Many of the workarounds involve eliminating required voltages to make replacing easier. Are there any good options for somebody who wants to keep the original displays and MPU?

Indeed. Somebody skilled could rewind just the damaged winding by hand... difficult and tedious, but possible. Get the same gauge wire and count the wraps (or find out the rated winding resistance to match it). Alternatively, figure out the winding ratio but you still need to know or count the wraps of the primary.

This is an interesting thread, and that's what I was thinking too. IMO, many ways to approach the problem. Source or make power supplies for the various DC output voltages thereby bypassing the PS (you still need the AC display offset voltages). Or source various transformers for all AC voltages, keeping the original PS.

I searched eBay and an original transformer came up last month listed for $180.00, but sold for less. Patience may pay off here.

Part number B-17921

If I fully understand the Pinwiki, one would need to duplicate the following four AC voltages feeding their original power supply:

• 69
• 5
• 11.5
• 14

(I do not know the power specifications)

I am browsing the transformer offerings at Digikey and it appears that you could find various transformers to get close to all of those for the $120 to $150 range. I found a transformer with a 70 volt secondary for around $71. And I found one with a 14-volt secondary. There are quite a few with a 5 volt secondary. Nothing that has exactly 11.5 volts, but a 12-volt should work; after all, a 5-volt variation in primary translates to a ½-volt variation in secondary, so an original might be putting out 12 volts with a slightly higher wall voltage. Some of these have multiple output voltages, like both a 5-volt and 12-volt output, so one could get clever and eliminate one transformer.

As long as the power ratings are high enough, I don't see why a combination of 3 or 4 transformers providing the four AC voltages wouldn't work.

Yes... or base it on the Pinwiki fusing mod specifications, and over-engineer it to be safe. I see nothing there about the 69 volts, but that may already be fused. I would also imagine that any System 1 or 80 game would have the same power requirements for these displays.

EDIT:

• 69 VAC (Futaba displays circuit is fused ¼-amp or ½-amp in System 80)
• 11.5 VAC (fused 2-amp as per mod)
• 14 VAC (fused ¾-amp as per mod)

• 5 VAC with a center tap for DC offset
• 3 VAC with a center tap for DC offset

https://www.pinwiki.com/wiki/index.php/Gottlieb_System_1#Workaround_for_Dead_Small_Transformer

"The small transformer supplies 69vac (ending up as 60vdc and 42vdc) for the displays, the display offset voltages, 5vac for the displays, 11.5vac (ending up as +5vdc), and 14vac (ending up as -12vdc)."

Yes, good point. I noticed a variation of ¼-amp to ½-amp fuses for these cases. The 70-volt transformer on Digikey is rated for 2 amps so it should be a moot point.

https://www.digikey.com/en/products/detail/hammond-manufacturing/167L70/455346

These seem to be viable candidates. All have more ampacity than required, some a lot more simply because the heavier version was cheaper. Although lots of choices, so these are only suggestions that will work. ~$140 total

• 12 VAC @ 3.34 Amps max. - https://www.digikey.com/en/products/detail/triad-magnetics/TCT40-03E07K/2638188, $20.30
• 14 VAC @ 2 Amps max. - https://www.digikey.com/en/products/detail/hammond-manufacturing/166L14/270130, $21.26
• 5 VAC @ 1 Amp max. - https://www.digikey.com/en/products/detail/hammond-manufacturing/166J5/455062, $29.19 (NEEDS a center tap for the DC offset voltage)
• 70 VAC @ 2 Amps max. - https://www.digikey.com/en/products/detail/hammond-manufacturing/167L70/455346, $71.20

• EDIT: and 3 VAC with a center tap for the DC offset voltage.

NOTE: I believe the original transformer might have an input lug for the DC offset voltage, similar to System 80. So the offset might be something that would need to be engineered into this solution. The 70 VAC transformer above has a center-tap on the secondary winding so the DC offset voltage can be applied here.

Thank you for clarification.

What about the DC offset for the displays? Is this another lug?

The 70 VAC transformer I spec'd out above has a center-tap on the secondary so the DC offset voltage can be applied here.

EDIT: No! DC offset voltages need to be applied to center taps on the 5 VAC and 3 VAC windings.

Screen Shot 2023-09-07 at 9.18.40 PM (resized).png

That's very good news. An OEM replacement would be your easiest option.