Date: Mon, 15 Feb 2010 09:41:56 -0800
From: Michael Tope <W4EF@dellroy.com>
Subject: [Amps] L-4PS Transformer Buzz
I just installed the Harbach PM-400 in the L-4PS power supply for one of
my Drake L-7 amps after I popped a rectifier diode in the old bridge:
http://www.harbachelectronics.com/main/page_products_drake_l4l4bl7.html
Electrically, the amp and power supply appear to work perfectly with the
Harbach board. Plate voltage and RF output are as expected. There is one
problem, however. Last night about 20 minutes after I fired up the power
supply I noticed a loud 60 Hz buzz coming from the supply.
## whoa, stop. did it buzz b4 u added the harbach mod ??
Pressing on
the sides of the cabinet or changing the physical orientation of the
supply didn't seem to help. When I switch to the low-voltage setting on
the L-7, the buzz stops. Also if I let the supply cool off the buzz
stops for a while and then returns after the supply warms up. Looking at
the supply in the dark, I saw no evidence of sparking. Additionally, the
amplitude of the buzz seems to be totally unaffected when I go from
standby to full RF output power.
Any ideas on what might be causing this problem?
## try disconnecting the HV AC sec leads [ both of em] from the
FWD.. tape em.. then turn the supply back on, then toggle between
SSB / CW position. I think Carl is right, the xfmr is trying to tell u
something.
## If it still buzz's with sec disconnected, then at least you have isolated
the harbach mod / FWD and 8 x caps, etc. It may be mech vibration,
how loud ..is 'loud' ?? Are you sure it's not metal work, 2 x bleeders
[ toss the bleeder's, then ur cab will run stone cold, and B+ will NOT
rise at all].. or mounting posts for bleeders , or something below
chassis, either breaker etc ?
## this buzzing is one problem I have never heard of in a L4-PS,
and I have 3 of em .
later.... Jim VE7RF
Thanks,
Mike W4EF......................
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|