Philco 49-702
 

Just picked up a very nice Philco 49-702. But much to
my surprise, Sams has nothing on it in the way of a schematic.
Simarly there is nothing in Sams about a 50-T702, which is
mentioned in a post by ERIC on 10-14-2002. This thing may
be a little too early for Sams. It is a 7 inch estat thing
with a power transformer and a lot of 6AG5s and octals and
loctals.

Any help here with a schematic would be much appreciated.
I hate tearing into these things without diagrams. It seems
like each and every one of these ancient sets is its own
free-style creation when it comes to ckt design.

I recapped one of these things a while back, I don't remember if I had a schematic, possibly in Beitmans.

I can tell you right off though you're probably going to have problems with the High Voltage transformer, it seems they all fade out after 15-20 minutes of operation, mine does.

I'll look for the schematic and get back later.

Eric

No Luck, Beitmans has a schematic for the 48-700 but not the 49-702.

I must have done mine without, lacking a schematic I'd take a lot of close up pictures of the chassis and start recapping. :yes:

I have a schematic and some other info for it. Please PM me your address and I'll mail it to you. It'll be easier for me to make a photocopy than to scan it.

John

Eric and John, thanks for helping me out. I checked Beitmans at your suggestion
and did not find it either. I don't know why this particular set got ignored by
the schem. publishers. It looks like it was definitely on the economy end of Philco's
lineup. Anyway it looks like John has the answer.

If these HV RF transformers don't want to keep working I wonder if baking them
out and then vacuum impregnating them with wax or transformer varnish would
help out. Maybe it would add too much capacitance.

Chuck at myvintagetv.com has a website where he made a module to correct the HV problem in these and said it works very well. The module is located on his website here at http://www.myvintagetv.com/philco_hv.htm and is complete with a schematic for those who want to build one. While your there check out his nice collection and restorations.
-Tony

The problem with that module is those transformers are really expensive.

I think the philco transformer is a donut shaped thing and sealed with something, I don't know if they would be amenable to baking.

I repaired an RF transformer in a 10" set by washing it in hot soapy water till it was clean, baking it dry at a low temp then spraying it (more like drenching it actually) with Dielectric Epoxy, several coats and it worked fine.

I have a couple of these Philcos, one fades badly after 10 mins on, the other was converted in the past using a transformer from some other type of electrostatic set, it wasn't done very well though because it only works sometimes.