The PHILCO Phorum

What type of battery does this radio take? I have the similiar model 60 in my collection and was curious.
thanks
Chris

Hi Chris

A two-volt storage battery (172R) or a two volt dry battery (P-166) and a combination B-C dry battery (P-962). The B-C battery supplies the following voltages: 135, 67-1/2, -3 and -7.

If used with the dry battery, the original Philco specifications called for a Type 6 ballast tube to be used. Otherwise, there is a metal jumper across the large pins of the Type 6 socket.

The 38B performs well, if you don't mind the lack of AVC.

Ron,
Thanks. Might try and win it. It is currently on e-bay. Did you get my e-mails?
Chris

Yes, stand by for reply...

Ron,

Typically, how much current draw is on the 2V battery? Just curious.

Bill

720 milliamps, according to the service bulletin. A 1-amp-hr battery would last about an hour's worth of playing time.

Your 2-volt "A" battery needs to be beefy.

Building a suitable high current power supply can be a challenge. Some that I've built have worked quite well, but the voltage regulator can run quite hot.

I've built some around the high current version of the LM317 adjustable regulator that comes in a TO-3 package (don't remember the exact number offhand).

Anyone have a good high current power supply circuit they'd like to share?

Bill

I've built these supplies using an LM338T regulator which is rated at 5A, and comes in a TO-220 package. Yes, I know, 5A is overkill for the Model 38...but the TO-220 came in quite handy in terms of size reduction and operating temperature. Clip a heatsink on top and it is good to go. When powering a Model 38, it runs warm instead of red hot as an LM317 would.

I had to build one of these power supplies INTO the chassis of a Model 38 once for a client. Worked out quite well. I had to mount the power transformer on top of the chassis where the unused Type 6 ballast socket was (removing that socket to allow space for the transformer wires to pass through), and a perfboard with the power supply components directly underneath.

I'll scan the schematic of my design later today and post here.

Quickie scan from some notes I made some time ago.



I'll try to clean up this image and repost later. But for now, this should get you started...