Re: 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 21:24:02 2011