This all started when I was about 12 years old. Our neighbors had this cool 1941 Philco console radio in their attic, I was fascinated by radios and record players, and they let me mess with it. It had a record player with Philco’s “Beam of Light” system for the phono pickup, I took it apart to see how it worked, and was fascinated by it. Fast-forward about 60 years and I found a console with this record player, bought it, and set about restoring it.

An ad for the radio

An ad for the radio

The first thing I did was to get the radio chassis working. This involved replacing lots of capacitors and a few resistors, restringing the dial cord, replacing the output transformer, and cleaning gunk out of switches, pots, and the tuning capacitor. I didn’t do a museum quality restoration on the chassis, I did what I needed to do to make it work well and made a couple of mods to reduce hum and noise inherent in the original design.

Chassis with many replaced capacitors

Chassis with many replaced capacitors

Then it was on to the record changer. This is really an amazing contraption, not that easy on your records, people came up with many better mechanisms after 1941. I had the turntable re-flocked, idler wheels retreaded, cleaned the mechanism with automotive brake cleaner, adjusted some things, and I had a working record changer. I scavenged a record cutting accessory from a parts turntable and mounted it on this one. The switch and lights for the recorder are hand wired, they were missing from the parts unit. Both tonearms were repainted. The record cutting head is totally dead so that’s just for show at this point.

The record changer with "Beam of Light" pickup

The record changer with “Beam of Light” pickup

The last challenge in the record changer was the “Beam of Light” pickup. The light worked but the stylus bushings had turned to concrete and the photocell was tired. I made some temporary bushings from rubber bands so the stylus could move the mirror.

I looked at things I might do to replace the photocell and found some long, skinny, photodiodes for cheap on eBay so I bought a bag and thought I’d try something cute; I made a new cell out of two of these photodiodes paralleled in opposite polarity and set the light beam right between the two cells. When both cells get the same amount of light their currents cancel. A 3000 Ohm load is a good current to voltage converter and this gives me about .8 Volts peak to peak at clip. A heavily modulated 78 gives you about .3 Volts peak to peak so there’s plenty of headroom. When correctly aligned there is 0 Volts DC from the pickup at rest and the voltage goes + or – when the stylus moves left to right. A DC coupled phono pickup!! Now that’s bass!! The signal is hot enough to feed the preamp directly without the transformer and “antenna cable” originally used with the old photocell.

Replacement "push-pull" photocell

Replacement “push-pull” photocell

The stylus was originally canted to one side by 30-40 degrees. I believe this was to correct for nonlinearity in the original single-ended photocell arrangement. The push-pull cell seems quite linear. I unsoldered the stylus and moved it so its tangential to the record groove and this sounded better with my two cell arrangement.

I got around to replacing the temporary bushings with clear silicone. I used a small rubber o-ring for a watch crown to hold the stylus shaft centered while the silicone cured. It might be a little stiffer than I’d like and a different silicone could adjust that, however there’s lots of friction and lots of tone arm mass so your stylus can’t be too compliant.

Push-Pull photocell schematic

Push-Pull photocell schematic

Here’s a video of the record changer in action. The output of the push-pull photocell is fed directly into the video recorder’s line input so you can hear the phono pickup without the added coloration and noise from the radio and speaker.

Video of Philco “Beam of Light” record changer

This restoration is still in progress. Unfortunately the cabinet suffered some bad water damage in the past. It will never be a good quality restoration but I hope to make it presentable. Stay tuned…