Re: A/R II voltage running up

The 0.1 ohm 7W resistor (R24) is not the issue. It likely looks like it is
reading high due to the multimeter lead resistance. Hold the leads together
and read that value (call that the zero value), then read across the
resistor and subtract the zero value.

Obviously enough power is getting through R24, in fact, too much. Check
first R29 and R30, the 10 ohm, 1/2W resistors. They are what fail most
commonly due to bad edge finger contacts (they burn).

Another possible and probable problem could be that either Q2 (TIP32) or Q3
(2N3055) is shorted such that the regulator IC cannot turn down the output
voltage because one of them is leaking.

If those parts are okay, check that the sense leads are okay (J7 pin 3 for
+5V & pin 2 for gnd). Next check R7 (7.5k) and R6 (3.9k). These two
resistors in series with 1k pot R8 control the regulator. Check R3 (33 ohm)
and R1 (270 ohm). I forget off the top of my head what they do for the
regulator. It is entirely possibly that the LM305 regulator (Q1) is shot.
Bob Roberts supplies them but hopefully it'll be something simpler than
that.

If the chips on the main board were really running at 6V... then may the
force be with you.

William Boucher

----- Original Message -----
From: "Kirk Spradling" <kspradling@kc.rr.com>
To: <vectorlist@vectorlist.org>
Sent: Sunday, March 22, 2009 10:03 PM
Subject: Re: VECTOR: A/R II voltage running up

> Pulled one lead of ALL resistors on the +5vdc side and found that the
> .1ohm 7watt 3% resistor is showing .45ohm resistance. Does this need to
> be a wirewound resistor or will a ceramic work ok? I've seen several
> different types, non-inductive is more expensive.
>
> Recommendations?
>
> Thanks!
>
> Kirk S.
> ----- Original Message -----
> From: "Kirk Spradling" <kspradling@kc.rr.com>
> To: <vectorlist@vectorlist.org>
> Sent: Sunday, March 22, 2009 4:16 PM
> Subject: VECTOR: A/R II voltage running up
>
>
>> Hi,
>>
>> Rebuilding my Tempest P/S after noticing the voltage was at 6.05 volts.
>> Attempted to adjust it and could only get down to 5.4vdc. Installed the
>> Bob Roberts shotgun repair kit, big blue replacement, new pcb and harness
>> connector kit and am still having the same issues. Measuring a voltage
>> drop of about 0.125 on the +5vdc from P/S to Game PCB and less than .02
>> on the gnd. No burn marks on the pcb and edge connectors are in good
>> shape.
>>
>> Who knows anything about looking for issues in the feedback system?
>> Should I just start lifting resistors in the feedback area and taking
>> readings to see if any have gone open? The pot does adjust the voltage,
>> it just won't go down any further. Have tested all diodes on that side
>> as well.
>>
>> Thanks,
>>
>> Kirk S.
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>>
>
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Received on Sun Mar 22 23:09:16 2009