> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Robert
> Jarratt
> Sent: 02 November 2015 23:18
> To: 'General Discussion: On-Topic and Off-Topic Posts'
> Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis Lind
> Sent: 02 November 2015 21:44
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load
>
> 2015-11-02 2
2015-11-02 22:05 GMT+01:00 Robert Jarratt :
>
>
>
> I have just uploaded all the corrections. So the connector names on the
> risers should now correspond. I have also corrected the area on the primary
> control module around C403 and R407.
>
> Regards
>
> Rob
>
>
Checked the new one. There are st
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Robert
> Jarratt
> Sent: 02 November 2015 20:36
> To: 'General Discussion: On-Topic and Off-Topic Posts'
> Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load
>
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis Lind
> Sent: 02 November 2015 13:20
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load
>
> 2015-11-01 1
2015-11-01 17:35 GMT+01:00 Robert Jarratt :
>
>
> > > > Maybe you can publish your schematic somwhere. It is much easier to
> > > > come
> > > up
> > > > with ideas to pin point problems if we all view the same schematic.
> > > > I
> > > think it
> > > > would be possible to identify the problem w
>
> Then you've not come across the ones in TK50Z desktop cases (and a few
> other things). They don't like operating without a minimum load,
No, probably not. Actually I may have one somewhere, but have never had to
repair it, so have never run it without a load.
Thanks for the warning though!
On 01/11/2015 18:47, tony duell wrote:
I've yet to find a DEC PSU that fails destructively if not loaded, it
is more likely to just trip the overvoltaeg protection crowbar, shut
down, then try to restart and repeat the cycle, tweeting as it goes
Then you've not come across the ones in TK50Z des
[Chopper transistor]
> This one is a D905.
I assume that's a 2SD905 (the '2S' is often left off the package). From the data
I've seen that certainly could be used as a chopper transistor.
-tony
>
> You mentioned DEC PSUs, this one is actually made by ASTEC. I will use a
Firstly, every Astec PSU I've seen has been a swticher. They probably did make
linear PSUs, but not common...
Secodnly, it may have been made to a DEC design (rather than just a
specification).
I believe you replace
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of tony
duell
> Sent: 01 November 2015 18:54
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load
>
>
> > Th
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of tony
duell
> Sent: 01 November 2015 18:47
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load
>
> >
> >
> That said, it's possible that there may be an auxiliary linear regulator in
> there. That's common
> for additional outputs with modest current needs, especially in older
> designs where the
> switching circuitry takes a lot of individual components. A TO-3 can isn't
> what I would expect
>
> If it has a transistor at the primary side, and a high frequency transformer,
> it's a switching supply.
> Those want a load, usually. Especially the older ones.
If there are large-ish electrolytics (100's of uF) with a voltage rating around
200V and no reason to
believe that there is a
> On Nov 1, 2015, at 12:37 PM, Robert Jarratt
> wrote:
>
> ...
> Hmmm Until your email I was pretty confident this was a switcher. But
> your description of a linear PSU seems to fit. I have posted three photos of
> the main board here: http://1drv.ms/1KQkTBp can you tell from that what kin
>> Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load
>>
>>
>>> On Nov 1, 2015, at 7:12 AM, Robert Jarratt
>> wrote:
>>> Some of you may recall I have a faulty H7864 PSU, which failed a while
>>> ago with a loud pop, but no obvious physi
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Paul
Koning
> Sent: 01 November 2015 16:52
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load
>
>
> >
> On Nov 1, 2015, at 7:12 AM, Robert Jarratt
> wrote:
>
> Some of you may recall I have a faulty H7864 PSU, which failed a while ago
> with a loud pop, but no obvious physical damage. I replaced the blown
> transistor (on the primary side of the large transformer), but when I power
> it on, th
> > > Maybe you can publish your schematic somwhere. It is much easier to
> > > come
> > up
> > > with ideas to pin point problems if we all view the same schematic.
> > > I
> > think it
> > > would be possible to identify the problem without comparing the two
> > > PSUs
> > at
> > > least in thi
2015-11-01 15:04 GMT+01:00 Robert Jarratt :
>
>
> > -Original Message-
> > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis
> Lind
> > Sent: 01 November 2015 12:46
> > To: General Discussion: On-Topic and Off-Topic Posts
> >
> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis Lind
> Sent: 01 November 2015 12:46
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load
>
> söndag 1 novem
söndag 1 november 2015 skrev Robert Jarratt :
> Some of you may recall I have a faulty H7864 PSU, which failed a while ago
> with a loud pop, but no obvious physical damage. I replaced the blown
> transistor (on the primary side of the large transformer), but when I power
> it on, the transistor
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