>
>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
Hi all,
just a short question, I have seen so much that I start
doubting everything :-(
After you pressed the CLR key on the 11/34 console
(to get a clear start point), if you *only* press the
CNTRL key, nothing should happen, right?
[ on my 11/34, when I press CLR (release it), the press
the CNTRL key (only that one), the 7-segment displays go
all OFF, and when the are on again, they show the value
that was in them before I pressed CNTRL. Also, BUS ERR
goes on. ]
I checked the signals. That the displays go blank is logical,
because the DRIVE1 thru DRIVE6 signals remain '1' for 400 ms.
But that is the result ... what is the cause ...?
- Henk, PA8PDP.
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>
>Subject: RE: Discharging a VT100 CRT
> From: "Julian Wolfe" <fireflyst at earthlink.net>
> Date: Wed, 09 Nov 2005 18:12:10 -0600
> To: "'General Discussion: On-Topic and Off-Topic Posts'" <cctalk at classiccmp.org>
>
>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.
Like I said DEC made a truckload of these with a 50V cap where a 75V or
higher cap should have been used. Most died in the first two years.
Those that werent used much lasted decades, but failure was enevitable
due to an undervoltage part.
>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.
There were s a few issues with those too, but they were overall good.
>I wish everything I owned was built like this.
DEC tried, often succeeded.
Allison
>
>-----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
>>
>>
>>
>>
>
>
>From: "Sebastian Br?ckner" <sb at thebackend.de>
>
>Sridhar Ayengar schrieb:
>> Sebastian Br?ckner wrote:
>>> I know that those machines are supposed to run continuously but it
>>> can't be quite normal that every other time I power it up one of the
>>> supplies dies. Any hints? Is there a way to fix those things or to
>>> prevent them from blowing up altogether?
>>
>> Are you sure that you've wired your premises electrics correctly? That
>> could cause power supplies to keep blowing.
>
>Well... that could be the cause. I'm running the machine off a 16A fuse
>although it is designed for 25A IIRC.
>Of course the fuse could blow on power up but I didn't expect that to do
>any damage to the power supplies... maybe that was a very bad idea(tm)?
>
>> Do you have enough power supplies for the boards and other options you
>> have installed in the system? That could be doing it too. Or if you
>> had a boardset with an unfused short in it or something, although I
>> would think there's probably fuses in the backplane or something.
>
>After losing supplies with the original configuration (24 CPUs, ~18 SCSI
>channels, 1.5GB RAM) I stripped the machine to a fairly minimal
>configuration (something like 4 cpus, 512mb ram, no extra scsi). The
>problem didn't go away.
>
>Once it boots (and doesn't blow as soon as I turn it on) it runs without
>problems. And since it worked in that exact configuration for years for
>the previous owner (continuously powered on though) I expect it to be
>fully working. He also said that he often had to replace the power
>supplies after power cuts, so it might just be normal...
>
>Sebastian
>
Hi
One thought. If it uses transformers anywhere, connected
to the AC ( even switchers often do this for initial voltages ),
you need to put a MOV on the input leads. The problem is
( and I've actually seen this ) that when you cut the AC,
the core holds some energy. Since it can't pass this to
the input leads ( you know, that 90 degree phase thing ),
it causes the voltage to spike on the secondaries. Many
negative regulators could not handle the spike.
Second thought. If it is using switchers, make sure you
are providing the right AC voltage. Many of the older
switchers would actually run on 120V when setup for 220V,
for a short time. They would eventually blow in a minute
or so. The problem is that with the lower voltage, the
switcher would be running too long a duty cycle. This
would smoke the transistor because there would either
be some overlap or the cores would saturate. In either
case, it would blow the supply.
Dwight
I've noticed that what passes for 3.5" blank media nowadays is downright
awful. I've got a "work diskette" that's a Verbatim Datalife with a date
code of sometime in 1997. Like the Energizer bunny, it just keeps going
and going. Newly-purchased media seems to last about 3 months of use,
tops.
Are there any sources for good reliable NEW media?
Cheers,
Chuck
>
>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
>
>
>
>
Hi David,
I don't have a store, just a LOT of DEC parts. Send me a list of what you
need and I'll check on it. I have one of the largest PDP8 selections around.
Where are you located? Feel free to call me at 217-586-5361 between 10 AM and 8:30
PM Chicago time.
Thanks, Paul
Hi David,
I Should have them both in stock, but will have to pull them out and test
them. I have two VT or Wt78's in stock, and possible a few Decmates. Maybe even
some software.
Thanks, Paul
On Nov 9 2005, 14:22, Sridhar Ayengar wrote:
> Zane H. Healy wrote:
> > I'd love to get a nice SGI Octane2 or Tezro, but I sure can't
justify
> > the expense!
> Why not get an Onyx2? They've come down in price a lot. I was
thinking
> of picking one up myself.
I suspect it's not the purchase price, but the electrickery costs.
Just one module out of my O2K -- which is essentially the same machine
as an Onyx2 but without the graphics pipelines -- eats more than a
typical PDP in my collection. They make excellent hair driers and
space heaters though.
--
Pete Peter Turnbull
Network Manager
University of York
On Nov 9 2005, 17:38, Jules Richardson wrote:
> Wow, that's pretty awesome. They did some very cool stuff - I was in
the
> game too late to see the earlier stuff and only worked with the
Origin
> 200 / 2000 hardware. At the museum we've gained a 4D/25, pair of
> Indigos, various Indys and an Indigo2 - but I'd love to get hold of
some
> of the larger / older systems. It's not much to show for a company
who's
> name lots of people have heard of.
Hmm... my Origin2000 *might* be looking for a home, and so might one
other at York. That would make a 32-CPU 2-rack machine (both have the
necessary router boards and I have the Craylink cables) plus some
peripherals. Interested?
Do you want an O2 or two? There might be some moderately large
Challenge machines available too.
> Lyle Bickley wrote:
> > The largest repository of SGI documentation outside of SGI itself
is:
> > http://futuretech.blinkenlights.nl/sgi.html
>
> Initial glance and that looks like a useful resource!
It's well known, and I can confirm that Ian is very helpful.
--
Pete Peter Turnbull
Network Manager
University of York
