[AMPS] More SB-220 amusement(!)

[Rich Measures]

>Rich Measures wrote:
>> 
>> >At 09:58 AM 9/18/97 -0800, you wrote:
>> 
>> NOTE -- Although the e-mail input from Mr. Smith was not posted to the
>> [AMPS] group, I'm guessing that other amplifier owners might like to be
>> included in the ongoing analysis and repair process.  Thus, I am posting
>> this reply to the group.
>> 
>> >>>On Thu, 18 Sep 1997 10:39:52 Pete Smith <n4zr@contesting.com> writes:
>> >>>>
......
>> Which, if any, resistor(s) on the metering circuit board have changed R?
>> The 1.0 and 0.82 ohm units are of special interest.
>
>I'll have to check when I get home, but I believe it was probably the
>1.0 ohm (I think, from memory) in the plate metering circuit.  does this
>change your diagnosis?
>
Yes.  If the resistance of the 0.82 ohm grid current meter shunt resistor 
is within specifications, but the anode/plate current meter shunt 
resistor is kaput, something else may have happened.  The next thing I 
would do is measure the grid/filament C and the grid/filament breakdown 
V.   
....... ...... 
>> The gradual element is a bit of a puzzler.
>
>Yeah, to me too.  If it had been only the plate current reading, I would
>have said it was just the shunt failing, but the RF output was also
>declining, so I gotta look further.
I would be inclined to test the accuracy of the 2, current metering 
circuits.  
>Thanks for your help.
You are welcome, Pete.
cheers
Rich---

R. L. Measures, 805-386-3734, AG6K   


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