Re: VAX 4000 PSU (H7874) Schematics
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 > 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 Straße 42, 09600 Oberschöna, USt-Id: DE253710583 >> i...@tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741 >> >> -- Aaron Jackson PhD Student, Computer Vision Laboratory, Uni of Nottingham http://aaronsplace.co.uk
Re: VAX 4000 PSU (H7874) Schematics
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 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 Straße 42, 09600 Oberschöna, USt-Id: DE253710583 > i...@tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741 > >
Re: VAX 4000 PSU (H7874) Schematics
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 Straße 42, 09600 Oberschöna, USt-Id: DE253710583 i...@tsht.de Fax +49 3731 74200 Tel +49 3731 74222 Mobil: 0172 8790 741
Re: VAX 4000 PSU (H7874) Schematics
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@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
Re: VAX 4000 PSU (H7874) Schematics
> 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.
Re: VAX 4000 PSU (H7874) Schematics
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
Re: VAX 4000 PSU (H7874) Schematics
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@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. > >
VAX 4000 PSU (H7874) Schematics
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.
