[Drake] Re: [drakelist] Drake L-4/L-7 Power Supply Board

[VE3AX]

Guys:

The L4B/L-7 power supply replacement board will probably take you about 2 
hours to install, at least the 1st time you do it.  It takes quite a while 
just to get all the screws out of the cabinet and remove that large Heyco 
strain relief and the primary cord.  Both have to be removed to get the top 
of the cabinet off.

The leads to the old cap boards can just be snipped as there is plenty of 
length and you really need to re-do the ends for insertion into the new 
board anyways.  Getting the old boards out is a bit tricky as they are a 
tight fit - one will just slide out, but on the side  with the ceramic 
standoff and the 0.82 ohm resistor you need to loosen one end of the bracket 
holding the bleeder resistor on that side.

Both boards can be removed and probably should be removed, though I suppose 
you could leave one of them in.  The new board installs on the side WITHOUT 
the ceramic standoff/0.82 ohm resistor.

Only 4 leads connect to the board - two from the transformer, the outgoing 
HV lead, and a piece of wire you save from the original hook-up that 
connects the 120v tap to a terminal strip in the bottom - that's all! 
Pretty simple indeed!

The two 50w bleeders (R-9 and R-10), the "fuse resistor" (R-12, a 0.82 
ohm/2w), and R-11 (5k/7w) located under the chassis are retained.

I brought up the protoype on a Variac just to be safe - probably a good plan 
for anyone - but this will entail (for most of us with only 110VAC Variacs) 
re-wiring the power supply AND THE AMP for 110VAC for testing.  Don't forget 
after that you have to re-wire the primary in BOTH AMP AND PS to take it 
back to 220VAC primary.  Of course you do run your amps on 220VAC, don't 
you!!!!

If anyone has any questions don't hesitate to drop me an e-mail.  Mike has 
produced another winner in my books and I'd hate to see us miss the 
opportunity!

73

Peter
VE3AX