14 Dec
2004
14 Dec
'04
7:08 a.m.
Hi
Sure sounds like a thermal limit switch. It could also
be a Poly-Fuse.
As for voltage of the transformer, if it is bad, one can
still determine the ratio by cutting the wires off with
a single cut per turn and then count the wires for the
primary and secondary. One does have to watch out if there
are taps, other than center tap.
Dwight
From: "Vintage Computer Festival"
<vcf(a)siconic.com>
So after beating the shit out of this stupid TI power supply (none of your
suggestions worked, thanks) I come to find that it does have an internal
fuse and that it is complete intact. Wonderful. This thing is shot
beyond repair at this point. It wasn't intended to ever be opened
apparently.
Anyway, hopefully I can figure out what this pile of garbage was supposed
to be putting out. Of course, there are no markings on the housing of the
transformer.
There is an IC in here. It's inline with the hot side of the input
voltage. The markings are thusly:
UMI EI
X25 150(degree symbol)C
2.5A 250V~
A varistor?
Anyway, this is a heap of junk now.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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14 Dec
14 Dec
10:36 a.m.
What was the model of this silent700? I have one at home, working, and
can put a VM on the P.S. for you, assuming it's the same and all that.
Markings on transformer cube?
terminal model number?
15 Dec
15 Dec
10:55 a.m.
On Tue, 14 Dec 2004, Tom Jennings wrote:
What was the model of this silent700? I have one at
home, working, and
can put a VM on the P.S. for you, assuming it's the same and all that.
It's the portable unit: Model 703.
Markings on transformer cube?
None.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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11:21 a.m.
On Wed, 15 Dec 2004, Vintage Computer Festival wrote:
On Tue, 14 Dec 2004, Tom Jennings wrote:
Michael S. answered this for you, correct? 20VAC nominal?
What was the model of this silent700? I have one
at home, working, and
can put a VM on the P.S. for you, assuming it's the same and all that.
It's the portable unit: Model 703.
> Markings on transformer cube?
11:32 a.m.
On Wed, 15 Dec 2004, Tom Jennings wrote:
On Wed, 15 Dec 2004, Vintage Computer Festival wrote:
But across which pins??? The power connector on the terminal has three
pins. Which ones want voltage and which one wants ground?
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
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On Tue, 14 Dec 2004, Tom Jennings wrote:
Michael S. answered this for you, correct? 20VAC nominal? What was the model of this silent700? I have one
at home, working, and
can put a VM on the P.S. for you, assuming it's the same and all that.
It's the portable unit: Model 703.
> Markings on transformer cube? 
1:34 p.m.
Vintage Computer Festival wrote:
But across which pins??? The power connector on the
terminal has three
pins. Which ones want voltage and which one wants ground?
Look inside it. In any case, since it's AC, it doesn't *matter* which
is voltage and which is ground. There's no "polarity" as such, since
the secondary of the transformer is going to be floating.
Gordon.
1:58 p.m.
New subject: Are HP 2671's repairable?
Are parts available to repair a HP 2671G printer?
I'd like to replace the geared belt that drives the print-head.
I'm not at all sure that the head can be removed from this belt
so I may be talking about a complete head and belt assembly
which I'd assume is unobtainium.
If its just a matter of attaching the head to a replacement
belt, does anyone have the specs or a source for the belt?
Apparently whatever these belts are made of gets old in a
bad way, they become sticky and brittle, both are bad for
drive belts.
Given this, I'm assuming even a new-old stock drive belt would
not be servicable.
2:15 p.m.
New subject: Are HP 2671's repairable?
I have one of these printers.....
I think this is the device with the contradictory notices on the bottom.
One says something like 'Do not remove cover, no user serviceable parts
inside'. The other says 'To remove cover, undo the 4 indicated screws'.
Hmm...
When I got mine, it didn't have any paper in it. I guessed thermal fax
paper would work (it does), but the shop I went to only had 210mm wide
rolls (European standard), the 2671 (and US fax machines, I think) take
216mm wide paper. Well, I spent a bit of time making a couple of spacers
to fit on the end of the roll spindle to get it in the right place, and
it worked pretty well. But I was darn annoyed when I went to a different
branch of the same shop to find they also had 216mm wide fax paper...
Are parts available to repair a HP 2671G printer?
Some are, some aren't, I guess. Much of the electronics, for example, is
standard TTL chips....
I'd like to replace the geared belt that drives the print-head.
I'm not at all sure that the head can be removed from this belt
It's been a long sime since I've been inside mine, and I don't really
want to strip it down tonight. How is the belt fixed to the head. I would
guess they can be separated (normally it's possible to replace just the
belt on HP thermal printers).
so I may be talking about a complete head and belt
assembly
which I'd assume is unobtainium.
If its just a matter of attaching the head to a replacement
belt, does anyone have the specs or a source for the belt?
Can you not measure up the old belt, measure the pitch of the teeth on
the sprockets, etc?
-tony
2:53 p.m.
New subject: Are HP 2671's repairable?
At 07:58 PM 12/15/04 -0500, you wrote:
Are parts available to repair a HP 2671G printer?
I'd like to replace the geared belt that drives the print-head.
I'm not at all sure that the head can be removed from this belt
so I may be talking about a complete head and belt assembly
which I'd assume is unobtainium.
If its just a matter of attaching the head to a replacement
belt, does anyone have the specs or a source for the belt?
Apparently whatever these belts are made of gets old in a
bad way, they become sticky and brittle, both are bad for
drive belts.
Given this, I'm assuming even a new-old stock drive belt would
not be servicable.
Bob,
I just send you a message about this but here's an additional comment.
Given this, I'm assuming even a new-old stock drive
belt would
not be servicable.
I took some old belts out of a HP-85 and took them to an industrial
belting company (Florida Belting) and they matched them up with current
production belts. Their belts are orange and I think they're made of Kevlar
so they shouldn't have the melting problem.
Joe
4:05 p.m.
New subject: Amiga 3000 Mother Board replacement
I have a friend with an Amiga 3000. It appears that the backup battery has
leaked on the mother board causing it to no longer function.
Does anyone know where to find a replacement motherboard?
Any other suggestions would be appreciated.
4:29 p.m.
New subject: Amiga 3000 Mother Board replacement
Best bet would be to find one on e-bay, or www.softhut.com.
Gary Hildebrand
St. Joseph, MO
I have a friend with an Amiga 3000. It appears that
the backup battery has
leaked on the mother board causing it to no longer function.
Does anyone know where to find a replacement motherboard?
Any other suggestions would be appreciated.
5:29 p.m.
New subject: Amiga 3000 Mother Board replacement
Hello Gene
On 12/16/04, you wrote:
I have a friend with an Amiga 3000. It appears that the backup
battery has leaked on the mother board causing it to no longer
function.
Does anyone know where to find a replacement motherboard?
Any other suggestions would be appreciated.
c.s.a.marketplace, Amibench or Ebay. I doubt Software Hut has them,
and if they do, you will pay a premium price. I bought one off
c.s.a.marketplace, and one of the CIA's has already blown. PITA
tearing it down and pulling the CIA's off my spare motherboard to
replace it. Anyone know if it is the left or the right one looking
from the front of the case, that controls the mouse?
Regards
--
Mike Leavitt ac998(a)lafn.org
19 Dec
19 Dec
10:18 a.m.
New subject: Amiga 3000 Mother Board replacement
Hello Gene
On 16/12/04, you wrote:
I have a friend with an Amiga 3000. It appears that the backup battery has
leaked on the mother board causing it to no longer function.
Does anyone know where to find a replacement motherboard?
Any other suggestions would be appreciated.
Sorry for the late response. Have you tried placing
a wanted add on Amibench. The link is on my website
if you don't have it. Look in LINKS on the menu.
http://www.scuzz.org.uk/amiga/a_amiga_inframe.htm
I found German Ebay much better for getting A3000
and A4000 stuff, though I've never had any luck
with motherboards, I just finish up with whole
computers.
Regards scuzz
Amiga A1200 Blizzard 1230IV - YAM generated mail
http://www.scuzz.org.uk/
15 Dec
15 Dec
2:01 p.m.
Vintage Computer Festival wrote:
But across which pins??? The power connector on the
terminal has three
pins. Which ones want voltage and which one wants ground?
Gordon wrote:
Look inside it. In any case, since it's AC, it
doesn't *matter* which
is voltage and which is ground. There's no "polarity" as such, since
the secondary of the transformer is going to be floating.
Sure, but the third pin isn't necessarily floating with regard to the
other two. For instance, if the third pin is a center tap on the
secondary, leaving it open may cause problems. Possibly including
damage to the device, since unbalanced loads between the ends and the
center tap will drag it around. For instance, suppose it's 18V RMS CT.
The peak voltage between the ends of the secondary will be about 25.4V,
and the peak between either end and the center tap will be about 12.7V.
But suppose the center tap is open, and there is three times the load
between one end and the center tap as between the other end and the
center tap. The voltage between the ends will still have a peak of
25.4V, but the third terminal will now peak at 19V from one end and
only 6.3V from the other. If there's electronics in the device that
was designed for the nominal 12.7V peak and can't withstand the 19V
peak, damage may occur.
This is just like losing the neutral connection on AC power
distribution.
On the other hand, the third pin of the connector could be a safety
ground that may or may not be electrically connected to the transformer
secondary.
Sellam is quite right that he needs to know what the third pin is
supposed to be.
3:19 p.m.
> But across which pins??? The power connector on
the terminal has three
> pins. Which ones want voltage and which one wants ground?
You can almost certainly figure all this out from you now-smashed
P.S. Smack it to smaller bits so's you can see how it's
physically wired. It's even possible thr 3rd pin isn't used,
tied to one of the others, ground, etc. If there's only two
wires in the cable, etc.
I'll try to look at mine tonight.
21 Dec
21 Dec
3:01 p.m.
On Wed, 15 Dec 2004, Tom Jennings wrote:
Ok, I finally got around to figuring out this power supply. I've found
that the center pin on the connector is indeed connected to the center tap
on the transformer, with the outer pins each connected to either end of
the transformer.
There is .3 ohms between the end taps, and .7 ohms between the center tap
and either end tap. So I suppose this means there's 20VAC across the
outer pins and ~10VAC between either outer pin and the center pin?
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
> But
across which pins??? The power connector on the terminal has three
> pins. Which ones want voltage and which one wants ground?
You can almost certainly figure all this out from you now-smashed
P.S. Smack it to smaller bits so's you can see how it's
physically wired. It's even possible thr 3rd pin isn't used,
tied to one of the others, ground, etc. If there's only two
wires in the cable, etc.
I'll try to look at mine tonight.
15 Dec
15 Dec
11:11 p.m.
Eric Smith wrote:
Sellam is quite right that he needs to know what the
third pin is
supposed to be.
Which is why I said to look inside the terminal!
I think I've got one of these in my Mum's loft. Next time I'm up north
I'll try and dig it out. I'm pretty sure it ran just fine on around
18VAC across the outer two pins.
Gordon.
16 Dec
16 Dec
6:47 a.m.
["Eric Smith" <eric(a)brouhaha.com>]
Sure, but the third pin isn't necessarily floating
with regard to the
other two.
It is if you leave it unconnected.
For instance, if the third pin is a center tap on the
secondary, leaving it open may cause problems. Possibly including
damage to the device, since unbalanced loads between the ends and the
center tap will drag it around.
If the centre-tap is left open, there will be no loads, balanced or
not, between it and anywhere; it then becomes equivalent to an
otherwise similar transformer with no centre-tap at all.
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse(a)rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
9:03 a.m.
I wrote:
> For instance, if the third pin is a center tap on
the
> secondary, leaving it open may cause problems. Possibly including
> damage to the device, since unbalanced loads between the ends and the
> center tap will drag it around.
der Mouse wrote:
If the centre-tap is left open, there will be no
loads, balanced or
not, between it and anywhere;
Incorrect, as explained below.
it then becomes equivalent to an
otherwise similar transformer with no centre-tap at all.
The transformer, yes, but the loads will have problems.
Imagine a circuit with a transformer with a 24VAC RMS
center-tapped secondary:
______ ________________
\ || / __|__
/ || \ load1 20 ohm resistive load
\ || / _____
120VAC / || \_______________|
\ || / __|__
/ || \ load2 60 ohm resistive load
\ || / _____
______/ || \_______________|
With everything wired correctly, the loads will each see 12VAC RMS.
Ohm's law tells us that load 1 will draw 600 mA RMS, and load 2 will
draw 200 mA RMS.
Now break the center tap connection. From your statement you apparently
expect that the loads will get no power at all. But that's not what
happens, because the loads are in series and there is still a complete
electrical circuit, albeit not the intended one. Instead, now the
loads form a voltage divider. The current through both loads must
now be the same. Since the combined load has a series resistance of
80 ohms, the current must be 300 mA RMS. Using Ohm's law we can
calculate that load 1 will see 6VAC RMS, and load 2 will see 18VAC RMS.
If load 2 was not designed to tolerate the higher-than-expected voltage
and current, it may be damaged.
And that's for constant purely resistive loads. When the loads vary,
as is typical with most electronic devices, the voltage across each
load will also vary.
As I stated earlier, this is exactly the kind of problem you have with
split-phase or three-phase electrical mains wiring when the neutral
connection in faulty, and that commonly leads to destruction of
equipment. I have a wall-wart that originally had a flat front surface
(the side opposite the plug), but due to a lost neutral on a three-phase
circuit, the front is now hemispherical! I'd have to conclude that the
electrical and/or thermal fuse in the wall-wart did not do its job
correctly; it eventually fused but it should have done so much sooner.
Eric
10:36 a.m.
If the
centre-tap is left open, there will be no loads, balanced or
not, between it and anywhere;
Incorrect, as explained below.
7150
days inactive
7155
days old
19 comments
13 participants
participants (13)
-
ac998＠lafn.org -
ard＠p850ug1.demon.co.uk -
bshannon＠tiac.net -
dwight.elvey＠amd.com -
eric＠brouhaha.com -
gehrich＠tampabay.rr.com -
ghldbrd＠ccp.com -
gordon＠gjcp.net -
korioko＠freeuk.com -
mouse＠Rodents.Montreal.QC.CA -
rigdonj＠cfl.rr.com -
tomj＠wps.com -
vcf＠siconic.com