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Philco model 70 rebuild - by Tim P.
#2

Tim

As we spoke of it,

start with removing the tubes, checking all coils for opens.
Remove the electrolytics,
Remove the tuning cap and old grommets,
and then you will have an easy to clean chassis.

Check the big multi-tap resistor at the bottom (in your photo - on the right) for being intact.
I think we have different versions - it seems to me you have the resistor that has the chassis connect to its very first pin and I have the version where it is the second pin.

Otherwise they look very much the same, even those two overlapping caps at the top's middle are the same (I was wondering if this is how it was originally).

I do not necessarily do that every time, but when the tubes are out, restuff only the backelite that is the closest to the electrolytics (AC filter caps) AND add a 1W 100K or even 0.5W 1M resistor across the filter, solder a good chord, and bring it up on Variac measuring the transformer output voltages at the same time (start from the rectifier voltages).
(before you do it check the chord and the cap for shorts - though the Variac should help with short without creatin any much smoke).

When bringing it up if you see the voltage rising unimpeded (it does not struggle to get to the value listed in the manual, say at 20V it should be the (manual value/110V)*20V - then bring the Variac all the way to 110V, see if it is where it should be, then check the other voltages (I think there are just two - filaments for RF and filament for the output tube), and should they all be OK, proceed with recapping.

Pay attention to the power switch - it could be oxidized after that long and it is not easily disassembled, but in my experience it self-heals once you apply real voltage to the chord and turn it of an on several times (not too fast).

If not - start thinking if you want to get the replacement transformer or maybe a new chassis.

Then proceed with recapping.


Messages In This Thread
Philco model 70 rebuild - by Tim P. - by TV MAN - 01-29-2014, 11:46 AM
RE: Philco model 70 rebuild - by Tim P. - by morzh - 01-29-2014, 03:01 PM



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