ID these backlight lamps?

[Rick M.]

Hey guys,

I have this neat old Zenith Circle of Sound clock radio from the mid-70s. It still works well; the radio is very strong and it sounds GREAT for a clock radio. The mechanical clock part even works. However, one of the backlights for the radio dial burnt out recently. The lamp does seem to be replaceable, but I have no idea what kind it is. It's basically a tiny little incandescent bulb with a rubber holder/socket. I haven't tried removing the lamp yet; not sure if it just slides out or if wires will need to be spliced. I can always solder in a new lamp if necessary.

Any ideas on what kind of lamps these are? Here's some pics if they help:

Pic of clock radio assembled for reference:


Lit up (all backlights were working at the time this pic was taken):


With cover removed and radio dial opened:


Lamps:




Any ideas? Please let me know what kind these are so I can find a replacement lamp to get the dial fully lit again! Thanks in advance.

[joe_347V]

Cool clock radio, interesting clock display too.

Anyway, I would assume the bulb would just pull out the rubber holder like the bulbs behind car dashboards. It wouldn't surprise me if they're the same type of bulbs too but in a different voltage.

If you can pull them out there should be a number stamped on the bulb.

[Mike]

very nice clock! yeah the model number is usually inked on the base or near it. hope you get it working!

[Rick M.]

Thanks for the input guys! I'll try pulling the bulb out and see if there's a part number on it.

[Mike]

If you can't see a part number, try using a magnifying glass with a fluorescent black light. Sometimes if the etch is faded away you can still see it under a BLB.

[joe_347V]

Yeah, that will also help on some faded labels, name plates, and fluorescent lamp etches.

[Rick M.]

Thanks for the suggestion guys! I do have a BLB tube for one of my undercabinet fluorescent fixtures, so I'll definitely put the Zenith's bulb under that if I can't make out the model number.

[Rick M.]

Well, I tried pulling the bulb out but it wouldn't budge...I can't see the bulb's base directly, but the rubbery holder appears to be attached to the bulb itself. The rubber won't move either...the top half of the rubber (what can be seen in the pic) appears to be a small rubber ring, and the bottom part (underneath the reflector that the bulbs are in) appears to be something that was sprayed or brushed on...it's a tar-like material.

Any other ideas? I may have to scrape off the tar to get the bulb out.

[Rick M.]

I was able to slide the bulb out! Turns out the rubber things were just holders after all. I had to splice the wires since the bulb was wired directly to the circuit (no socket), but it's no big deal since I still have enough wire to work with. I measured the bulb's voltage to be roughly 15.2 volts. I went on eBay and bought a 16 volt bulb of the same size (I went with a 16 volt bulb over a 15 volt one just to be safe). I'll show you the end result once I get the replacement bulb and install it!

I also bought an LED strip light to light the clock part. The clock has an internal neon NE-2 bulb, but that also burnt out recently. I can't get to the neon bulb without ripping the paper scrolls that the clock digits are on, so I opted to add something external. I'll show you pictures of that too once it's done.

[Mike]

Hey Rick, how come all your pics are that gray image now?

[joe_347V]

Hmm, odd I still see his pics. Mike can you post (or email me) a screenshot of what you're seeing?

Cool that you were able to find replacement bulbs for it though. I think a lot of radios had bulbs rated for a higher voltage than what fed it for longer life.

[Mike]

sure i'll send you a screen show via email

[Rick M.]

Hey Rick, how come all your pics are that gray image now?

Hmm, odd I still see his pics. Mike can you post (or email me) a screenshot of what you're seeing?

Oh, sorry about that guys! I exceeded the monthly allotted bandwidth for my Photobucket account, so Photobucket blocked all of my images until the end of the month when the bandwidth usage resets to zero (Photobucket's bandwidth limit for free accounts is ridiculously small ). All of my pics should be restored within a few days though.

Cool that you were able to find replacement bulbs for it though. I think a lot of radios had bulbs rated for a higher voltage than what fed it for longer life.

Very true. I'm hoping that getting a slightly higher voltage bulb than what the source is giving will help the bulb last a while like the original ones.

[Mike]

oh yep the pics are all normal now. and yeah getting a higher voltage lamp will make the lamp last longer but if it's the same wattage as the old one it'll be a tad dimmer. It shouldn't be a huge difference though and I'd replace both lamps just so you don't have to reopen it again.

[Rick M.]

I'd replace both lamps just so you don't have to reopen it again.

That's definitely a good idea...my guess is that the remaining working lamp is nearing the end of its life, and the display would probably look better if both bulbs are exactly the same brightness.