[Central-Electronics] 600L questions

[radioart at frontiernet.net]

Hi Tom,

What wattage is that 1K resistor in the cathode circuit?  Can you monitor 
the voltage across that resistor and from the grids, pin 2, to ground. 
Sounds like something is shorting out to HV somewhere in that circuit.  If 
you can monitor those voltages you might a clue to the problem....

Good luck, Dennis, k0eoo

-----Original Message----- 
From: Tom Hankins
Sent: Friday, July 31, 2015 9:07 PM
To: central-electronics at mailman.qth.net
Subject: [Central-Electronics] 600L questions

Anybody out there with good understanding of the 600L circuits-mainly the
12at7 in the mismatch control circuit? I have a problem with burning up the
cathode resistor and it shorts the tube also. It must be drawing a huge
amount of current because the resistor goes up rather violently. It has
happened 2 times and after the 1st I replaced the socket and all surrounding
wiring along with the 12at7 tube. Worked fine on the bench for a few days
and passed all power out tests and a final check after putting it back in
the cabinet caused to light up again with a lot of smoke. The relay coil
shows a proper 10K and I wonder if anyone has seen one with an intermittent
short?

Any help or suggestion on who I could discuss it with would be welcome.
Thanks!

Tom Hankins

K0EOA

______________________________________________________________
Central-Electronics mailing list
Home: http://mailman.qth.net/mailman/listinfo/central-electronics
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Central-Electronics at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html