Jon -
See below ...
kilo4wit wrote:
I'm in the process of getting some c-lines back to life. Befor I even
started to delve into these boxes, I am making the assumption that I
will need to replace electrolytics. I ordered all new single value
cans of near values from Mouser.
I have a few questions on voltages:
AC-4
Pin #10 is showing 717VDC verse 650VDC
Pin #11 is showing 292VDC verse 250VDC
These are OK, just at peak because bleeder current only.
Pin #9 showing -60VDC - OK
This voltage is adjustable with the BIAS pot on the side. Should vary
from -50 to -100 VDC with no load. This is the most critical voltage.
If this fails, it can cause catastrophic damage to the transmitter,
even if it has been left in STANDBY. These filter caps should be
replaced, regardless. Watch polarity, as they are "upside down".
Pin #6/#4 showing 14VDC - OK
This should be ~ 14 V AC between these two pins. This is the "12.6VAC"
filament supply, at no load.
No hum is observed with 0 load. What would cause the higher than spec
voltages? Should I replace caps on general principal?
Best is to use the AC-4R upgrade kit from heathkitshop.com. It replaces
all but a couple of components and puts them on one PC board. I think
the transformer, fuse and BIAS pot are about all that is not replaced.
R-4C
Unit burnt transformer on start-up. I don't know the history of this
unit. I received a replacement transformer. What would cause it to
burn up? Capacitors in the power section?
Most likely cause is shorted filter caps. Drop-in replacement caps are
available from hayseedhamfest.com, although currently there may be a
supply problem.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
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