30 Dec
2002
30 Dec
'02
11:45 a.m.
I have two different Lisa machines and both have a jittery display (one
1.2AMP PSU, 1 1.8 AMP PSU). I've followed the instructions in the Sun
Rem. guide to adjust the power supply output. This works immediately
after the adjustment, but the problem gradually comes back over time. I
adjusted both machines around the September timeframe and the jitters
have back on both machines. I'd like to get both of these machines in
top-shape so I can have them running at my New Years party =)
Before I go through the adjustment again, is there anything else I
should be checking? I've also tried adjusting the V.Hold, but this
doesn't seem to make a difference. Maybe I'm not using a precise enough
adjustment?
Thanks,
Jeff
30 Dec
30 Dec
12:01 p.m.
Oh that's a no-brainer.
Obviously: You have a jitterbug.
(expects to be thrown bodily off the List at any moment)
You have not siad what you mean by 'jitter', and I am not a Lisa owner..
perhaps this is a symptom common to the breed. But I would ask: is it
horizontal, vertical, is the raster fragmenting, is the brightness
varying?
Is it a power supply problem that you are adjusting? If so, when it
returns, is it time related? Temperature related? I see you have made the
adjustment in Sept., but nothing since then? If it takes three months for
the problem to return, I'd be tempted to adjust for the party, then fix it
afterward....
Just my two cents, and worth every penny of it.
Cheers and Happy New Year!
John
12:14 p.m.
On Mon, 2002-12-30 at 21:04, John Lawson wrote:
You have not siad what you mean by 'jitter',
and I am not a Lisa owner..
perhaps this is a symptom common to the breed. But I would ask: is it
horizontal, vertical, is the raster fragmenting, is the brightness
varying?
The "jitter" manifests itself as a very slight (distance-wise) and rapid
vertical bouncing. The brightness is very consistent.
Is it a power supply problem that you are adjusting?
If so, when it
returns, is it time related? Temperature related? I see you have made the
I'm pretty sure it's a power-releated problem as adjusting the supply
temporarily fixes the problem. Heat may play a role in this, as the
jitter subsides to some degree when the system heats up. The
adjustments were made to a "warm" system.
adjustment in Sept., but nothing since then? If it
takes three months for
the problem to return, I'd be tempted to adjust for the party, then fix it
afterward....
I'll do this for now, but it shouldn't need to be adjusted so often.
It's a rather arduous process.
Just my two cents, and worth every penny of it.
Cheers and Happy New Year!
John
12:16 p.m.
I thought I'd add that the adjustments _do_ hold after the systems cool
down. I ran the machines off and on during the week after the
adjustments without a problem, even during extended on/off cycles - they
just don't seem to hold very well over time.
Jeff
On Mon, 2002-12-30 at 21:16, Jeffrey H. Ingber wrote:
On Mon, 2002-12-30 at 21:04, John Lawson wrote:
You have not siad what you mean by
'jitter', and I am not a Lisa owner..
perhaps this is a symptom common to the breed. But I would ask: is it
horizontal, vertical, is the raster fragmenting, is the brightness
varying?
The "jitter" manifests itself as a very slight (distance-wise) and rapid
vertical bouncing. The brightness is very consistent.
Is it a power supply problem that you are
adjusting? If so, when it
returns, is it time related? Temperature related? I see you have made the
I'm pretty sure it's a power-releated problem as adjusting the supply
temporarily fixes the problem. Heat may play a role in this, as the
jitter subsides to some degree when the system heats up. The
adjustments were made to a "warm" system.
adjustment in Sept., but nothing since then? If
it takes three months for
the problem to return, I'd be tempted to adjust for the party, then fix it
afterward....
I'll do this for now, but it shouldn't need to be adjusted so often.
It's a rather arduous process.
Just my two cents, and worth every penny of it.
Cheers and Happy New Year!
John
12:29 p.m.
On Mon, 30 Dec 2002, Jeffrey H. Ingber wrote:
I thought I'd add that the adjustments _do_ hold
after the systems cool
down. I ran the machines off and on during the week after the
adjustments without a problem, even during extended on/off cycles - they
just don't seem to hold very well over time.
Well, speaking as an electronics geek, and, as I said, knowing nothing
Lisa-specific... all this points to accelerated aging of components
either in the power supply, (which I somewhat doubt, for no real 'reason')
or in the sweep and drive circuits of the CRT. Many old components have
an 'end-of-life' runup, and they exhibit the same symptoms (or
meta-symptoms) exactly as you describe.
I of course must defer to the Lisa Mechanics out there. I'm basically
trying to make amends for that awful pun.
Cheers
John
2:06 p.m.
At 09:18 PM 12/30/02 -0500, you wrote:
I thought I'd add that the adjustments _do_ hold
after the systems cool
down. I ran the machines off and on during the week after the
adjustments without a problem, even during extended on/off cycles - they
just don't seem to hold very well over time.
Jeff
I've had this problem on dec VR-201's, and it was usually due to bad
solderjoints getting worse, or failing resistors/caps in the vertical
section of the monitor.
31 Dec
31 Dec
5:27 a.m.
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30 Dec
30 Dec
10:46 p.m.
This happened to my Lisa, after consulting with some Lisa experts found
the fix was really easy. Take the top cover off the Lisa to expose the
Lisa Video Board. You'll see 3 small Pots on top of the video board,
over time the contacts oxide to cause the jitter....now with the Lisa on
and with a small screw driver, *slightly* adjust each pot to wipe away
the oxidation..return the pot to the original setting.
-Chandra
-----Original Message-----
From: cctalk-admin(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]
On Behalf Of Jeffrey H. Ingber
Sent: Monday, December 30, 2002 8:47 PM
To: cctalk(a)classiccmp.org
Subject: Lisa jittery screens
I have two different Lisa machines and both have a jittery display (one
1.2AMP PSU, 1 1.8 AMP PSU). I've followed the instructions in the Sun
Rem. guide to adjust the power supply output. This works immediately
after the adjustment, but the problem gradually comes back over time. I
adjusted both machines around the September timeframe and the jitters
have back on both machines. I'd like to get both of these machines in
top-shape so I can have them running at my New Years party =)
Before I go through the adjustment again, is there anything else I
should be checking? I've also tried adjusting the V.Hold, but this
doesn't seem to make a difference. Maybe I'm not using a precise enough
adjustment?
Thanks,
Jeff
31 Dec
31 Dec
8:42 a.m.
Bingo!
That fixed the jittering on both machines to a large degree. I hit the
pots with a quick burst of contact cleaner and that finished off the
problem completely. The display is as good as new.
Thanks a bunch!
Jeff
On Tue, 2002-12-31 at 07:47, Chandra Bajpai wrote:
This happened to my Lisa, after consulting with some Lisa experts found
the fix was really easy. Take the top cover off the Lisa to expose the
Lisa Video Board. You'll see 3 small Pots on top of the video board,
over time the contacts oxide to cause the jitter....now with the Lisa on
and with a small screw driver, *slightly* adjust each pot to wipe away
the oxidation..return the pot to the original setting.
-Chandra
-----Original Message-----
From: cctalk-admin(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]
On Behalf Of Jeffrey H. Ingber
Sent: Monday, December 30, 2002 8:47 PM
To: cctalk(a)classiccmp.org
Subject: Lisa jittery screens
I have two different Lisa machines and both have a jittery display (one
1.2AMP PSU, 1 1.8 AMP PSU). I've followed the instructions in the Sun
Rem. guide to adjust the power supply output. This works immediately
after the adjustment, but the problem gradually comes back over time. I
adjusted both machines around the September timeframe and the jitters
have back on both machines. I'd like to get both of these machines in
top-shape so I can have them running at my New Years party =)
Before I go through the adjustment again, is there anything else I
should be checking? I've also tried adjusting the V.Hold, but this
doesn't seem to make a difference. Maybe I'm not using a precise enough
adjustment?
Thanks,
Jeff
5:26 a.m.
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5:48 a.m.
> I have two different Lisa machines and both have
a jittery display (one
> 1.2AMP PSU, 1 1.8 AMP PSU). I've followed the instructions in the Sun
> Rem. guide to adjust the power supply output. This works immediately
> after the adjustment, but the problem gradually comes back over time. I
> adjusted both machines around the September timeframe and the jitters
> have back on both machines. I'd like to get both of these machines in
> top-shape so I can have them running at my New Years party =)
As I recall, my Lisa had some sort of display problem when I first got it
and when I went to twiddle the various monitor board trim pots, the problem
cleared up. It was just old dirty contacts on the CRT adjustment potentiometers
that caused the problem. As long as you keep track of where they started, you
can often wiggle them back and forth a bit to re-establish a "good" contact.
--tom
6:14 a.m.
This is the problem I had with my Lisa...check my post if anyone wants
directions on how do adjust.
-Chandra
-----Original Message-----
From: cctalk-admin(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]
On Behalf Of Tom Uban
Sent: Tuesday, December 31, 2002 2:52 PM
To: cctalk(a)classiccmp.org
Subject: Re: Lisa jittery screens
> I have two different Lisa machines and both have
a jittery display
(one
> 1.2AMP PSU, 1 1.8 AMP PSU). I've followed
the instructions in the
Sun
> Rem. guide to adjust the power supply output.
This works
immediately
> after the adjustment, but the problem gradually
comes back over
time. I
> adjusted both machines around the September
timeframe and the
jitters
> have back on both machines. I'd like to get
both of these machines
in
> top-shape so I can have them running at my New
Years party =)
As I recall, my Lisa had some sort of display problem when I first got
it
and when I went to twiddle the various monitor board trim pots, the
problem
cleared up. It was just old dirty contacts on the CRT adjustment
potentiometers
that caused the problem. As long as you keep track of where they
started, you
can often wiggle them back and forth a bit to re-establish a "good"
contact.
--tom
7810
days inactive
7811
days old
11 comments
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