[Milsurplus] Harris RF-110A A6?

[J. Forster]

Gene,

If you want to send me a scan of the circuit and a summary of your
measurements, off list, I'll take a look.

-John

================


> John, I've spent 6 months putting a dmm to everything. I know how almost
> all
> nodes change (or do not change) in voltage. I have a manual that has
> detailed circuit diags and theory of operation. Yet I am unable to find
> the
> cause. I have not done any shotgun parts replacement, but I have replaced
> two zeners and 1 transistor. But no luck.
>
> One of the problems is that this card is in a small card cage in the amp.
> I
> do not have an extender board so testing things takes a lot of time.
>
> I do think getting a spare board would greatly facilitate the process.
>
> 73 Eugene W2HX
> -----Original Message-----
> From: J. Forster [mailto:jfor at quik.com]
> Sent: Monday, July 27, 2009 11:03 PM
> To: Eugene Hertz
> Cc: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] Harris RF-110A A6?
>
> Have you put a DMM on the thing to see which voltages rise and which
> don't?
> That'd sure help narrow it down. Shotgun parts replacement is a BAD idea.
>
> -John
>
> ===============
>
>
>> Hello all. Been troubleshooting a bias supply problem for over 6 months.
>> I'm
>> close to the end of my rope doing the component-level troubleshooting so
>> I
>> thought I'd send out a call.
>>
>> Anyone have a spare A6 board that they would care to sell?  I might as
>> well
>> get a spare A5 board too in case the problem is somewhere there. I don't
>> think it is.
>>
>> Let me know what you have!
>> thanks
>>
>> 73 Eugene W2HX
>>
>> PS. In case you're interested in the details:
>>
>> 1. The final bias is fine in AB1 mode. The problem is only in CW/RATT
>> mode.
>> 2. overtime, the bias increases until the tubes start to conduct.
>> Typical
>> range for the grid voltage in CW/RATT goes from -90VDC when first
>> started
>> up
>> and slowly drifts to about -72 and the tubes are conducting.
>> 3. I have pulled the tubes, so this is not the cause
>> 4. I do not have to have the HV on for the bias voltage to shift
>> 5. I have replaced several components over time with no improvement
>>
>>
>>
>>
>>
>>
>>
>>
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