7 Jun
2018
7 Jun
'18
12:49 p.m.
I am trying to repair a VAX 4000 power supply. Does anyone have the
schematics? I can't find anything on BitSavers and I'm not completely
convinced it was even designed by DEC.
The VAX turns on and the status LED stays on F. The DC lamp does not
illuminate on the PSU. 5V rail appears fine but there is nothing from
the 12V rail. There were some *very* dodgy looking caps which I have
replaced, and some *very* exploded MOSFETs, which I have also
replaced.
If anyone has schematics, or know where I might find them, it would be
much appreciated.
Thanks,
Aaron.
7 Jun
7 Jun
12:55 p.m.
There is a guy named at Joel from global-itcorp.com who has experience with
these, he may have an idea. Tell him you spoke with Bill Degnan.
b
On Thu, Jun 7, 2018 at 3:49 PM, Aaron Jackson via cctalk <
cctalk at classiccmp.org> wrote:
I am trying to repair a VAX 4000 power supply. Does
anyone have the
schematics? I can't find anything on BitSavers and I'm not completely
convinced it was even designed by DEC.
The VAX turns on and the status LED stays on F. The DC lamp does not
illuminate on the PSU. 5V rail appears fine but there is nothing from
the 12V rail. There were some *very* dodgy looking caps which I have
replaced, and some *very* exploded MOSFETs, which I have also
replaced.
If anyone has schematics, or know where I might find them, it would be
much appreciated.
Thanks,
Aaron.
8 Jun
8 Jun
3:38 a.m.
Thanks Bill. I emailed him, some decent advice but mostly prices :)
Aaron
Bill Degnan writes:
There is a guy named at Joel from global-itcorp.com
who has experience with
these, he may have an idea. Tell him you spoke with Bill Degnan.
b
On Thu, Jun 7, 2018 at 3:49 PM, Aaron Jackson via cctalk <
cctalk at classiccmp.org> wrote:
> I am trying to repair a VAX 4000 power supply. Does anyone have the
> schematics? I can't find anything on BitSavers and I'm not completely
> convinced it was even designed by DEC.
>
> The VAX turns on and the status LED stays on F. The DC lamp does not
> illuminate on the PSU. 5V rail appears fine but there is nothing from
> the 12V rail. There were some *very* dodgy looking caps which I have
> replaced, and some *very* exploded MOSFETs, which I have also
> replaced.
>
> If anyone has schematics, or know where I might find them, it would be
> much appreciated.
>
> Thanks,
> Aaron.
>
>
--
Aaron Jackson
PhD Student, Computer Vision Laboratory, Uni of Nottingham
http://aaronsplace.co.uk
12:58 a.m.
On Thu, 7 Jun 2018, Aaron Jackson wrote:
The VAX turns on and the status LED stays on F. The DC
lamp does not
illuminate on the PSU. 5V rail appears fine but there is nothing from
the 12V rail. There were some *very* dodgy looking caps which I have
replaced, and some *very* exploded MOSFETs, which I have also
replaced.
If that's all that you replaced, no wonder it still doesn't work ;-)
Usually shorted power transistors in SMPSUs also break one or more fusable
resistors, maybe some diodes, maybe the driver IC or transistors.
So if you have anything that "exploded" in the power supply, be sure there
is more work to be invested that replacing the obious parts.
Christian
3:38 a.m.
On Thu, 7 Jun 2018, Aaron Jackson wrote:
Haha, okay, seems reasonable. I'll have to probe about a lot more
then. Not giving up quite yet, even though everything I have read about
this power supply has said that it is difficult to repair. So far, I
would agree with such a statement.
Thanks,
Aaron.
The VAX turns on and the status LED stays on F.
The DC lamp does not
illuminate on the PSU. 5V rail appears fine but there is nothing from
the 12V rail. There were some *very* dodgy looking caps which I have
replaced, and some *very* exploded MOSFETs, which I have also
replaced.
If that's all that you replaced, no wonder it still doesn't work ;-)
Usually shorted power transistors in SMPSUs also break one or more fusable
resistors, maybe some diodes, maybe the driver IC or transistors.
So if you have anything that "exploded" in the power supply, be sure there
is more work to be invested that replacing the obious parts.
Christian 
6:04 a.m.
Aaron Jackson via cctalk wrote:
Difficult to repair? Probably since it is the worst switching PSU Desing
I ever meet, at least from seriveability and the mechanical point of view.
I own an 4000/300 with an working again PSU (after some capacitor
changes) and I habe an PSU from a friend here..its works sometimes,
mostly not.
Regards,
Holm
--
Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
info at tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741
On Thu, 7 Jun
2018, Aaron Jackson wrote:
Haha, okay, seems reasonable. I'll have to probe about a lot more
then. Not giving up quite yet, even though everything I have read about
this power supply has said that it is difficult to repair. So far, I
would agree with such a statement.
Thanks,
Aaron. The VAX turns on and the status LED stays on F.
The DC lamp does not
illuminate on the PSU. 5V rail appears fine but there is nothing from
the 12V rail. There were some *very* dodgy looking caps which I have
replaced, and some *very* exploded MOSFETs, which I have also
replaced.
If that's all that you replaced, no wonder it still doesn't work ;-)
Usually shorted power transistors in SMPSUs also break one or more fusable
resistors, maybe some diodes, maybe the driver IC or transistors.
So if you have anything that "exploded" in the power supply, be sure there
is more work to be invested that replacing the obious parts.
Christian
8:58 a.m.
I have one or two mostly new 4000 supplies here, plus two working 4000's.
Did not know until recently this was an issue, I guess I have been lucky.
b
On Fri, Jun 8, 2018 at 9:04 AM, Holm Tiffe via cctalk <cctalk at classiccmp.org
wrote:
Aaron Jackson via cctalk wrote:
Difficult to repair? Probably since it is the worst switching PSU Desing
I ever meet, at least from seriveability and the mechanical point of view.
I own an 4000/300 with an working again PSU (after some capacitor
changes) and I habe an PSU from a friend here..its works sometimes,
mostly not.
Regards,
Holm
--
Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
info at tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741
> On Thu, 7 Jun 2018, Aaron Jackson wrote:
>> The VAX turns on and the status LED stays on F. The DC lamp does not
>> illuminate on the PSU. 5V rail appears fine but there is nothing from
>> the 12V rail. There were some *very* dodgy looking caps which I have
>> replaced, and some *very* exploded MOSFETs, which I have also
>> replaced.
>
> If that's all that you replaced, no wonder it still doesn't work ;-)
> Usually shorted power transistors in SMPSUs also break one or more
fusable
> resistors, maybe some diodes, maybe the
driver IC or transistors.
> So if you have anything that "exploded" in the power supply, be sure
there
is more
work to be invested that replacing the obious parts.
Christian
Haha, okay, seems reasonable. I'll have to probe about a lot more
then. Not giving up quite yet, even though everything I have read about
this power supply has said that it is difficult to repair. So far, I
would agree with such a statement.
Thanks,
Aaron.
9 Jun
9 Jun
2:58 a.m.
Hopefully you have changed the caps before the leak all over your board
:)
Bill Degnan writes:
I have one or two mostly new 4000 supplies here, plus
two working 4000's.
Did not know until recently this was an issue, I guess I have been lucky.
b
On Fri, Jun 8, 2018 at 9:04 AM, Holm Tiffe via cctalk <cctalk at classiccmp.org
--
Aaron Jackson
PhD Student, Computer Vision Laboratory, Uni of Nottingham
http://aaronsplace.co.uk
wrote:
> Aaron Jackson via cctalk wrote:
>
> > > On Thu, 7 Jun 2018, Aaron Jackson wrote:
> > >> The VAX turns on and the status LED stays on F. The DC lamp does not
> > >> illuminate on the PSU. 5V rail appears fine but there is nothing from
> > >> the 12V rail. There were some *very* dodgy looking caps which I have
> > >> replaced, and some *very* exploded MOSFETs, which I have also
> > >> replaced.
> > >
> > > If that's all that you replaced, no wonder it still doesn't work
;-)
> > > Usually shorted power transistors in SMPSUs also break one or more
> fusable
> > > resistors, maybe some diodes, maybe the driver IC or transistors.
> > > So if you have anything that "exploded" in the power supply, be
sure
> there
> > > is more work to be invested that replacing the obious parts.
> > >
> > > Christian
> >
> > Haha, okay, seems reasonable. I'll have to probe about a lot more
> > then. Not giving up quite yet, even though everything I have read about
> > this power supply has said that it is difficult to repair. So far, I
> > would agree with such a statement.
> >
> > Thanks,
> > Aaron.
>
> Difficult to repair? Probably since it is the worst switching PSU Desing
> I ever meet, at least from seriveability and the mechanical point of view.
>
> I own an 4000/300 with an working again PSU (after some capacitor
> changes) and I habe an PSU from a friend here..its works sometimes,
> mostly not.
>
> Regards,
>
> Holm
>
> --
> Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
> Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
> info at tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741
>
>
2388
days inactive
2390
days old
7 comments
4 participants
participants (4)
-
aaron＠aaronsplace.co.uk -
billdegnan＠gmail.com -
cc＠informatik.uni-stuttgart.de -
holm＠freibergnet.de