04-03-2017, 08:48 PM
Short Update. Started at the power supply - there are four rail pairs +/-5v, +/-15v, and +/-25v. Both the 5v and 15v rails were low - about 4.7v and 14v respectively. According to the manual the tolerances are very tight so 15v has to be within +/- 0.04v. I managed to adjust it to the right level. There is no adjustment on the +5v - it come straight out of a 7805. There is however a tantalum between input and ground so I replaced it and to my surprise 5v is now spot on. The 15v had then risen to 16v so I adjusted is back to the correct level. I tested the old cap in my Chinese tester and the value showed fine but ESR was high at just under 2 Ohms.
There is no + or - 25v. Transformer output looks good, diodes look good, clean 35v on -25v side electrolytic but lots of ripple on the cap for the +25v side. Will need to order up some electrolytics. On closer examination this 25v circuit has signs of extensive work done in the past so I guess I'm walking in someone else's footsteps at this stage. Hopefully I'll get further than he/she did!
Cheers,
John
There is no + or - 25v. Transformer output looks good, diodes look good, clean 35v on -25v side electrolytic but lots of ripple on the cap for the +25v side. Will need to order up some electrolytics. On closer examination this 25v circuit has signs of extensive work done in the past so I guess I'm walking in someone else's footsteps at this stage. Hopefully I'll get further than he/she did!
Cheers,
John
Time flies like an arrow, fruitflies like a banana!
