9 Nov
2005
9 Nov
'05
11:23 p.m.
Subject: RE: Discharging a VT100 CRT
From: "Julian Wolfe" <fireflyst at earthlink.net>
Date: Wed, 09 Nov 2005 16:51:13 -0600
To: "'General Discussion: On-Topic and Off-Topic Posts'" <cctalk
at classiccmp.org>
Yep, you know your stuff Allison. C102 and 103 are both 50v caps according
to the schematic. Should I replace them with equivalent electrolytic 100v
caps? I'm not an electrician, but I've built working stuff with a soldering
iron when given the right parts.
Perfectly reasonable thing to do. Look for other stressed parts while there.
If I can build this into a better VT100 and not have to
open it again for a
good long time, it'll be worth my time and trouble now.
I've done a few of them and never seen them fail. Considering that the
original lasted typically 2 years at 100% power on you can see it should last.
FYI: the original problem was a 50V part in a circuit that had 70+ Volt spikes.
Part was simply mis spec'ed. I remember seeing 5 refrigerator (large ones)
boxes full of failed boards due to that error.
Allison
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Allison
Sent: Wednesday, November 09, 2005 1:21 PM
To: cctalk at classiccmp.org
Subject: RE: Discharging a VT100 CRT
Subject: RE: Discharging a VT100 CRT
From: "Julian Wolfe" <fireflyst at earthlink.net>
Date: Wed, 09 Nov 2005 12:43:29 -0600
To: "'General Discussion: On-Topic and Off-Topic Posts'"
<cctalk at classiccmp.org>
Well, you were right. Something did blow on the VT100 video board, and in
a
bad way. It looks very much like it was that
diode you speak of, cause
there's a huge burnmark on the board at the contact points of the diode.
If
that's not an "I died" indicator, I
don't know what is.
Can anyone tell me what diode to buy to replace it? I'm thinking of
getting
a replacement video board, and then replacing the
diode on that, just in
case it took something else with it. The whole "y" trace has a brownmark
around it that the diode was connected to, and that has a big cap next to
it.
Check the diode first as often they survive. If it didn't it may be
the 1A 1000V device (1n4007 will work) at CR102. The cap is correct value
(22uf) but about half the required working voltage so it shorts after a
long time. I forget if it was C102 or c103 and the working voltage should
be at least 100V but not more than 160V. or so memory says.
Allison
10 Nov
10 Nov
12:12 a.m.
The whole situation makes a lot of sense now too. I wonder if the cause of
this wasn't a weak cap. They do "dry out" after sitting for a long time
like that anyway, which I believe this one had.
Usually with old monitors, I try to leave them on if possible, and just turn
the brightness and/or contrast down so they don't burn in. That's what I've
done with the VT220 I have and it seems to be much happier as a result...and
bonus with the VT220, because it has its own built in screen saver.
I wish everything I owned was built like this.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Allison
Sent: Wednesday, November 09, 2005 5:23 PM
To: cctalk at classiccmp.org
Subject: RE: Discharging a VT100 CRT
Subject: RE: Discharging a VT100 CRT
From: "Julian Wolfe" <fireflyst at earthlink.net>
Date: Wed, 09 Nov 2005 16:51:13 -0600
To: "'General Discussion: On-Topic and Off-Topic Posts'"
<cctalk at classiccmp.org>
Yep, you know your stuff Allison. C102 and 103 are both 50v caps according
to the schematic. Should I replace them with equivalent electrolytic 100v
caps? I'm not an electrician, but I've built working stuff with a
soldering
iron when given the right parts.
Perfectly reasonable thing to do. Look for other stressed parts while
there.
If I can build this into a better VT100 and not have to
open it again for a
good long time, it'll be worth my time and trouble now.
I've done a few of them and never seen them fail. Considering that the
original lasted typically 2 years at 100% power on you can see it should
last.
FYI: the original problem was a 50V part in a circuit that had 70+ Volt
spikes.
Part was simply mis spec'ed. I remember seeing 5 refrigerator (large ones)
boxes full of failed boards due to that error.
Allison
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Allison
Sent: Wednesday, November 09, 2005 1:21 PM
To: cctalk at classiccmp.org
Subject: RE: Discharging a VT100 CRT
Subject: RE: Discharging a VT100 CRT
From: "Julian Wolfe" <fireflyst at earthlink.net>
Date: Wed, 09 Nov 2005 12:43:29 -0600
To: "'General Discussion: On-Topic and Off-Topic Posts'"
<cctalk at classiccmp.org>
Well, you were right. Something did blow on the VT100 video board, and in
a
bad way. It looks very much like it was that
diode you speak of, cause
there's a huge burnmark on the board at the contact points of the diode.
If
that's not an "I died" indicator, I
don't know what is.
Can anyone tell me what diode to buy to replace it? I'm thinking of
getting
a replacement video board, and then replacing the
diode on that, just in
case it took something else with it. The whole "y" trace has a brownmark
around it that the diode was connected to, and that has a big cap next to
it.
Check the diode first as often they survive. If it didn't it may be
the 1A 1000V device (1n4007 will work) at CR102. The cap is correct value
(22uf) but about half the required working voltage so it shorts after a
long time. I forget if it was C102 or c103 and the working voltage should
be at least 100V but not more than 160V. or so memory says.
Allison
6997
days inactive
6998
days old
1 comments
2 participants
participants (2)
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fireflyst＠earthlink.net