Hi all,
Previously, I believe I discussed with some of you an L4B I recently acquired.
To recap,......Looked good cosmetically, internals looked good with no visual
burnt or dark areas and no signs of arcing. However, when fired up, I found
that the plate current read around 2000v on low plate and 3000v on high plate
(ssb). This seems way high to me (read on the rf unit meter). During this
short time, the power supply got very warm. Also when switching from cw to
ssb, the deck and supply made some noise (vibration or oscilation somewhere).
At that point, I decided to rebuild the power supply as a first step to be sure
I had the correct and clean b+. A fairly old unit by serial number, so I
figured it was due before I went any further.
Now we are all up to date.
I just completed re-building the L4 supply with a kit from Harbach Electronics.
The kit went well, and from start to finish, it took about 2 hours time. I
tripple checked all the solder joints and connections. Having no 220 variac,
and not wanting to convert both the deck and supply to 110 and back again, I
chose to plug it in and see how it goes.
At first all seemed fine. The amp was idleing with no rig or antenna
connected. The power supply stayed way cooler than before and all seemed ok so
far. Everything lit up, filaments lights, meters ect. However, I still saw
around 1900v on the cw position (low plate). After a few minutes, I flipped
the switch to high plate(ssb), heard a "boing" sound, saw 2900v on the meter,
and a lot of noise and oscillation from the RF deck. I quickly pulled the
plug. I could not tell for sure, but the most of the noise seemed to be coming
from the rear of the rf deck near or from the transformer.
I don't have any high voltage volt meters (past 1500v) so I can't check any
contacts directly. Any suggestions on troubleshooting???.....I don't think
things are right !!
David
Wd9cmd
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