[Heathkit] DX-60 Problem

[Harry Vaught]

I bought a DX-60 at a local antique mall a couple of weeks ago.  I paid 
too much, but it was nearly mint, cosmetically, and I had gotten a 
really nice HQ-170C at the same booth last year.  I should have known...

Both bandswitch wafers were broken and the shaft was frozen at the panel 
bushing.  I got the shaft freed, epoxied the wafers and powered up. 
There were fireworks from the 6DE7.  I replaced it with a 6EW7, since 
AES was out of 6DE7's.  Since then I've rewired and recapped the power 
supply and replaced a charcoaled R13, the 8.2 ohm resistor in the 6146 
cathode circuit.

The voltages on the modulator tube are a mess.  I get 500-600 volts on 
pin 6, the first section plate and on pin 2, the second section grid. 
Same on pin 9, the second section cathode.  I've isolated the modulator 
tube by disconnecting incoming and outgoing connections.  Nothing makes 
any difference except disconnecting the high voltage, or removing the 
tube.  I'm lucky I haven't cooked the new tube.

Screen voltage on the 6146 is ok for CW, but high for AM.  Key-down bias 
on the driver is about -24 volts instead of -85.

The documentation has no resistance chart, only voltages.  I've checked 
voltages and connections through the various switches 'til I'm 
exhausted, but I'm no good at deducing problems from voltages alone.

Does any DX-60 guru out there have any suggestions as to where I should 
look?  If I don't fix it pretty soon, someone's going to get a nice 
looking bargain.  I don't like things that don't work and I can't fix.

Harry Vaught, KT4AE
Maryville, Tennessee