6 Nov
2017
6 Nov
'17
8:14 p.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at 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 at
classiccmp.org>
Subject: Re: H7826 PSU, No Signal On Transformer
Outputs
On 2017-Nov-05, at 9:14 AM, Rob Jarratt via cctalk wrote:
signal."
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
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