SB-401 Excess Grid Drive

[Allen Jones]

Last evening I started going through a very nice
SB-401 I bought at Dayton a few years ago.  It is
nearly spotless and shows few signs of use.  It has
the crystal pack installed.

I started by tuning into a 50 Ohm load on 80M and
everything seemed to be fine with 100+ watts out and a
decent note in the monitor receiver.  After a while I
noticed the grid meter go full scale in either keydown
or tune.  Reducing the level control had no effect. 
The only way to reduce it was to detune the drive
control.  40 and 20M also acted the same way.  I
didn't try 15 or 10M.  I powered down for a while and
tried again. Things were normal for a few minutes but
the problem eventually started again.  Power out stays
in the 100W region.

I tried a different 6CL6 driver, cleaned the
bandswitch contacts and the level control with no
change.  I also checked to make sure all the hardware
used to mount the pc boards was tight.

Any ideas?

Allen, W9DZ

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html