Hello.
Same cindy. I posted in the past about a power tube for this sparton. It blew and smoked as I was playing with antenna.
Today I moved it out to check things, and spotted some dark spots on my carpet. Appears to be wax. I can't get a measurement on the FC, but it does ohm out. There is also another type of coil of sorts around the speaker magnet. This I am not fimilar with. It too has wax, ohms out for continuity.
Can't read schematic for what size field coil to replace it with, nor what to do with the magnet part.
The FC is covered in a black, either wax or tar, very messy and sticky substance. So I prefer to just replace it. I am sure this is what blew the power tube.
Just need some direction. I have my last 5Y3 to put in this radio. I always use the dim bulb tester, so that is not a problem. Problem is this is new territory for me with this speaker. Any help or directions would be greatly appreciated.
Thanks a million for all the help, now and in the past.

Hi Cindy:

You also have a PushPull output transformer that might be shorted. You can measure it from CT to each end to see if both side measure the same resistance. Also measure each of the 3 leads to ground to be sure there's no shorting to the frame of the transformer.

BTW.. that field coil should measure 800ohms.

If you remove the two 6f6 output tubes when you power on.. you should measure about +250vdc B+ on pin 3 (plate) of the 6F6 tube sockets.

C35 should have had all 3 sections replaced. Has that been done with correct polarity?
I am thinking maybe you did that as you said it died while listening to it.

You can find a better schematic here.... but you'll need a DaJa-VU viewer to read it. You can find that free on the net anywhere.

http://techpreservation.dyndns.org/schematics/manufacturer.htm

:You can find a better schematic here.... but you'll need a DaJa-VU viewer to read it. You can find that free on the net anywhere.
:
:http://techpreservation.dyndns.org/schematics/manufacturer.htm
:
Will get back on it in a couple of days. It was working great. What of the coil around the magnet? All electrolytics were working fine as did radio for quite some time. Thanks for all the info.

Cindy:
You said "All electrolytics were working fine as did radio for quite some time. "
... But that doesn't tell me if they have been replaced with NEW ones.

Old electrolytics may appear to work "fine" while they are actually slowly leaking and getting worse.
So if these are the old original electrolytic filter caps...Replace them.
... that would be MY first likely suspect pulling down your B+ and killing the 5y3 rectifier.

If you haven't replaced these 3 caps.. do it now..
They are the worst possible offenders ....like a time-bomb in your radio.

All the paper/wax caps should be replaced as well.
These are not "optional" considerations.
ALL paper caps by now are leaking to some degree and/or have changed value.

So 1st step is to replace the electrolytic filter caps C35 - A, B & C
Then test. If B+ is ok.. then proceed.
Then replace all paper caps one at a time checking radio play after each cap change.

: Cindy:
:You said "All electrolytics were working fine as did radio for quite some time. "
:... But that doesn't tell me if they have been replaced with NEW ones.
:
:Old electrolytics may appear to work "fine" while they are actually slowly leaking and getting worse.
:So if these are the old original electrolytic filter caps...Replace them.
:... that would be MY first likely suspect pulling down your B+ and killing the 5y3 rectifier.
:
:If you haven't replaced these 3 caps.. do it now..
:They are the worst possible offenders ....like a time-bomb in your radio.
:
:All the paper/wax caps should be replaced as well.
:These are not "optional" considerations.
:ALL paper caps by now are leaking to some degree and/or have changed value.
:
:So 1st step is to replace the electrolytic filter caps C35 - A, B & C
:Then test. If B+ is ok.. then proceed.
:Then replace all paper caps one at a time checking radio play after each cap change.
:
:
:
:
Thanks Peter,
But I have already changed all the electrolytics with new ones, as well as all caps. Those as well as the cord is always my first step. This radio was a curse from the beginning. The lady who bought it for 4.00 said,"You won't have to do anything to this one.".Then she waited months to give it to me. She should have kept the lousy thing.
I do have a degree in electronic engineering technologies. Been some time back. I always worked on computers, DVD and CD players. But since the terrorist act, found it harder to get parts like I used to, since I am not a dealer.
So, since I collect antiques, I decided to restore old radios and phonographs. This is only the second of many restorations, I have had terrible luck with. I will eventually get it, as I most of the time do.
This is one of those that you want to tear down and totally rebuild one step at a time, just to get even with it. BTW the field coil is a disaster. Now to find one that is 800 ohms. Is there also a field coil of sorts on the speaker magnet, or is this just the speaker coil? It is rolled and covered in either a rubber or old cloth tape. It has two heavy wires like the field coil, probably 18 ga. (haven't stripped them to find out yet),that come out of it and attach to the bus where the field coil attaches. I have never seen this set-up before. Clues?

Hi Cindy:
Well there'sd no radio that can't be fixed.. just a little more challenging.. that's all.

It is good that all caps are new!

Now, ...That coil on the speaker should, in fact, be the field coil. Remember these were the days before high quality permanent magnets.. so the field coil was placed over the pole piece in the rear of the speaker to create magnetism to return the speaker cone (attached to the voice coil positioned to float around the pole-piece )to neutral as the voice coil, with its opposing magnetic field, pulled the cone forward more or less with modulation.

If in fact the field coil is shot...
(The old speaker will not operate without the field-coil as an electrodynamic magnet)

So ...You can do any of 3 things:

1. Find another field coil or speaker w/field coil.. or get this one rewound. ( Hank Brazeal in Alabama can do it and farily priced)

2. Replace the field coil with a choke rated for about 8-10 Henries and about 100-120 ma depending on your B+ load... (may be lighter like 60-80ma)..
... you will also need a dropping resistor to compensate for the missing 800 ohms that the field coil presented.. so you can adjust the B+ properly.

3. The easiest and least costly idea ... is to remove the field coil and speaker completely and replace the speaker with a newer style 4-ohm PM (permanent magnet) speaker... and in place of the field coil you should probably use a 1k or 1.2k ohm resistor of sufficient wattage. ( this option would require you to increase the first filter cap to about 20uf and 40-50uf for the next two caps.

:Hi Cindy:
:Well there'sd no radio that can't be fixed.. just a little more challenging.. that's all.
:
:It is good that all caps are new!
:
:Now, ...That coil on the speaker should, in fact, be the field coil. Remember these were the days before high quality permanent magnets.. so the field coil was placed over the pole piece in the rear of the speaker to create magnetism to return the speaker cone (attached to the voice coil positioned to float around the pole-piece )to neutral as the voice coil, with its opposing magnetic field, pulled the cone forward more or less with modulation.
:
:If in fact the field coil is shot...
:(The old speaker will not operate without the field-coil as an electrodynamic magnet)
:
:So ...You can do any of 3 things:
:
:1. Find another field coil or speaker w/field coil.. or get this one rewound. ( Hank Brazeal in Alabama can do it and farily priced)
:
:2. Replace the field coil with a choke rated for about 8-10 Henries and about 100-120 ma depending on your B+ load... (may be lighter like 60-80ma)..
:... you will also need a dropping resistor to compensate for the missing 800 ohms that the field coil presented.. so you can adjust the B+ properly.
:
:3. The easiest and least costly idea ... is to remove the field coil and speaker completely and replace the speaker with a newer style 4-ohm PM (permanent magnet) speaker... and in place of the field coil you should probably use a 1k or 1.2k ohm resistor of sufficient wattage. ( this option would require you to increase the first filter cap to about 20uf and 40-50uf for the next two caps.
:
:
This is exactly what I love about this site. Someone who is willing to share their knowledge and experience. Peter, you just saved this beauty. I will get on this one asap. I printed out the info you just gave me so I can follow it step by step...Thank you so much. You have a great day....