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Questions about the inverter in a Thinkpad 770

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Anonymous
a b D Laptop
May 21, 2005 2:04:52 AM

Archived from groups: comp.sys.laptops (More info?)

Three years ago, I bought a used Thinkpad 770. It worked for quite some
time, but occasionally I heard a sort of crackling or frying sound coming
from inside it. Finally, it just gave out. When I turned it on, the LCD (the
status panel, not the display screen) would dim out in a few seconds and the
computer would then do nothing.

I had two repair shops look at it. Both said it was probably the system
board. I did not want to spend a lot more money on repair (especially with
these particular shops -- but that's another story.)

I put it aside and bought another Thinkpad, which is working fine. But,
in hopes of resurrecting the original one, last week I bought a TP770 system
board on eBay. The seller advertised it as tested and working, and that was
true. When I got the 770 back together and applied power, it began to boot up
normally. But then I heard that frying sound again. I immediately pulled out
the power plug. (There was no battery in the unit.)

So my questions are:

1. Does this sound like a short or leakage in the inverter?

2. If I run the unit in order to troubleshoot it, am I likely to
burn out the new system board?

Chris Winter
Anonymous
a b D Laptop
May 21, 2005 2:04:53 AM

Archived from groups: comp.sys.laptops (More info?)

Christopher P. Winter wrote:
> Three years ago, I bought a used Thinkpad 770. It worked for quite
> some time, but occasionally I heard a sort of crackling or frying
> sound coming from inside it. Finally, it just gave out. When I turned
> it on, the LCD (the status panel, not the display screen) would dim
> out in a few seconds and the computer would then do nothing.
>
> I had two repair shops look at it. Both said it was probably the
> system board. I did not want to spend a lot more money on repair
> (especially with these particular shops -- but that's another story.)
>
> I put it aside and bought another Thinkpad, which is working fine.
> But, in hopes of resurrecting the original one, last week I bought a
> TP770 system board on eBay. The seller advertised it as tested and
> working, and that was true. When I got the 770 back together and
> applied power, it began to boot up normally. But then I heard that
> frying sound again. I immediately pulled out the power plug. (There
> was no battery in the unit.)
>
> So my questions are:
>
> 1. Does this sound like a short or leakage in the inverter?
>
> 2. If I run the unit in order to troubleshoot it, am I likely to
> burn out the new system board?
>
> Chris Winter

I think it is time to open the LCD case and inspect the inverter. If it
is the inverter it would have to have a completed circuit to be
"crackling" and that isn't good, even if not producing high voltage. You
won't damage the mainboard if the entire LCD is disconnected *if that is
the source of the crackling*, so I would check the inverter first.
Otherwise, you have some problem on the mainboard, and that seems to be
unlikely to have occured on both the old and new boards. Also, did you
note any physical damage on the old board? Is there a separate power
management board that could be the source?

Q
Anonymous
a b D Laptop
May 23, 2005 7:00:55 AM

Archived from groups: comp.sys.laptops (More info?)

"Christopher P. Winter" wrote:
>
> Three years ago, I bought a used Thinkpad 770. It worked for quite some
> time, but occasionally I heard a sort of crackling or frying sound coming
> from inside it. Finally, it just gave out. When I turned it on, the LCD (the
> status panel, not the display screen) would dim out in a few seconds and the
> computer would then do nothing.
>
> I had two repair shops look at it. Both said it was probably the system
> board. I did not want to spend a lot more money on repair (especially with
> these particular shops -- but that's another story.)
>
> I put it aside and bought another Thinkpad, which is working fine. But,
> in hopes of resurrecting the original one, last week I bought a TP770 system
> board on eBay. The seller advertised it as tested and working, and that was
> true. When I got the 770 back together and applied power, it began to boot up
> normally. But then I heard that frying sound again. I immediately pulled out
> the power plug. (There was no battery in the unit.)
>
> So my questions are:
>
> 1. Does this sound like a short or leakage in the inverter?
>
> 2. If I run the unit in order to troubleshoot it, am I likely to
> burn out the new system board?
>
> Chris Winter

.... you plugged a charger into your first 770 and it fried when you turned it
on.. you got another 770, plugged it in(the same charger I assume), turned it on
and now it fried.. Does anyone else see a pattern here?

did you see/smell smoke? If you have a voltmeter, check to voltage out of the
brick. If the status panel(small thin LCD below the screen) is blank/dead, most
likely system board is gone too.

1) It doesnt sound like a short in the inverter, but a short from the system
board to ground(case), or a bad brick(charger)

2) Until you chk the voltage out of the brick, or check for shorts to ground I
wouldnt power it up.

What I might suggest, you ditch the 770's and get a 600. Even a vanilla
600(2645-51U) can be upgraded to a 300 to 400mhz(if you can find one) cpu, carry
more RAM, is lighter, better built and easier to get into. I've fooled with
MANY 770's(I have a pile of 770 parts -cheap-) and dropped them like a bad habit
when I discovered the 600 series. The 600x will take up to an 850mhz cpu. Your
HD and RAM from the 770 will work in the 600 as well.

Good luck,

TJ
=================================================================
Pilots track their lives by the number of hours in the air,
as if any other time isn't worth noting....
Michael Rarfit
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Anonymous
a b D Laptop
May 23, 2005 9:26:04 PM

Archived from groups: comp.sys.laptops (More info?)

On Mon, 23 May 2005 03:00:55 GMT, "Capt. Wild Bill Kelso, USAAC"
<Dec7.1941@cableaz.com> wrote:

>"Christopher P. Winter" wrote:
>>
>> Three years ago, I bought a used Thinkpad 770. It worked for quite some
>> time, but occasionally I heard a sort of crackling or frying sound coming
>> from inside it. Finally, it just gave out. When I turned it on, the LCD (the
>> status panel, not the display screen) would dim out in a few seconds and the
>> computer would then do nothing.
>>
>> I had two repair shops look at it. Both said it was probably the system
>> board. I did not want to spend a lot more money on repair (especially with
>> these particular shops -- but that's another story.)
>>
>> I put it aside and bought another Thinkpad, which is working fine. But,
>> in hopes of resurrecting the original one, last week I bought a TP770 system
>> board on eBay. The seller advertised it as tested and working, and that was
>> true. When I got the 770 back together and applied power, it began to boot up
>> normally. But then I heard that frying sound again. I immediately pulled out
>> the power plug. (There was no battery in the unit.)
>>
>> So my questions are:
>>
>> 1. Does this sound like a short or leakage in the inverter?
>>
>> 2. If I run the unit in order to troubleshoot it, am I likely to
>> burn out the new system board?
>>
>> Chris Winter
>
>... you plugged a charger into your first 770 and it fried when you turned it
>on.. you got another 770, plugged it in(the same charger I assume), turned it on
>and now it fried.. Does anyone else see a pattern here?
>

Actually, I plugged it into the power brick I'm using for my other
Thinkpad (the one that works fine, as I mentioned.) The voltage out of it
reads 16.5V no load. I plugged it into the old TP770 system board (now
disconnected from keyboard and LCD) and again read 16.5V. I know of no way to
measure the full-load voltage without disassembling a working laptop.

This brick is the one that came with my first Thinkpad (the 770). Its P/N
is 83H6339. Output rating: 16V at 3.36A.

The other brick is P/N 02K7010. It too has an output rating of 16V at
3.36A. Today I measured its no-load voltage as 16.3V. This one came with my
second Thinkpad -- a TP770Z.

Oddly enough, it was this second brick that I took with my first Thinkpad
when I brought it in for repair. It's true that the repair shop told me this
brick was intermittently producing over-voltage output. I didn't believe it
then, and I don't believe it now.

Can we agree that the power brick is not the problem?

>did you see/smell smoke? If you have a voltmeter, check to voltage out of the
>brick. If the status panel(small thin LCD below the screen) is blank/dead, most
>likely system board is gone too.
>

No sign of smoke associated with this "frying" sound -- ever. I might
also mention that the frying sound occurred intermittently for months with no
apparent effect on laptop operation -- before the original failure. The
screen did black out momentarily a time or two, accompanied by a "snap" like
an arc-over. Yes, I should have done something about that earlier. IIRC, the
frying sound and the arc-snap never occurred at or near the same time.

>1) It doesnt sound like a short in the inverter, but a short from the system
>board to ground(case), or a bad brick(charger)
>
>2) Until you chk the voltage out of the brick, or check for shorts to ground I
>wouldnt power it up.
>
>What I might suggest, you ditch the 770's and get a 600. Even a vanilla
>600(2645-51U) can be upgraded to a 300 to 400mhz(if you can find one) cpu, carry
>more RAM, is lighter, better built and easier to get into. I've fooled with
>MANY 770's(I have a pile of 770 parts -cheap-) and dropped them like a bad habit
>when I discovered the 600 series. The 600x will take up to an 850mhz cpu. Your
>HD and RAM from the 770 will work in the 600 as well.
>

Well, that's a thought. I'll check out what's available on eBay. But if I
buy another laptop in the near future, I'll probably go for one of the T20
series.

Chris
Anonymous
a b D Laptop
May 24, 2005 10:27:38 AM

Archived from groups: comp.sys.laptops (More info?)

"Christopher P. Winter" wrote:
>
> On Mon, 23 May 2005 03:00:55 GMT, "Capt. Wild Bill Kelso, USAAC"
> <Dec7.1941@cableaz.com> wrote:
>
> >"Christopher P. Winter" wrote:
> >>
> >> Three years ago, I bought a used Thinkpad 770. It worked for quite some
> >> time, but occasionally I heard a sort of crackling or frying sound coming
> >> from inside it. Finally, it just gave out. When I turned it on, the LCD (the
> >> status panel, not the display screen) would dim out in a few seconds and the
> >> computer would then do nothing.
> >>
> >> I had two repair shops look at it. Both said it was probably the system
> >> board. I did not want to spend a lot more money on repair (especially with
> >> these particular shops -- but that's another story.)
> >>
> >> I put it aside and bought another Thinkpad, which is working fine. But,
> >> in hopes of resurrecting the original one, last week I bought a TP770 system
> >> board on eBay. The seller advertised it as tested and working, and that was
> >> true. When I got the 770 back together and applied power, it began to boot up
> >> normally. But then I heard that frying sound again. I immediately pulled out
> >> the power plug. (There was no battery in the unit.)
> >>
> >> So my questions are:
> >>
> >> 1. Does this sound like a short or leakage in the inverter?
> >>
> >> 2. If I run the unit in order to troubleshoot it, am I likely to
> >> burn out the new system board?
> >>
> >> Chris Winter
> >
> >... you plugged a charger into your first 770 and it fried when you turned it
> >on.. you got another 770, plugged it in(the same charger I assume), turned it on
> >and now it fried.. Does anyone else see a pattern here?
> >
>
> Actually, I plugged it into the power brick I'm using for my other
> Thinkpad (the one that works fine, as I mentioned.) The voltage out of it
> reads 16.5V no load. I plugged it into the old TP770 system board (now
> disconnected from keyboard and LCD) and again read 16.5V. I know of no way to
> measure the full-load voltage without disassembling a working laptop.
>
> This brick is the one that came with my first Thinkpad (the 770). Its P/N
> is 83H6339. Output rating: 16V at 3.36A.
>
> The other brick is P/N 02K7010. It too has an output rating of 16V at
> 3.36A. Today I measured its no-load voltage as 16.3V. This one came with my
> second Thinkpad -- a TP770Z.
>
> Oddly enough, it was this second brick that I took with my first Thinkpad
> when I brought it in for repair. It's true that the repair shop told me this
> brick was intermittently producing over-voltage output. I didn't believe it
> then, and I don't believe it now.
>
> Can we agree that the power brick is not the problem?
>
> >did you see/smell smoke? If you have a voltmeter, check to voltage out of the
> >brick. If the status panel(small thin LCD below the screen) is blank/dead, most
> >likely system board is gone too.
> >
>
> No sign of smoke associated with this "frying" sound -- ever. I might
> also mention that the frying sound occurred intermittently for months with no
> apparent effect on laptop operation -- before the original failure. The
> screen did black out momentarily a time or two, accompanied by a "snap" like
> an arc-over. Yes, I should have done something about that earlier. IIRC, the
> frying sound and the arc-snap never occurred at or near the same time.
>
> >1) It doesnt sound like a short in the inverter, but a short from the system
> >board to ground(case), or a bad brick(charger)
> >
> >2) Until you chk the voltage out of the brick, or check for shorts to ground I
> >wouldnt power it up.
> >
> >What I might suggest, you ditch the 770's and get a 600. Even a vanilla
> >600(2645-51U) can be upgraded to a 300 to 400mhz(if you can find one) cpu, carry
> >more RAM, is lighter, better built and easier to get into. I've fooled with
> >MANY 770's(I have a pile of 770 parts -cheap-) and dropped them like a bad habit
> >when I discovered the 600 series. The 600x will take up to an 850mhz cpu. Your
> >HD and RAM from the 770 will work in the 600 as well.
> >
>
> Well, that's a thought. I'll check out what's available on eBay. But if I
> buy another laptop in the near future, I'll probably go for one of the T20
> series.
>
> Chris

If its been crackling/hissing for a while, then quit, I'd leave it. Big, heavy,
clunky.. not really what you could call user friendly, tho I really liked the
volume and speakers clear of wrists.
yep, seems like a lotta work for the 770. The T-series are great, but the 600
series are cheaper. I have several of each, a T20 with a 900mhz chip and a
wonderful 1.13ghz T23(i'm on now). I had done numerous mods to the 770, cpu's
from 200 to 400mhz, and the 600 series(my fav's), but the 600X work the best. I
have three 850mhz 600X's that started life at 500mhz that the kids use, and the
900mhz T20 is the wife's. That one really screams for a T20, just runs a little
warm ;) 

TJ
(aka Dr. von FrankenPad)
=================================================================
Pilots track their lives by the number of hours in the air,
as if any other time isn't worth noting....
Michael Rarfit
Anonymous
a b D Laptop
May 28, 2005 9:08:00 PM

Archived from groups: comp.sys.laptops (More info?)

On Mon, 23 May 2005 03:00:55 GMT, "Capt. Wild Bill Kelso, USAAC"
>
>What I might suggest, you ditch the 770's and get a 600. Even a vanilla
>600(2645-51U) can be upgraded to a 300 to 400mhz(if you can find one) cpu, carry
>more RAM, is lighter, better built and easier to get into. I've fooled with
>MANY 770's(I have a pile of 770 parts -cheap-) and dropped them like a bad habit
>when I discovered the 600 series. The 600x will take up to an 850mhz cpu. Your
>HD and RAM from the 770 will work in the 600 as well.
>

Thank you. I have a 770 with the inverter failing and found a
600E(P366, 96MB). Swapped the RAM from the 770 and now have 128MB.

With the 600's thinner case the floppy and DVD-ROM won't fit. The
floppy I only use rarely and found the connector cable so that's OK.
Do you know any way of using the DVD-ROM from the 770 in the 600?

Any other suggestions as to parts worthwhile swapping?

--
If you can't figure out my address from this,
then we probably don't have a lot to talk about:
bpoulton$vcn:bc:ca
!