HEC Amps

[Radio Tech]

I have 2 of these HEC amps
Both are mobile.
Built by Built by Holden Electronics CO in Texas
One has 3 tubes model M200D
The other is a small 2 tube amp model M125C

Has anyone ever seen any schematics of either of these amps?

Just for giggles I want to take the M200D out of the mobile case and build it back into a base unit.
Just for the learning process and experimentation of course.
This amp has a 12bq6 driving two 6lf6's

Been a long time since I built an amp. Years ago I built several 2 tube amps using 6lq6, tv tans formers with doubling circuit.

I think it would be fun to revisit and learn this again. But a schematic of the amp would help.

Thanks

 

[Radio Tech]

Found what I was looking.

Holden Electronics Company M-200E

 

[Radio Tech]

Should be an easy build. 700 volts on the plates. Probably can do that with a 350 volt transformer @300 mils with a doubling circuit.
It is grounded grid.
Well, here goes nothing!

 

[Captain Kilowatt]

A 350 volt transformer will give you about 980 volts DC if you use a voltage doubler. Remember the DC voltage is 1.415 times the AC voltage for a simple capacitor type filter and twice that with a voltage doubler.For 700 volts you would need a transformer with an AC output of about 500 volts with a simple filter and only 250 volts with a voltage doubler circuit.

 

[Radio Tech]

A 350 volt transformer will give you about 980 volts DC if you use a voltage doubler. Remember the DC voltage is 1.415 times the AC voltage for a simple capacitor type filter and twice that with a voltage doubler.For 700 volts you would need a transformer with an AC output of about 500 volts with a simple filter and only 250 volts with a voltage doubler circuit.

Correct you are. Thanks for reminding me about the 1.415 formular.
But just thinking here, will have to look at the specks on those tubes again. May be able to get away with 980 volts. Or just find a transformer to handle the 700.

Thanks for the comment.

 

[Radio Tech]

6LF6 Specs

Mechanical Data
Bulb .......................................... T-12
Base .......................................... Duodecar 12-Pin
Maximum Overall Length ...................... 4.950 In.
Maximum Seated Height ....................... 4.570 In.
Maximum Diameter ............................ 1.563 In.
EIA Base ...................................... 12GW
Top Cap ....................................... Small C1-1Electrical Data
Heater Voltage ................................ 6.3 V
Heater Current ................................ 2.0 ADirect Interelectrode Capacitances (approx)
PentodeInput ......................................... 37 pf
Output ........................................ 18.5 pf
Grid to Plate ................................. 3.0 pf
Maximum Ratings (Design Center Values)
PentodePlate Voltage ................................. 990 V
Grid No. 2 Voltage ............................ 275 V
Plate Dissipation ............................. 40 W
Grid No. 2 Dissipation ........................ 9 W
Bulb Temperature (At Hottest Point) ........... 300 °CCharacteristics and Typical Operation
Class A AmplifierPlate Voltage ................................. 160 V
Grid No. 2 Voltage ............................ 160 V
Grid No. 1 Voltage ............................ 0 V
Plate Current ................................. 1400 mA
Grid No. 2 Current ............................ 45 mACharacteristics and Typical Operation
Hortz Defl AmplifierDC Plate Supply Voltage ....................... 990 V
Peak Positive-Pulse Plate Voltage ............. 8000 VDC
Grid No. 3 Voltage ......................... 50 VDC
Grid No. 2 Voltage ......................... 275 V
Peak Negative-Pulse Grid No. 1 Voltage ........ 550 V
Peak Cathode Current .......................... 1400 mA
Plate Dissipation ............................. 40 W

 

[Radio Tech]

Well, found someone that has one of the old phantom 500.
These things has 3 700+ volt transformers in them.
Really to expensive to retube and the power supply board is toast.

So if I can swing this deal I will have a lot of parts.