[Don Bowey]

On 9/10/07 4:21 AM, in article , "Ron(UK)"
wrote:

Radiosrfun wrote:
"Michael A. Terrell" wrote in message
...
Anthony Fremont wrote:
Eeyore wrote:
robb wrote:
PROBLEM : a group of 3 (+/-) *momentary switch* buttons on UIC
board used to change memory values do not make any changes when
pressed.
They're probably worn out.
All three of them at the same time?......yeah. Besides, he said he
tested
them already with a multimeter.

Never trust a demented donkey for repair advise.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Isn't the title of this thread a bit misleading and unfair? It's not "all"
brits - just one!



That's just typical of Americans, they ALL generalise!
--- please note

No we don't. We generalize.



Ron

[John Hudak]

robb wrote:
"DaveM" wrote in message
...
"robb" wrote in message
...
hello,

i posted some circuit board pics on the

"alt.binaries.schematics.electronic"

under topic ---- "pfaff UIC circuit board" to

if that will help formulate some ideas on how to repair.

thanks for any help,
rob

"robb" wrote in message
...
hello,

The way I would attack this problem would be:
Use your ohmmeter to trace the common connections from the switches to the
ribbon cable, then make sure that you have continuity through the ribbon
cable.
From there, trace the circuit to whatever component(s) they connect to.
As another poster mentioned, they might be strobed using a CAS/RAS
technique.
If either signal is missing, then the circuit won't respond to set of
switches.
It's pretty much useless to attempt to troubleshoot your problem using the
pictures you posted. You really need to get into the circuit with your
ohmmeter
and trace the circuitry. Draw a rudimentary diagram of your tracing. See
You can also power up the boards and look at the switches with a scope.
You
will probably see pulses on one side of the switches. Press one of them
and
trace the resulting signal back through the circuit and see where it goes
away.
You'll have to find data sheets on the ICs involved, so plan on doing some
Googling. Search for the part number of the part, and datasheet. Like
this:
7401 datasheet

That should get you in the ballpark.

Cheers!!!
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters
in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra



Thanks Dave,

I appreciate your helpful answer.

I have a tough enough time with single layer trace board this is 2 layers
zig zagging through the board all over ( i know a joke to most with 6 -8
layers now common place) and well i just nowstumbled onto holding the board
up to a strong light to see both traces at same time.

I now know some of the switches feed into a DM7496N a "5 bit Parallel in
Parallel out shift register" but that does not really help me as i am not
sure of functional purpose of switches feeding a shift register other than
to count pulses maybe ?


Depending on the config, shift registers were often used as switch
debouncers.
Sorry I can't help with any more diagnosis.
J

and button lines also feed into the SN75518N a "VFD driver chip" which
does not make alot of sense to me either ?

originally i was just hoping it was a simple obvious failed component the
tracing stuff is more of a struggle
anyways thanks for the help i plan to struggle through it a bit more

thanks,
rob

[Ron(UK)]

Don Bowey wrote:
On 9/10/07 4:21 AM, in article , "Ron(UK)"
wrote:

Radiosrfun wrote:
"Michael A. Terrell" wrote in message
...
Anthony Fremont wrote:
Eeyore wrote:
robb wrote:
PROBLEM : a group of 3 (+/-) *momentary switch* buttons on UIC
board used to change memory values do not make any changes when
pressed.
They're probably worn out.
All three of them at the same time?......yeah. Besides, he said he
tested
them already with a multimeter.
Never trust a demented donkey for repair advise.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Isn't the title of this thread a bit misleading and unfair? It's not "all"
brits - just one!


That's just typical of Americans, they ALL generalise!
--- please note

No we don't. We generalize.

All of you?

[Arfa Daily]

"Ron(UK)" wrote in message
...
Don Bowey wrote:
On 9/10/07 4:21 AM, in article , "Ron(UK)"
wrote:

Radiosrfun wrote:
"Michael A. Terrell" wrote in message
...
Anthony Fremont wrote:
Eeyore wrote:
robb wrote:
PROBLEM : a group of 3 (+/-) *momentary switch* buttons on UIC
board used to change memory values do not make any changes when
pressed.
They're probably worn out.
All three of them at the same time?......yeah. Besides, he said he
tested
them already with a multimeter.
Never trust a demented donkey for repair advise.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Isn't the title of this thread a bit misleading and unfair? It's not
"all"
brits - just one!


That's just typical of Americans, they ALL generalise!
--- please note

No we don't. We generalize.

All of you?

Only when they are wearing sox with a red color ... ;~)

But actually, both are correct, depending on which side of the pond you live
....

Arfa

[Michael A. Terrell]

Radiosrfun wrote:

I "used" to give him some credit in the past - waited to see where he was
coming from - or going to...... I'm curious - does he perhaps have a twin -
we know about from elsewhere? I don't think I need to mention the name to
you Michael.

I had a very brief chat (on yahoo) with another Brit who shall we say -wears
the same shoes - a nut case. Well, I guess they have their share, we have
ours.
Maybe if we find them all through chatting, we can help the Authorities
round them all up.


Its time to help out the poor brits, again. We need to supply them
with new Electroshock Therapy Machines.

Their current design just isn't up to the job at hand. It has
settings for Fop, Layabout, and Damn Demented Donkey.

What they need is the new model with 'Straighten out your ****, or
else', "You've been warned', "This is you last chance!', and 'Cinder'
settings.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

[Ron(UK)]

Michael A. Terrell wrote:


What they need is the new model with 'Straighten out your ****, or
else', "You've been warned', "This is you last chance!', and 'Cinder'
settings.

Ahh, the American way.. god bless America

[John Robertson]

On 2007-09-09 07:47:44 -0700, "robb" said:


"Eeyore" wrote in message
...


robb wrote:

hello,

i am trying to repair a fault with an user interface circuit (UIC) board
and
control board out of an old 1987's computerized programmable Pfaff
sewing
machine (made in Western Germany).

a for fun project for me , a challenge

programming consists of storing values in memory locations using keys
( +/-
buttons) on UIC board

PROBLEM : a group of 3 (+/-) *momentary switch* buttons on UIC board
used
to change memory values do not make any changes when pressed.

They're probably worn out.

Graham


hi,
thanks for reply and help.

is there a good way to test this ?

I would be convinced of that if they were all highly used keys... but
there are a total of 6 micro switches (for 3 buttons +/-) and they are not
typically all used with same frequency. One set is used most, one maybe
half that and the others very in-frequently as the nature of the values it
changes are not frequently used they are a convinience.

on the same board exists other buttons (same exact switch style) used more
frequently than these and they are still working ?? if that means anything

plus continuity tests just at switch connections to board shows changes as
as expected. The values may be no good but i get a continuity change that
matches with known working button/switches.

I am posting pics of the circuits on the binaries schematics page if that
will help ?

thanks again for your help ,
rob

I'd be pulling out a Logic Probe about now and checking what happens on
the lines to the switches. One of them at least should be pulsing (the
strobe). If the switches that do not work share the same Strobe or
Return line and no other switches do them your problem is either a bad
connection (most likely) or a failed driver on the strobe (next likely)
or damaged return gate.

Read up on digital troubleshooting, there are a number of books at
libraries that cover this and based on the period of construction for
this sewing machine one can hope they used off-the-shelf parts so it
will be easy to fix.

John :-#)#
--
(Please post followups or tech enquires to the newsgroup) John's
Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com "Old pinballers never die, they
just flip out."

[Gary Tait]

"robb" wrote in
:

and button lines also feed into the SN75518N a "VFD driver chip" which
does not make alot of sense to me either ?

They use the same I/O lines to multiplex the display and the keypad. Not at
all uncommon.

[robb]

"Gary Tait" wrote in message
...
"robb" wrote in
:

and button lines also feed into the SN75518N a "VFD driver chip" which
does not make alot of sense to me either ?

They use the same I/O lines to multiplex the display and the keypad. Not
at
all uncommon.


Thanks Gary,

Could you elaborate on that a bit more ? as i am a mere amateur

i have traced one side of switches back to the Q22-Q30 lines ?

the general layout is ...
that two button/switches {increment, decrement} will share a line to one
Q## output and repeat for 12 pairs of buttons (total 12x2 or 24
button/switches)

the other side of the switches get bundled/connected together into two
groups of 12, that each group shares one line down the ribbon to the main
controler board (with 12k resistor just before going down ribbon wire)

so the Q## pins on the SN75518 are Outputs ... So i guess there is some sort
of timed pulsing and controler board has to figure out which button was
pressed ?

thanks for your help,
rob

[robb]

"robb" wrote in message
...

i am trying to repair a fault with an user interface circuit (UIC) board
and
control board out of an old 1987's computerized programmable sewing
machine

a for fun project for me , a challenge


ok i have posted partial schemat that i made by hand for the pertinent part
of the button circuit board it does not include the VFD connections which
are inline with the button connections nor the indiocator LEDS that mostly
just connect to the DM7496 chips.

id therea good way to turn a MM into logic probe ? i am using the Fluke 177
true RMS meter


thanks again for any help,
rob

[robb]

that was posted on the

alt.binaries.schematics.electronic

rob
"robb" wrote in message
...

"robb" wrote in message
...

[robb]

"robb" wrote in message
...

i am trying to repair a fault with an user interface circuit (UIC) board
and
control board out of an old 1987's computerized programmable sewing
machine

a for fun project for me , a challenge


first thanks to everyone for your time and help,

OK, so i followed most of suggestions from everyone

check and follow traces from the switches, to ribbon, to the VFD SN75518
and to the main board ( traces ok ) then probe signals from the buttons
(problem)
so i connected up my toy O-Scope (you'd never guess and fall on floor) and
found no signal from the two VFD pins going to two broken butons and a
mangled signal to the other button that does not work

i noticed several pins not connected to anything with good wave form can i
just reroute the broken lines to those or do i need to just replace ic ?

thanks again for help from all that tried,
rob

[Michael A. Terrell]

"Ron(UK)" wrote:

Michael A. Terrell wrote:


What they need is the new model with 'Straighten out your ****, or
else', "You've been warned', "This is your last chance!', and 'Cinder'
settings.

Ahh, the American way.. god bless America


Have any stray British EE donkeys that you'd like to test it on?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida