HP-35 power unit: Failing Vgg voltage

[robjordan]

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?



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