> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Brent > Hilpert via cctalk > Sent: 06 November 2017 19:44 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org> > Subject: Re: H7826 PSU, No Signal On Transformer Outputs > > On 2017-Nov-05, at 9:14 AM, Rob Jarratt via cctalk wrote: > > I have moved on with the work on the H7826 PSU in the TURBOchannel > Extender. > > However I have found that there appears to be no signal at all on the > > output windings of the transformer. I have posted all the details of > > what I have been doing here > > http://robs-old-computers.com/2017/11/05/repair-progress-on-the-h7826- > > power- supply/, and I would welcome any suggestions as to what might > > cause this? > > "I then checked the primary side of the transformer and I could see a signal." > > > You don't describe the nature of the signal, but regardless, seeing a voltage > signal at some point on the primary is not a guarantee that current is flowing > through the primary, current being necessary for induction and getting > anything out of the secondaries. >
I saw alternating signals on a number of the inputs to the transformer, but I didn't note which pins at the time :-( Surely all you need is an alternating voltage to produce an output on the secondary side? > It depends on the primary side driver arrangement, (going by the H7861 > schematic DEC used some funky arrangements, is the 7826 schematic > available?), For example you might see a voltage signal from the high-side > driver, but the low-side driver could be faulty.= I have not looked for a schematic, but I severely doubt there is one, in this case the markings on the board don't even have component labels! I could try to trace it out, but it is quite difficult with this board. Regards Rob
