blown resister [resolved]

pfontana · 3376

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Offline pfontana

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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
« Last Edit: April 08, 2020, 05:06:38 AM by Paul Birkeland »


Offline Paul Birkeland

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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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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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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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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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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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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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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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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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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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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.

Offline pfontana

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Reply #11 on: April 07, 2020, 07:36:51 PM
Hi,
I built the replacement board with the new Zeners.  The D board tests within ranges, except the OA is 296V.
Should I be concerned I'm slightly outside the 300V +/- 1%?
thanks again!
Philip


Offline Paul Birkeland

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Reply #12 on: April 08, 2020, 05:06:28 AM
That is just showing the tolerances of the resistors to set the OA voltage.  As long as your Kreg voltage is above 3V and below 32V on the side without the blue trim pot, there's nothing to worry about there.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

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