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline pfontana

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Re: blown resister
« Reply #2 on: March 17, 2020, 08:58:58 AM »
Hi,
I'll start with a fresh board on the D side.

The A side, the board tests within range, except for the oA.
That reads 350V instead of 300V.
Any ideas offhand?
thanks,
Philip

Offline Paul Birkeland

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Re: blown resister
« Reply #3 on: March 17, 2020, 10:00:50 AM »
How are the Kreg voltages?  That 350V indicates that the regulator is not functioning.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline pfontana

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Re: blown resister
« Reply #4 on: March 17, 2020, 10:48:54 AM »
The kreg was 13.59DC.
Any ideas?
Philip

Offline Paul Birkeland

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Re: blown resister
« Reply #5 on: March 17, 2020, 02:40:06 PM »
Can you post some photos of that board?  Is the little red jumper installed on the top side of the board?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline pfontana

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Re: blown resister
« Reply #6 on: March 17, 2020, 06:29:01 PM »
Problem fixed....
I reversed the 330K 3W and 147K 1/2W resistors on the board.  I corrected the two resistors and it tests great!
Thanks,
Philip

Offline pfontana

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Re: blown resistor
« Reply #7 on: March 23, 2020, 07:29:54 PM »
Hi,
I built a new D board and attached it.
The measurements are:
IA 518V
OA 0V
46U 0V

Any ideas?
thanks,
Philip

Offline pfontana

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Re: blown resister
« Reply #8 on: March 23, 2020, 10:23:27 PM »
I reviewed my work and went to check in my voltages again.

This time the D board 90R9F blew up.

Any ideas what I did this time?
I checked my work three times for the board and for wiring it up to D.

See pics...
 :(

Offline Paul Birkeland

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Re: blown resister
« Reply #9 on: March 24, 2020, 04:50:35 AM »
Problems with the tube socket wiring can cause these boards to blow, as can installing any of the zener diodes backwards.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Doc B.

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Re: blown resister
« Reply #10 on: March 24, 2020, 07:54:57 AM »
Yup, usually a bad zener string.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.