Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Canadian Philco model 706A Bing Crosby (46-1201
#1

I though that I should mention that this radio is playing now, and quite well, what I wanted to know is if anyone has the schematic and voltage specs for the 46-1201 with a voltage doubler, not the version on Nostalgia Air with the typical AC/DC style half wave rectifier? I have the schematic for the Canadian 706A but the voltages are way off, it pegs the maximum plate voltage at 120 which seems out to lunch, the 48-1201 shows 180 VDC but there are circuit differences, a Pi circuit power supply with resistors for example. The voltage I was getting was almost twice that, no surprise for a voltage doubler, I was getting 210 volts at the screen grid and plate of the 50L6, the maximum rating is 200. As I didn't want to burn up the tubes I tried reducing the size of the filter condensers by half to reduce the B+ voltage and it made no difference, still came out at 210 volts. There was a 90 ohm resistor in series with the plate of the first diode of the 50X6 rectifier, it dropped the input voltage by about 12 volts from 122 to 110 AC, since it was burned a bit I replaced it with a wire wound 225 ohm resistor which dropped the input voltage down to 95 volts AC, now the plate voltage is down to 176 volts DC at the 50L6.
However the plate voltage at the 7C6 first audio/second detector/AVC tube is currently running at 140 volts, while the tube manual says this isn't near the maximum in flicking through my Philco service manuals I could not find another set with that high of a plate voltage on that tube, the closest was maybe in the 100 volt range. It seems that 176-180 volts DC is acceptable for the rest of the tubes as I have found similar voltage ratings in other Philcos for the 7A8 and the 7B7, and it isn't out of line for a 50L6 or 50A5. I'm thinking of installing a larger value of plate resistor in series with the 7C6, perhaps a 470k ohm in place of the 220K ohm. Does anyone have any suggestions?
Best Regards
Arran




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 42-345 Restoration/Repair
Yes, 57 is an electrolytic cap that should be 12 mfd 400 volts according to the parts list from the Phorum library schem...RodB — 06:01 PM
Philco 42-345 Restoration/Repair
Looks like if I am reading it correctly it looks like the silver capacitor#57 that appears to be a replacement is of a l...osanders0311 — 05:09 PM
Philco model 38 code 121 not receiving signal.
Thanks Arran. Yeah this plastic is pretty thin. It's a little thinner than the original stuff. It kinda reminds me of p...Stormlord5500 — 04:37 PM
Testing a speaker and output transformer Trutone A2-G
The equivalent of one short turn is basically the same as that of a shorted load. If it is the primary's turn, then the ...morzh — 03:53 PM
Testing a speaker and output transformer Trutone A2-G
I've never had an output transformer become shorted, the failure mode is usually an open primary, or in a center tapped ...Arran — 03:52 PM
Philco model 38 code 121 not receiving signal.
As long as the plastic sheeting isn't too thick, I think that the thickness of photographic film would be just about rig...Arran — 03:19 PM
Philco model 38 code 121 not receiving signal.
Well why not! :lol:Stormlord5500 — 03:14 PM
Philco model 38 code 121 not receiving signal.
Good luck next thing you know you will be winding coils just for the fun of it. DavidDavid — 11:29 AM
Testing a speaker and output transformer Trutone A2-G
morzh Short-circuited turns can be considered as a half-dead transformer. But on this case transformer will hot and s...Vlad95 — 11:01 AM
Testing a speaker and output transformer Trutone A2-G
I am not sure how a transformer could be weak. It could be inadequate, but only when you replace the original with somet...morzh — 09:56 AM

[-]
Who's Online
There are currently no members online.

>