RE: Adjusting K6100 (tempest) HV / b+

Got it, Q902 (another MPSA06) was bad. Replaced it I can now get B+ up to
where it belongs. The voltages going into Q903 were all wrong so this was
next up the chain.

As for possible improper parts / values the part I took out was marked
oddly. I suspect a house part but can't be sure.

It has a 2 in a circle then 71. Next line is -1

Thanks for the pointers.

David

From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Mark Shostak
Sent: Saturday, October 08, 2011 6:24 PM
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: Adjusting K6100 (tempest) HV / b+

The pass transistor is the power trani regulating the supply to the fbt.

Most of that is easier to troubleshoot in-circuit, so you can measure the
actual voltages, rather than pulling out something like a zener trying to
figure out if it's avalanching at the right voltage.

Make sure the reference voltage is correct on the zener. Going by
appearances makes the process a lot longer than it need be.

Be advised that many incorrect / can't adjust, symptoms on the HV cage are
caused by installation of improper parts / values during previous repairs.

-M

On Sat, Oct 8, 2011 at 8:11 PM, David Shoemaker <davids@oz.net> wrote:

Sounds reasonable.

But I don't follow "Pass transistor".

I pulled ZD901 and diode checked it, and it appears ok. I decided to pull
the adjustable resistor and if literally fell apart when it hit the bench J

Replaced it though and no change.

From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Mark Shostak
Sent: Saturday, October 08, 2011 5:23 PM
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: Adjusting K6100 (tempest) HV / b+

Check both sides of the pass transistor (make sure the rail is nominal)

Check the Zener

Check the parts between the Zener and the pass trani

On Sat, Oct 8, 2011 at 7:11 PM, David Shoemaker <davids@oz.net> wrote:

I just recapped a HV unit on a tempest. In the process I replaced Q901
(MSPA06) and R904 (470 1/2w).

The monitor turns on and has a reasonable display.

BUT: My B+ voltage is 56v (checked at Pin 5 of the J900). I can't find my
HV probe to check what the HV is at right now.

The pot on the HV board doesn't make any difference to the b+ voltage.

Before I start to just shotgun parts (R918 the adjustment pot, Q902, Q903)
anyone have any suggestions?

Thanks,

David

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Received on Sat Oct 8 21:52:03 2011