1958 Cadillac Car Radio 7270405, excessive A+ current draw

2/13/2012 9:24:29 PMDave Froehlich

Hello Again All,
We have now proven that I was wrong and the power transformer is good. Something is drawing excessive current in the filament or A circuit. I tried successively disconnecting the wires from the power switch and to me they all look like a short circuit between them and the chassis,except for 1. The one connected to the tube filaments would be of low resistance. I'll figure it out. Maybe it's one of the mica capacitors gone bad.
The radio is drawing 6 Amps when operating. 12 volts 6 amps (72 Watts) is excessive for a radio that's, according to the service data, only supposed to draw 3 amps. So something is not right. That's nothing for my car battery but way too much. The clip leads should not be getting so hot they could melt. But they still are. I've had enough for tonight.

Thanks,

Dave

2/14/2012 9:58:08 AMClifton

Dave,

Now that you have separated the branches of the 'A' circuit, just a matter of tracing them out to find the source of low resistance. May have more than one problem. Although it is probably not that common, check spark plate(s) for a short to chassis.

Clifton

:Hello Again All,
: We have now proven that I was wrong and the power transformer is good. Something is drawing excessive current in the filament or A circuit. I tried successively disconnecting the wires from the power switch and to me they all look like a short circuit between them and the chassis,except for 1. The one connected to the tube filaments would be of low resistance. I'll figure it out. Maybe it's one of the mica capacitors gone bad.
: The radio is drawing 6 Amps when operating. 12 volts 6 amps (72 Watts) is excessive for a radio that's, according to the service data, only supposed to draw 3 amps. So something is not right. That's nothing for my car battery but way too much. The clip leads should not be getting so hot they could melt. But they still are. I've had enough for tonight.
:
:Thanks,
:
:Dave
:

2/14/2012 2:31:19 PMWarren

You did mention before your clip leads are of small gauge. The radio draws 3 amps may be to much for those little clip leads. As voltage drops due to under gauge wires the current draw would go up.

2/14/2012 5:22:21 PMEdd

Sir Dave . . . . .

Maybe it's one of the mica capacitors gone bad.

Likely possibility ? Make that . . . . . .# 999

That's nothing for my car battery but way too much.

Now THAT's telling us that you ARE using a car battery and have enough dynamic current capability to solidly "thump the BEJESUS" out of that hefty "rewind" solenoid , that retensions the spring drive that drives the tuning treadle up the band as the air vaned escapement spins .

That is, if you are not skimping on the power feed line coming into the radio.

Why not physically move the tuning treadle to the left side of the BCB and assure that there would be no need for switch action to be occurring, such as when tuning is near the high end of the band and limit switch action then engages to trip the solenoid to reset the tuning treadle.

If the current is high and associated with the auto tuning relatching feature , closed /fused switch contacts would be suspicioned.

Any chance that you have already done some paper cap changes and posssibly miswired ?

Divide and Conquer . . . .although . . . dropping separate power feeder lines can sometimes prove a bit dicey . . . . .

73's de Edd

If you throw a cat out your car window is it kitty litter ?.

:You did mention before your clip leads are of small gauge. The radio draws 3 amps may be to much for those little clip leads. As voltage drops due to under gauge wires the current draw would go up.
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