[Heathkit] DX-60 Problem
Harry Vaught
hlv at frozenlady.com
Mon Mar 13 10:25:53 EST 2006
So far, I've recapped the power supply and replaced the plastic caps and
the paper electrolytics. The can is still good, I say, because there's
no hum in the CW note.
I'm still hoping that the tube is the problem. The modulator can be
isolated and the symptoms are there. The only way to get rid of the
high voltages where they don't belong is to remove HV from the tube. I
should know later this week.
I've checked the power supply resistors and they checked good. Maybe
they aren't good under stress, but I didn't have any 2-watt resistors of
the proper values in stock. I've ordered replacements for all the 1 & 2
watt resistors from AES.
My experience with my other 50's and 60's equipment has been that things
aren't that bad (except the Ranger. Maybe kit-built equipment had poorer
components). You could maybe get some improvement by a wholesale
replacement of caps and resistors, but that isn't my hobby.
Speaking of power supplies, were there different versions? I have DX-60
and DX-60B schematics from BAMA. Both these schematics show two 40mfd
caps with a 100 ohm 7 watt resistor between, in addition to the two
section can. My unit is a DX-60A. It only had one additional 40mfd cap
no 100 ohm resistor. At first I thought it was a construction error,
but I found a service bulletin to correct ripple which consisted of
adding a 40mfd cap and the 100 ohm resistor. Was there a period where
they were trying to get by with fewer components? The hookup in my unit
still didn't make any sense, but I'm no good without a schematic, and
this didn't match anything I had. I ended up re-wiring the power supply
per the "B" schematic.
Harry, KT4AE
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