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HP-35 power unit: Failing Vgg voltage
11-28-2022, 06:59 PM
Post: #5
RE: HP-35 power unit: Failing Vgg voltage
After some more investigation, I'm now of the opinion that the winding on the toroidal transformer between pins 3 and 4, the one which generates the -12V, is broken. It measures M-ohm range resistance in circuit. Annoyingly it's a version of the toroid which is encased in white gloop, like this picture. Maybe because it's a Singapore manufactured model?

[Image: hp35-article-image20-644x642.jpeg]

Just wondering on the off chance. Is there anyone who is or has been willing/able to replace these transformers? I guess they are only available from donor calculators, but thought worth checking just in case.

I guess I could try and DIY one but I'm way out of my comfort zone. Or unpick the gloop and see if I can repair this one.

Thanks
Rob

Rob
35, 12C, 17BII, 27S, 28S, 32SII, 48G, 49G, 50G, 35S.
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RE: HP-35 power unit: Failing Vgg voltage - robjordan - 11-28-2022 06:59 PM



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