14 Feb
2016
14 Feb
'16
8:13 p.m.
Hello list,
Some months ago I asked for help regarding one of my Vaxstation 4000,
whose power supply appeared to be dead. I have finally found the time
(and the mood) to take apart the PS from the machine and open it to take
a look. I have got to vandalize it a little bit, since one of the screws
was completely stuck in place... nothing that a creative use of a dremel
tool can' fix ;)
What I have found is one of the two big fuses near the mains connection
is blown. This _should_ be good news, since all what I have to do is to
find a compatible fuse. But I wonder what will I find when I replace it.
There is nothing obviously burnt in the PS. The big capacitors look good
(even shiny, once I've blown off the dust), and there is no funny smell
at all.
So, my next step will be to replace the thing and see if it blows up again.
Just a question for the repair savvy... is it safe to power up the PS
outside of the vaxstation?
I'll tell you how the thing evolves :)
regards,
14 Feb
14 Feb
8:16 p.m.
I wouldn't recommend doing it unloaded for more than a few seconds.
Map me the pin out so I can run it off an ATX supply ;)
Sent from my iPhone
On Feb 14, 2016, at 11:13, Jordi Guillaumes Pons
<jg at jordi.guillaumes.name> wrote:
Hello list,
Some months ago I asked for help regarding one of my Vaxstation 4000, whose power supply
appeared to be dead. I have finally found the time (and the mood) to take apart the PS
from the machine and open it to take a look. I have got to vandalize it a little bit,
since one of the screws was completely stuck in place... nothing that a creative use of a
dremel tool can' fix ;)
What I have found is one of the two big fuses near the mains connection is blown. This
_should_ be good news, since all what I have to do is to find a compatible fuse. But I
wonder what will I find when I replace it. There is nothing obviously burnt in the PS. The
big capacitors look good (even shiny, once I've blown off the dust), and there is no
funny smell at all.
So, my next step will be to replace the thing and see if it blows up again.
Just a question for the repair savvy... is it safe to power up the PS outside of the
vaxstation?
I'll tell you how the thing evolves :)
regards,
15 Feb
15 Feb
7:17 a.m.
Some things never change.. ;)
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
On February 14, 2016 2:16:11 PM Cory Smelosky <b4 at gewt.net> wrote:
I wouldn't recommend doing it unloaded for more
than a few seconds.
Map me the pin out so I can run it off an ATX supply ;)
Sent from my iPhone
On Feb 14, 2016, at 11:13, Jordi Guillaumes Pons
<jg at jordi.guillaumes.name>
wrote:
Hello list,
Some months ago I asked for help regarding one of my Vaxstation 4000, whose
power supply appeared to be dead. I have finally found the time (and the
mood) to take apart the PS from the machine and open it to take a look. I
have got to vandalize it a little bit, since one of the screws was
completely stuck in place... nothing that a creative use of a dremel tool
can' fix ;)
What I have found is one of the two big fuses near the mains connection is
blown. This _should_ be good news, since all what I have to do is to find a
compatible fuse. But I wonder what will I find when I replace it. There is
nothing obviously burnt in the PS. The big capacitors look good (even
shiny, once I've blown off the dust), and there is no funny smell at all.
So, my next step will be to replace the thing and see if it blows up again.
Just a question for the repair savvy... is it safe to power up the PS
outside of the vaxstation?
I'll tell you how the thing evolves :)
regards,
7:21 a.m.
On Mon, 15 Feb 2016, Dave McGuire wrote:
Some things never change.. ;)
ATX PSUs are far more abundant. ;)
-Dave
--
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects
7:53 p.m.
Some things never change.. ;)
ATX PSUs are far more abundant. ;) 
8:02 p.m.
On 02/15/2016 01:53 PM, Jordi Guillaumes i Pons wrote:
Well, I have replaced the fuse and it is still dead. I
have double
checked the PCB and I have found a part that seems to be charred.
http://i.imgur.com/4hpUKpb.jpg
I?m not sure what the big grey things are. I?d guess those are some
kind of resistors (labeled 2W10% 15K), but I have not seen something
like that before.
They are power resistors.
If so, the one horizontally in the pic seems to be
burnt. The PCB is charred underneath it, and no current goes thru it
accordint to my multimeter.
The little charring on the PCB may be conductive. I'd clean that off
first, before going any further.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
8:04 p.m.
The grey things are resistors, 15 kOhms and 20 kOhms from what i can see on the picture.
The 10% indicates the margin of error (so the 20 k one may actually be 18--22 kOhms). They
are rated at 2 Watts. They may be defect, I've seen these things break down in Teac
tape decks.
Verzonden?vanaf?mijn?BlackBerry?10-smartphone.
? Origineel bericht ?
Van: Jordi Guillaumes i Pons
Verzonden: maandag 15 februari 2016 19:53
Aan: HECnet Mailing List
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: Re: [HECnet] VS4000/60 power supply dead... or not?
Well, I have replaced the fuse and it is still dead. I have double checked the PCB and I
have found a part that seems to be charred.
http://i.imgur.com/4hpUKpb.jpg
I?m not sure what the big grey things are. I?d guess those are some kind of resistors
(labeled 2W10% 15K), but I have not seen something like that before. If so, the one
horizontally in the pic seems to be burnt. The PCB is charred underneath it, and no
current goes thru it accordint to my multimeter.
?
On the other hand, I will have a stupid trouble: I can?t remove the PCB from the chassis,
because one of the TORX screws is? well? screwed. The turndriver does not fix onto its
head. I guess I?ll have to do a compraption taking a derivation from the (suposed)
resistor out of the PCB. Unless there is any kind of magic for a broken screw head (and
no, I can?t vandalize this one).
Some things never change.. ;)
ATX PSUs are far more abundant. ;)
8:13 p.m.
Can you make a picture of the screw?
Normal resistors are 0.25 Watt. Cut out the burnt one (15 k) and replace w?ith eight
normal resistors of 120kOhms, put them in parallel.
See what happens.
Verzonden?vanaf?mijn?BlackBerry?10-smartphone.
? Origineel bericht ?
Van: Jordi Guillaumes i Pons
Verzonden: maandag 15 februari 2016 19:53
Aan: HECnet Mailing List
Beantwoorden: hecnet at Update.UU.SE
Onderwerp: Re: [HECnet] VS4000/60 power supply dead... or not?
Well, I have replaced the fuse and it is still dead. I have double checked the PCB and I
have found a part that seems to be charred.
http://i.imgur.com/4hpUKpb.jpg
I?m not sure what the big grey things are. I?d guess those are some kind of resistors
(labeled 2W10% 15K), but I have not seen something like that before. If so, the one
horizontally in the pic seems to be burnt. The PCB is charred underneath it, and no
current goes thru it accordint to my multimeter.
On the other hand, I will have a stupid trouble: I can?t remove the PCB from the chassis,
because one of the TORX screws is? well? screwed. The turndriver does not fix onto its
head. I guess I?ll have to do a compraption taking a derivation from the (suposed)
resistor out of the PCB. Unless there is any kind of magic for a broken screw head (and
no, I can?t vandalize this one).
Some things never change.. ;)
ATX PSUs are far more abundant. ;) 
16 Feb
16 Feb
12:22 a.m.
Yes They are wire wound power resisters that are made taking wire wound around a ceramic
base. From your markings it would mean it is rated @ 2watts within 10% of the rated value
of 15000 ohms (i.e. at least 13500 ohms and not more than 16500). These values tell you
the maximum current / voltage etc that can be running through it before it will burn up.
But the reason why those resisters are mechanically off the board is because they do get
very hot as they typically do carry a lot of current and put off a lot of heat as they
drop the voltage at that current.
You can try to test it with a DVM on resistance mode but it's going to tell you the
impedance of those two points in the circuit so if anything is parallel with the resister
you will pick up that also.
Sent from my iPad
On Feb 15, 2016, at 1:53 PM, Jordi Guillaumes i Pons <jg at jordi.guillaumes.name>
wrote:
Well, I have replaced the fuse and it is still dead. I have double checked the PCB and I
have found a part that seems to be charred.
http://i.imgur.com/4hpUKpb.jpg
I?m not sure what the big grey things are. I?d guess those are some kind of resistors
(labeled 2W10% 15K), but I have not seen something like that before. If so, the one
horizontally in the pic seems to be burnt. The PCB is charred underneath it, and no
current goes thru it accordint to my multimeter.
On the other hand, I will have a stupid trouble: I can?t remove the PCB from the chassis,
because one of the TORX screws is? well? screwed. The turndriver does not fix onto its
head. I guess I?ll have to do a compraption taking a derivation from the (suposed)
resistor out of the PCB. Unless there is any kind of magic for a broken screw head (and
no, I can?t vandalize this one).
Some things never change.. ;)
ATX PSUs are far more abundant. ;)
2996
days inactive
2997
days old
8 comments
5 participants
participants (5)
-
b4＠gewt.net -
clemc＠ccc.com -
hvlems＠zonnet.nl -
jg＠jordi.guillaumes.name -
mcguire＠neurotica.com