"230v drop across 7560 ohms gets me close to 6 watts across the array. So 10 watters will be good. Nice catch on that noted 25v drop across two different values!
Factor in a +/- 20 % tolerance and im fine. Thanks for the input."
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Randy Rago's Discussions
Part # 1445, voltage divider network
Started this discussion. Last reply by Randy Rago on Sunday. 5 Replies 0 Likes
Or if in the Zenith world, a "Candohm". In the masterpiece, its 3825; 980; 780; 1975 ohms. Im replacing it with discreet power resistors. 5 or 10 watters?
Masterpiece / Super XII overlap? transitional?
Started this discussion. Last reply by David C. Poland on Friday. 8 Replies 0 Likes
My Masterpiece has a dual 10Uf / 350v can, one cap in the G2/Cathode bias circuit of the first audio 6K7 and the other cap in what appears to be 3rd grid/plate circuits of all tubes. This…Continue
Masterpiece repair project
Started this discussion. Last reply by Randy Rago Nov 8. 35 Replies 0 Likes
I'm a member / restorer at the Asheville Radio Museum avlradiomusem.org and recently connected with a customer asking to restore a relative's Sott Masterpiece.Been in the tube radio fixin' hobby…Continue
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"They wattage can be calculated via Ohm's law and the power formula. However, to shortcut those calculations, if you make each a 5W unit, you should be ok. Making the big one (3825) a 10W unit would be prudent. I never noticed the schematic…"
"Nevermind, did the math. 6 watts, using 10 watters"
"I know, but thers no rating on the schematic. Or is a parts list published? Thx"
"Yes those Candohm resistors always seem to fail despite their apparent rugged appearance in many other radios. For durability it’s always wise to choose replacement resistors with an increased wattage rating."
Part # 1445, voltage divider network
Or if in the Zenith world, a "Candohm". In the masterpiece, its 3825; 980; 780; 1975 ohms. Im replacing it with discreet power resistors. 5 or 10 watters?
"Randy - A Scott Masterpiece is identified (compared to a Super 12):
- total of 14 tubes on the 2 chassis: 11 including the eye tube on the receiver and 3 on the power supply..
-absence of out put 6V6's on the receiver chassis - they were moved…"
"Tale to share. Some years ago I would work on tube radios over the winter. One of the more involved sets was a Hallicrafters SX28A which I did for someone.
The radio has never seen a malicious soldering iron in it’s life but due to the…"
"Me to, George. All caps done. Working through resistors now"
"Randy, and this is a general rule I’ve worked by in the past in my employment, all passive components are suspect and should be inspected one by one. I used to work at a military contractor many years ago and it was this same approach we used…"
"Ill reply to George and Kent first. Yes this cap can is a period piece, original cloth wiring and all. Maybe my description was wacky, but the sections share a common neg.
BTW, gotta love the cap symbols, looked like rectifiers on the schem.…"
"Scott used the 6K7-G an Audio stage tube, with the caution in the Phantom Tech Service Manual, page 5, that the tube needs a spiral filament heater to minimize hum issues.
If a hum issue, try a Sylvania 6K7-G, probably with the green print on the…"
"I agree with George - do the solder joints appear original? Is the component a period unit? If it was replaced, I would not trust it being factory spec.
As to the chicken and egg: The Super XII comes first, produced in 1938 and up through July…"
"Screen to Cathode bypass cap in a 6K7 first audio? That sounds very unusual since 6K7 tubes are variable-Mu and not generally suitable for audio only (which typically use straight-Mu gain tubes).
If it's a dual cap there usually is a common…"
Masterpiece / Super XII overlap? transitional?
My Masterpiece has a dual 10Uf / 350v can, one cap in the G2/Cathode bias circuit of the first audio 6K7 and the other cap in what appears to be 3rd grid/plate circuits of all tubes. This configuration does not appear in the masterpiece schematic but does appear on the super XII schematic. Which came first the chicken or the egg? Haha
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