Conversion of your 220-240VAC happens at the transformer, which is configuered with jumpers to accept different input mains voltages. The secondary outputs are still at their designed output levels (about 88.5VAC is the specification)
Quoted from Drumgold:Do I need to change both resistors on F2 and F3 (both these fuses are intact) and are they easy to identify?
From the link above, you need to replace both zener diodes (not resistors). Keep in mind that this mod will not fix your blown displays. It is only designed to lower the voltage to increase their lifespan. There is a high probability that your displays are outgassed, and the higher input voltage you have presently may have accelerated the failure. The best option, in my personal opinion, would be to switch to digital displays. They do not require the HV at all, because they are only powered by logic voltage.
Increasing Score Display Life.
Glass score displays are getting very EXPENSIVE. Because of this, it is important to make your current glass score displays last as long as possible. The best way to do this is to decrease the 100 volts (which powers the displays) to 91 volts. This can be done by replacing the zener diodes at ZR2 (Z2) and ZR4 (Z4) to a lower voltage diode
The original diodes used at ZR2, ZR4 are 1N4764A. These are 100 volt, 1 watt zener diodes. If you replace these with 1N4763A diodes, which are 91 volt, 1 watt zener diodes, only 91 volts (instead of 100 volts) will power the displays. This will make your displays slightly less bright, but it will also DRAMATICALLY increase their life span! Since glass score display tubes are becoming so expensive, this is highly recommended.
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