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Burnedfingers 22nd November 2008 11:50 AM

Hewlet Packard transformer
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Does anyone have any information on a #9100-0082 transformer?

I am looking for ratings and wire code.

It has a pair of green 6.3 volts?

a pair of gray

a pair of brown

a pair of yellow 5volts?

a pair of red with a red/yellow which has to be HV

a blk, blk/yellow, blk/red, blk green

Burnedfingers 22nd November 2008 11:53 AM

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another shot

Burnedfingers 22nd November 2008 11:56 AM

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last picture

unit bolts up to a blank Dynaco stereo chassis and as you can see it is quite a bit taller than the Dynaco transformer.

Now, how to figure what the hell it is and if it would work to build another amp.

Ty_Bower 22nd November 2008 12:47 PM

I've found the information in this thread to be useful when attempting to identify mystery power transformers:

Burnedfingers 22nd November 2008 06:12 PM

Ok my secondaries measure 21.6 ohms each or 43.2 across.

The secondary output is 830 with no load.

Would this give me about 400 volts out at about 275mA with cap input and 380mA with choke input?

Tom Bavis 22nd November 2008 11:57 PM

I would estimate current ratings of about 250 mA cap / 350 mA choke from your resistance readings.

Download the free PSU designer program from to estimate the output voltage with your rectifier of choice.

HollowState 23rd November 2008 03:55 AM

Re: Hewlet Packard transformer
2 Attachment(s)

Originally posted by burnedfingers
Does anyone have any information on a #9100-0082 transformer? I am looking for ratings and wire code.
I took a look through my old HP manuals and found the instrument your transformer was used in. It's from the type 738B AC/DC calibrator. This was essentially a well regulated DC supply with a 400~ oscillator and a power amplifier that used a pair of 6550s in PP with up to 300 volts output. It's a nice transformer. But I think the estimate of 350mA w/choke input is too much. Also, the unregulated DC out was 440V and was on the 6550 plates.

Tube compliment:
2) 6550
1) 12AU7
4) 12AX7
1) 6BA6
1) 6CL6
1) 6AU6
1) 6AV5GA
1) 5U4GB
1) 5651A


I am looking for ratings and wire code.
a pair of green...............6.3V for 2/6550, 12AU7, 12AX7, 6BA6

a pair of gray.................6.3V for 6AU6, 6CL6, 12AX7

a pair of brown...............6.3V for 6AV5GA, 2/12AX7 (regulator/elevated)

a pair of yellow 5volts?....yes

a pair of red with a red/yellow which has to be HV...yes

a blk, blk/yellow.............115V

blk/red, blk green...........115V

blk+blk/red....................230V (blk/yel & blk/grn tied together)

Burnedfingers 23rd November 2008 11:25 AM

Thanks for the info.

Do you think I can use it for a Dynaco clone project?

I'm missing the bias winding so can I use a voltage divider off one leg of the AC then rectify it to come up with my B- and then go to my bias pots?

Tekko 23rd November 2008 12:03 PM

Yes you can.

kevinkr 23rd November 2008 03:02 PM

The voltage regulator is quite an interesting design as well, better than my long ago efforts using differential error amplifiers in that it should have a lot more open loop gain. I'm inclined to investigate further.. Thanks to HollowState for posting the schematic...

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