A Beginner's Journey: The Philco 40-190 - Printable Version
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RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 07-28-2012
Whoops. Yes, part #13, not #1. The coil still has continuity--4.6 ohms (schematic calls for 3.5).
And yes, I'm taking a bit of time off of this project, like about the length of time it takes for my fingerprints to grow back. Or at least the tip of my finger to heal.
If you're familiar with this chassis (and from what I recall, it got around) then you know I'm also at the "tight" end of the chassis where some serious dexterity is required. That being said, I'm still having fun with it and although annoyed, I'm not yet discouraged. I have too many other radios backed up in the stack behind this one to quit now!
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-02-2012
And... been giving it some thought. Took a closer inspection of the dodgy socket that I repaired with the epoxy and have determined that the two layers of tan fiber have warped sufficiently that almost all the pin sockets are loose. This leads me to believe that I will forever have problems with that socket until I give up and replace it.
So... I now have an excuse to go parts shopping up at Spark Museum (formerly American Museum of Radio & Electricity) in Bellingham, WA. The curator (through a friend) informs me that they have plenty of sockets to choose from.
Edison's Law states that I should take the tube that I need to seat with me when I go.
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-17-2012
Tube socket obtained; discovered the magic behind the retaining ring that allows for the socket portion to be rotated to the correct keyhole orientation. Next challenge:
Is there any reason I can't take a couple of screws and nuts to attach the new socket instead of attempting to replace the metal grommets? The only down side to this method is that I will have to drill a hole in the chassis for the grid cap wire. (I'll probably drill it big enough that I can slip a rubber insulating grommet into the hole, ensuring isolation of the 'cap wire.)
RE: A Beginner's Journey: The Philco 40-190 - jerryhawthorne - 08-23-2012
Deck Ape, I have replaced a couple of those dang sockets, not nearly as much as some of the experts but a nice pan head screw coming down from the top or a nylon screw and a nylon nut on the bottom as they get a little close to HV underneath. Most I have done were on rectifier sockets. I find the hardware at ACE.
Jerry
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-27-2012
Found the nylon bits at the local hardware store. Also obtained a grommet for anti-chafing gear for the grid cap wire. Replaced a bunch of components on the power and volume switches, figured out a few differences owing to the 6J8 tube... got as far as the band switch with a rat's nest of rubber wiring and thought, "this has gone well so far... I think I'll stop and tackle that fresh tomorrow."
I figure 2-3 more hours into the chassis and I'll be ready to live dangerously and bring out the variac.
RE: A Beginner's Journey: The Philco 40-190 - TA Forbes - 08-27-2012
The rubber wiring will convince you to specialize in 1930-38 Philcos as I have. That being said, I have a 42-321 that will soon be on the repair table. The unprintable words you may hear from the direction of NC will be me.
Keep up the good work. The 40-190 is an attractive set.
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-28-2012
Thank you for the cheering squad!
I'm on the home stretch now--a couple of awkward bits to get to, aside from replacing that socket. I'm stripping the socket down now, so I can tie up several loose ends inside the chassis. And yes, I broke the repair again (as well as one other pin mount on the same dying socket). I'm understanding the hatred of the rubber wire, but I must say I find the petrified jackets easier to deal with than the gooey ones.
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-28-2012
I think I have it all complete, but something isn't right. put the juice to it via variac and somewhere around 90v started getting small arcs in the rectifier tube. A small curl of smoke came from somewhere under the chassis, so I immediately powered down. Now to investigate WTH...
RE: A Beginner's Journey: The Philco 40-190 - TA Forbes - 08-28-2012
Pull the rectifier and see if the same occurs.
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-29-2012
Okay, I'll do that--after I go back with the schematic in hand and check some values to make sure that I've got the right components. It's a rookie mistake, but I'm a rookie.
...and, with some sort of beginner's luck, find the smoked component.
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-29-2012
Found the smoked component. It was the 150-ohm, 1-watt resistor (#60 on the schematic) which is tied to the negative end of the 12mF cap (#61) and a lug where the 15-ohm resistor (#59) ultimately goes to ground on the bakelite block. It still checks out at 152 ohms, but there is some definite discoloration on the body.
Given the center of the rectifier tube lit up dramatically, it's getting some pretty hefty unauthorized voltage somewhere... I will fire it up again tomorrow without the rectifier tube and see what giveth. I'm sure as heck not dropping my spare 84 into the chassis until I figure out what happened.
(Oh, I'll also ohm out the transformer to see if there are any clues. Something I should've done beforehand, perhaps. D'oh!)
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-30-2012
Checked out the power transformer...
Schematic calls for:
7 ohms @ input (wht/wht), measured 10
>.1 ohm @ ground (blk), measured 1.6
170/180 ohms on the output legs (yel/grn/yel), I measured 130/140
I'm spelling it out in case I did something not-quite-right. These measurements are with the rectifier out...
AND...
Another rookie mistake. I also forgot to check the windings on the output transformer. Gives the impression of being open on all counts. Dead, dead, brown bread. I suspect this is why I had the problems I had... I guess my next step(s) are to check the other chassis to see if, against odds, my transformers there are viable/closer to spec, or to start looking for replacements.
Any advice, coaches?
RE: A Beginner's Journey: The Philco 40-190 - Ron Ramirez - 08-30-2012
I would say 90% or better of the 1939-1942 Philco sets with audio output transformers under the chassis have bad audio output transformers.
However, an open audio output tranny should not cause your rectifier to put on a light show.
RE: A Beginner's Journey: The Philco 40-190 - DeckApe - 08-30-2012
After a day of ignoring the radio altogether ('Ramirez Helpful Hint #4--if it's not going well, set it down and walk away for a couple of days; you'll see the problem when you come back'), I started tracing the schematic. Part #44, 10Mohm resistor (which, as a result of the jolt, now measures at about 17Mohm) leads to a joint where a black wire comes to the joint between the 150 and 15 ohm resistors (60 &59); nearby is a bare wire off the rectifier that joins the blue and white trace from the speaker before going to the positive side of the 12mfd cap.
I crossed 'em, and I bet that's got a LOT to do with where all H**l broke loose. I'll also probably do some more tracing and verifying before I juice it up again, replacing all smoked resistors while I do so. (I figured this out between the schematic and the handy reference chassis. Interestingly enough, that 10Mohm resistor is nowhere to be found on my 40-190.)
Now to find if the Hammond 125E worked for another Philco Phan before ordering it as a replacement output transformer.
STILL NOT DISCOURAGED!
RE: A Beginner's Journey: The Philco 40-190 - codefox1 - 08-30-2012
Over a hundred posts. Hope some of us are still alive when set get's fixed. Any old output transformer should work OK.