battery op. Fairbanks Morse chassis #72..dry vs wet caps

7/26/2009 11:05:43 PMG. Berg ..help please..

Hi all...This set (Fairbanks Morse cahssis 72) uses a 6v battery to run the entire thing. It has a "power pack" with a vibrator and two VERY large "dry" caps. One cap is 35mf & 35mf @ 150 other is 1000mf @ 6v. MY QUESTION IS...: Can I replace these using wet elctro. caps... (I have made for first section a block of wet electro. caps 47mf & 47 mf at 160V and other section I have 990mf at 50v...) Would this be ok? Also on schematic they are C34,C35, C36. THANKS FOR ANY HELP..I gues my real question is ...Can I use "wet" caps for this since it uses a vibrator mechanism?

7/27/2009 12:35:04 AMEdd

Sir Gee Berg. . . .

In all of the references here on site the FM Chassis 72 and even a later 72 with additional alphabetical suffixes, I am seeing nothing but an AC line powered chassis circa '37 ? on the first one and somewhat of a later time frame on the 72 alpha numerical numbered series of three.

With no like referencing to your given capacitor number series.

Could your unit be using an adaptive add on power supply with the use of merely a vibrator transformer , a few caps and resistors and being mainly dependant upon a synchronous vibrator.

Therein that design would would require no rectifier tube and only the B+ filter caps mentioned. . . .however those values seem
a bit high in their capacitance value for those olden times, but also quite low in voltage value rating.

The only logical one might be the 1000 ufd @ 6V for filter / decoupling the 6V filament supply. I would certainly like to see its casing SIZE, if it is a common paper capacitor .

Your mentioned, selected replacements are what we call "dry" electrolytic caps. . .actually moist inside...as compared to the
first generation of electrolytics which actually had an electrode inside surrounded with wet electrolyte.

Otherwise your selective types and values seem all right . . . pending our really needing to see a schematic for the unit.

73's de Edd

7/27/2009 12:50:59 AMG. berg OHH good god I am half awake!!! Sorry Ed....I meant Montgomer Ward model 62-374

OOOOPS ..the radio I am working on is a Montgomery Wards model 62-374....GEEZ my bad....Sorry Ed

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:Sir Gee Berg. . . .
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:In all of the references here on site the FM Chassis 72 and even a later 72 with additional alphabetical suffixes, I am seeing nothing but an AC line powered chassis circa '37 ? on the first one and somewhat of a later time frame on the 72 alpha numerical numbered series of three.
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:With no like referencing to your given capacitor number series.
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:Could your unit be using an adaptive add on power supply with the use of merely a vibrator transformer , a few caps and resistors and being mainly dependant upon a synchronous vibrator.
:
:Therein that design would would require no rectifier tube and only the B+ filter caps mentioned. . . .however those values seem
:a bit high in their capacitance value for those olden times, but also quite low in voltage value rating.
:
:The only logical one might be the 1000 ufd @ 6V for filter / decoupling the 6V filament supply. I would certainly like to see its casing SIZE, if it is a common paper capacitor .
:
:Your mentioned, selected replacements are what we call "dry" electrolytic caps. . .actually moist inside...as compared to the
: first generation of electrolytics which actually had an electrode inside surrounded with wet electrolyte.
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:
:Otherwise your selective types and values seem all right . . . pending our really needing to see a schematic for the unit.
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:73's de Edd
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7/27/2009 1:41:05 AMEdd

Sir Gee Berg. . . .

Indeed that circuit is exactly as I expected the FM to be if it should have been it. And the cap values that you selected should be fine.

The only difference from what I had initially mentioned, was of the filament supply having to be dropped down to 2VDC via the series inserted 4.95 ohm filament dropping resistor . . . R20 and THEN being filtered by the 1000 ufd unit. Now do note that it is filtering the negative buss, so be sure to note that its POSITIVE lead gets installed to ground. ( Eeeewwwww. . . . . those tubes filaments certainly are power gobblers as compared to the two upcoming series of battery tubes to later follow them. )

Standard hook up procedure on the pi section network filter B+ capacitors, with their negatives going to ground.

THASSIT. . . . now go to bed. . . .ha ha

73's de Edd

7/27/2009 4:49:57 AMG. berg.. THANKS Ed....(77108:77105)

I had 6V 1000mf cap hooked up backwards....Re-did it thanks to you..THANKS...Almost missed that...

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:Sir Gee Berg. . . .
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:Indeed that circuit is exactly as I expected the FM to be if it should have been it. And the cap values that you selected should be fine.
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:The only difference from what I had initially mentioned, was of the filament supply having to be dropped down to 2VDC via the series inserted 4.95 ohm filament dropping resistor . . . R20 and THEN being filtered by the 1000 ufd unit. Now do note that it is filtering the negative buss, so be sure to note that its POSITIVE lead gets installed to ground. ( Eeeewwwww. . . . . those tubes filaments certainly are power gobblers as compared to the two upcoming series of battery tubes to later follow them. )
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:Standard hook up procedure on the pi section network filter B+ capacitors, with their negatives going to ground.
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:THASSIT. . . . now go to bed. . . .ha ha
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:73's de Edd
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7/29/2009 3:56:44 PMG. Berg(77211:77108)

Got this 1938 Airline (Montgomer Wards) model 63-374 6v set up and running....Neat how you can use ONLY a 6v battery to run the set....coools

I had 6V 1000mf cap hooked up backwards....Re-did it thanks to you..THANKS...Almost missed that...
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::Sir Gee Berg. . . .
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::Indeed that circuit is exactly as I expected the FM to be if it should have been it. And the cap values that you selected should be fine.
::
::
::The only difference from what I had initially mentioned, was of the filament supply having to be dropped down to 2VDC via the series inserted 4.95 ohm filament dropping resistor . . . R20 and THEN being filtered by the 1000 ufd unit. Now do note that it is filtering the negative buss, so be sure to note that its POSITIVE lead gets installed to ground. ( Eeeewwwww. . . . . those tubes filaments certainly are power gobblers as compared to the two upcoming series of battery tubes to later follow them. )
::
::
::Standard hook up procedure on the pi section network filter B+ capacitors, with their negatives going to ground.
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::THASSIT. . . . now go to bed. . . .ha ha
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::73's de Edd
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