Re: Great, my VT52 is shot.

[Mattis Lind via cctalk]

måndag 20 april 2020 skrev Chris Zach via cctalk :

> As I wrote earlier in the thread I think it is a good idea to check the V
>> sync and H sync signals to check that they are right in pulse length and
>> shape.
>>
>
> Good starting point. From the schematics would that be scope probe to J1
> pin 5 for horizontal and j1 pin 9 for vertical? Also which is J1, and how
> are they numbered :-) Also is there a good ground reference point?


I have a picture of the connector on my page. Have a look there. The
connector have the standard color codes to map to numbers. Black for zero,
Brown for one. Etc.


>
> Also is there a document that links the part numbers on the boards with
> what's on the schematics?


No DEC document. When I did my repair I mapped all ICs to the board but not
the connectors, sorry. You can find all here. Including links to schematis
and maintenance manual: http://www.datormuseum.se/home/dec-vt5x


> There are indeed electrolytic capacitors in the vertical deflection circuit
>> but I am not sure if that would make the beam move much faster since for a
>> faster move of the beam also requires a higher voltage over the deflection
>> coil to create a faster ramp up of the current trough it. But it is
>> definitely worth checking. Especially since the scan lines are sloping a
>> bit and not straight as one would expect.
>>
>
> I would believe a capacitor failure due to heat, any ones in particular I
> should check?


C45 and C42 could be useful to check.


>
> So do I. And now we need Chris to do some measurements on it to get
>> further.
>>
>
> More than happy, just haven't worked on TV sets before and would rather
> not blow off my hand. I'm guessing the really dangerous voltage is the one
> on the bottom left that comes off the step up transformer over to the odd
> plug going into the VT52 rear bulkhead (HV to display)


What you could do is what I did. To remove all control board on the bottom
and lay it out flat on the table. Make a small circuit that create a
composite video signal and feed it into a standard composite video monitor
or TV set. If you remove a jumper to th CRT logic there will be no HV at
all generated.

/Mattis


>
> C
>

Re: Great, my VT52 is shot.

[Brent Hilpert via cctalk]

On 2020-Apr-19, at 3:09 PM, Chris Zach via cctalk wrote:

>> As I wrote earlier in the thread I think it is a good idea to check the V
>> sync and H sync signals to check that they are right in pulse length and
>> shape.
> 
> Good starting point. From the schematics would that be scope probe to J1 pin 
> 5 for horizontal and j1 pin 9 for vertical? Also which is J1, and how are 
> they numbered :-) Also is there a good ground reference point?
> 
> Also is there a document that links the part numbers on the boards with 
> what's on the schematics?
> 
>> There are indeed electrolytic capacitors in the vertical deflection circuit
>> but I am not sure if that would make the beam move much faster since for a
>> faster move of the beam also requires a higher voltage over the deflection
>> coil to create a faster ramp up of the current trough it. But it is
>> definitely worth checking. Especially since the scan lines are sloping a
>> bit and not straight as one would expect.
> 
> I would believe a capacitor failure due to heat, any ones in particular I 
> should check?
> 
>> So do I. And now we need Chris to do some measurements on it to get further.
> 
> More than happy, just haven't worked on TV sets before and would rather not 
> blow off my hand. I'm guessing the really dangerous voltage is the one on the 
> bottom left that comes off the step up transformer over to the odd plug going 
> into the VT52 rear bulkhead (HV to display)


Using the schematic and maintenance manual from bitsavers:
http://bitsavers.org/pdf/dec/terminal/vt52/MP00035_VT52schem.pdf

http://bitsavers.org/pdf/dec/terminal/vt52/EK-VT52-MM-002_maint_Jul78.pdf

Monitor schematic: MP00035_VT52schem pdf-page 10
Monitor board component layout: MP00035_VT52schem pdf-page 8

There are *two* horizontal signals from the logic to the monitor (plus the 
vertical & video).

There are some waveform diagrams for what to expect around the monitor board 
presented in the maint manual: 
EK-VT52-MM-002_maint_Jul78 pdf-page 92

Something else that might help with diagnosis is taking pictures of the screen 
with known, simple elements on the screen.
e.g.:
- clear the screen
- take pic if it doesn't clear
- type a simple character like a "-"or "1"
- pic
- type a half line or full line of characters
- pic
- type different characters on two different lines
- pic

The idea being to find out, from simple known patterns, where the pixels end up 
being displayed,
so it may be possible to figure out what's happening with the scan, whether 
it's getting stretched, folding over, etc.

Yes, you want to watch out for HV around the flyback transformer.
The very HV is reasonably insulated, but there's also a few-hundred volts 
around the open componentry around the focus and intensity controls, the stuff 
feeding the neck end of the CRT.

Re: Great, my VT52 is shot.

[Chris Zach via cctalk]

As I wrote earlier in the thread I think it is a good idea to check the V
sync and H sync signals to check that they are right in pulse length and
shape.


Good starting point. From the schematics would that be scope probe to J1 
pin 5 for horizontal and j1 pin 9 for vertical? Also which is J1, and 
how are they numbered :-) Also is there a good ground reference point?


Also is there a document that links the part numbers on the boards with 
what's on the schematics?



There are indeed electrolytic capacitors in the vertical deflection circuit
but I am not sure if that would make the beam move much faster since for a
faster move of the beam also requires a higher voltage over the deflection
coil to create a faster ramp up of the current trough it. But it is
definitely worth checking. Especially since the scan lines are sloping a
bit and not straight as one would expect.


I would believe a capacitor failure due to heat, any ones in particular 
I should check?



So do I. And now we need Chris to do some measurements on it to get further.


More than happy, just haven't worked on TV sets before and would rather 
not blow off my hand. I'm guessing the really dangerous voltage is the 
one on the bottom left that comes off the step up transformer over to 
the odd plug going into the VT52 rear bulkhead (HV to display)


C

Re: pdp11/84 PMI memory: What is the problem with Q bus?

[Jerry Weiss via cctalk]

On 4/19/20 2:29 PM, Chris Zach via cctalk wrote:
So I picked up an 11/84 CPU, 3mb of memory, and a 11/84 Unibus card on 
Ebay. Goal is to speed up my fastest 11 here


For boot time, the diagnostics run in 13 seconds (from when it starts 
to prompt) on the 11/73 board I have and 13 seconds on the 11/84 
board. This is with a camintonn 2mb half height memory board.


Put in the first PMI module above the 11/84 CPU and tried it out. This 
is a CA rev board which apparently only works in a Unibus pdp11 and 
not a Q-bus one. Apparently it does work.


So what exactly was the bug with the older PMI memory? Block mode DMA, 
I'm using an MTI ESDI controller which can do 16 word block DMA on Q 
Bus. Something else


EK-MSV1J-UG 001 documents the the versions that don't do Q-Bus Cycles.  
uNOTE # 028 indicates that MSV-11 JB/JC (M8637-B/C) doesn't do block 
mode. I suspect the MTI card  falls back to single cycle DMA. Also RT11 
simply may not challenge the configuration sufficiently to demonstrate 
the limitations of the -CA memory variant.



I have not seen any document that describes this as a "bug", so it must 
be a "feature"  /s




  Jerry

Unusual Punched Cards

[Donald via cctalk]

This card is shorter than 40 columns but I can't tell if it has been cut off
or not. I only have 1 so I can't let it go.

 

http://www.ibmjunkman.com/cards/?Holder=2551
 =0

 

You can search on Style and select different ones.

pdp11/84 PMI memory: What is the problem with Q bus?

[Chris Zach via cctalk]

So I picked up an 11/84 CPU, 3mb of memory, and a 11/84 Unibus card on 
Ebay. Goal is to speed up my fastest 11 here


For boot time, the diagnostics run in 13 seconds (from when it starts to 
prompt) on the 11/73 board I have and 13 seconds on the 11/84 board. 
This is with a camintonn 2mb half height memory board.


Put in the first PMI module above the 11/84 CPU and tried it out. This 
is a CA rev board which apparently only works in a Unibus pdp11 and not 
a Q-bus one. Apparently it does work.


So what exactly was the bug with the older PMI memory? Block mode DMA, 
I'm using an MTI ESDI controller which can do 16 word block DMA on Q 
Bus. Something else?


Here's the output from RT11.

.show all

RT-11FB (S) V05.05
Booted from DU6:RT11FB

USR is set SWAP
EXITis set SWAP
KMONis set NOIND
TT  is set NOQUIET
ERROR   is set ERROR
SL  is set OFF
EDITis set KED
FORTRAN is set FORTRA
KMON nesting depth is 3
Global .SCCA flag is disabled

PDP 11/83 Processor
2048KB of memory
Floating Point Accelerator Unit
Extended Instruction Set (EIS)
Memory Management Unit
ECC Memory
Cache Memory
PMI Memory
60 Cycle System Clock

Device I/O time-out support
Error logging support
Memory parity support
System job support
Global .SCCA support
FPU support
Extended unit support

DeviceStatus   CSR Vector(s)
----   --- -
  EL  Not installed   00   000
  LD  Installed   00   000
  BA  Installed   00   000
  DY  Not installed   177170   264
  VM  Installed   177572   250
  SP  Installed   00   110
  XL  Not installed   176500   300 304
  DL  Installed   174400   160
  MS  Not installed   172522   224
  DU  Resident172150   154
  LS  Not installed   176510   310 314
  NL  Installed   00   000

TT  (Resident)
DU  (Resident)
DU6 = DK , SY
MQ  (Resident)
LD
DL
VM
SP
BA
NL
9 free slots

Job  Name  Console Level StateLowHigh  Impure
---    --- - ----  --
 0   RESORC   0  0   Run 00 103232 105046

No multi-terminal support

Address   ModuleWords
---   ---
16IOPAGE 4096.
132174DU 5570.
103274RMON   5856.
001000..BG..16990.

LD0 is  DU6:RTTST.DSK[6000.]

Great, my VT52 is shot.

[Mattis Lind via cctalk]

Den sön 19 apr. 2020 kl 17:22 skrev Jon Elson :

> After looking at the video, and Mattis' description of the
> sweep method, I'm guessing a counter
> in the chain has gone bad.  Assuming this uses a 5 x 7
> character matrix, then there would be probably
> a divide by 6 for the scan across each character plus space
> between, then a counter for the number
> of characters per line, a counter for the 8 or 9 raster scan
> lines for each row, and then a counter
> for the number of rows.  At least one of those counters
> might be counting too fast.  Does the vertical just give one
> reset pulse, or does it give a pulse to bump the trace down
> the screen one scan line at a
> time?  Also, a cap in the vertical sweep circuit may have
> gone bad, causing the vertical to move too
> fast, as evidenced by sloping lines on the screen.
>

As I wrote earlier in the thread I think it is a good idea to check the V
sync and H sync signals to check that they are right in pulse length and
shape.

There are indeed electrolytic capacitors in the vertical deflection circuit
but I am not sure if that would make the beam move much faster since for a
faster move of the beam also requires a higher voltage over the deflection
coil to create a faster ramp up of the current trough it. But it is
definitely worth checking. Especially since the scan lines are sloping a
bit and not straight as one would expect.

The interesting thing is that the counter chain that develops the V and H
sync signals are different from the on the ones that generate addresses to
the picture memory. There are separate X and Y counters that addresses the
memory and then for each scan line the lower bits of the accumulator are
used for addressing the char ROM together with the information from screen
memory.

The VT52 is a quite complex juggle where counters interact with the program
which runs in sync with all operations.

So,  yes,  a counter might have gone bad. Myself I have never seen a
counter that has counted too fast unless the input was too fast. But I
probably still have peculiarities to experience.



>
> Just guessing from a distance.
>

So do I. And now we need Chris to do some measurements on it to get further.

/Mattis


>
> Jon
>

HP 41-CX

[David Brownlee via cctalk]

I've come into possession of an HP 41-CX calculator - unfortunately it
appears to have had batteries left in it which have left corrosion on
the internal contacts.

(some pics: https://photos.app.goo.gl/48bE7WJZP8R4PF9a9 )

My classic hardware tendencies tend to run more towards the "can run
*nix" end, and while I could just clean it up and throw it on eBay I
wondered if anyone here has a 41C shaped soft spot and would be
interested? (happy to trade/part trade for something they already have
for which they are less fond if that works :)

David

Re: Great, my VT52 is shot.

[Jon Elson via cctalk]

After looking at the video, and Mattis' description of the 
sweep method, I'm guessing a counter
in the chain has gone bad.  Assuming this uses a 5 x 7 
character matrix, then there would be probably
a divide by 6 for the scan across each character plus space 
between, then a counter for the number
of characters per line, a counter for the 8 or 9 raster scan 
lines for each row, and then a counter
for the number of rows.  At least one of those counters 
might be counting too fast.  Does the vertical just give one 
reset pulse, or does it give a pulse to bump the trace down 
the screen one scan line at a
time?  Also, a cap in the vertical sweep circuit may have 
gone bad, causing the vertical to move too

fast, as evidenced by sloping lines on the screen.

Just guessing from a distance.

Jon

correction OK Looking to purchase "Sensicall" and the ATT Code-Com" bell system attachment that woukd allow deaf to tap morse over phone lines thanks Ed at SMECC

[ED SHARPE via cctalk]

OK Looking to purchase "Sensicall" and the ATT Code-Com" bell system attachment 
that woukd allow deaf to tap morse over phone lines  thanks  Ed  at  SMECC 

OK Looking to purchase "Sensicall" and the ATT Code-Com" bell system attachment that woukd allow deaf to tap morse over phone lines

[ED SHARPE via cctalk]

OK Looking to purchase "Sensicall" and the ATT Code-Com" bell system attachment 
that woukd allow deaf to tap morse over phone lines  thanks  Ed  at  SMECC

Re: Unusual Punched Cards (Peter Van Peborgh)

[Tony Aiuto via cctalk]

Can you give us a clue as to the locale of those renaissance festivals.
That might prompt me to go.

On Sat, Apr 18, 2020 at 7:40 PM brianb1224 via cctech 
wrote:

> There is a lady who collects them also plus the wooden blooms usually at
> the renaissance festivals. Sorry I forgot her name.Sent from my Verizon,
> Samsung Galaxy smartphone
>  Original message From: Michael Thompson via cctech <
> cct...@classiccmp.org> Date: 4/18/20  2:14 PM  (GMT-06:00) To: cctech <
> cct...@classiccmp.org> Subject: Re: Unusual Punched Cards (Peter Van
> Peborgh) >> Guys,>> I have been collecting all types of computer punched
> cards for a few years> now. In the distant past I actually used them!>> I
> am desperately looking for two types I do not have been able to find a>
> sample of:> *   Jacquard fabric/carpet loom cards. OK, not computer but
> the> ancestor, for completeness of the history. There may be several
> formats of> these.>>Something like this?
> http://www.ricomputermuseum.org/Home/interesting_computer_items/jacquard-loom-cards--
> Michael Thompson