"Techie" question ??

[Ron Rich]

Hi All,

I was sittin' here, and my mind sorta drifted--as usual--so I'm wondering-- On Seeburg's wall boxes that used 25 VAC powered down to 6 vac for the lights, by an "Autoformer" (NOT "Transformer"), what would be the difference if they had used a resistor-- and any ideas why they did not ??  ( they used a resistor on the credit lamp ?)  TIA, Ron Rich

[robnyc]

Ron the answer is that a tran provides relatively constant current/voltage under load. A resistor would let voltage rise as lamps burned out hastening the burnout of the remaining  bulbs. It would also limit the choice of bulb to those that draw the correct current i.e. no using #47's where 55's were spec'd.

The 3W1 uses a resistor on the credit light, the 200's used the tran supply which is 5.1v (+-).

Rob

[Ron Rich]

Hi Rob,

Thanks---
But it is not a transformer--there is only one winding--two wires--one "in", other "out" thus it would seem to me it would "choke" down the voltage, as a resistor does ?? Ron Rich

[jukenorman]

Hi Ron,
It's an auto-transformer (single winding) that I assume Seeburg has abbreviated to "autoformer". Technically, there is a third wire on the winding which is grounded. The 25VAC is connected to one end of the transformer winding to ground and the 6VAC for the lights is picked off at one quarter of the winding above ground. Although there are losses in a transformer, there is much less loss than using a resistor.
Norman.

[Ron Rich]

Hi Norman,
Thanks-- I understand how that can work now-- probably shouldda l@@ked at the schematic (duh !)-- I'll bet they show that ! Will do so later when I am out in the shop ! Ron Rich

[robnyc]

Ron, I must have misconscrewed you question, I thought you were just asking why a tran was used instead of a resistor.

On the diagrams I have, Seeburg just called them "transformer" -didn't bother with the "auto" part.

Rob