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Dragging out an old nemisis-Philco 66 cathedral-SUCCESS - Printable Version

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RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-14-2014

I used my AllSun socket tester to see if the socket was correctly wired, and it was. I used the Klein MM200 to test the AC voltage at the socket and at the variac, and I got within decimals of 121 at both sockets. Voltage across transformer primary with the radio power switch on was 109v and across the filament of the 80 with no tube in was 5v.

The voltage at the house mains was the same with both DMMs.

RE: Dragging out an old nemisis-Philco 66 cathedral - morzh - 08-14-2014

Could your power switch be dirty?

RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-14-2014

Possibly, I could try to clean it. It is a replacement from Playthings of the Past, and I just put it on without opening it up. Come to think of it, it may not open. It is a Mallory replacement (the Mallory replacement book listed it as the one that goes in a 66).
It's an inefficient way to go about things, but I'm going to make a tube map (pin numbers and their connections on the schematic for each tube) and just go tube-by-tube checking the map. I'm still thinking I have the grounding wrong on the daughterboard. Those three or for caps/resistors on the daughterboard that are connected to each other at their grounded ends (on my 66, there was a single wire that ran to all of them and then to one end of C13). Where do they ground on yours?

Also, I have C50 (the two filter caps) grounded at C51, and I have C49 grounded on the chassis at the ground terminal attached to the 6A7 where the 20K resistor they added in the service notes is attached.

I think I need to rest it the rest of this evening and get a fresh start tomorrow. I'll make the map tonight, check it tomorrow and then go work on the chassis. Thanks for the help.

RE: Dragging out an old nemisis-Philco 66 cathedral - Mondial - 08-14-2014

Are you making your voltage measurements with the dim bulb in the AC circuit, or with line voltage applied directly to the set?

If you have the bulb connected in series, all the voltage measurements will be low to some extent.

RE: Dragging out an old nemisis-Philco 66 cathedral - morzh - 08-14-2014

(wow...dod not even occur to me this could be possible Icon_lol )

Not only the measurements would be low but the actual voltages too! Icon_lol

RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-14-2014

Good to know. I'd sort of like to keep it in the line for now, until I sort out the other problem. At least this way, I have some warning if I'm cooking the transformer. By the way, yesterday, I heard some low volume static after I redid the filter circuit. Today, not so much, but the dim bulb has a bit more glow to it than it did before.
One good thing about working on radios: if the electronics aren't working for me, I can always go out to the garage and do cabinet work. I've been stripping two small cabinets since I posted last, and I feel pretty good about it. 5050 Lacquer thinner and acetone, some gloves and elbow grease and the Crosley 66TC and the Air King 4604A cabinets look much better without all those cracks, scratches, and ugly on them. I may finish stripping them tonight, and do some veneer repair tomorrow. Stain and let them sit for 48. Makes me feel good to see positive results. That Air King was ugly. I kind of like it now.

RE: Dragging out an old nemisis-Philco 66 cathedral - morzh - 08-14-2014

You need to disconnect the lamp and plug it directly to measure voltages.
Do you understand why?

RE: Dragging out an old nemisis-Philco 66 cathedral - TV MAN - 08-16-2014

Get the bulb outta there. Use a 1 - 1.5a or so fuse if you are worried about the trans. The bulb is mainly for checking for shorts, initial power ups and so on. It is a big fat resistor in your line cord. Get proper power to the set and see what you get.

Fyi, I have seen a lot of goofy things pass in power /audio output transformers over the years. Anything can happen in 70-80 year old electronic parts!

RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-17-2014

Point taken from both of you. I've had the fates conspire to keep me out of the workroom for a couple of days, but I got in for 30 minutes today. Before I take off the training wheels and get rid of the apparatus, I wanted to double check my reading of the schematic. I went tube-by-tube looking from radio to schematic-to tube manual looking for errors in wiring because the thing that kept me using the dim bulb was a glow coming from the bulb about 60 seconds after startup. I am still concerned that my grounding is done correctly, but I did find a rather embarrassing mistake at C40. I had transposed the connections for the 75 grid cap and C42 & R43. I had them backwards. I fixed it, and I desoldered a few sketchy solders I had done, started it up and had a momentary squeal, then nothing. I turned the volume switch and get a bit of static as it moves, but nothing from the tuning cap turning. Touching the soldering iron to the caps of the 75 and the 6A7 give a respectable buzz, on the 78, a softer one. Touching the volume switch gets a loud buzz, too. I don't have time for voltages today (without the 40 watt bulb stealing voltage), but I should have a new set of numbers by tomorrow. Am I right in thinking that my output stage issues might be almost over here and I can start working on getting the 6A7 to oscillate? Voltages first, though. Thanks for the help. And the patience.

RE: Dragging out an old nemisis-Philco 66 cathedral - morzh - 08-17-2014

See if you

1. Have all your tube shields in.
2. The 75 tube's shield should have the grid cap wire INSIDE it.
3. The bulb glows first more due to inrush, which has several parts to it, the slowest (others last last than a second) being the large current shooting through cold filaments before they warm up.

RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-17-2014

Morzh, about those three components on the daughterboard that have their grounded sides tied together (on my set, it was C27, R45, C46, and C42 that had a single lead that tied them all together and grounded them on end of C13), they just ground to the chassis, right?

Also, one more ignorant question: the grid cap of the 6A7 connects to the side of the tuning gang near the FRONT of the chassis (by the volume pot) or to the BACK of the chassis near the 6A7? My work-in-progress understanding of the schematic is that it connects to the front terminal, yeah?

спасибо

RE: Dragging out an old nemisis-Philco 66 cathedral - morzh - 08-17-2014

I am not at home, I am in FL.

whatever is grounded is to the chassis, one way or another. i had to rewire some of the daughterboard as it was recapped in an ugly way.

as for 6A7 grid cap, as I remember, it goes to the tuning cap section that is in front closer to the knob.

RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-17-2014

Great. I think I'm in the part where I get out the signal generator, now. I'll post voltages tomorrow, but the set is doing all the things my "Elements" book says it should to rule out the output stage, now. Still no signal even if I put an antenna on the grid cap of the 6A7.

RE: Dragging out an old nemisis-Philco 66 cathedral - morzh - 08-18-2014

Yep, it's ripe for sig gen.

RE: Dragging out an old nemisis-Philco 66 cathedral - ccomer1955 - 08-18-2014

C17, C19, C22, C24, and C13 have been messed with pretty severely. When I got the set, they were screwed down tight, so I backed them all off just a bit, but I'll be having to find the IF from scratch. Start with the grid cap of the 75 and the first two trimmers, then move to the grid cap of the 6A7 and the other two trimmers, and finally try to find 600KC with C13? Assuming the 6A7 is oscillating at some point. I can move my Philco 42-340 into the workroom and see if I can hear oscillation, first. Any advice here is appreciated.