L4B
 

Has anyone ever replaced the transformer in the power supply with a
heaver transformer?

If so, who could I contact to do that for me?

What would be the advantages?

Thanks!

Fred
WA4PAV

L4B
 

Fred,

I have done what you're speaking of on one of my L4B's. The original
supply is not the best design and does create some noteworthy heat. I
used a Dahl transformer with a full-wave rectifier. I also use
Zener-derived bias voltages. The thing runs cooler and should last a
long time. I didn't care to up-grade the cooling in the amp itself, so
the power levels are about the same, maybe a just a bit more. On the
other hand, my second L4B still is running just fine after re-building
the diode boards and changing to bias over to Zeners. The bleeder
resistor doesn't smell anymore, either. As far as who might do the work
for you, I can't offer you a source.


Fred Cameron wrote:
Has anyone ever replaced the transformer in the power supply with a
heaver transformer?

If so, who could I contact to do that for me?

What would be the advantages?

Thanks!

Fred
WA4PAV

L4B
 

If I understand what you have done, you have lowered the plate voltage of
the finals as compared with the original circuit running with the red rocker
switch in the SSB position. Did this seem to affect the linearity of the
amplifier when operating SSB?

John, N9JG

"K3HVG" wrote in message
...
Fred,

I have done what you're speaking of on one of my L4B's. The original
supply is not the best design and does create some noteworthy heat. I used
a Dahl transformer with a full-wave rectifier. I also use Zener-derived
bias voltages. The thing runs cooler and should last a long time. I
didn't care to up-grade the cooling in the amp itself, so the power levels
are about the same, maybe a just a bit more. On the other hand, my second
L4B still is running just fine after re-building the diode boards and
changing to bias over to Zeners. The bleeder resistor doesn't smell
anymore, either. As far as who might do the work for you, I can't offer
you a source.

[snip]

L4B
 

John, No, not quite correct. In reality the Dahl transformer upped the
B+ about 7% and it also doesn't sag, key-down. Linerity appears just
fine. The idle current is down about 50%. The bias circuit is almost
identical to the Heath SB-220.

John, N9JG wrote:
If I understand what you have done, you have lowered the plate voltage of
the finals as compared with the original circuit running with the red rocker
switch in the SSB position. Did this seem to affect the linearity of the
amplifier when operating SSB?

John, N9JG