I love the aesthetics and build quality of my Philco 9200 tube tester.
It's a fine example of functional industrial art IMO. It's so steampunk it has a scroll, not that it is any different from any other tube tester. At the hart of the tester is a transformer with 18 different secondary taps!
Anyway, I made the mistake of spraying the switches and tube contacts with Deoxit. It now indicates filament leakage no matter what tube I put in. I hypothesize there's some current leakage going on due to pools of deoxit at tube socket sites.
Is this a feasible explanation?
I assume Deoxit conducts electricity to a degree?
If I could isolate the tube sockets completely I'd stand a better chance of chasing down the leakage. Unfortunately, there is no switch position that does that. Impedance back through the transformer secondary's makes this a Thevenin parallel path nightmare with the power off so it's difficult to obtain any useful info using an ohm meter.
I think I might just remove the scroll and submerge the entire circuitry in a pan of alcohol, swish around, let dry, and retest. it's virtually impossible to get even a q-tip between socket pins with all the wiring present.
I thoroughly understand the circuit now. I've made neon bulb voltage measurements during the tests which line up with what I am seeing.
Any other suggestions?
It's a fine example of functional industrial art IMO. It's so steampunk it has a scroll, not that it is any different from any other tube tester. At the hart of the tester is a transformer with 18 different secondary taps!
Anyway, I made the mistake of spraying the switches and tube contacts with Deoxit. It now indicates filament leakage no matter what tube I put in. I hypothesize there's some current leakage going on due to pools of deoxit at tube socket sites.
Is this a feasible explanation?
I assume Deoxit conducts electricity to a degree?
If I could isolate the tube sockets completely I'd stand a better chance of chasing down the leakage. Unfortunately, there is no switch position that does that. Impedance back through the transformer secondary's makes this a Thevenin parallel path nightmare with the power off so it's difficult to obtain any useful info using an ohm meter.
I think I might just remove the scroll and submerge the entire circuitry in a pan of alcohol, swish around, let dry, and retest. it's virtually impossible to get even a q-tip between socket pins with all the wiring present.
I thoroughly understand the circuit now. I've made neon bulb voltage measurements during the tests which line up with what I am seeing.
Any other suggestions?
I had the same question after cleaning the switches in a precision instrument and checked Deoxit. Its non-conductive (GigaOhms) and similar to Teflon in capacitance http://store.caig.com/core/media/media.nl?id=1366&c=ACCT113328&h=3f3b4fab58a5c760e2e1&whence=
You may have dislodged some dirt into the wrong place causing the neon light to glow. Clean around the lamp and its connections with 91% isopropyl with a Q-tip. Hopefully it will fix things.
You may have dislodged some dirt into the wrong place causing the neon light to glow. Clean around the lamp and its connections with 91% isopropyl with a Q-tip. Hopefully it will fix things.
I found the short!. A phenolic floor mounted solder tab that holds the coupling cap attached to the Neon bulb had an invisible but dead short to an adjacent pin. I light swipe with a nylon brush was enough to clear it. Voila! I believe i must have created that short when I unsoldered one end of the cap to measure it.
Thanks 1audio for your input.
Thanks 1audio for your input.