4 Feb
2014
4 Feb
'14
4 p.m.
Hello all,
I'm looking for DEC vt101 schematics and maintenance manual.
I've a vt101. The power supply and logic board is ok. All power levels and video
signals are supplied to the video board properly, but there is no dispay on the crt and
I'm suspecting that the video board is defective.
Andreas
4 Feb
4 Feb
4:38 p.m.
Hello all,
I'm looking for DEC vt101 schematics and maintenance manual.
I've a vt101. The power supply and logic board is ok. All power levels
and video signals are supplied to the video board properly, but there is
no dispay on the crt and I'm suspecting that the video board is defective.
I thought the VT101 video board was the same as the one in the VT100, so
the VT100 pritset might be of use.
But...
There are at least 3 different VT100 video boards that I've seen, there
may be otehrs. I've not seen them all in the printsets. So even with the
printset you may not have the information you need.
Msot of the time, problems on the VT10x video boards are in the
horizotnal output area. The flyback transformer -- separately moutned on
the chassis -- fails, and often takes out the horizontal output
transistor. Im any case, findign a flyback transformer is not easy.
AS with all small mono monuitors there's a bt you can do without a
schematic. First see if the CRT heater is glowing. It runs off the 12V
line, so if it's out eitherh the eater is open :-(, the 12V line is
misisng, or there's a simple fault on the PCB. Sometimes (and I cna't
rememebr if the VT10x is like this) there's a picofuse in series with the
supply. A failed horizontal output stage can blow that, removign power
fro tmeh entire monitor section.
If you have an EHT meter, measure the fianl anode votlage. Expect about
12kV.
Measure the CRT pin voltages, even if you can't check the final anode
votlage. The pinout is the normal one :
1 : control grid
2 : cthode
3 : heater
4 : haaterr
5 : control grid
6 : first anode
7 : focus anode.
Expect a few hundred votlas on the 2 anodes. One of pins 3,4 is likely to
be groudned, expect about 11.5V on the other one. A few10's of votls on
the cathode. THat should give you an idea of whether all the high votlges
are misisng (hoizontal outptu trouble), jsut oen is misisng
(rectifier/capacitor problems of that supply most likely) or withehr the
CRT is biased well beyond cut-off (grid very -ve wrt cathode).
-tony
7:01 p.m.
In article <A0D359BF-E535-4137-8398-B93BBC5C002D at t-online.de>,
Andreas Holz <aswood at t-online.de> writes:
I'm looking for DEC vt101 schematics and
maintenance manual.
<http://terminals.classiccmp.org/wiki/index.php/DEC_VT101> is
everything I know about.
There is a pocket service guide linked from there, but unfortunately,
it is offline from it's original source on vt100.net.
If anyone has a copy squirrelled away somewhere, I'll make sure the
mirror on manx is available at least.
If you find additional documentation specific to the VT101 online, I'd
appreciate a URL so I can add it to the wiki.
--
"The Direct3D Graphics Pipeline" free book
<http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://ComputerGraphicsMuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://LegalizeAdulthood.wordpress.com>
7:02 p.m.
Also, because the VT101 is very similar to the VT100, the
information for it may be enough to get you going.
<http://terminals.classiccmp.org/wiki/index.php/DEC_VT100>
--
"The Direct3D Graphics Pipeline" free book
<http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://ComputerGraphicsMuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://LegalizeAdulthood.wordpress.com>
10 Feb
10 Feb
2:01 p.m.
* On Tue, Feb 04, 2014 at 10:00:41PM +0100, Andreas Holz <aswood at t-online.de>
wrote:
Hello all,
I'm looking for DEC vt101 schematics and maintenance manual.
I've a vt101. The power supply and logic board is ok. All power
levels and video signals are supplied to the video board properly,
but there is no dispay on the crt and I'm suspecting that the video
board is defective.
The flyback transformer is a prime suspect as well. There were two
versions of flyback transformer on the VT100/101: a potted version,
and a version with exposed coil windings. The version with exposed
windings has a much higher failure rate.
If your flyback transformer is bad, you can buy a new (not NOS,
actually new) flyback transformer for around $25!
http://tkc8800.com/page/VT100-Flyback-transformer-replacement
Andreas
-Seth
3:07 p.m.
I measured the resistance of the flyback transformer as of four Ohms. From my point of
view this is a proper value.
Andreas
Gru?
Andreas Holz
Am 10.02.2014 um 20:01 schrieb Seth Morabito <lists at loomcom.com>:
* On Tue, Feb 04, 2014 at 10:00:41PM +0100, Andreas
Holz <aswood at t-online.de> wrote:
Hello all,
I'm looking for DEC vt101 schematics and maintenance manual.
I've a vt101. The power supply and logic board is ok. All power
levels and video signals are supplied to the video board properly,
but there is no dispay on the crt and I'm suspecting that the video
board is defective.
The flyback transformer is a prime suspect as well. There were two
versions of flyback transformer on the VT100/101: a potted version,
and a version with exposed coil windings. The version with exposed
windings has a much higher failure rate.
If your flyback transformer is bad, you can buy a new (not NOS,
actually new) flyback transformer for around $25!
http://tkc8800.com/page/VT100-Flyback-transformer-replacement
Andreas
-Seth
11 Feb
11 Feb
3:49 p.m.
I measured the resistance of the flyback transformer as of four Ohms.
From my point of view this is a proper value.
Unofrtunately DC resistance measurments on a flyback transformer tell you
very little. A single shorted turn in that winding will not change the DC
resistnace enough to see. A shorted turn in anotehr windign will not
change the resistance at all. But either will extract enough energy to
prevent the flyback from resonating, will cause the primary currnet to go
very high and will damage the output transistor.
The only useful test is a ringing test. Basically, you resonate the
widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
(the nromal way is a nopen-collect drier using a BU406 or similar
trasnsitor) and look at the waveform on a 'scope. A good flyback will
show many osciallations before they decay to 'invisible', a bad one will
probably not oscillate at all.
-tony
4:22 p.m.
Tony sent me a circuit design for a ringing tester. I converted this into a
TinyCad drawing from which I was able to create a stripboard design. If
anyone wants this I can send it to them.
Regards
Rob
On 11 February 2014 20:49, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I measured the resistance of the flyback transformer as of four Ohms.
From my point of view this is a proper value.
Unofrtunately DC resistance measurments on a flyback transformer tell you
very little. A single shorted turn in that winding will not change the DC
resistnace enough to see. A shorted turn in anotehr windign will not
change the resistance at all. But either will extract enough energy to
prevent the flyback from resonating, will cause the primary currnet to go
very high and will damage the output transistor.
The only useful test is a ringing test. Basically, you resonate the
widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
(the nromal way is a nopen-collect drier using a BU406 or similar
trasnsitor) and look at the waveform on a 'scope. A good flyback will
show many osciallations before they decay to 'invisible', a bad one will
probably not oscillate at all.
-tony
4:49 p.m.
Rob,
thank you, would be nice to get your stripboard design.
Also thanks to Tony to justify my naive attempt to check the transformer by measuring its
resistance.
I'm just checking sources to get replacement transformers. There aren't much left.
Will try to get some transformers as spares.
Andreas
Am 11.02.2014 um 22:22 schrieb Jarratt RMA
<robert.jarratt at ntlworld.com>:
Tony sent me a circuit design for a ringing tester. I converted this into a
TinyCad drawing from which I was able to create a stripboard design. If
anyone wants this I can send it to them.
Regards
Rob
On 11 February 2014 20:49, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
>>
>> I measured the resistance of the flyback transformer as of four Ohms.
>> From my point of view this is a proper value.
>
> Unofrtunately DC resistance measurments on a flyback transformer tell you
> very little. A single shorted turn in that winding will not change the DC
> resistnace enough to see. A shorted turn in anotehr windign will not
> change the resistance at all. But either will extract enough energy to
> prevent the flyback from resonating, will cause the primary currnet to go
> very high and will damage the output transistor.
>
> The only useful test is a ringing test. Basically, you resonate the
> widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
> (the nromal way is a nopen-collect drier using a BU406 or similar
> trasnsitor) and look at the waveform on a 'scope. A good flyback will
> show many osciallations before they decay to 'invisible', a bad one will
> probably not oscillate at all.
>
> -tony
>
5:54 p.m.
I am away from home all week. I have the files with me but I don't have the
system with the software on it to check I actually have the right files. I
will reply privately with the files because I don't think the list accepts
attachments.
Regards
Rob
On 11 February 2014 21:49, Andreas Holz <aswood at t-online.de> wrote:
Rob,
thank you, would be nice to get your stripboard design.
Also thanks to Tony to justify my naive attempt to check the transformer
by measuring its resistance.
I'm just checking sources to get replacement transformers. There aren't
much left. Will try to get some transformers as spares.
Andreas
Am 11.02.2014 um 22:22 schrieb Jarratt RMA
<robert.jarratt at ntlworld.com
:
Tony sent me a circuit design for a ringing tester. I converted this
into a
TinyCad drawing from which I was able to create a
stripboard design. If
anyone wants this I can send it to them.
Regards
Rob
On 11 February 2014 20:49, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
>>
>> I measured the resistance of the flyback transformer as of four Ohms.
>> From my point of view this is a proper value.
>
> Unofrtunately DC resistance measurments on a flyback transformer tell
you
> very little. A single shorted turn in that
winding will not change the
DC
> resistnace enough to see. A shorted turn in
anotehr windign will not
> change the resistance at all. But either will extract enough energy to
> prevent the flyback from resonating, will cause the primary currnet to
go
> very high and will damage the output
transistor.
>
> The only useful test is a ringing test. Basically, you resonate the
> widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
> (the nromal way is a nopen-collect drier using a BU406 or similar
> trasnsitor) and look at the waveform on a 'scope. A good flyback will
> show many osciallations before they decay to 'invisible', a bad one will
> probably not oscillate at all.
>
> -tony
>
7:02 p.m.
I have a box of them, used, along with the monitor boards and almost all
vt1xx logic boards. I have some of the boards handy, but the rest I won't
be able to dig out for a while due to more pressing personal priorities. I
will post when I find them.
Thanks, Paul
On Tue, Feb 11, 2014 at 4:54 PM, Jarratt RMA <robert.jarratt at ntlworld.com>wrote:
I am away from home all week. I have the files with me
but I don't have the
system with the software on it to check I actually have the right files. I
will reply privately with the files because I don't think the list accepts
attachments.
Regards
Rob
On 11 February 2014 21:49, Andreas Holz <aswood at t-online.de> wrote:
Ohms.
will
Rob,
thank you, would be nice to get your stripboard design.
Also thanks to Tony to justify my naive attempt to check the transformer
by measuring its resistance.
I'm just checking sources to get replacement transformers. There aren't
much left. Will try to get some transformers as spares.
Andreas
> Am 11.02.2014 um 22:22 schrieb Jarratt RMA <
robert.jarratt at
ntlworld.com
:
Tony sent me a circuit design for a ringing tester. I converted this
into a
> TinyCad drawing from which I was able to create a stripboard design. If
> anyone wants this I can send it to them.
>
> Regards
>
> Rob
>
>
> On 11 February 2014 20:49, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
>
>>>
>>> I measured the resistance of the flyback transformer as of four >>
From my point of view this is a proper value.
>
> Unofrtunately DC resistance measurments on a flyback transformer tell
you
> very little. A single shorted turn in that
winding will not change the
DC
> resistnace enough to see. A shorted turn in
anotehr windign will not
> change the resistance at all. But either will extract enough energy to
> prevent the flyback from resonating, will cause the primary currnet to
go
>> very high and will damage the output transistor.
>>
>> The only useful test is a ringing test. Basically, you resonate the
>> widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
>> (the nromal way is a nopen-collect drier using a BU406 or similar
>> trasnsitor) and look at the waveform on a 'scope. A good flyback will
>> show many osciallations before they decay to 'invisible', a bad one
>
probably not oscillate at all.
>
> -tony
>
9:52 a.m.
On Monday (02/10/2014 at 02:01PM -0500), Seth Morabito wrote:
* On Tue, Feb 04, 2014 at 10:00:41PM +0100, Andreas
Holz <aswood at t-online.de> wrote:
Except that Dalbani no longer have them. I placed an order with them a
couple weeks ago, which they happily accepted and took the money only
to respond a few days later that they actually did not have any stock
and do not know when they will have more.
Thanks... NOT!
Alternative sources should be identified and failing that, we should
try to get some parameters about them so that we can consider having
them custom made or find close substitutes later.
Chris
--
Chris Elmquist
Hello all,
I'm looking for DEC vt101 schematics and maintenance manual.
I've a vt101. The power supply and logic board is ok. All power
levels and video signals are supplied to the video board properly,
but there is no dispay on the crt and I'm suspecting that the video
board is defective.
The flyback transformer is a prime suspect as well. There were two
versions of flyback transformer on the VT100/101: a potted version,
and a version with exposed coil windings. The version with exposed
windings has a much higher failure rate.
If your flyback transformer is bad, you can buy a new (not NOS,
actually new) flyback transformer for around $25!
http://tkc8800.com/page/VT100-Flyback-transformer-replacement
3821
days inactive
3829
days old
11 comments
7 participants
participants (7)
-
ard＠p850ug1.demon.co.uk -
aswood＠t-online.de -
chrise＠pobox.com -
legalize＠xmission.com -
lists＠loomcom.com -
robert.jarratt＠ntlworld.com -
useddec＠gmail.com