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Laserjet III DC power supply probs

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Anonymous
a b α HP
a b ) Power supply
May 2, 2005 9:43:09 AM

Archived from groups: sci.electronics.repair,comp.periphs.printers,comp.sys.hp.hardware (More info?)

Hi folks,

has anyone out there ever managed to troubleshoot the DC power supply
in one of these dinosaurs? Mine's developed a fault in the 24V supply,
killing the fans and main motor < 1 minute after powerup. Input from
the AC module remains stable (220VAC) , as does the 5V output since the
panel still functions and gripes about a "SERVICE 55". According to the
service manual, 55 indicates a DC controller error, but I've ruled
that out since the 24V output from the DC PSU still drops after
detaching the DC controller.

I'd appreciate any comments on diagnosing this baby on the component
level. Sure, replacing the entire module is a piece of cake, but hardly
worth the cost when I can get an LJ4+ for the same price (which of
course isn't quite as rock solid)...

Thanks 'n' stuff!

--GanjaTron
Anonymous
a b α HP
a b ) Power supply
May 2, 2005 12:22:42 PM

Archived from groups: sci.electronics.repair,comp.periphs.printers,comp.sys.hp.hardware (More info?)

Go to www.anderson-tech.com and look for the toll free number. Give Mr.
Anderson a call. He may be able to help you out.

"GanjaTron" <ganjatron@gmx.net> wrote in message
news:1115037789.059181.223020@z14g2000cwz.googlegroups.com...
> Hi folks,
>
> has anyone out there ever managed to troubleshoot the DC power supply
> in one of these dinosaurs? Mine's developed a fault in the 24V supply,
> killing the fans and main motor < 1 minute after powerup. Input from
> the AC module remains stable (220VAC) , as does the 5V output since the
> panel still functions and gripes about a "SERVICE 55". According to the
> service manual, 55 indicates a DC controller error, but I've ruled
> that out since the 24V output from the DC PSU still drops after
> detaching the DC controller.
>
> I'd appreciate any comments on diagnosing this baby on the component
> level. Sure, replacing the entire module is a piece of cake, but hardly
> worth the cost when I can get an LJ4+ for the same price (which of
> course isn't quite as rock solid)...
>
> Thanks 'n' stuff!
>
> --GanjaTron
>
Anonymous
a b α HP
a b ) Power supply
May 2, 2005 5:05:29 PM

Archived from groups: sci.electronics.repair,comp.periphs.printers,comp.sys.hp.hardware (More info?)

The LJ4, LJ4+ and LJ5 are just as rock-solid as the LJ3. They all have better
power-saving features. Retire the LJ3 unless you can get one for free to
scavenge for parts... Ben Myers

On 2 May 2005 05:43:09 -0700, "GanjaTron" <ganjatron@gmx.net> wrote:

>Hi folks,
>
>has anyone out there ever managed to troubleshoot the DC power supply
>in one of these dinosaurs? Mine's developed a fault in the 24V supply,
>killing the fans and main motor < 1 minute after powerup. Input from
>the AC module remains stable (220VAC) , as does the 5V output since the
>panel still functions and gripes about a "SERVICE 55". According to the
>service manual, 55 indicates a DC controller error, but I've ruled
>that out since the 24V output from the DC PSU still drops after
>detaching the DC controller.
>
>I'd appreciate any comments on diagnosing this baby on the component
>level. Sure, replacing the entire module is a piece of cake, but hardly
>worth the cost when I can get an LJ4+ for the same price (which of
>course isn't quite as rock solid)...
>
>Thanks 'n' stuff!
>
>--GanjaTron
>
Related resources
Anonymous
a b α HP
a b ) Power supply
May 3, 2005 12:46:29 AM

Archived from groups: sci.electronics.repair,comp.periphs.printers,comp.sys.hp.hardware (More info?)

Let me know how you make out. I have several PS and remnants in the
shop which I can let go at modest price. Contact me
therepairman at optonline.net


On 2 May 2005 05:43:09 -0700, "GanjaTron" <ganjatron@gmx.net> wrote:

>Hi folks,
>
>has anyone out there ever managed to troubleshoot the DC power supply
>in one of these dinosaurs? Mine's developed a fault in the 24V supply,
>killing the fans and main motor < 1 minute after powerup. Input from
>the AC module remains stable (220VAC) , as does the 5V output since the
>panel still functions and gripes about a "SERVICE 55". According to the
>service manual, 55 indicates a DC controller error, but I've ruled
>that out since the 24V output from the DC PSU still drops after
>detaching the DC controller.
>
>I'd appreciate any comments on diagnosing this baby on the component
>level. Sure, replacing the entire module is a piece of cake, but hardly
>worth the cost when I can get an LJ4+ for the same price (which of
>course isn't quite as rock solid)...
>
>Thanks 'n' stuff!
>
>--GanjaTron
Anonymous
a b α HP
a b ) Power supply
May 4, 2005 12:41:47 PM

Archived from groups: sci.electronics.repair,comp.periphs.printers,comp.sys.hp.hardware (More info?)

yourtown@newyork.com wrote:
> Let me know how you make out. I have several PS and remnants in the
> shop which I can let go at modest price.

Assuming this is a thermal problem, I poked around with cold spray in
there -- to no avail. None of the suspect components (regulators, etc)
reacted to cooling. Without schematics, I'm pretty screwed anyway...

--GT
Anonymous
a b α HP
a b ) Power supply
May 4, 2005 10:26:09 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

ato_...@hotmail.com wrote:

> If you are happy to dig into component level,

Well... not exactly *happy*... :^)

> there are probably a
> couple or so of 6-legged opto-couplers in the DC PSU.

Optocouplers in a PSU? Didn't see those. I'll take a closer look.

> That was the problem with my HP (Canon engine) laser.

All old(er) HPs use Canon engines, AFAIK.

> You will probably find a service manual on the internet, try
> http://www.eserviceinfo.com/
> for starters, though there are other sites. You might have to
> do a bit of digging on the ESI site as it's indexing seems a
> bit flakey, may be ok when you get the hang of it.

Thanks for the link! Found some interesting stuff on there, though as
you point out, the index *is* pretty convoluted.

> Other than that it's a case of following logic level signals
> and strategic measuring of voltages. Like does the fuser
> lamp come on at start up, if not why? Does it start to
> cycle?

The fuser draws its power from the AC PSU, right? I doubt that's the
problem though, particularly when both fans are dead.

Thanks for the reply, mon!
Anonymous
a b α HP
a b ) Power supply
May 4, 2005 10:28:05 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

On 4-May-2005, "GanjaTron" <ganjatron@gmx.net> wrote:

> Assuming this is a thermal problem, I poked around with cold spray in
> there -- to no avail. None of the suspect components (regulators, etc)
> reacted to cooling. Without schematics, I'm pretty screwed anyway...

If you are happy to dig into component level, there are probably a
couple or so of 6-legged opto-couplers in the DC PSU. might be
worth monitoring voltages across the LED's and their o/p to see
if they are respondingt to drive. The LED's are known to die.
That was the problem with my HP (Canon engine) laser. Ended
up putting in a 6-pin skt, and a red LED in series with the opto
LED drive. Now red LED lights in sympathy with the fuser lamp,
if fuser doesn't light diagnosis is simple.
..
You will probably find a service manual on the internet, try
http://www.eserviceinfo.com/
for starters, though there are other sites. You might have to
do a bit of digging on the ESI site as it's indexing seems a
bit flakey, may be ok when you get the hang of it.

Other than that it's a case of following logic level signals
and strategic measuring of voltages. Like does the fuser
lamp come on at start up, if not why? Does it start to
cycle?
May 5, 2005 12:26:10 AM

Archived from groups: sci.electronics.repair,comp.periphs.printers,comp.sys.hp.hardware (More info?)

as old as this thing is, and the heat over the years, it wouldnt surprise me
that the radial electrolytics in the power supply is leaking or dried.

I know this is a far cry from a fax machine, but I worked on a fax machine
with similar problems, Recapped the power supply, and all went away.


"GanjaTron" <ganjatron@gmx.net> wrote in message
news:1115037789.059181.223020@z14g2000cwz.googlegroups.com...
> Hi folks,
>
> has anyone out there ever managed to troubleshoot the DC power supply
> in one of these dinosaurs? Mine's developed a fault in the 24V supply,
> killing the fans and main motor < 1 minute after powerup. Input from
> the AC module remains stable (220VAC) , as does the 5V output since the
> panel still functions and gripes about a "SERVICE 55". According to the
> service manual, 55 indicates a DC controller error, but I've ruled
> that out since the 24V output from the DC PSU still drops after
> detaching the DC controller.
>
> I'd appreciate any comments on diagnosing this baby on the component
> level. Sure, replacing the entire module is a piece of cake, but hardly
> worth the cost when I can get an LJ4+ for the same price (which of
> course isn't quite as rock solid)...
>
> Thanks 'n' stuff!
>
> --GanjaTron
>
Anonymous
a b α HP
a b ) Power supply
May 5, 2005 10:48:01 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

On 5-May-2005, "GanjaTron" <ganjatron@gmx.net> wrote:

> The fuser draws its power from the AC PSU, right? I doubt that's the
> problem though, particularly when both fans are dead.

Yes, fuser (in mine) draws power from AC PSU. There is a power
board and a logic board in the AC PSU (Canon SX), and the DC PSU
feeds it with assorted signals. The logic board has a fattish resistor
of 1K2 driving the power boards opto-coupler, the one I added an
extra LED in series. Opto drives triac, with the extra red LED,
LED goes on/off, triac goes on/off, fuser lamp goes on/off. Now
it's easier to trouble shoot. AC PSU also has a relay in series
with mains supply to triac. I found I could short it out for testing,
so I put a domestic lamp in place of the fuser lamp, set it up
on a table, and drove it with a 9V battery and resistor, for testing.
Saved installing and uninstalling the PSU all the time.

DC PSU has opto couplers, there is an isolated switch mode,
raw AC in. It's txfmr drives all the rectifiers, logic etc, there
are output V level sensors, and their o/p feeds back to the
isolated switch mode. So we have a mains side, and
an isolated logic side.
Anonymous
a b α HP
a b ) Power supply
May 6, 2005 11:50:06 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

On 6-May-2005, "GanjaTron" <ganjatron@gmx.net> wrote:

> > DC PSU has opto couplers, there is an isolated switch mode,
> > raw AC in. It's txfmr drives all the rectifiers, logic etc, there
> > are output V level sensors, and their o/p feeds back to the
> > isolated switch mode. So we have a mains side, and
> > an isolated logic side.

My DC PSU is Sanken, tracing through it I found the raw
mains AC (from the AC PSU) was rectified, smoothed, and
used to drive a switchmode, with multiple output windings
on its switchmode txfmr. Same principle as late TV's with
switchmode supplies. The rectified output from the DC side
is fed back through opto-couplers to alter the switchmode
duty cycle, and hence regulate the DC logic side. I found
2 opto-couplers in mine. Possibly mine isn't the same
model as yours, can't get my PSU number without
pulling printer apart, but I would expect, as its from the
same era and company, to be similar.

From what you say, control panel still stays working, but
not the motors, suggests that the switchmode is still
running (otherwise how is the contol panel being supplied?)
yet the motors DC supply isn't there, since they stop.

Fuser seems ok, it lights up and goes out, so its supply,
opto-coupler, triac probably ok.

Start up (in mine) seems to inolve the fuser thermistor,
if it doesn't see the fuser getting hot it shuts down.
There are also several protective paper path sensors,
any one of which can create a fault condition.

You really need a schematic (or at least a block
schematic) so you can find and monitor the DC levels
at where they plug into the chassis.
Anonymous
a b α HP
a b ) Power supply
May 8, 2005 1:28:23 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

ato_zee@hotmail.com wrote:

> I found
> 2 opto-couplers in mine. Possibly mine isn't the same
> model as yours, can't get my PSU number without
> pulling printer apart, but I would expect, as its from the
> same era and company, to be similar.

It's a Sanken PS10059K. I now remember reading something about
optocouplers for regulation in Sam Goldwasser's SMPS FAQ. I think the
two optocouplers you mention are 2 TLP634 6-pin DIP ICs sitting side by
side between the primary and secondary sides. But how do I test them???

> From what you say, control panel still stays working, but
> not the motors, suggests that the switchmode is still
> running (otherwise how is the contol panel being supplied?)
> yet the motors DC supply isn't there, since they stop.

Actually, the PSU emits a very faint high pitched whine when the fans &
motor stop, so apparently it shuts down partially.

> You really need a schematic (or at least a block
> schematic) so you can find and monitor the DC levels
> at where they plug into the chassis.

All I have is the block diagram in the service manual -- no schematics.
I've monitored the voltages, and it's definitely the DC PSU, but I
can't figure out the exact component.

--GanjaTron
May 8, 2005 6:16:39 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

I think everyone got distracted and ignored the "55 error" in the post.
In an HPIII a 55 error is a communications error between the DC
controller and the Formatter board. Both need to be replaced. If you go
to fixyourownprinter.com and type HPIII 55 error in the search box,
you'll see the info. There is also a service manual available for free
download. If you so decide, you can get replacement parts as well.


ato_...@hotmail.com wrote:
> On 8-May-2005, "GanjaTron" <ganjatron@gmx.net> wrote:
>
> > It's a Sanken PS10059K. I now remember reading something about
> > optocouplers for regulation in Sam Goldwasser's SMPS FAQ. I think
the
> > two optocouplers you mention are 2 TLP634 6-pin DIP ICs sitting
side by
> > side between the primary and secondary sides. But how do I test
them???
> >
> From what you say, I suspect that the high pitched whine, mentioned
> below suggests a DC PSU overload. Shorted or partially shorted
> DC rail. So I'd keep the opto's as suspects, but look elsewhere
first.
> It's hard to test opto's in situ, took mine out, and put in 6-pin
sockets.
> Then you can bench test them, energise with 9V battery, 1k in series,
> on the LED side. Try another LED, same 9V with another 1k on the
> other side. Apply 9mA to opto side should turn output side LED on,
> and it should stay latched on, until you disconnect the battery, and
> start again. If you desolder carefully you can probably put it back
> (which is why I used a skt) afterwards.
>
> > > From what you say, control panel still stays working, but
> > > not the motors, suggests that the switchmode is still
> > > running (otherwise how is the contol panel being supplied?)
> > > yet the motors DC supply isn't there, since they stop.
> >
> > Actually, the PSU emits a very faint high pitched whine when the
fans &
> > motor stop, so apparently it shuts down partially.
> >
>
> Several approaches to testing switchmodes. One is a wind up Variac.
> The other that has worked many times for me is to have a battery
> of domestic lamp skts, in parallel, in series with the mains.
> Then plugging in lamps lets increasing amounts of current through.
> With luck you can get the PSU to stay running, at reduced
> input voltage, while you poke around with a meter. I've got
> the holders on a board, mains lead in and out.
>
> Sometimes in the absence of a full schematic I have to trace
> PCB tracks/components, and draw it. Of course it may not
> be in the motor supply line, but an overload somewhere else.
> With switchmodes, with shorted rails, I often break/disconnect
> one rail at a time to see if it stays up. Also do rail to ground
> resistance checks. You can also, for low voltage rails, eg 12V,
> wire auto bulbs in series, you can find 5W, 8W, 10W, up to
> about 50W at 12V as appropriate, they are ok for 5V rails
> as well. The one in series with the shorted rail comes pretty
> well full on, but the switchmode should stay running. Once you
> stop the switchmode going into spasm and shutting down
> you stand a chance of diagnosing which rail is causing the
> problem, then by splitting the circuit down (by lifting one leg
> of components) just where the problem is. Diagnosing
> switchmodes has a learning curve, then you get to do it
> with some confidence.
>
> > > You really need a schematic (or at least a block
> > > schematic) so you can find and monitor the DC levels
> > > at where they plug into the chassis.
> >
> > All I have is the block diagram in the service manual -- no
schematics.
> > I've monitored the voltages, and it's definitely the DC PSU, but I
> > can't figure out the exact component.
Anonymous
a b α HP
a b ) Power supply
May 8, 2005 11:04:24 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

On 8-May-2005, "GanjaTron" <ganjatron@gmx.net> wrote:

> It's a Sanken PS10059K. I now remember reading something about
> optocouplers for regulation in Sam Goldwasser's SMPS FAQ. I think the
> two optocouplers you mention are 2 TLP634 6-pin DIP ICs sitting side by
> side between the primary and secondary sides. But how do I test them???
>
From what you say, I suspect that the high pitched whine, mentioned
below suggests a DC PSU overload. Shorted or partially shorted
DC rail. So I'd keep the opto's as suspects, but look elsewhere first.
It's hard to test opto's in situ, took mine out, and put in 6-pin sockets.
Then you can bench test them, energise with 9V battery, 1k in series,
on the LED side. Try another LED, same 9V with another 1k on the
other side. Apply 9mA to opto side should turn output side LED on,
and it should stay latched on, until you disconnect the battery, and
start again. If you desolder carefully you can probably put it back
(which is why I used a skt) afterwards.

> > From what you say, control panel still stays working, but
> > not the motors, suggests that the switchmode is still
> > running (otherwise how is the contol panel being supplied?)
> > yet the motors DC supply isn't there, since they stop.
>
> Actually, the PSU emits a very faint high pitched whine when the fans &
> motor stop, so apparently it shuts down partially.
>

Several approaches to testing switchmodes. One is a wind up Variac.
The other that has worked many times for me is to have a battery
of domestic lamp skts, in parallel, in series with the mains.
Then plugging in lamps lets increasing amounts of current through.
With luck you can get the PSU to stay running, at reduced
input voltage, while you poke around with a meter. I've got
the holders on a board, mains lead in and out.

Sometimes in the absence of a full schematic I have to trace
PCB tracks/components, and draw it. Of course it may not
be in the motor supply line, but an overload somewhere else.
With switchmodes, with shorted rails, I often break/disconnect
one rail at a time to see if it stays up. Also do rail to ground
resistance checks. You can also, for low voltage rails, eg 12V,
wire auto bulbs in series, you can find 5W, 8W, 10W, up to
about 50W at 12V as appropriate, they are ok for 5V rails
as well. The one in series with the shorted rail comes pretty
well full on, but the switchmode should stay running. Once you
stop the switchmode going into spasm and shutting down
you stand a chance of diagnosing which rail is causing the
problem, then by splitting the circuit down (by lifting one leg
of components) just where the problem is. Diagnosing
switchmodes has a learning curve, then you get to do it
with some confidence.

> > You really need a schematic (or at least a block
> > schematic) so you can find and monitor the DC levels
> > at where they plug into the chassis.
>
> All I have is the block diagram in the service manual -- no schematics.
> I've monitored the voltages, and it's definitely the DC PSU, but I
> can't figure out the exact component.
Anonymous
a b α HP
a b ) Power supply
May 9, 2005 5:14:46 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

Yes, rather than taking the time to troubleshoot and repair components, REPLACE
them !!!! Even when this printer was HP's top-of-the-line, HP techs never
repaired individual components.

But if you like challenges, have at it. I have enough challenges in my life
without attempting board repairs... Ben Myers

On 8 May 2005 14:16:39 -0700, Dani@spamtothehand.com wrote:

>I think everyone got distracted and ignored the "55 error" in the post.
>In an HPIII a 55 error is a communications error between the DC
>controller and the Formatter board. Both need to be replaced. If you go
>to fixyourownprinter.com and type HPIII 55 error in the search box,
>you'll see the info. There is also a service manual available for free
>download. If you so decide, you can get replacement parts as well.
>
>
Anonymous
a b α HP
a b ) Power supply
May 15, 2005 12:32:49 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

Well, I've recapped the PSU... no dice. :^(

--GanjaTron
May 15, 2005 7:58:33 PM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

GanjaTron wrote:
> Well, I've recapped the PSU... no dice. :^(
>
> --GanjaTron
>
The simplest solution would probably be to go to your favorite computer
graveyard and pick up a "parts" machine (or two), then replace a board
at a time.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
Anonymous
a b α HP
a b ) Power supply
May 16, 2005 12:17:12 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

So stated by other postings in this thread... Ben Myers

On Sun, 15 May 2005 15:58:33 GMT, CJT <abujlehc@prodigy.net> wrote:

>GanjaTron wrote:
>> Well, I've recapped the PSU... no dice. :^(
>>
>> --GanjaTron
>>
>The simplest solution would probably be to go to your favorite computer
>graveyard and pick up a "parts" machine (or two), then replace a board
>at a time.
>
>--
>The e-mail address in our reply-to line is reversed in an attempt to
>minimize spam. Our true address is of the form che...@prodigy.net.
May 16, 2005 1:53:59 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

Ben Myers wrote:
> So stated by other postings in this thread... Ben Myers

Sorry ... guess I came in late.

>
> On Sun, 15 May 2005 15:58:33 GMT, CJT <abujlehc@prodigy.net> wrote:
>
>
>>GanjaTron wrote:
>>
>>>Well, I've recapped the PSU... no dice. :^(
>>>
>>>--GanjaTron
>>>
>>
>>The simplest solution would probably be to go to your favorite computer
>>graveyard and pick up a "parts" machine (or two), then replace a board
>>at a time.
>>
>>--
>>The e-mail address in our reply-to line is reversed in an attempt to
>>minimize spam. Our true address is of the form che...@prodigy.net.
>
>


--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form che...@prodigy.net.
Anonymous
a b α HP
a b ) Power supply
May 16, 2005 3:04:28 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

Nothing wrong with reinforcing what others have already stated. It's not like
the majority rules, but... Ben Myers

On Sun, 15 May 2005 21:53:59 GMT, CJT <abujlehc@prodigy.net> wrote:

>Ben Myers wrote:
>> So stated by other postings in this thread... Ben Myers
>
>Sorry ... guess I came in late.
>
>>
>> On Sun, 15 May 2005 15:58:33 GMT, CJT <abujlehc@prodigy.net> wrote:
>>
>>
>>>GanjaTron wrote:
>>>
>>>>Well, I've recapped the PSU... no dice. :^(
>>>>
>>>>--GanjaTron
>>>>
>>>
>>>The simplest solution would probably be to go to your favorite computer
>>>graveyard and pick up a "parts" machine (or two), then replace a board
>>>at a time.
>>>
>>>--
>>>The e-mail address in our reply-to line is reversed in an attempt to
>>>minimize spam. Our true address is of the form che...@prodigy.net.
>>
>>
>
>
>--
>The e-mail address in our reply-to line is reversed in an attempt to
>minimize spam. Our true address is of the form che...@prodigy.net.
Anonymous
a b α HP
a b ) Power supply
May 17, 2005 8:52:56 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

"GanjaTron" <ganjatron@gmx.net> wrote in message
news:1116273372.255613.217250@z14g2000cwz.googlegroups.com...
>
> ato_...@hotmail.com wrote:
>
> > With switchmodes going into spasm lift/break one rail at a time until
> > it doesn't spasm/shutdown.
>
> You mean actually *severing* paths on the PCB? Isn't that rather
> drastic? :^)

Standard repair method.
--
N
Anonymous
a b α HP
a b ) Power supply
May 17, 2005 10:05:02 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

On 17-May-2005, "NSM" <nowrite@to.me> wrote:

> > > With switchmodes going into spasm lift/break one rail at a time until
> > > it doesn't spasm/shutdown.
> >
> > You mean actually *severing* paths on the PCB? Isn't that rather
> > drastic? :^)
>
> Standard repair method.

The DC power supply feeds the rest of the printer,
lift the outputs, one by one, at the socket the PSU plugs into. If it's
an overload in one of the modules, it'll stop shutting down. The
PSU shutting down may only be a symptom of trouble elsewhere.
May 18, 2005 5:36:50 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

NSM wrote:
> "GanjaTron" <ganjatron@gmx.net> wrote in message
> news:1116273372.255613.217250@z14g2000cwz.googlegroups.com...
>
>>ato_...@hotmail.com wrote:
>>
>>
>>>With switchmodes going into spasm lift/break one rail at a time until
>>>it doesn't spasm/shutdown.
>>
>>You mean actually *severing* paths on the PCB? Isn't that rather
>>drastic? :^)
>
>
> Standard repair method.

Perhaps in some circles.

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Anonymous
a b α HP
a b ) Power supply
May 18, 2005 9:33:18 AM

Archived from groups: comp.periphs.printers,comp.sys.hp.hardware,sci.electronics.repair (More info?)

"CJT" <abujlehc@prodigy.net> wrote in message
news:428A9C31.8020809@prodigy.net...
> NSM wrote:

> > Standard repair method.
>
> Perhaps in some circles.

The circles competent repairmen travel in, yes.
--
N
!