HI Rick,
I use the relay NO contact to switch my Ameritron AL80 and
have done so for 20+ years with no problem. Still using the
original 3-500Z with full output. I wouldn't operate QSK CW with
this arrangement but for tune and SSB there is no problem that I
can see.
You have had a lot of suggestions and you seem to have
discounted all of them. However since it failed while you were
using the tune position I will throw out something that hasn't
been suggested. Though 572B's are very robust and are not easily
damaged could you have burned out the grids? It seems you get the
correct idle current so likely grids are ok but it might be worth
it to put in a used pair of 811a's and see what happens.
It might also be a bad filament choke (shorted turn) or grid
choke if it uses one.
73 Jim K4CGY
--- Rick Denney <rick@rickdenney.com> wrote:
>
> The band switches all look good and test good, with both DC and
> RF (at
> low levels from my MFJ-259) continuity through all bands. The
> problem
> behavior is the same no matter what the position of the band
> switch.
>
> I didn't do it to get more power--I know that the amp is
> constrained
> by the power supply. I did it to get graphite plates instead of
> sheet-metal plates with those soft, shiny bits in the middle
> where I
> cooked them, heh, heh.
>
You will
> > have to use manual PTT to accomplish RX to TX switching.
>
> I thought of this later, and that was the reason for my
> question. The
> only time I see the hot switching as a problem is when I use
> the
> "Tune" button. I'm normally using the SSB mode, and as long as
> I don't
> start talking until everything's keyed up, there shouldn't be
> much
> signal making heat when it switches. But I was doing a lot with
> the
> tune button during my testing. Once I get it working again, I
> will use
> the amp-control switch on my foot switch to key the amp.
>
> I would have thought that hot-switching would be primarily
> visible
> with burned contacts on the T/R relay, but there's no evidence
> of that
> and the relay works perfectly. It might have taken out a
> component,
> but dang it there aren't that many components in an AL-811, and
> I've
> tested many of them.
>
> Keeps those cards and letters coming.
>
> 73, Rick, KR9D
>
> ---
> Richard W. Denney, Jr. PE|Iteris, Inc.
> Associate Vice President |107 Carpenter Dr. Ste 230 |
> 703.925.3819
> rwd@iteris.com |Sterling, VA 20164 |Fax
> 703.471.1757
>
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