[Info-vax] rx2620 power supplies / VRM voltage low

[George Cornelius]

In article <n9ffne$omg$1 at panix2.panix.com>, kludge at panix.com
 (Scott Dorsey) writes:
> George Cornelius <cornelius at eisner.decus.org> wrote:
>>Anyone else had problems with rx2620 power supplies?
>>
>>We have been helping someone in-house who has a laboratory
>>instrument with attached rx2620 and no hardware contract.
>>
>>We are not hardware support people but got him around his
>>last two hardware problems - bad scsi cable, (soft?) ecc
>>errors that appeared to be interfering with boots - but
>>he now has chronic power issues.
>>
>>The iLo MP shows a message like "VRM non-recoverable voltage
>>low - check all boards at this address".  VRM's - voltage
>>regulator modules - are on the motherboard and generate
>>regulated voltages from the output of the power supplies.
>>
>>Swapping out the power supply resolves this.  Over and over
>>again.  We get about a month out of a supply.
> 
> Where are you getting these supplies?
> 
>>Just recently tried inserting two supplies (these are used/
>>refurbed, with 90 day warranty).  One of these died within
>>a day or so - different error, indicating defunct supply.
> 
> Who is refurbing these?
> Are they actually refurbing them, or are they just fixing whatever is
> broken?  Are all the electrolytic capacitors in them new?
>

Thanks for the response.  These are all great comments and
help us focus a bit.  Yes, one of the electronics techs
is the one who referred the original scsi issue to us
after replacing array controller did not help.  He also
helped with the purchase of the original replacement
supply, from an "approved" vendor.  Lab supervisor thought
he was buying new but after it eventually failed, I
noticed corrosion on the case due to something having
dripped onto it from above - no doubt electrolytics
leaking from the supply above it! 

So we lined up a local vendor and he has been buying from
them.  Their supplies are significantly less expensive
than the first one he bought, and come with warranty,
but are failing as well.  Looks like it's time for
a long discussion with our suppliers.

No time to write more, but this is very helpful. Thank
you.

>>Soon after - replacement supply not yet in - VRM voltage
>>low error returns.
>>
>>Ideas?
> 
> Check ALL the power supply rails.  See if one of them actually is low.
> Swap the "bad" power supply into another machine and see if they give the
> same error.
> 
> When supply rails are pulled down, it's almost always because of bad
> electrolytic decoupling capacitors.  If you buy a "refurbed" supply, it 
> should have new electrolytics throughout, and they should be high grade
> high temperature ones.
> 
> If you have a supply that "tests good" but has 20-year old capacitors
> throughout, it will not last very long before another cap fails in it.
> 
> Now, you might have bad electrolytics on the CPU board as well... and I
> would certainly inspect the board for bulging or leaking ones even if
> you don't have an ESR tester to check them in-circuit.
> 
> Does the customer have an electronics tech on staff who can check caps?

See above.

And I do have a Fluke meter that can go down to 10 or maybe even 1 nF
caps - I'll check if it is specified for in-circuit testing.

[...]

>>Oh - and did I tell you we have no Itanium experience?
> 
> This is a good way to get some!

Yes, several years' worth in just a few months.

George