23 Jun
1997
23 Jun
'97
7:13 a.m.
Picked up one of these the other day, no power supply, anyone know what
this monster needs for the 3 pin powersupply connection? {pinouts}
23 Jun
23 Jun
4:44 a.m.
Date: Mon, 23 Jun 1997 11:13:59 -0500
Reply-to: classiccmp(a)u.washington.edu
From: "Bill Girnius" <thedm(a)sunflower.com>
To: "Discussion re-collecting of classic computers"
<classiccmp(a)u.washington.edu>
Subject: IBM PCjr
X-To: "Classic" <classiccmp(a)u.washington.edu>
Picked up one of these the other day, no power supply,
anyone know what
this monster needs for the 3 pin powersupply connection? {pinouts}
Center tapped ransformer is used. Both 17v ac at 2amp each on each
outmost pins, center pin is the center tapped wire for transformer.
Kind of kludge. But I worked out a pinout for that power slot to use
regular efficient power supply via a custom adapter.
Jason D.
3:39 p.m.
Center tapped ransformer is used. Both 17v ac at
2amp each on each
outmost pins, center pin is the center tapped wire for transformer.
Are you _sure_ about this (as in 'Have you measured it'). My PC-jr was
missing the power brick, and I must get round to making one. A glance at
the PSU schematic convinced me it wasn't tapped to earth, but it could
have been.
If you know for sure, could you please confirm this so I don't blow up my
PSU card.
Jason D.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
6:38 a.m.
Tony,
> Center tapped ransformer is used. Both 17v ac
at 2amp each on each
> outmost pins, center pin is the center tapped wire for transformer.
I vaguely
remembered had to run up the power card with dc
transformer so I could puzzle out last one or two voltages on it.
Had to do several steps to find all the voltages.
4:50 p.m.
Tony,
> > Center tapped ransformer is used. Both 17v ac at 2amp each on each
> > outmost pins, center pin is the center tapped wire for transformer.
I vaguely remembered had to run up the power card with
dc
transformer so I could puzzle out last one or two voltages on it.
Had to do several steps to find all the voltages.
From there, wired up a adapter which worked. Note, it is not 24vac
on each line! it is 12v on each wires if you buy center tapped
transformers you will see like that added up by outside two wires
measured. It goes like that marked on the transformer and the
transformer has three wires, of two wires same color and one is
different color, then it's a center tapped.
I'm not sure I understand that at all. I assume you're saying that it's a
12-0-12 trasformer (or actually 17-0-17 - I am _sure_ 17V is mentioned
somewhere in the IBM manual).
Do you agree with the circuits I've just sent out? If not, could you
please tell me where I've gone wrong?
Hello? Knock, knock...:) Anyway I did clearly
remember that 17v ac
Yes, I'm here...
on each wire (of two) and the center tap on one
wire.
The power card rectify and regulates all the voltages for the
Yep, I'll agree to that.
computer. That sort of thing I did build several
power supplies
based on center tapped transformers, using center tap as common.
Consider this: Take two aa battries and wire up in series, total
voltage is 3v assuming they're fresh. But put a wire as common
between two batteries and measure two wires in turn without swapping
those probes! This will give you one positive 1.5v and negative
1.5v which that how center tapped transformer power supplies in this
Yes, that sounds 100% reasonable. I may be from Cambridge, but I do
understand _some_ electrical engineering :-) (Seriously, I had to explain
jsut that to a 3rd year student in electrical engineering the other
week..... There is something wrong with the world.)
After all 'There is no such thing as ground' What you take as a 0V
reference is entirely up to you.
configuration worked. But part of the circuity
requires components
to rectify and smooth out the ripples caused by ac to dc
rectification process then final voltage regulation to complete the
inefficient ac to dc conversion process.
The inefficiency in a linear PSU is in the regulator (which wastes energy
as heat) and not (in general) in the rectifier or smoothing circuit. Of
course a high-frequency SMPS can get away with smaller smoothing
capacitors and a smaller (ferrite-cored) transfoemer.
Efficient power supplies are switching type, little heat
and low losses in conversion process plus very light weight.
But they use same design in outputs (secondaries but for some who
knows electronics, these uses high frequency or fast recovery diodes)
See my comment on that crazy Zenith PSU that I mentioned in an earlier
post....
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
7:42 a.m.
Tony,
Done and replied! :)
I'm not sure I understand that at all. I assume you're saying that it's a
12-0-12 trasformer (or actually 17-0-17 - I am _sure_ 17V is mentioned
somewhere in the IBM manual).
Oh, It was just a unloaded probing run to figure out
what voltage is
there because my reference is all screwed up. Actually did it with a
regular small transformer not those center tapped ones.
Sorry.
Do you agree with the circuits I've just sent out?
If not, could you
please tell me where I've gone wrong?
Yours is fine. :)
> Hello? Knock, knock...:) Anyway I did clearly
remember that 17v ac
Don't take as a poke, I was just in jest, good mood. :)
Yes, I'm here...
Whew.
Yes, that sounds 100% reasonable. I may be from Cambridge, but I do
understand _some_ electrical engineering :-) (Seriously, I had to explain
jsut that to a 3rd year student in electrical engineering the other
week..... There is something wrong with the world.)
You got my ears peaked up.
What was that trouble with this 3rd
student's error?
After all 'There is no such thing as ground' What you take as a 0V
reference is entirely up to you.
Really? Common, ground, 0V, neutral, power return
makes my mind spin
but I adapt to what you're talking about...so you're not talking
mumbo-jumbo stuff. :)
The inefficiency in a linear PSU is in the regulator (which wastes energy
as heat) and not (in general) in the rectifier or smoothing circuit. Of
course a high-frequency SMPS can get away with smaller smoothing
capacitors and a smaller (ferrite-cored) transfoemer.
I know about this linears heating problem and I do have a old Asus
P/I-P55TP4XEG pentium which has one on board. HOT as sun and must
air-forced cooled on it keep it bit warm not hot. :) But my Asus
P/I-P55T2P4 rev 3.x new board now uses switchers on it and they use
tiny heatsinks and stayed cool even they're able to channel 10amp
through them. Impressive. And more IMPRESSIVELY is that Asus's new
VX and TX boards uses these SMT switchers without any heatsink,
relying on ground planes to spread heat out and radiated off.
Why I had to get new one? Old XEG I/O chip blown by static
accidently but I removed that SMT 100 legged IC and it worked again
for other purposes for now.
Efficient power supplies are switching type, little heat
and low losses in conversion process plus very light weight.
But they use same design in outputs (secondaries but for some who
knows electronics, these uses high frequency or fast recovery diodes)
See my comment on that crazy Zenith PSU that I mentioned in an earlier
post.... --
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
Jason D.
5:57 p.m.
Yes, that
sounds 100% reasonable. I may be from Cambridge, but I do
understand _some_ electrical engineering :-) (Seriously, I had to explain
jsut that to a 3rd year student in electrical engineering the other
week..... There is something wrong with the world.)
You got my ears peaked up.
What was that trouble with this 3rd
student's error?
After all 'There is no such thing as ground' What you take as a 0V
reference is entirely up to you.
Really? Common, ground, 0V, neutral, power
return makes my mind spin
but I adapt to what you're talking about...so you're not talking
mumbo-jumbo stuff. :) I know about this linears heating problem and I do
have a old Asus
I have a 5V 50A _linear_ in one of my Unibus expanison boxes (a 3rd party
one - DEC almost always used SMPS's). It runs hot.
Jason D.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
1:09 p.m.
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 379 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/19970623/c35c0b12/at…
6:14 p.m.
A couple of things. Firstly I had to explain that
if you connect
cells/batteries in series then the voltages add but if you connect (equal
voltage) them in parallel the voltage is unchanged but the internal
resistance and capacity are increased.
Gees, you'd confuse me, too, if you tried to
convince me that paralleling cells
will increase internal resistance.
Tim.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
3:04 p.m.
On Mon, 23 Jun 1997, Bill Girnius wrote:
Picked up one of these the other day, no power supply,
anyone know what
this monster needs for the 3 pin powersupply connection? {pinouts}
There's been a huge boring discussion going on forever on the list. I
know of about 2 or 3 of these sitting in thrift shops right now. Send me
e-mail and I'll go pick one up for you, and you can just reimburse me for
the cost+shipping. Same goes for ayone else interested.
Sam
-------------------------------------------------------------------------------
Computer Historian, Programmer, Musician, Philosopher, Athlete, Writer, Jackass
24 Jun
24 Jun
5:06 a.m.
[PC-jr PSU]
There's been a huge boring discussion going on
forever on the list. I
Err, I thought that repair and restoration questions were welcome here. If
not, then I appolgise and will unsubscribe. What I find _extremely_ boring
are the lists of machines/bits that people have just bought from the
garage sale/thrift store/wherever. Such messages seem to be simply 'Oh how
lucky I am' type things.
PC-jr's are not common over here. I've only ever seen one - the one I
bought. The transformer bricks are equally rare and shipping one from the
States would cost a lot more than making one from new parts. And there
will come a time when there are no more working transformer bricks and
you'll need to make your own, in which case having measurements taken from
one that was working will be rather useful info.
Sam
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
5:51 a.m.
Hello Tony,
Actually 34vac 2amp center tapped
transformer. The center tap goes
to ground, what else how can negative voltages can be generated so
it needs this ground. The both outside 2 pins for 17v ac lines goes
there. The card rectify it to generate 3 dc voltages, two is
positive and other one is negative. Bulk of the components is used
to generate 5vdc, and a wimpy 12vdc source for the floppy drive and
fan. And last one is in very small current negative current -12v dc
which takes this voltage and go through a 7905 regulator to get -5v
dc, both voltages are strictly for serial use and little use for
else.
Funny, instead of 60hz, you get the same type of circuit design in
secondary side in lots of switching power supplies with few minor
differences.
The limits to overdrive if you do, both card and slot is due to the
current limit allowance per contact on that slot. :( Leave it to be
and parallel the seperate power sources to the sidecars if they have
them. Another problem with this is that 3 connections is not enough
to carry more than 2amp on each socket.
By the way, I am Electomechanical major in training "on hold". :)
From memory the central pin is chassis ground and
the outside 2 are 18V AC
at about 3A. The manual doesn't give the schematics of the
transformer unit (it does
for the PSU card in the main unit), and it's not clear from the
description whether the AC input is centre-tapped to ground or not.
Looking at the schematics, I think that it is _NOT_
Oh yes, I did saw the techref for the outside PSU transformer is
pretty simple just a disconnectable center tapped transformer.
One thing I hated that they did not give us the that schematics for
that power card module which I revsere engineered instead!
Jason D.
4:18 p.m.
Hello Tony,
Actually 34vac 2amp center tapped
transformer. The center tap goes
I was wrong. It's 17-0-17V, then. That's what I will use.
From memory the central pin is chassis ground and
the outside 2 are 18V AC
at about 3A. to ground, what else how can negative voltages can be
generated so
it needs this ground. The both outside 2 pins for 17v ac lines goes
Well, it could use a switching regulator. OK, I know it doesn't do so for
the negative voltages - obviously I wasn't thinking straight earlier...
there. The card rectify it to generate 3 dc voltages,
two is
positive and other one is negative. Bulk of the components is used
to generate 5vdc, and a wimpy 12vdc source for the floppy drive and
The 5V regulator seems to be a switching one, which is what I'd have
expected.
fan. And last one is in very small current negative
current -12v dc
which takes this voltage and go through a 7905 regulator to get -5v
dc, both voltages are strictly for serial use and little use for
else.
Funny, instead of 60hz, you get the same type of circuit design in
secondary side in lots of switching power supplies with few minor
differences.
Yes, is that suprising? After all, a switching supply is nothing magical.
You still need to transform the AC output into DC and regulate it. Of
course you can always perform some regulation on an SMPS by varying the
drive waveforms on the primary side.
Talking of bad design (I was earlier...) I've seen some _crazy_ SMPS's in
my time. In a Zenith monitor there's a supply that combines the
reliability of a switcher with the efficiency of a linear. It rectifies
the mains, feeds it to a free-running chopper (no regulation applied
here), shoves that into a little transformer, rectifies the output and
feeds it (about 18V DC) into a linear regulator that uses the power-on LED
as the reference. It's the only monitor that _requires_ a green power-on
LED. When my blew up (chopper failed, etc), I replaced the entire mess
with a little torroidal transformer. It was cheaper than a new chopper
transistor and a lot simpler.
Then there are the Boschert 2-stage supplies that are used in Sanders
printers and PERQ 1's (and probably elsewhere). A shorted chopper in one
of those (which is a very common failure mode) will blow up 2 more
expensive power transistors and then take out a number of small
transistors, the chopper control IC (a good old 723), a few passives and a
couple of PCB tracks. I had to sort out such a mess once - I can provide
the full story if anyone's interested.
The manual
doesn't give the schematics of the transformer unit (it does
for the PSU card in the main unit), and it's not clear from the
description whether the AC input is centre-tapped to ground or not.
Looking at the schematics, I think that it is _NOT_
Oh yes, I did saw the techref for the outside PSU transformer is pretty simple just a disconnectable center tapped
transformer.
One thing I hated that they did not give us the that schematics for
that power card module which I revsere engineered instead!
But that is. The PSU card schematics (starting from the 3 pin connector)
were included.
Jason D.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
7:10 a.m.
Tony,
Ok,
Huh? That would make sense because the linear regulator in T220 case
is limited to 1.5amp which it requires measly 3.6amp on that 5v
lines.
I was wrong. It's 17-0-17V, then. That's what I will use.
Great.
to ground, what else how can negative voltages
can be generated so
it needs this ground. The both outside 2 pins for 17v ac lines goes
Well, it could use a switching regulator. OK, I know it doesn't do so for
the negative voltages - obviously I wasn't thinking straight earlier...
there. The card rectify it to generate 3 dc
voltages, two is
positive and other one is negative. Bulk of the components is used
to generate 5vdc, and a wimpy 12vdc source for the floppy drive and
The 5V regulator seems to be a switching one, which is what I'd have
expected. Yes, is that suprising? After all, a switching supply
is nothing magical.
You still need to transform the AC output into DC and regulate it. Of
course you can always perform some regulation on an SMPS by varying the
drive waveforms on the primary side.
Hmmm...I fix PC powers and modern SMPS for the
computer all the time
to save $. Around here in canada costs above $60cdn for a new
200watt PSU.
Talking of bad design (I was earlier...) I've seen some _crazy_ SMPS's in
my time. In a Zenith monitor there's a supply that combines the
reliability of a switcher with the efficiency of a linear. It rectifies
the mains, feeds it to a free-running chopper (no regulation applied
here), shoves that into a little transformer, rectifies the output and
feeds it (about 18V DC) into a linear regulator that uses the power-on LED
as the reference. It's the only monitor that _requires_ a green power-on
LED. When my blew up (chopper failed, etc), I replaced the entire mess
with a little torroidal transformer. It was cheaper than a new chopper
transistor and a lot simpler.
Ewwww.... that is bit overkill to design that! But closed loop
switchers is very efficient and compact but that transformer is
certainly larger than the orignals.
Are you talking about this beige tiny 12" green or amber monitor with
angular back? In this, chopper trans pops and kills one resistor.
They are usually either TTL or composite.
I have a working zenith Eazy PC with hd in it. Slow and buggy. :)
Then there are the Boschert 2-stage supplies that are
used in Sanders
printers and PERQ 1's (and probably elsewhere). A shorted chopper in one
of those (which is a very common failure mode) will blow up 2 more
expensive power transistors and then take out a number of small
transistors, the chopper control IC (a good old 723), a few passives and a
couple of PCB tracks. I had to sort out such a mess once - I can provide
the full story if anyone's interested.
Hmmm... you could email me privately
with this account of yours. :)
I have a astec PSU switcher that one big transistor on masssive
heatsink driving BOTH switching transformers.
Is one of that odd design?
Odd... That's not in my TechRef...
Well it was on different page I think, I did not have it as I was
looking through it and copying few vital items. But it did show the
pinouts only. Oh yeah, the power card does have a 2 pin connector
near the transformer input, that is wired directly to the center
tapped to the motherboard ground. It is required to make PCjr work
reliably.
Check your techref, mine is different book is incorrect but my
analysis is correct and was used to power up PCjr via SMPS box: pin
1 is -5v, 2 and 3 is ground, 4 through 7 is 5v, 8 and 9 is ground
again, finally 10 is 12v. I guess it did not require -12v. oops. :)
Relation of pin A1 starts from front end works backwards to back for
pin A10.
For the transformer, it is 33watt fused, 17ac-0-17vac in same
order as power input for the power board.
By the way, where I could buy this real techref and how much?
Soooo, I could fix up it with addons to XT standards.
But that is. The PSU card schematics (starting from
the 3 pin connector)
were included.
My source version didn't. :(
Thanks.
Jason D.
5:26 p.m.
The 5V
regulator seems to be a switching one, which is what I'd have
expected.
Huh? That would make sense because the linear regulator in T220 case
is limited to 1.5amp which it requires measly 3.6amp on that 5v
lines. Yes, is that suprising? After all, a switching
supply is nothing magical.
You still need to transform the AC output into DC and regulate it. Of
course you can always perform some regulation on an SMPS by varying the
drive waveforms on the primary side.
Hmmm...I fix PC powers and modern SMPS for
the computer all the time
to save $. Around here in canada costs above $60cdn for a new
200watt PSU.
Talking of bad design (I was earlier...) I've seen some _crazy_ SMPS's in
my time. In a Zenith monitor there's a supply that combines the
reliability of a switcher with the efficiency of a linear. It rectifies
the mains, feeds it to a free-running chopper (no regulation applied
here), shoves that into a little transformer, rectifies the output and
feeds it (about 18V DC) into a linear regulator that uses the power-on LED
as the reference. It's the only monitor that _requires_ a green power-on
LED. When my blew up (chopper failed, etc), I replaced the entire mess
with a little torroidal transformer. It was cheaper than a new chopper
transistor and a lot simpler.
Ewwww.... that is bit overkill to design that! But closed loop switchers is very efficient and compact but that
transformer is
certainly larger than the orignals.
Actually, the 50Hz 30VA transformer was no larger than the original
bits...
Are you talking about this beige tiny 12" green
or amber monitor with
That's the one.
angular back? In this, chopper trans pops and kills
one resistor.
Well, I had shorted turns in the chopper transformer (tested on a homebrew
'ring tester'). It didn't seem worth rewinding.
They are usually either TTL or composite.
I have a working zenith Eazy PC with hd in it. Slow and buggy. :)
I still have mine on a much-hacked PC/AT
Then there are the Boschert 2-stage supplies that
are used in Sanders
printers and PERQ 1's (and probably elsewhere). A shorted chopper in one
of those (which is a very common failure mode) will blow up 2 more
expensive power transistors and then take out a number of small
transistors, the chopper control IC (a good old 723), a few passives and a
couple of PCB tracks. I had to sort out such a mess once - I can provide
the full story if anyone's interested.
Hmmm... you could email me privately
with this account of yours. :) By the way, where I could buy this real techref and
how much?
Soooo, I could fix up it with addons to XT standards.
I got mine from IBM about 2 months ago. I'll try and find the part
number/form number to order it if you like.
Jason D.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
8:20 a.m.
Tony,
Ok that is no problem with PCjr matter. :)
Too bad that happened!
That is pretty rare for me.
Yep, so do I. Most SMPS faults are pretty simple (at
least if the
transformer has not got shorted turns...). And it's certainly worth doing
for the more obscure supplies (i.e. not generic PC ones...)
Shorted turns is very,
very rare in SMPS that I came across.
Long run of lucky I guess.
> > as the reference. It's the only monitor
that _requires_ a green power-on
> > LED. When my blew up (chopper failed, etc), I replaced the entire mess
> > with a little torroidal transformer. It was cheaper than a new chopper
> > transistor and a lot simpler.
> >
Using LED as a reference? That is poor idea to do that! It should
have put the sense line on that heavy current line to work.
Hmmm your hack to feed 20vac there looked better! :)
Actually, the 50Hz 30VA transformer was no larger than
the original
bits...
Cool!
Are you talking about this beige tiny 12"
green or amber monitor with
That's the one.
angular back? In this, chopper trans pops and
kills one resistor.
Well, I had shorted turns in the chopper transformer (tested on a homebrew
'ring tester'). It didn't seem worth rewinding. I still have mine on a much-hacked PC/AT
Oh yea,
it looked nice and impossibly compact.
I prefer TTL there than composite unless it is for color.
It may as well go here - it's just about on-topic....
The basic circuit design is :
1) Rectify/double the AC mains input to give 340V DC
2) Feed that into a non-isolated 'flyback' converter to step it down to
150V.
hi frenquency ac or dc at that point?
3) Feed the output of that into a free-running
push-pull oscillator using
a couple of big power transistors.
Well, I can't imagine that would able to
work if the power is ac to
that push/pull trans?
4) That oscillator drives the primary of the main
transformer
Snip! loads of worthless protection info... :)
drive to (2) if it overcurrents.
Now, here's what goes wrong.
1) The chopper (2) shorts. The output of that stage now leaps to 340V
(since there's a DC path through the shorted transistor and the inductor)
Ah! Not a transformer just a giant inductor driven by that chopper?
:) that would be a biggest OUCHIE! Why not jerryjig a design to
clamp down based on voltage level when exceeding 150v at this point
when chopper went so it will blow the fuse instead?
2) The oscillator (3) continues running, so the 5V
line leaps to about 12V
3) The crowbar trips, shorting the output to ground
4) The overcurrent trip tries to work, but as the chopper (2) is shorted,
it doesn't do a darn thing.
Other option, Why not use this output of this crowbar to trip other
clamper at the 340vdc output to blow the fuse instantly?
You want to blow the fuse first before the last 2 trans dies
resulting in expensive heap of smelly stuff. :)
5) The 2 oscillator transistors short as well. The
total load on the 340V
line is now the 3 shorted transistors, a few low-resistance inductors, and
the 0.12 Ohm sense resistor. The latter explodes, feeding 340V into the
sense circuitry, which dies expensively, often taking some PCB tracks with
it.
6) The fuse fails...
What a load of smelly results and worthless fuse there! :(
I got mine from IBM about 2 months ago. I'll try
and find the part
number/form number to order it if you like.
Thank you, I will find out how it costs when I have that part
number.
Jason D.
24 Jun
24 Jun
4:47 a.m.
New subject: SMPS's (was PC-jr)
[Zenith Monitor]
DC. It's smoothed by a smallish capacitor.
[...]
Absolutely...
That would have meant an extra optoisolator at least. And would you trust
a thyristor to short a 340V line at essentially unlimited current?
Using LED as a reference? That is poor idea to do
that! It should
have put the sense line on that heavy current line to work.
I think you misunderstood me. It does sample the output of the PSU. But it
compares it to the 2V-ish across the power-on LED rather than using a
zener or something similar.
[Boschert 2-stage]
1)
Rectify/double the AC mains input to give 340V DC
2) Feed that into a non-isolated 'flyback' converter to step it down to
150V.
hi frenquency ac or dc at that point? 1) The chopper
(2) shorts. The output of that stage now leaps to 340V
(since there's a DC path through the shorted transistor and the inductor)
Ah! Not a transformer just a giant inductor driven by that chopper? :) that would be a biggest OUCHIE! Why not jerryjig
a design to
clamp down based on voltage level when exceeding 150v at this point
when chopper went so it will blow the fuse instead?
I'm not sure you could. The voltage at that point rises as the PSU is
loaded (to compensate for losses in the transformer and oscillator). I
suspect the crowbar would still kill the oscillator transistors and cause
a lot of other damage before the overvoltage trip did a darn thing.
2) The oscillator (3) continues running, so the
5V line leaps to about 12V
3) The crowbar trips, shorting the output to ground
4) The overcurrent trip tries to work, but as the chopper (2) is shorted,
it doesn't do a darn thing.
Other option, Why not use this output of this crowbar to trip other
clamper at the 340vdc output to blow the fuse instantly?
You want to blow the fuse first before the last 2 trans dies
resulting in expensive heap of smelly stuff. :) Jason D.
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill
9924
days inactive
9925
days old
17 comments
5 participants
participants (5)
-
ard12＠eng.cam.ac.uk -
dastar＠crl.com -
jpero＠mail.cgo.wave.ca -
shoppa＠alph02.triumf.ca -
thedm＠sunflower.com