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Tony, thanks for the reply, will remove all of them also. Bob w8exv

Hi Jacques Your words seem good to me until “IF the R7 were open, a positive grid voltage (quite close to the cathode one) could not be measured at all”… I don’t understand that. “could not

This might help. 1-4-5-1, RF BLOCKING PROBE The inexpensive DVM’s and VOM’s work fine unless you are trying to measure a dc voltage with RF present, like the plate, grid or cathode of an

Hi Don, simple: the 6K8 is made as a triode + hexode, sharing the same cathode, so the cathode bias resistor (R8) voltage depends on both the triode and hexode sections. So even if the triode section

Jacques +++ Yes that’s what I tried to say a bit too generally. It is probably only the grid[S] that cant reliably take the capacitance of a “wire probe” or whatever the term is, and mostly at

I mentioned in a previous post that I sniffed the LO with a GDO. The LO is not working. Tom

Jacques & TomNot mentioned so far was the use of another working radio to see if the oscillator is alive.? The oscillator frequency should be either above or below the received frequency spaced by

NO do NOT leave them in the radio they like to go off like an M80 73 Tony WA4JQS -- This email has been checked for viruses by AVG antivirus software. www.avg.com

Tom, I guess that this “big old mica capacitor” is C7, which decouple the 6K8 cathode to GND, in parallel with C8 (0.05?F, 200V). IF it is a REAL mica cap (not the “postage stamp” PIO ones),

Thank you, Jim and Jacques. Frankly, I'm not concerned about DMM inaccuracies and their probable or possible causes. The voltage readings I reported are proof enough that something is wrong,

Hi Jim, I agree with all you wrote, but apparently, Don doubted that the DVM connection to the LO of this S-20R could “kill” the oscillator. I experienced that before: and this is why a 1Meg

TomJacques is right on the money, with a positive triode grid voltage on pin 5 of the 6K8, just about all of the other voltage readings will be off except for perhaps the heater voltage.? It is worth

My sx-100mk2a has several black cat caps, woud it be ok to leave these in or replace them also. thanks in advance Bob w8exv

My 410B has a built in 22 megohm isolation resistor built into the DC probe. My GR VTVM does not but I put a one meg resistor in series with it. It has a 10 meg input resistance so the extra megohm

Richard do your DVM’s have an isolation probe for capacitance decoupling back to the DOT? Resistance of DVMs can be very high, but test wires have capacitance that will mess with tuned circuits as

Thank you, Don. No, the set was not operating when I acquired it last year. It is dead on all bands. Over the winter I through it and replaced all resistors and capacitors, upgraded the power cord to

Thank you, Jacques. The problem is on all bands. I have replaced all the resistors and capacitors in this set except for a large mica cap buried under the oscillator coil assembly. I was hoping not to

A DMM and a VTVM are essentially the same. I prefer the term "electronic voltmeter". The voltages for the S-20R were probably taken with a passive VOM. I don't remember if the meter characteristics

Hello Tom Around the HF, especially the LO, I wonder if you can trust a DMM having only wires {no isolation probe } at some pins. It never did work while you have had it? Assume, you tried another

Hi Tom, The triode section of the 6K8 is effectively not oscillating, and that explain all the voltage readings you got. There should be an open coil somewhere, or an open capacitor in the oscillator