Vintage Philco AM Radio Restoration

RE: Vintage Philco AM Radio Restoration

D_Hersey — Fri, 23 May 2014 13:54:05 GMT

You should google 'all american 4' and 'all american 5' this device uses six active devices, but I bet the extra one(s) are for the power conversion that was necessary to get this device ready for line operation.

RE: Vintage Philco AM Radio Restoration

D_Hersey — Fri, 23 May 2014 13:47:26 GMT

I don't seek to be alarmist, but there is this generational thing where most electronics nowadays is powered by 5V or less and current draws are low, so people are wrongly sanguine. I'm just saying, play it safe. The potentials here aren't that great, and mostly imply pain rather than mortality. I went hiking at Garden of the Gods Monday, where a young girl died Tuesday. I still wouldn't advocate closing nor guard-railing of the facility. I certainly advocate caution when dealing in dangerous things. I just bought some antique equipment from a guy who touched the HV of an old school TV when he was a kid. 30KV. It shot him across the room, he was in hospital for a week, but he recovered fully. When working with high potentials, make sure your work area is very neat. It would be tragic to suffer secondary issues involved with landing. Just remember the joke about the physicist who implored the young man not to jump off the Empire State building: "Don't! You have so much potential!" Every time we double the potential, we increase the danger by a factor of four.

The big caps should sit with a jumper across them for awhile before you take them out to replace them. Don't wanna get shocked? Don't be lazy and operate your device open-frame. You can take out your tubes and put them on a tube-tester. replace them, screw the chassis back together, then power-up. That your device sorta-works now indicates that not too much diagnostic intervention will likely be necessary. If you are patient, you can use clip-probes to your volt-meter and power-up remotely. The RF front-end probably cannot be directly monitored anyway, as the energies used there are so slight that the perturbation of the observer would be insuperable. I think you should check for a torn speaker cone. Disposable rubber gloves help, they have, typically, a real high dielectric, but don't protect against punctures to the glove.

Also, clean up this device with appropriate solvents and compressed air at no more that 15psi. I knew a TV repairman who insisted upon cleaning everything before allowing himself to have a diagnostic thought, as so many of his client's devices remitted upon clean-up.

Do you understand superhet and AM detection?

RE: Vintage Philco AM Radio Restoration

Problemchild — Fri, 23 May 2014 10:55:17 GMT

Might be worth a look at this guy's stuff

https://www.youtube.com/watch?v=JZiwJaJqt6Y

RE: Vintage Philco AM Radio Restoration

D_Hersey — Fri, 23 May 2014 05:31:08 GMT

HV.

Use an isolation transformer, this limits the power when you get zapped. It does not protect you from charged-up capacitors, however. The VARIAC protects the circuit, turn it up slowly. Touching HV with one hand will cause all of the nerves in your arm to actuate, broken arms/separated shoulders are the #1 injury in the trade. Turning your body into a conduction path by touching HV while touching another potential is much more problematic. You have an electrically-activated organ roughly between your arms that you sorta need. At the very least, only use one hand at a time. Make sure your table and floor are non-conductive. Use appropriate tools. Modern electronics typically shunt-down the filter caps upon power-down, back then men were made of sterner stuff. Just because the power is off, doesn't mean that the filter caps have drained. If your filter caps are paper, dielectric absorption may cause your cap to charge back up after you have measured it to be zero.

Is your insurance paid up?

RE: Vintage Philco AM Radio Restoration

D_Hersey — Fri, 23 May 2014 05:04:44 GMT

Somethings you have to do out-of-hand: Get yourself an appropriate isolation transformer and VARIAC. Replace all 'lytics and paper capacitors. Make sure your unit has been de-powered a coupla hours before you do this. Measure all other passives and replace them if they have drifted.

There is a kind of thermistor that has been developed subsequently that can make life much easier on your heater elements. It is called an inrush current limiter.

Are you used to working with HV?

----------

There are many old devices that generate great sound! Man did not grow a brain all-of-a-sudden, whatever the current mythos states in this regard.

http://www.antiqueradiomuseum.org/consoleradios.htm

(took thirty seconds to find)