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Old 5th November 2011, 09:40 PM   #1
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Default Old HP transformer - what is it?

I retrieved an old transformer from a dead power supply

HP 9100-0181

Google is giving me nothing useful on this guy, can anyone tell me what the specs are? I've measured some voltages that are obviously for heaters (13.7 VAC), others are for B+ (815 VAC!!!)

I'm thinking maybe it's to be used with 110 VAC mains (13.7 VAC * 110/240 = 6.3 VAC)

Is it ok to use the primary with 240 VAC? Maybe the insulation on the secondaries won't survive a doubling of their voltage?

Thanks
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Old 5th November 2011, 09:59 PM   #2
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If the primary was designed to operate at 110-125, I would not attempt to use it at 240.
What kind of power supply? What was the original configuration of the rectifiers?
Look at the high voltage capacitors in the original supply.
The voltage rating of the caps should give you a hint.
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Old 5th November 2011, 10:13 PM   #3
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Excellent suggestion, I'll see if these guys have been thrown out or not. Now that you mention it, if I can find the chassis rear, this might tell me everything. Still, lots of transformers can be configured to take either mains voltage, this is where a specification would be great.
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Old 5th November 2011, 10:23 PM   #4
DF96 is offline DF96  England
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A transformer can be configured to handle either mains voltage, usually by having two primary windings (used in series or parallel). It would be very unusual for a 110V transformer to be so over-specified for magnetic saturation that it can used unchanged on 230V.
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Old 5th November 2011, 10:57 PM   #5
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Quote:
Originally Posted by DF96 View Post
A transformer can be configured to handle either mains voltage, usually by having two primary windings (used in series or parallel). It would be very unusual for a 110V transformer to be so over-specified for magnetic saturation that it can used unchanged on 230V.
Understood, I've ditched any thought of using 240 VAC on the primary unless I get my hands on a spec explicitly okaying it. If none shows up, I'll consider the economics of an equally sized (it's 5.6 kg!!) mains step down transformer.
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Old 5th November 2011, 11:01 PM   #6
DF96 is offline DF96  England
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Can you measure the primary current when on 240V? A lamp limiter will give you a rough idea. If it takes low current when run without a secondary load, and doesn't get hot, then you may be able to use it.
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Old 5th November 2011, 11:19 PM   #7
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Quote:
Originally Posted by DF96 View Post
Can you measure the primary current when on 240V? A lamp limiter will give you a rough idea. If it takes low current when run without a secondary load, and doesn't get hot, then you may be able to use it.
I'll try this lamp limiter (when I can find an old style bulb ), but I'm still worried about insulation breakdown.

There's a second consideration for me, I was thinking of using this as a bench supply. If I have the primary on 110, then the (unloaded) secondary voltages are 82 VAC, 110 VAC, 216 VAC and 373 VAC. These look like better voltages for the circuits I'd likely experiment with, more useful than the 240 V primary voltages.

--edit
just noticed, if I use the 216 VAC as the primary winding, am I sorted?

Last edited by highfieldrebel; 5th November 2011 at 11:24 PM. Reason: brain ripple
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Old 6th November 2011, 12:29 AM   #8
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It's times like this when it helps to have filing cabinets full of old Hewlett-Packard manuals. Your 9100-0181 transformer is the power transformer from an HP type 214A pulse generator. This used a good number of small tubes plus a pair if 7534's in parallel single ended operation for the output drive. The PS schematic is large, so I scanned it in two parts.
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Last edited by HollowState; 6th November 2011 at 12:36 AM.
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Old 6th November 2011, 12:36 AM   #9
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This is awesome, thank you so much sir, I look forward to scrutinising the schematic on tomorrow!

Thanks
Steve

BTW is your avatar a halloween costume?
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Old 6th November 2011, 12:53 AM   #10
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Originally Posted by highfieldrebel View Post
BTW is your avatar a halloween costume?
How could you possibly think that? It's really me at the computer. Actually my left eye should wink, but the forum software won't do it.
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Last edited by HollowState; 6th November 2011 at 01:10 AM.
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