An interesting problems Steve, I can't wait to hear comments from the group.
Regarding changing the HV caps, they're expensive and if one of them is
breaking down occasionally, I would think it would be apparent by
checking the temperature of each of the caps. Don't touch them with your
hands, obviously::> A non contact thermometer should work. Of course,
the problem might be that one is going open also, so it might not be any
different temperature than the other caps.
Bye the way, the values of the caps you have are the same value as the
original, I wonder if a later version of the ssb220's were made with
Nichicon caps?
If you can't find any other answer to the problem, you can remove them
from the circuit (leaving them otherwise intact in the amp) and
substitute in smaller capacitance values with the same or higher voltage
rating, which won't operate the amp in xmit mode, but should be ok for
testing. A couple of 2.5KV oil filled caps can be jumpered in to test
with since the problem is apparent in receive mode.
I might suspect the 100K equalizing resistors might not be small enough
in resistance to do the job-but it's a guess.
I'm actually interested in a used amp, which is why I am monitoring the
list. I chase dxcc and 100 watts just doesn't make it these days in
pileups, especially with my modest antennas and because so many have
solid state 500w (and up) amps::> I think the SB220 isn't useful for me
as it doesn't have the WARC bands although it might be able to be converted.
Regards,
Art
On 1/20/19 11:02 AM, Steve London wrote:
> I have an SB-220, of unknown lineage.
>
> While using it, I noticed that on receive, listening on my receiver, I
> was hearing a strong tick, tick, tick sound, about 3 ticks per second.
> With a little experimentation, I noticed the tick rate was higher in
> the SSB position than the CW position. At audio frequencies, I
> localized the source to the HV area of the amp. My guess would be
> filter capacitors, rectifiers or equalizing resistors. A few more data
> points - the equalizing resistors are not the original - they are
> 100K, rather than the original 30K. The electrolytics are Nichicon
> 200uF, 450 WV, 85 degree C. That's probably not original, either. I
> don't see any cracked resistors. Best course of action ? Replace the
> electrolytics ?
>
> 73,
> Steve, N2IC
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