The PHILCO Phorum
Philco 41-608 BOL Help - Printable Version

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Philco 41-608 BOL Help - timshow - 08-24-2025

Hello, I am restoring a Philco Beam-of-Light phonograph with an HR-1 record cutter/recorder. It's the Model 41-608 radio/phono. Everything seems to be powering on, but I am not getting any sound from the speaker when playing a record. I suspect that maybe the transformer that connects to the BOL arm my not be functioning properly. Questions:
1. Is there a replacement for the Philco d 32-8148m transformer on the market?
2. If worse case scenario, can I replace the pickup arm with a traditional needle arm?
Thank you for any help in advance.

RE: Philco 41-608 BOL Help - sam - 08-24-2025

Did you replace photo cell  if not it will not work

RE: Philco 41-608 BOL Help - timshow - 08-26-2025

I checked the photo cell with a volt meter and it appeared to be working.

RE: Philco 41-608 BOL Help - timshow - 08-26-2025

I checked the photocell with a volt meter and appears to be working properly.

RE: Philco 41-608 BOL Help - timshow - 08-26-2025

I checked the photocell with a volt meter and it appears to be working properly.

RE: Philco 41-608 BOL Help - timshow - 08-26-2025

I tested it using a volt meter and it appeared to be working properly.

RE: Philco 41-608 BOL Help - MrFixr55 - 08-26-2025

I have not worked on a BOL (Beam of Light) pickup but there should be more info on this unique system in the Phorum. Check for several things:
Is the source lamp lit? I believe that it is driven by the local oscillator Ensure that the mirror is attached to the mechanism. this is how the light beam is modulated by the Audio signal from the record.

You can check the transformer or choke (whatever the device is) with a DVM.
Here is a link to the alignment and diagnostic procedure from PhilcoRadio.com:
https://philcoradio.com/repairbench/phono.htm

Hope this helps.

RE: Philco 41-608 BOL Help - timshow - 08-27-2025

The source lamp is working and the mirror is attached. The light beam is hitting the sensor. Thanks

RE: Philco 41-608 BOL Help - MrFixr55 - 08-27-2025

Hi Tim,
You can check the transformer by ohming between ground and the transformer side of cap #51 on the schematic. (Per the schematic, this is an "autotransformer", where the primary and secondary are actually the same winding.) You should get a reading. Then read between the 2 photocell terminals. You should get a lower reading. However, I don't know what those readings should be. I think that part of the reason for this transformer is impedance matching, and the other reason for the transformer is to filter out the high frequency AC driving the source.

Also verify that the needle does move and that somehow the needle / mirror mechanism has not frozen solid. However, I think that it is suspended in rubber so there should be some compliance.

One other thing. The phono preamp is used solely for the BOL pickup. It is not used by any other part of the radio. So it could be that the BOL is good but the preamp is bad. Try touching the same junction between the autotransformer and Cap#51 with a screwdriver while touching the shaft. This should inject a hum into the amp. If you do not hear a hum, try the other side of the cap. If no hum on either side, troubleshoot the preamp. If you hear a hum on only on the tube side of Cap 51, the transformer may be shorted. The preamp tube and the detector / 1st AF amp are both type 7C6 so you can swap them. In addition, Loctal sockets and tube pins are notorious for getting dirty and intermittent (I don't know why 7 and 9 pin miniature tubes don't have the same issue).

If you want to substitute another tonearm, hopefully the turntable was made for several years, but the BOL was made only for the 1941 and 1942 model years. Non-BOL arms from a similar Philco Turntable from 1940 or 1946 may fit. I would recommend against excessively hacking the BOL head to fit another cartridge, as it is rather rare.

I have not heard a BOL live, but there is one on you tub e. I'm sure that it is much cleaner than a crystal or ceramic cartridge and as good as a GE RPX or other magnetic cartridge of that period.

RE: Philco 41-608 BOL Help - Arran - 09-01-2025

I think that it needs to be mentioned that the BOL machines are all at least 83 years old, as such the paper capacitors, as well as a good number of the resistors, are going to need replacement for the units to work reliably, if they still work at all. If an auto transformer has continuity then it's probably fine, barring something like shorted turns in the winding, so I would say say that the problem is elsewhere. The problem is either ahead of the autotransformer, or after it, if there is a paper capacitor, or resistors after it, check the resistors, and replace the capacitor, or capacitors. A bad tube is possible, I'm not familiar with how these BOL sets are wired but if the pre-amp tube sits on standby, such as being operated with the heater on, but no B+ for the anode, that can cause failure. Flakey tube sockets are another curse of sets with locktal tubes, which is why they often need the socket contacts and tube pins cleaned.
Regards
Arran

RE: Philco 41-608 BOL Help - timshow - 09-05-2025

Arran,
per your message: "You can check the transformer by ohming between ground and the transformer side of cap #51 on the schematic. (Per the schematic, this is an "autotransformer","
I do not see a schematic. Am I missing something here?

RE: Philco 41-608 BOL Help - MrFixr55 - 09-05-2025

Hi Tim,

The above quote in your message to Arran came from my previous post. the schematic for the radio is in our Philco Library, in the 1941 yearbook. This set has 2 different runs, Code 121 and Code 122. For your convenience, I am posting 2 links: one for Model 41-608 Code 121, the other for Model 41-608 Code 122.

https://philcoradio.com/library/download/service%20info/yearbooks/1941/split/Part55-Philco%201941%20RMS%20Year%20Book.pdf

https://philcoradio.com/library/download/service%20info/yearbooks/1941/split/Part56-Philco%201941%20RMS%20Year%20Book.pdf

In both cases, the autotransformer is denoted in the schematic as number 54. Do remember to try the "Hum Test" that I noted in Post #9.

Hope this helps.