Does anyone have a schematic for this device?
I have an old General Electronic Dist. Model 200 Signal Generator that does not work. There is no filament lit on either of 6C4 or 12AU7 tubes. There is an 80 ohm resistor in parallel with the 6C4 filament pins 3 & 4. There is no other wire connecting to pin 3. There appears to have been a lead soldered to it but it was either cut off or broke.
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:Does anyone have a schematic for this device?
:Try bama.sbc.edu
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:I have an old General Electronic Dist. Model 200 Signal Generator that does not work. There is no filament lit on either of 6C4 or 12AU7 tubes. There is an 80 ohm resistor in parallel with the 6C4 filament pins 3 & 4. There is no other wire connecting to pin 3. There appears to have been a lead soldered to it but it was either cut off or broke.
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::Does anyone have a schematic for this device?
F a a a a t chance on schematic availability. . .
on that "well known and highly popular" unit , but possibly, with the unit only missing its filament supply…
how’s about these considerations.
Firstly. . . . . that the unit is utilizing a transformer in its power supply design and then the use of either a selenium rectifier or a silicon diode for its rectifier for B+ production, the latter if of newer vintage.
That covers the B+ aspect, with the 12AU7 tube serving for AF oscillator and modulator tube …most likely… and then the 6C4 being the RF oscillator medium.
The filament supply would be a no brainer IF the filament supply was merely to be 6.3 VAC wherein
that 6.3 was used so that the 12AU7 could be ran using 6.3VAC @ 300 ma and the 6.3 VAC @ 150 ma be paralleled so that both of the tubes are using 6.3VAC @ 450 ma.
BUT
now with you mentioning that the 6C4 had 80 ohms of resistance shunting it, that suggests of them wanting to get the current consumption of the combo upward in order to be able to then connect the parallel pair in series with a higher than 150 ma drain such as the 6C4 is consuming alone. With that shunting value of 80 ohms that would develop a total series current of ~228 ma with that additional series element. Now, a thing that comes to mind, is a series pilot lamp, but if that was the case in the utilization of a common 150 ma 6.3VAC lamp as the 47 / 1847, that would require an additional shunting resistor across that lamp in order to then place it in series. OTHERWISE they would have merely placed the 6C4. . . 6.3VAC @ 150 ma tube in series with a 6.3 @150 MA lamp.
So now the poser. . . . .why the 80 ohm shunt across the 6C4.. . possibly if in series with a 150 MA pilot lamp, to drop the voltage a bit for thermal stability of the oscillator tube ?
So if the part on the power transformer is holding true, they just might be using a 12.6 VAC filament winding on the transformer vice the norm of a 6.3 VAC winding . I have certainly seen Heath and Eico using that filament supply voltage.
You should be able to track down the filament winding (hopefully green wiring coding) coming from the power transformer and then measure and resolve the question as to the amount of AC voltage present and see which of those two filament connections get routed on over to the 12AU7 (Pins 4-5-9) and the 6C4 (Pins3-4) filament connections. Any feed back on the connections would help ascertain if the idea was for the 12AU7 to be operated at 12.6VAC @ 150 ma with a series connection or 6.3VAC @300 ma with its filament sections paralleled. That would then give some idea on the 6C4’s manner of connection.
Specifically. . . be looking for wiring interconnects between the 6C4 and the 12AU7 filament connection pins.
Give us some feedback…as it seems that all that might be needed to get a working unit again is to restore the filament circuitry.
73's de Edd
ACin -> Power_switch -> 12AU7_pin-9 -> 12AU7_pins-4&5(parallel) -> 6C4_pin-4&80-Ohm_resistor -> 6C4_pin-3&other_end_of_80-Ohm_resistor -> nowhere.
It looks like there is a missing component from 6C4_pin-4 to the other side of ACin@6C4_pins-5&6.
It seems to me that this type of circuit would not be very efficient, although cheap. If the filament path is running at 300ma, 120Vac - 6.3Vac - 6.3Vac = 107.4Vac * .3A = 32Watts!
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:F a a a a t chance on schematic availability. . .
:on that "well known and highly popular" unit , but possibly, with the unit only missing its filament supply…
:how’s about these considerations.
:
:Firstly. . . . . that the unit is utilizing a transformer in its power supply design and then the use of either a selenium rectifier or a silicon diode for its rectifier for B+ production, the latter if of newer vintage.
:That covers the B+ aspect, with the 12AU7 tube serving for AF oscillator and modulator tube …most likely… and then the 6C4 being the RF oscillator medium.
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:The filament supply would be a no brainer IF the filament supply was merely to be 6.3 VAC wherein
:that 6.3 was used so that the 12AU7 could be ran using 6.3VAC @ 300 ma and the 6.3 VAC @ 150 ma be paralleled so that both of the tubes are using 6.3VAC @ 450 ma.
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: BUT
: now with you mentioning that the 6C4 had 80 ohms of resistance shunting it, that suggests of them wanting to get the current consumption of the combo upward in order to be able to then connect the parallel pair in series with a higher than 150 ma drain such as the 6C4 is consuming alone. With that shunting value of 80 ohms that would develop a total series current of ~228 ma with that additional series element. Now, a thing that comes to mind, is a series pilot lamp, but if that was the case in the utilization of a common 150 ma 6.3VAC lamp as the 47 / 1847, that would require an additional shunting resistor across that lamp in order to then place it in series. OTHERWISE they would have merely placed the 6C4. . . 6.3VAC @ 150 ma tube in series with a 6.3 @150 MA lamp.
:
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:So now the poser. . . . .why the 80 ohm shunt across the 6C4.. . possibly if in series with a 150 MA pilot lamp, to drop the voltage a bit for thermal stability of the oscillator tube ?
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:So if the part on the power transformer is holding true, they just might be using a 12.6 VAC filament winding on the transformer vice the norm of a 6.3 VAC winding . I have certainly seen Heath and Eico using that filament supply voltage.
:
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:You should be able to track down the filament winding (hopefully green wiring coding) coming from the power transformer and then measure and resolve the question as to the amount of AC voltage present and see which of those two filament connections get routed on over to the 12AU7 (Pins 4-5-9) and the 6C4 (Pins3-4) filament connections. Any feed back on the connections would help ascertain if the idea was for the 12AU7 to be operated at 12.6VAC @ 150 ma with a series connection or 6.3VAC @300 ma with its filament sections paralleled. That would then give some idea on the 6C4’s manner of connection.
:
: Specifically. . . be looking for wiring interconnects between the 6C4 and the 12AU7 filament connection pins.
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:Give us some feedback…as it seems that all that might be needed to get a working unit again is to restore the filament circuitry.
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:73's de Edd
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With your full clarification on the additional wiring. . . .now, that sounds just like the type of test equipment that one would not
want to be using in servicing…….with its incorporation of a HOT
Chassis. . . . no less.
If that was my unit, and problem to solve, I would already be installing two back to back filament transformers as is shown on the accompanying thumbnail. Thus, solving the filament supply problem and additionally providing AC line isolation of the instrument.
73's de Edd