The Fine Things are Always Hand Made
I have ahd a nice Phantom for 8 years and finally decided to get into it. 46 caps later, it was working quite well on the bench.
Assembled back in Acusticraft cabinet and BANG POP! Off!
I thought the 8 wire speaker cable had shorted internally, but the output transformer seems to be the issue.Tar melted a little and appears to have spewed a bit around the V C leads. SO.... anyone have a good spare?
12" Magnavox, trans number 18653.
I''l look for Sylvania, "green leaf" Triodes for this baby.
I have the same issue with my 16. So far, no luck finding the spiral wound tubes. Different tubes produce different amounts of hum - at least that's what I've found.
The first AF (1st audio audio) tube can be a hum source - as per the Owners Manual. Swap other 6J5's into the 1st AF tube socket. So start there.
Scott evidently was using Sylvania "G" tubes starting late 1930's. But try any other 6J5 tubes you may have.
I had the RF tube cause hum in a Scott Super 12. Filament to cathode leakage can also cause Hum.
Beware, the first audio tube is after the volume control, so pulling that tube will give a loud pop sound regardless of the volume control position. Consider turning off the radio between tubes.
Nice looking Midwest.
I'll try that next time I play with it. Now have a couple tube Hi FI amps to do for someone.
I am out of 6J5 G tubes and they are pricey. Have 6J5 metals but not going to use those, not sure if the case goes to a pin and if said pin is used for a tie point.
I now see an AllWave and a Philharmonic I will bid on Saturday.
6J5's normally have pin 1 connected to the metal shell. You would certainly have to make sure that pin 1 is not used as a tie point other than ground. The audio people have driven up the prices of good 6J5G's.
They sure have. I may actually have some if I look through ALL my tubes. That will take a while. Good winter project to play musical tubes to find the least hum combination. It is so pronounced I am leaning towards a cathode/heater issue as mentioned above.
Suggest you at least try metal 6J5s to see if the hum reduces.
Also, regarding caps replaced, did you dismount these two assemblies inside to replace caps inside:
- the RF diode (back apron) ? and
- the IF diode (between the socket for the 3rd IF and the middle partition ?
Yes I did replace the caps in those cans. Not too difficult. The surprising thing was the resistors were all withing tolerance , except the two that overheated. That's pretty amazing.
I'll get back to the tubes in future.
Those resistors may be casualties of leaking cap(s).
They were a casualty of whatever was shoring the RF stage on the variable cap. (fixed)
So, today I went to an auction all primed for another Scott.
A REALLY nice 16, I bid to $750, went for $770.
A REALLY nice AllWave I bid to $1,500, went for $1,700
A nice Philharmonic with some missing trim I bid to $1,700, went for $2,000.
I REALLY WISH I HAD WON THE ALLWAVE, but chickened out. Usually never spend near that for a radio, and I have a LOT of them.