19 Nov
2015
19 Nov
'15
4 p.m.
While I look into what is wrong with my H7864, I'd like to use a modern PSU
to power my machine (actually an rtVAX 1000).
I think I would need to deal with the following problems:
1. Finding the right connectors (ideally, I am sure I could rig up
something more temporary).
2. A way to power the fans, which I believe are 15V, perhaps they
would run on 12V as I wouldn't run the machine for long periods anyway, or I
could just use PC fans.
3. Emulate the DC OK and P OK signals, I suspect these would be simple
+5V signals which could perhaps just come from the +5V of the PSU anyway
(unless there is a problem with that).
4. The most difficult bit, I suspect, would be the PSU LTC signal ,
which I believe is some kind of clock. I don't know what the spec of the
signal is, but I will get a scope on a working one to see (NB don't want to
risk a working PSU on this machine in case it was a problem with the machine
itself that caused the first PSU to fail, I don't mind sacrificing a modern
PSU if need be).
Has anyone done this before?
Regards
Rob
24 Nov
24 Nov
3:52 p.m.
I haven't looked into this at all and I suspect it's probably quite tricky
indeed. I did look around a while back drew a blank.
If you need another dead MV2 let me know, the one I collected is still sat
in the garage.
Regards,
Mark.
On 20 November 2015 at 00:00, Robert Jarratt <robert.jarratt at ntlworld.com>
wrote:
While I look into what is wrong with my H7864, I'd
like to use a modern PSU
to power my machine (actually an rtVAX 1000).
I think I would need to deal with the following problems:
1. Finding the right connectors (ideally, I am sure I could rig up
something more temporary).
2. A way to power the fans, which I believe are 15V, perhaps they
would run on 12V as I wouldn't run the machine for long periods anyway, or
I
could just use PC fans.
3. Emulate the DC OK and P OK signals, I suspect these would be
simple
+5V signals which could perhaps just come from the +5V of the PSU anyway
(unless there is a problem with that).
4. The most difficult bit, I suspect, would be the PSU LTC signal ,
which I believe is some kind of clock. I don't know what the spec of the
signal is, but I will get a scope on a working one to see (NB don't want to
risk a working PSU on this machine in case it was a problem with the
machine
itself that caused the first PSU to fail, I don't mind sacrificing a modern
PSU if need be).
Has anyone done this before?
Regards
Rob
4:21 p.m.
Thanks Mark,
I probably don't have space for another one really, and yours is the one in the big
enclosure anyway (like this:
http://www.trailingedge.com/comphave.html?theKey=deccmicrovax2&byCompan…)y=0), if I
remember right, which has a different PSU.
Mine is one of these: http://www.cosam.org/images/uvaxii/front.jpg
We should try to get that one of yours working at the next Legacy. Have you thought about
whether to go for April?
Regards
Rob
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Mark
Wickens
Sent: 24 November 2015 23:52
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
I haven't looked into this at all and I suspect it's probably quite tricky
indeed. I
did look around a while back drew a blank.
If you need another dead MV2 let me know, the one I collected is still sat in the
garage.
Regards,
Mark.
On 20 November 2015 at 00:00, Robert Jarratt <robert.jarratt at ntlworld.com>
wrote:
> While I look into what is wrong with my H7864, I'd like to use a
> modern PSU to power my machine (actually an rtVAX 1000).
>
>
>
> I think I would need to deal with the following problems:
>
>
>
> 1. Finding the right connectors (ideally, I am sure I could rig up
> something more temporary).
>
> 2. A way to power the fans, which I believe are 15V, perhaps they
> would run on 12V as I wouldn't run the machine for long periods
> anyway, or I could just use PC fans.
>
> 3. Emulate the DC OK and P OK signals, I suspect these would be
> simple
> +5V signals which could perhaps just come from the +5V of the PSU
> +anyway
> (unless there is a problem with that).
>
> 4. The most difficult bit, I suspect, would be the PSU LTC signal ,
> which I believe is some kind of clock. I don't know what the spec of
> the signal is, but I will get a scope on a working one to see (NB
> don't want to risk a working PSU on this machine in case it was a
> problem with the machine itself that caused the first PSU to fail, I
> don't mind sacrificing a modern PSU if need be).
>
>
>
> Has anyone done this before?
>
>
>
> Regards
>
>
>
> Rob
>
>
6:05 p.m.
On 11/24/2015 05:52 PM, Mark Wickens wrote:
I haven't looked into this at all and I suspect
it's probably quite tricky
indeed. I did look around a while back drew a blank.
I built up a Micro-VAX II system out of boards, backplanes
and assorted junk. I made my own power supply. The power
supply is actually easy, just +5 and +12, with a touch of
-12 for serial I/O.
The only tricky thing is the power-OK and reset logic, which
really wasn't all that tricky, either.
I had a power and thermal safety control panel on it
repurposed from the original 3rd party IBM mainframe memory
box that would shut it down if there was an abnormal voltage
or cooling failure.
Jon
11:34 p.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
Sent: 25 November 2015 02:05
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
On 11/24/2015 05:52 PM, Mark Wickens wrote:
Thanks Jon. I think standard PC PSUs only do +5 and +12, so how did you do -12?
For P OK and DC OK I found this:
http://home.windstream.net/engdahl/powerup_reset_circuit.htm, but just for test purposes I
assume I could connect the +5 direct to P OK and DC OK.
Thanks for the other email, sounds like I wouldn't need to do anything with LTC.
Regards
Rob
I haven't looked into this at all and I
suspect it's probably quite
tricky indeed. I did look around a while back drew a blank.
I built up a Micro-VAX II system out of boards, backplanes and assorted junk. I
made my own power supply. The power supply is actually easy, just +5 and
+12, with a touch of
-12 for serial I/O.
The only tricky thing is the power-OK and reset logic, which really wasn't all
that tricky, either.
I had a power and thermal safety control panel on it repurposed from the
original 3rd party IBM mainframe memory box that would shut it down if there
was an abnormal voltage or cooling failure.
Jon
25 Nov
25 Nov
8:36 a.m.
On 11/25/2015 01:34 AM, Robert Jarratt wrote:
I did not use PC power supplies, I used a couple industrial
power supplies. I built this system in 1986.
But, generic PC power supplies DO have a little bit of -12 V
for serial cards. The standard PCI connector
has a -12 V pin. PCIe seems to have dropped the -12V supply.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
Sent: 25 November 2015 02:05
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
On 11/24/2015 05:52 PM, Mark Wickens wrote:
Thanks Jon. I think standard PC PSUs only do +5 and +12, so how did you do
-12? I haven't looked into this at all and I
suspect it's probably quite
tricky indeed. I did look around a while back drew a blank.
I built up a Micro-VAX II system out of boards, backplanes and assorted junk. I
made my own power supply. The power supply is actually easy, just +5 and
+12, with a touch of
-12 for serial I/O.
The only tricky thing is the power-OK and reset logic, which really wasn't all
that tricky, either.
I had a power and thermal safety control panel on it repurposed from the
original 3rd party IBM mainframe memory box that would shut it down if there
was an abnormal voltage or cooling failure.
Jon For P OK and DC OK I found this:
http://home.windstream.net/engdahl/powerup_reset_circuit.htm, but just for test purposes I
assume I could connect the +5 direct to P OK and DC OK.
BPOK needs to pulse low
after power is stable, BDCOK should
be high when power is OK. Or, at least, that's what I got
from the drawing you linked to.
Jon
9:01 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
Sent: 25 November 2015 16:37
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
On 11/25/2015 01:34 AM, Robert Jarratt wrote:
12?
I did not use PC power supplies, I used a couple industrial power supplies. I
built this system in 1986.
But, generic PC power supplies DO have a little bit of -12 V for serial cards.
The standard PCI connector has a -12 V pin. PCIe seems to have dropped the -
12V supply.
Thanks, that should do the job then.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon
Elson
Sent: 25 November 2015 02:05
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and
Off- Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
On 11/24/2015 05:52 PM, Mark Wickens wrote:
Thanks Jon. I think standard PC PSUs only do +5 and +12, so how did you do -
I haven't looked into this at all and I
suspect it's probably quite
tricky indeed. I did look around a while back drew a blank.
I built up a Micro-VAX II system out of boards, backplanes and
assorted junk. I made my own power supply. The power supply is
actually easy, just +5 and
+12, with a touch of
-12 for serial I/O.
The only tricky thing is the power-OK and reset logic, which really
wasn't all that tricky, either.
I had a power and thermal safety control panel on it repurposed from
the original 3rd party IBM mainframe memory box that would shut it
down if there was an abnormal voltage or cooling failure.
Jon For P OK and
DC OK I found this:
http://home.windstream.net/engdahl/powerup_reset_circuit.htm,
but just for
test purposes I assume I could connect the +5 direct to P OK and DC OK.
BPOK needs to pulse low after power is stable, BDCOK should be high when
power is OK. Or, at least, that's what I got from the drawing you linked to.
Jon
9:09 a.m.
On 11/25/2015 11:01 AM, Robert Jarratt wrote:
My reading of the Qbus spec is that P OK and DC OK are
active high. That diagram tells me that both control
signals are driven the same way because the two circuits
are identical except for the timing caps. When the power
is OK the output of the inverters is low, so the
transistors are off, presumably allowing the signals to
float high. When the power is not OK, the inverters are
high, turning on the transistors and shorting the signal
to ground. But, I am no expert, and could have interpreted
those circuits all wrong. Regards Rob
Yup, I read the circuit the same way.
Jon
10:46 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jon Elson
Sent: 25 November 2015 17:10
To: General at classiccmp.org; Discussion at classiccmp.org:On-Topic and Off-
Topic Posts
Subject: Re: Replacing MicroVAX II PSU With a Modern PSU
On 11/25/2015 11:01 AM, Robert Jarratt wrote:
Ah, I misread your earlier response, I thought you were saying something different.
Regards
Rob
My reading of the Qbus spec is that P OK and DC
OK are active high.
That diagram tells me that both control signals are driven the same
way because the two circuits are identical except for the timing caps.
When the power is OK the output of the inverters is low, so the
transistors are off, presumably allowing the signals to float high.
When the power is not OK, the inverters are high, turning on the
transistors and shorting the signal to ground. But, I am no expert,
and could have interpreted those circuits all wrong. Regards Rob
Yup, I read the
circuit the same way.
11:38 a.m.
My reading of the Qbus spec is that P OK and DC OK are
active high. That diagram
They are, for a very logical reason. Remember you can wire-AND open-collector signals
-- that is link them together so that any driver can pull the line low and the line will
only be high if all driver transistors are cut off. Now if you have a large system
with multiple boxes and power supplies then any supply can pull P OK and DC OK low
if there is a problem. Only if all supplies are present and correct will the signals be
high.
-tony
24 Nov
24 Nov
6:07 p.m.
On 11/24/2015 05:52 PM, Mark Wickens wrote:
4. The most difficult bit, I suspect, would be
the PSU LTC signal ,
which I believe is some kind of clock. I don't know what the spec of the
signal is, but I will get a scope on a working one to see (NB don't want to
risk a working PSU on this machine in case it was a problem with the
machine
itself that caused the first PSU to fail, I don't mind sacrificing a modern
PSU if need be).
The line time clock is a vestige of the Q-bus LSI-11
heritage. As far as I know, there is a reserved bus signal,
but it was NOT implemented on the UVAX-II system. (I don't
have my print set anymore.)
Jon
3315
days inactive
3320
days old
10 comments
4 participants
participants (4)
-
ard＠p850ug1.demon.co.uk -
elson＠pico-systems.com -
mark＠wickensonline.co.uk -
robert.jarratt＠ntlworld.com