[Gene Pederson]

I just bought a full recapped Philco 45 "butterfly". After playing it for about 45 minutes I shut it down and put my hand on the power transformer. It feels pretty warm. Not hot enough so you can't hold your hand on it but warm.

From past experiences, I haven't had any other sets do this that I can remember. What can be causing this?? Any info would be appreciated.

Gene

[Phlogiston]

What is your power line voltage?

[Arran]

Fully recapped by whom? If the transformer is running a little warm I think the work done warrants a closer inspection. One thing many people overlook is checking the resistors, if those are off they can increase the plate current, especially on a power output tube.
Regards
Arran

[gvel]

At today's line voltages, wouldn't you all say this is normal? It's not too hot to touch, and there isn't any sizzling heard!

I'm not familiar with this radio, but there are a handful of ways to correct the "problem." The easiest, get a variac, and run the radio through it. Or a power resistor could be used - to drop the line voltage. Best method, use a bucking transformer, to do the same.

Search the 'net - you'll find all the info needed!

I've read, on many occasions, if the transformer is "warm" - as explained - it's OK. On the other hand, I've also read on many occasions, your radio will like you better, if you reduce the line voltage. Some claim to reduce incoming to 110 V, and you won't notice a difference.

When I have a radio on the bench, it's run through a variac, with reduced voltage. Once it leaves, it's on it's own!

[Gene Pederson]

Phlogiston,
My line voltage at the outlet is 119v.
I have now set the radio up on the variac to run @ 110v to see what it does.

I will post back the results.

Arran, I don't know who the person was that did the recap, and in looking at the underside of the chassis the only thing that looks questionable is whether they took the bakelilte block caps out of the circuit entirely or not.


Gene

[gvel]

At 110 V, you won't notice a difference in performance. The transformer should run cooler.

[Arran]

I have a lot of problems with this assumption that the power line voltage is always to blame for a warm running power transformer, these sets were intended to run at least at a nominal voltage of 117 volts at 60 CPS, or 115 volts at 25 CPS, 119-120 volts does not sound excessive. on top of that I don't think that the Philco model 45 was noted for having a marginal power transformer unlike a brand Z set. While it certainly doesn't harm anything running the set at a lower line voltage, given that the set was worked on in recent years I think that it is just plain common sense to check the quality of their work first if the transformer is running warm. There are a lot of fly by night type "restorers" who will recap a set without even checking the original resistors, will clip and pigtail new parts on the leads of old ones, or even parallel an old part with a new part, not to mention making wiring errors. Unless I know who did the work I assume that something may have been done wrong.
Regards
Arran

[Phlogiston]

Well, see if that makes a difference. My line voltage is 126V. Dropping the primary voltage to 108 made almost a 100V (high Voltage secondary) change on the Zenith 52 I am working on now.

My DVM has no trouble measuring current at 400V, so I break the HV line at the rect and measure the current draw. Sometimes you have to guestimate from the tube guide and add the values up to get an expected total. If your measurement is very far off - 10 or 15 ma high - start looking for a reason.

Be careful.