Replacement 24 VAC 5VAC transformator 3-wire autoformer

Power Transformers
1

Hi,
in a junction box of a jukebox wurlitzer 2000 there’s a 24V to 5V AC autoformer, which powers the lights. Since this is a 3 wire version, I am looking for a replacement part, if that exists at all.

Original part number, per parts list in manual is 65609, from the schematics that looks like a step-down (24vac to 5.5vac) autotransformer.

Anyone who can help with this ?

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2

Hello Nick,

I’ve seen your activity on other forums.

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May I recommend caution. A mistake with this autotransformer could damage the larger phono transformer that provides the 24 VAC. That would be a difficult and costly repair.

Recommendations:

  1. DO NOT install that 12 VAC center tapped (6-0-6) transformer. Know that a transformer’s magnetics are designed for economy. There is a relationship between the voltage and the magnetic field. Excess voltage will cause core saturation with resulting high current spikes on the peaks of the AC waveform. Your phono transformer provides 24 VAC. Applying this to a 12 VAC winding of the pseudo replacement autotransformer will result in the saturation I mentioned. In my opinion, it’s not worth the risk.

  2. Since the unit still works and looks to be in good shape considering its original design and age, you could let it be.

  3. You could attempt to find an in kind replacement. However, given the collectability of this gem the cost is likely out of reach. But then again, if you keep looking you may one day find a replacement.

  4. You could modify the circuit to accept a conventional transformer such as this Hammond. This new transformer would be connected to the 120 VAC input - effectively in parallel with the phone transformer. The 6.3 VAC winding would then be used to power the 5 V lamps. A resistor could be used to drop the voltage down to 5 volts.

  1. You could install LEDs or LED strips in place of the lamps with power derived from an alternative source. You could then unsolder the autotransformer if you are worried about it. This option would allow you to preserve the unit with the option of restoring it sometime in the future. It would also allow you to change the color. For example, I’ve seen vintage stereo with blue LEDS - it provides a nice touch even if it isn’t original.

Best Wishes.

APDahlen

P.S. Should you chose option #4, this community may be able to help you refine the transformer and select an appropriate resistor. To do that we would need to know the type and total number of incandescent lamps used in the unit.

2 Likes
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for now the old transformer will stay in place.

I have an appointment with a company that revises electromotors and makes custom transformers, the motor needs to be revised and I’ll try and get a quote for an exact replacement.

Since I have already replaced all tl lighting with led strips, I might take this route.
The seller I get them from sells, as it happens, 12V and 24V DC LED strips. Sadly they don’t sell a transformer that does the trick from 24 VAC to DC.

I’m not sure if it’s the “make a selection” light or the bulbs behind the push buttons for the booklets.
The make a selection light should only light up if there’s credit on the jukebox, the other two I could do seperately, but I reckon the depart from the same 5V transformer.

I’ll have another closer look tomorrow but it’s no easy job to say the least.

1 Like
4

Speedy update: the selection light lights up, with use of a 150 ohm resistor, coming from a 24 V source if I read the schematics correctly

I’ll place led in it’s place and disconnect the light bulbs for the time being, before soldering and disconnecting the transformer.

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1 Like
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Glad we could help.

Please let us know how the repair progresses.

P.S. If the Wurlitzer becomes too easy, you could always take up relay-based pinball machine repair :slight_smile: