[Amps] Suggestions - I broke my amp - part 2
Larry
lknain at nc.rr.com
Wed Nov 17 17:17:23 PST 2010
Not that I know of. The amp was working except it needed new parasitic suppressors. I
replaced the suppressors, the plate RFC, and the plate blocking cap. The output network
itself was not touched except that I changed a pair of doorknobs (200pf each) with a 500pf
doorknob that gets switched in parallel with the tuning cap for 160. I also added an additional
200pf doorknob that gets switched in parallel with the loading cap for 160. They look correct
with an ohmmeter.
I am going over things yet again and reheating solder connections just in case I missed something.
73, Larry W6NWS
----- Original Message -----
From: Dave M
To: w6nws at arrl.net ; amps at contesting.com
Sent: Wednesday, November 17, 2010 7:15 PM
Subject: RE: [Amps] Suggestions - I broke my amp - part 2
Possible arc over and short of the tune cap ??
......................................................................................................
73 VE3DV , Dave
> From: lknain at nc.rr.com
> To: amps at contesting.com
> Date: Wed, 17 Nov 2010 18:42:29 -0500
> Subject: Re: [Amps] Suggestions - I broke my amp - part 2
>
> It turns out it doesn't matter about the bandswitch position - same result
> in all positions regardless
> of the transmitter freq. The bandswitch seems OK by visual inspection and
> with an ohmmeter.
> I have to wonder where the power is going. No arcing, no noticeable heating
> so far but I
> don't run it too long since it is obviously not working correctly.
>
> 73, Larry W6NWS
> ----- Original Message -----
> From: "Gary Schafer" <garyschafer at comcast.net>
> To: <n8de at thepoint.net>; "'Larry'" <w6nws at arrl.net>; "'Larry'"
> <lknain at nc.rr.com>
> Cc: "'Amps'" <amps at contesting.com>
> Sent: Tuesday, November 16, 2010 10:17 PM
> Subject: RE: [Amps] Suggestions - I broke my amp - part 2
>
>
> > If the output relay was open there would be a large dip in plate current
> > when the tune control was tuned with drive applied.
> >
> > Open bandswitch or switch on the wrong band is most likely. Try another
> > band.
> >
> > 73
> > Gary K4FMX
> >
> >> -----Original Message-----
> >> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> >> Behalf Of n8de at thepoint.net
> >> Sent: Tuesday, November 16, 2010 7:53 PM
> >> To: Larry; Larry
> >> Cc: Amps
> >> Subject: Re: [Amps] Suggestions - I broke my amp - part 2
> >>
> >> One thought:
> >>
> >> Have you checked the output relay to see if it makes contact when fired?
> >>
> >> If the output of the amp wasn't making it to the antenna, the symptoms
> >> you describe would be happening. No RF getting past the relay due to
> >> the relay NOT closing properly would give no output to your RF meter,
> >> right?
> >>
> >> 73
> >> Don
> >> N8DE
> >>
> >>
> >> Quoting Larry <lknain at nc.rr.com>:
> >>
> >> > A number of you offered suggestions a couple of weeks ago and I checked
> >> those
> >> > suggestions a couple of times. I have finally got back to trying to
> >> > track down what
> >> > is probably a silly error on my part that has broken my
> >> > Clipperton-L. The mods were
> >> > triggered by the destruction of the original parasitic suppressors.
> >> > The amp was
> >> > working - just not well in all conditions.
> >> >
> >> > I replaced the power supply board (just an upgrade to better
> >> > supply), replaced the
> >> > plate RFC to an Ameritron AL-572 RFC along with the parasitic
> >> > suppressor board,
> >> > changed the plate bypass cap at the power supply side of the plate
> >> > RFC to a 0.002uf
> >> > value, changed the plate blocking cap to 0.002uf, changed the
> >> > filament RFC to a
> >> > bigger unit, and changed a couple of doorknobs for 160 (unrelated to
> >> > the original
> >> > problem of the parasitic suppressors). I haven't gotten to 160 yet.
> >> > The current effort
> >> > is using 40. The current result is still no output
> >> >
> >> > 1. There is plate current (as measured by the panel meter) and there
> >> > is plate voltage.
> >> >
> >> > 2. I don't have a HV probe but I could measure at the plate voltage
> >> > (at the plate caps)
> >> > as the voltage was dropping after turning off the power switch and
> >> > it tracked with the
> >> > panel meter.
> >> >
> >> > 3. The idle current seems OK.
> >> >
> >> > 4. The plate current follows keying. The plate current changes as it
> >> > should as the driving
> >> > power is increased or decreased.
> >> >
> >> > 5. Adjusting the output cap controls has no noticeable effect on the
> >> > plate current (no dip
> >> > etc).
> >> >
> >> > 6. Using an ohmmeter there is continuity (short) from the output
> >> > network side of the plate
> >> > blocking cap (on the cap lead) to the output connector. From the
> >> > other side of the
> >> > plate blocking cap (on the cap lead) to the power supply there is
> >> > continuity (short).
> >> > Thinking perhaps the new blocking cap might be bad I replaced it
> >> > with a pair of 0.001uf
> >> > in parallel but still have the same result. (I remeasured the shorts
> >> > after replacing the
> >> > blocking cap.)
> >> >
> >> > 7. The output relay is switching as it should. None of the wiring to
> >> > the relay was touched
> >> > in this mod.
> >> >
> >> > It has been a long time since I worked on an amp. I am sure I am
> >> > overlooking something
> >> > small and silly. I was hoping one of the gurus here might have a
> >> > pointer or suggestion of
> >> > something I might have missed.
> >> >
> >> > Thanks
> >> >
> >> > 73, Larry W6NWS
> >> > _______________________________________________
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> >> >
> >>
> >>
> >>
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>
>
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