Heathkit sb-614

[datsun66]

Does anyone have the troubleshooting guide for the station monitor. I'm having trouble with the old machine.
Bob.
KE7KPB

 

[Radio Tech]

Hey Bob,
Do not have a trouble shooting guide but here is the schematic.
http://www.tech-systems-labs.com/schematic/SB-614.pdf

What are you seeing with the monitor scope?
Like any equipment of this vintage it is always good to check capacitors, charred, discolored resistors, broken wiring, and weak solder joints.

If the monitor comes on and you do not have a trace check C121, 122, and 123. These are 0.1mf oil caps. They look like an electrolytic. Just not polarized.

NOTE
These are in the -1400 volt circuit so please be careful.

Post back your findings.

 

[datsun66]

I am going through the setup and all I get is the dot. The voltages are weird on the transistors Q118, voltage on collector should be 85 volts and I am getting 165vdc. On Q117 collector, the voltage should be 5.5 vdc and I get 1.3 vdc. All I get is a spot on the scope and I did check components and checked for bad or broken traces.
Fun.
KE7KPB

 

[Radio Tech]

Fun Indeed.
Check R151. Should be a 10k 7 watt resistor. It drops the 180 volt supply to 85 volts.
Also check your source voltage on FET 116. It should be zero on the gate.
You get -1400 on pin 2 of the crt?

 

[datsun66]

I did check the 4 7watt resistors. All good but I am wondering if they fail under load.
1400v is there