5 Feb
2006
5 Feb
'06
7:49 p.m.
Hi List,
I have here a uVAX II in a ba23 box, most likely not powered up for 2 or 3
years.
The innards are clean, no nasty smells, no other trace of prior problems.
Even so, to minimise the risk of damage I'm going to disconnect all the 5v &
12v leads, then attach some suitable dummy load(s), switch on and wait for
smoke.
Does this seem an appropriate plan? Can anyone point me to pinouts for the
various supply leads from an H7864?
Does anyone have any other recommendations/experience of going though this
process, and is there anything I've missed that I should have included
above?
Cheers,
Pete
--
Pete Edwards
"Prediction is very difficult, especially if it's about the future" - Niels
Bohr
5 Feb
5 Feb
8:49 p.m.
At 12:49 AM 2/6/2006 +0000, you wrote:
Hi List,
I have here a uVAX II in a ba23 box, most likely not powered up for 2 or 3
years.
The innards are clean, no nasty smells, no other trace of prior problems.
Even so, to minimise the risk of damage I'm going to disconnect all the 5v &
12v leads, then attach some suitable dummy load(s), switch on and wait for
smoke.
Does this seem an appropriate plan? Can anyone point me to pinouts for the
various supply leads from an H7864?
Does anyone have any other recommendations/experience of going though this
process, and is there anything I've missed that I should have included
above?
All wise precautions. Many others recommend also using a variac to bring up
the voltage slowly, in stages, letting the capacitors reform for a few
hours at each stop. That also affords more chances to check for smoke
leakage. If you have an ammeter in line, you can watch for outrageous
current draw once you get closer to design voltage.
Most of us would have to find someone to borrow a sufficiently beefy variac
from, however. (I would.)
[Computing] A successful tool is one that was used to do something
undreamed of by its author. --S. C. Johnson
--... ...-- -.. . -. ----. --.- --.- -...
tpeters at nospam.mixcom.com (remove "nospam") N9QQB (amateur radio)
"HEY YOU" (loud shouting) WEB ADDRESS http//www.mixweb.com/tpeters
43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square
EN53wc
WAN/LAN/Telcom Analyst, Tech Writer, MCP, CCNA, Registered Linux User 385531
8:54 p.m.
All wise precautions. Many others recommend also using
a variac to bring up
the voltage slowly, in stages, letting the capacitors reform for a few
hours at each stop. That also affords more chances to check for smoke
leakage. If you have an ammeter in line, you can watch for outrageous
current draw once you get closer to design voltage.
Unless the uVax hasn't been powered up since the day it left the factory,
the capacitors will not need to be reformed. It take quite a long time for
modern (i.e. post-1950) electrolytics to even start thinking about going
bad.
William Donzelli
aw288 at osfn.org
6 Feb
6 Feb
6:54 p.m.
At 12:49 AM 2/6/2006 +0000, you wrote:
It is a very bad idea to 'run up' a swtich mode PSU (which this is) on a
Variac. SMPSUs appear as conatant power loads, as the input voltage
decreases, the current increases. Some supplies will blow their chopper
transistors under such conditions.
If you want to re-form the capacitors (and I don;t think it's necessary,
I've never had problems with capacitors in computer power supplies), take
them out of the circuit, and reform them using a bench supply and a resistor.
One thing I would recoemnd is that you check all the fans are running. If
not, either replace them or repair them (I do the latter...).
-tony
Hi List,
I have here a uVAX II in a ba23 box, most likely not powered up for 2 or=
3
years.
The innards are clean, no nasty smells, no other trace of prior problems.
Even so, to minimise the risk of damage I'm going to disconnect all the =
5v
&
12v leads, then attach some suitable dummy
load(s), switch on and wait f=
or
smoke.
Does this seem an appropriate plan? Can anyone point me to pinouts for t=
he
various supply leads from an H7864?
Does anyone have any other recommendations/experience of going though th=
is
process, and is there anything I've missed
that I should have included
above?
All wise precautions. Many others recommend also using a variac to bring =
up=20
8 p.m.
On 06/02/06, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
It is a very bad idea to 'run up' a swtich mode PSU (which this is) on a
Variac. SMPSUs appear as conatant power loads, as the input voltage
decreases, the current increases. Some supplies will blow their chopper
transistors under such conditions.
Having witnessed the effect of a sustained brownout (I think it went down
to 50V for about 15 minutes) on a UPS-less machine room full of kit with
240V switched mode PSUs, I know that's a no-no. I think the survival rate
was about 20%.
--
Pete Edwards
"Prediction is very difficult, especially if it's about the future" - Niels
Bohr
7 Feb
7 Feb
5:12 p.m.
Pete Edwards wrote:
On 06/02/06, Tony Duell <ard at
p850ug1.demon.co.uk> wrote:
While working doing tech support for retail EPOS equipment, I had a
batch of calls all for the same supermarket, all for tills that wouldn't
power on. About six, all logged at the same time.
So - phone the customer. Asked the customer services manager (for it is
them who deal with these things) if she could think of something that
might have caused this.
"Ah," she said, "yes. A JCB dug through a cable and blew up the
substation that we run off."
"Ok, then. Did they come up at all when power was restored?"
"Yes - for a while anyway, maybe about two hours"
"Right," I said, "What happened after two hours?"
"Well the standby genny ran out of diesel..."
That'll be six new power supplies, then. And billable, at that.
Gordon.
It is a very bad idea to 'run up' a swtich mode PSU (which this is) on a
Variac. SMPSUs appear as conatant power loads, as the input voltage
decreases, the current increases. Some supplies will blow their chopper
transistors under such conditions.
Having witnessed the effect of a sustained brownout (I think it went down
to 50V for about 15 minutes) on a UPS-less machine room full of kit with
240V switched mode PSUs, I know that's a no-no. I think the survival rate
was about 20%.
6:42 p.m.
You'll all be pleased to hear it didn't explode or do any other wierd stuff.
Pity whoever despatched it into retrocomputingland(tm) stripped out all the
disks and controllers, but left a scsi connector on the bulkhead.
I don't remember BA23s being so flipping noisy!
--
Pete Edwards
"Prediction is very difficult, especially if it's about the future" - Niels
Bohr
6 Feb
6 Feb
10:58 a.m.
New subject: Signetics 8266
Hi, all,
I've run across an old calculator that uses a couple of Signetics 8266 data
selectors (selects one of two groups of 4-bit inputs). The problem is that
this part is different than the 74157 -- it inverts one set of the inputs,
and its select inputs are different. There's not enough room in the circuit
board to kludge in a logical replacement, and I've searched high and low to
try to find a couple of these. I'm positive that one of them is bad, as I
can watch the inputs with a scope, and compare with the outputs, and there's
one data line that is stuck high.
Anyone out there happen to have one or two of these laying around that
they'd be willing to part with for a reasonable price, or, perhaps know of a
supplier where I might be able to buy a few of them?
Rick Bensene
The Old Calculator Wen Museum
http://oldcalculatormuseum.com
11:14 a.m.
New subject: Signetics 8266
In a pinch, you might be able to fit a logical equivalent circuit
using either some surface mount parts or a PAL/GAL...
--tom
At 07:58 AM 2/6/2006 -0800, you wrote:
Hi, all,
I've run across an old calculator that uses a couple of Signetics 8266 data
selectors (selects one of two groups of 4-bit inputs). The problem is that
this part is different than the 74157 -- it inverts one set of the inputs,
and its select inputs are different. There's not enough room in the circuit
board to kludge in a logical replacement, and I've searched high and low to
try to find a couple of these. I'm positive that one of them is bad, as I
can watch the inputs with a scope, and compare with the outputs, and there's
one data line that is stuck high.
Anyone out there happen to have one or two of these laying around that
they'd be willing to part with for a reasonable price, or, perhaps know of a
supplier where I might be able to buy a few of them?
Rick Bensene
The Old Calculator Wen Museum
http://oldcalculatormuseum.com
6745
days inactive
6746
days old
9 comments
8 participants
participants (8)
-
ard＠p850ug1.demon.co.uk -
aw288＠osfn.org -
gordonjcp＠gjcp.net -
julesrichardsonuk＠yahoo.co.uk -
rickb＠bensene.com -
stimpy.u.idiot＠gmail.com -
tpeters＠mixcom.com -
uban＠ubanproductions.com