[Radioroslyn]

The latest is that I found that the 700mmfd cap placement is some what critical. I had close to the chassis and the 76 socket. Pulling it up and away helped a good deal. As it stands now everything is working ok w/the exception of the low end of band 5. The catch is that the line voltage thru the variac is abt 127 and my line is abt 113volts. Could just be the season w/the air conditioners running and such. Will probe in to it some more.
Did bake the sw coil. It looked ok and resistances were good too and clean the band switch again after giving a spray job. Just the spray was pretty worthless. Scrub it with a tooth brush and used 2doz qtips/MEK. That got it much cleaner. I was worried about the crud between the contacts along with contacts.
Redid the osc alignment and it went well on bands 1-4. BC band is within 10kc and the sw bands are within abt 30kc which is quite exceptable.

Gonna take a break from this thing and watch one of the favorite Brit noir movies https://www.youtube.com/watch?v=-zBrdZZTbGg  Lots angling players here out for themselves. A few table sets but a little hard to make out. Lots of views of London from 1950.

[EdHolland]

Thanks for the film recommendation

Interesting that the relatively minor changes brought dial calibration back closer to line. Might play with that on my set.

[Radioroslyn]

So guess what's back on the bench??
I had it back together and playing well but it did have a few bad habits that need some looking into. I made the ultimate decision to install a Philco speaker plug and socket. On the tombstone sets with the 10" spkr the top lip of the basket fits into a narrow cove at the top front edge of the cabinet. Both of the cabinets I have were close to firewood and the tops were apart. Now it could have been when I rebuilt the cabinet I didn't realize that was an important gap. Meaning that I might have clamped the top center section a little too tight so fitting the speaker is a little difficult. Add to that having the chassis hanging half in and half out of the cabinet makes it a bit of a chore.

I scared up the spares to make the improvement to find a couple of things. It's not a drop in replacement. The mounting holes in the socket are about 3/16" further apart vs the holes in the chassis. Do to the position of the mounting holes the flat on the plug will be on a diagonal vs parallel to the bottom edge of the chassis unless you redrill them.

As for the wiring from what I can tell a number of the P/P speakers have the same wiring. This would include 116X, 116B, 660, 200X, and 201X. So if you look at the socket and start with small pin. Call it #1 it's one of the 42's plate connection. In Philco speak it the white wire. Going clockwise #2 connects to the field coil/center tap of the output transformer. White/green wire. #3 connects to the lone field coil connection. White/blue wire. #4 connects to the other 42 plate. Green wire.

I would love to say I plugged it in and it worked dandy! But this **** thing has a rebellious mind of it's own and has developed a short in the hv line. The good new is I think I've come up with a couple more solutions for the lo problem. More later.

[Radioroslyn]

After replacing the speaker socket again (seemed like in had an internal short).  The hv came up for a few seconds and died. Problem is hv feed off of the field coil was showing a short of 2.3 ohm to ground.
The way the power supply is designed the hv is split into two parts. One side comes off the rectifier tube and into the filter choke. In turn that leg powers the output stage. The other the choke is connected to the field coil and field coil leg feeds all of the low level circuits. The leg off of the choke was at 265 or so.
Did find a couple of possibles in that giggling the wiring cause it to be intermittent. Started disconnecting wires to see if I could find it and guess where I ended up??? 2nd IF transformer[Image: https://philcoradio.com/phorum/images/sm...wisted.gif]. It came back to bite me! I didn't replace it back when it smoked the resistor. The resistor was fine this go around but it had a good shadow meter coil in parallel with it. Tomorrow I'll be pulling pigtales on the replacement ift and installing it.

[morzh]

Oh...don't grumble, you are having fun.

[Radioroslyn]

Mike, Methinks you have it backwards! I fix these confounded things so I have something to grumble about. [Image: https://philcoradio.com/phorum/images/sm...on_eek.gif] I used to be nice but now I'm turning in to a curmudgeon.[Image: https://philcoradio.com/phorum/images/sm...lleyes.gif]

Back to the grind.
Oh I should edit my remark about the speaker plug fitment. If you use one from a model 20 it's a good match in that it can be mounted so the flat is parallel to the bottom of the chassis. Will need to shave a little off as it will hit the qavc control. Plus elongate the screw holes. The 1st attempt was with a socket from a 116 chassis. That one will mount cockeyed.

Swapped out the 2nd IF transformer and the set was dead as a door nail. Well the audio was working but no mixer or IF. GRRRRRR[Image: https://philcoradio.com/phorum/images/sm...n_evil.gif] After some troubleshooting I found that was no hv on the plate of the 2nd IF amp (kill me now!!!) [Image: https://philcoradio.com/phorum/images/sm...wisted.gif] Bart measured the coil to find it was OK. [Image: https://philcoradio.com/phorum/images/sm...n_clap.gif] While I was digging around in the chassis I noticed that there was two blocks I neglected to restuff. One was the grid bypass on the qavc tube which doesn't seem all that important. If it was a dead short the avc line would "see" it thru the 4M resistor. Not that much of a big of a deal. The other was a dual .05. One section is the cathode bypass the the 2nd IF amp. Still not a bid deal as the cathode is fairly close to ground anyway. The other section was the plate bypass for 2nd IF amp. Now were getting somewhere.

Both blocks got new cap inside. I did take note that there was only wire connected to the plate bypass cap. Thought that the b+ must be connected to the coil but that wasn't the case. The wire was missing! Put a jumper over to b+ and it sprang to life! I'm not sure where the wire went but it may have been part of the wiring that was added when the Ktran transformer was added as a replacement. If so the wiring incorrect in that the 2nd IF amp was getting it's b+ from the wrong side of the shadowmeter.

Back to the original problem. Intermittent short in the 2nd IF transformer. I found the problem. There was a dinky fleck of solder that attached itself the mounting bracket (chassis ground) and was a few microns from the hv terminal at the base of the transformer. That problem is solved.

Did a few ancillary things cloth line cord, pop the bakelite grommet back in, align IF, and adjust shadowmeter. It's playing and sounds good. Have put it back in the cabinet for the acid test.

[morzh]

Gosh, Terry,

You did more things to it than there are parts in it

[Radioroslyn]

Managed to sort that pesky band 4/5 oscillator issue. It was driving me nutz!
After chatting with some folks here who have '40-'42 sets with failing oscillators I got thinking about the circuit. The hv is fed the the plate thru a 50 or 25k resistor. Perhaps this resistor is a compromise between having a proper plate load vs enough voltage to power the plate. Originally the design used a 50k and then it was lowered to 25k for "more reliable operation". More voltage but lower load resistance. Maybe a better component would be a rf choke. This would offer a high impedance load for the plate and very little voltage drop. Understanding that Philco was pinching every penny for a low price and profit. Choke might be another 20c over a resistor.
Grab a 2.5Mh choke and installed it and it worked!!! For about 2 minutes and started back to no signal below 6.8mc. GRRRRRR this set is such a tease.
Started back looking at the diagram and I noticed something curious. It has two separate grid leak resistors, one for the bc/pb with a 1000mmfd cap in parallel with it. The second one is for the three sw bands. Both are 10,000 ohms. All of the parts around the 76 osc tube I've check or replaced. I looked over the chassis and #18 is nowhere to be found! Solder in a new #18 and it's working dandy! I suspect that this set may have been built on a Fri or Mon. There is no alignment point at the low end of band 4 or 5 it could have easily gone unnoticed. Now the really curious thing is the 2nd 16B doesn't have that resistor in it either!

Time to put my feet up on the ottoman and relax. Enjoy the pleasant sounds of the 16B.

[Scott D]

Interesting. It seems far too many of the Philcos may have been made on Fridays or Mondays. LOL Thanks for sharing your fix. I may need someday.