DEC H745 regulator common failure modes?

Johnny Billquist bqt at
Fri Nov 27 04:29:32 CST 2015

On 2015-11-27 06:13, Pontus Pihlgren wrote:
> I can only say that they fail often. We have replaced lots in
> our 11/70. Luckily we have had spares.
> Sometimes the failure has been rather catastrofic with blown
> components. I think these modules run quite hot since
> discoloured pcb:s are common.

I think we more often see failures in the H744(0) modules, but we've had 
failures in both, yes.

Hot is a good guess, I think.


> /P
> On Thu, Nov 26, 2015 at 01:01:07PM -0800, Ian Finder wrote:
>> Hi folks,
>> I've begun repairing my PDP 11/40 and have tracked down the first major issue to the H745 (-15v) regulator.
>> Before I dig into it, I just wanted to see if there are any common known failure cases... Otherwise I'll just dive into troubleshooting it. :)
>> Thanks as always-
>> - Ian
>> Sent from my iPhone

Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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