[Collins] 30L-1 More questions

[Jim Brannigan]

Eric,
I don't think that WWII 811's are spec'ed for the 30L-1.  Start with a new
set of good quality 811A's.
In my opinion it is not necessary to buy a matched set.

burning up plate suppressors on 75M is a sign of parasitic oscillation.
Glowing red tubes with no drive, might mean oscillation or that they can't
handle the resting current.

I don't know if -10VDC bias is correct for the 30L-1.  The Handbook calls
for  -4.5VDC on 811A's in class B operation.  Check the bias circuit.

Jim


> OK guys, I am finally making progress on it.
>
> Found a a wiring error on the B+ line.   It was bypassing L13 and C34, go
figure.  So we looked really hard for any other novice repairs and did not
find anything else.
>
> It load's up, but it's really touchy tuning, something is still not right,
although we did get it tuned up on 75Meters.  It had around 600Watts output.
We did, however, burn up a 100 Ohm Suppressor Z2. The tubes get hot in 5
secs when not tuned with very low drive.  We suspect that the tubes may be a
problem as the top set runs a dull red when just keyed up without any drive.
We switched them to the lower position and the same two tubes still glowed
dull red, even in different sockets.
>
> I guess my questions are as follows.
>
> 1.  When keyed, the bias supply goes to around -10VDC.  Is this OK?
>
> 2.  It sounds like my tubes are not matched.  How critical is that?  I am
thinking about getting a set from RF parts the Taylor 811A's and wanted to
know if you guys used those before?  Or should I just go with K5SVC Cetrons,
although I do not believe he matches them.  I don't want to buy new tubes if
the amp still has trouble.
>
> The amp currently has JAN 811.  I know they are not 811A, but we should at
least get the ampo to run on these, right? These are from the 1944 and they
look the same.  Any ideas why 2 of them glow red when keyed without any
drive?  Maybe some type of oscillation?
>
> Any other ideas would be greatly appreciated.
>
> 73,
> Eric
> K8CCA