RE: DEC H7260 PSU fault

[Rob Jarratt via cctalk]

> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Glen Slick
> via cctalk
> Sent: 26 January 2018 01:17
> To: General Discussion: On-Topic and Off-Topic Posts 
> Subject: Re: DEC H7260 PSU fault
> 
> On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson via cctalk
>  wrote:
> > Hi all,
> >
> > I mentioned this in the thread where I'd asked about basic Microvax II
> > info, but it may have got lost in traffic...
> >
> > The machine's H7260 PSU is somewhat unwell - one of the internal
> > +5/12V supplies appears to be healthy, but the other has outputs which
> > are sitting at around 2.5V (both on the 5V and 12V rails) under a test load.
> >
> 
> Previously you also said:
> 
> > OK, the top PSU of the pair in this machine appears to be healthy. The
> > bottom one, however, sits at around 2.5V on both the +5V and +12V outputs.
> > That's without any cards, and the card-cage fan / temperature sensor
> > unplugged, i.e. just with my dummy loads in place, so it looks like
> > that PSU has issues (oh, and I tried decoupling the PSU from the
> > backplane and loading it via the drive connector, so it doesn't appear
> > to be a backplane issue).
> >
> 
> Looking here at page 107 of the maintenance print set, BA123-A Basic
> Enclosure Power Harness Wiring Diagram
> http://www.bitsavers.org/pdf/dec/vax/630/MP02071_630QB_Mar85.pdf
> 
> Did you disconnect the wiring harness from J10 completely? If you disconnected
> the temperature sensor module or the card-cage door interlock switch I would
> expect that the power supply might not operate normally.
> 
> I forget what the card-cage door interlock switch does, whether it prevents 
> the
> power supply from fully powering up, or if the power supply does fully power
> up but also turns the fans on full blast if the card-cage door is open which
> disrupts the normal cooling airflow.

If the door is open the fans run full blast.

> I would check what my BA123 does, but that would require too much moving of
> stuff about at the moment to get working space around it.

Re: DEC H7260 PSU fault

[Jules Richardson via cctalk]

On 01/25/2018 07:16 PM, Glen Slick via cctalk wrote:

On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson via cctalk

OK, the top PSU of the pair in this machine appears to be healthy. The
bottom one, however, sits at around 2.5V on both the +5V and +12V outputs.
That's without any cards, and the card-cage fan / temperature sensor
unplugged, i.e. just with my dummy loads in place, so it looks like that PSU
has issues (oh, and I tried decoupling the PSU from the backplane and
loading it via the drive connector, so it doesn't appear to be a backplane
issue).



Looking here at page 107 of the maintenance print set, BA123-A Basic
Enclosure Power Harness Wiring Diagram
http://www.bitsavers.org/pdf/dec/vax/630/MP02071_630QB_Mar85.pdf

Did you disconnect the wiring harness from J10 completely? If you
disconnected the temperature sensor module or the card-cage door
interlock switch I would expect that the power supply might not
operate normally.


I believe that I tried it both connected and disconnected, with no change 
in behavior, but I'll double-check (not until tomorrow evening now, though).


I need to look at how the signals on J10 interact with the entire PSU 
internals - it certainly seems to get a -15V feed from the lower PSU of the 
pair (the one that's causing me issues), but many of the wires run to the 
fourth, small PCB that's in the entire PSU assembly; I assume that one 
handles fan control as it also connects the the PSU fan and to J7 (which 
supplies the fan in the mass storage area)


It seems strange to me that one PSU of the pair would sit in an 
under-voltage condition due to a sensor issue while the other one would 
continue to operate normally, though; at this stage I think it's more 
likely that I've got a PSU fault (or a fault with the rectifier/relay board 
which supplies it - I'm most of the way through tracing a schematic for 
that board, so I can test some voltages sensibly tomorrow)


Will let you know how it goes...

Jules

Re: DEC H7260 PSU fault

[Glen Slick via cctalk]

On Thu, Jan 25, 2018 at 3:06 PM, Jules Richardson via cctalk
 wrote:
> Hi all,
>
> I mentioned this in the thread where I'd asked about basic Microvax II info,
> but it may have got lost in traffic...
>
> The machine's H7260 PSU is somewhat unwell - one of the internal +5/12V
> supplies appears to be healthy, but the other has outputs which are sitting
> at around 2.5V (both on the 5V and 12V rails) under a test load.
>

Previously you also said:

> OK, the top PSU of the pair in this machine appears to be healthy. The
> bottom one, however, sits at around 2.5V on both the +5V and +12V outputs.
> That's without any cards, and the card-cage fan / temperature sensor
> unplugged, i.e. just with my dummy loads in place, so it looks like that PSU
> has issues (oh, and I tried decoupling the PSU from the backplane and
> loading it via the drive connector, so it doesn't appear to be a backplane
> issue).
>

Looking here at page 107 of the maintenance print set, BA123-A Basic
Enclosure Power Harness Wiring Diagram
http://www.bitsavers.org/pdf/dec/vax/630/MP02071_630QB_Mar85.pdf

Did you disconnect the wiring harness from J10 completely? If you
disconnected the temperature sensor module or the card-cage door
interlock switch I would expect that the power supply might not
operate normally.

I forget what the card-cage door interlock switch does, whether it
prevents the power supply from fully powering up, or if the power
supply does fully power up but also turns the fans on full blast if
the card-cage door is open which disrupts the normal cooling airflow.
I would check what my BA123 does, but that would require too much
moving of stuff about at the moment to get working space around it.

RE: DEC H7260 PSU fault

[Rob Jarratt via cctalk]

> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Jules
> Richardson via cctalk
> Sent: 25 January 2018 23:07
> To: xx Classiccmp mailing list 
> Subject: DEC H7260 PSU fault
> 
> Hi all,
> 
> I mentioned this in the thread where I'd asked about basic Microvax II
info, but
> it may have got lost in traffic...
> 
> The machine's H7260 PSU is somewhat unwell - one of the internal +5/12V
> supplies appears to be healthy, but the other has outputs which are
sitting at
> around 2.5V (both on the 5V and 12V rails) under a test load.
> 
> Initial questions...
> 
> 1) Are schematics are available online? I couldn't find them (either under
the
> DEC p/n or the Astec AA13010 one), but perhaps they're buried in
schematics
> for a specific DEC machine somewhere.
> 


I doubt it. For the H7864 from the BA23 MicroVax II Enclosure I couldn't
find anything and in the end made my own schematic.


> 2) Upon initial glance, the 'first' board of the three in the PSU module
appears
> to be a pair of control relays, bridge rectifiers and capacitors,
supplying +/- DC
> voltages to the two individual PSU boards. Does anyone know if I can
disconnect
> these from the PSU boards safely* and measure their outputs, and if so
what
> voltages I should expect to see? That might be a good initial test before
> pointing a finger at the PSU board associated with the low outputs.
> 
> * I mean without component damage - I expect they might be sitting at a
> significant DC voltage, so there's an obvious personal safety aspect too
;-)
> 
> cheers
> 
> Jules

DEC H7260 PSU fault

[Jules Richardson via cctalk]

Hi all,

I mentioned this in the thread where I'd asked about basic Microvax II 
info, but it may have got lost in traffic...


The machine's H7260 PSU is somewhat unwell - one of the internal +5/12V 
supplies appears to be healthy, but the other has outputs which are sitting 
at around 2.5V (both on the 5V and 12V rails) under a test load.


Initial questions...

1) Are schematics are available online? I couldn't find them (either under 
the DEC p/n or the Astec AA13010 one), but perhaps they're buried in 
schematics for a specific DEC machine somewhere.


2) Upon initial glance, the 'first' board of the three in the PSU module 
appears to be a pair of control relays, bridge rectifiers and capacitors, 
supplying +/- DC voltages to the two individual PSU boards. Does anyone 
know if I can disconnect these from the PSU boards safely* and measure 
their outputs, and if so what voltages I should expect to see? That might 
be a good initial test before pointing a finger at the PSU board associated 
with the low outputs.


* I mean without component damage - I expect they might be sitting at a 
significant DC voltage, so there's an obvious personal safety aspect too ;-)


cheers

Jules

New DEC items from Sellam's collection for sale

[Sellam Ismail via cctalk]

Hey DEC-heads!

I added some more boards to my DEC list:

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Sellam