[robb]

hello here are pics of the circuit boards i amworking on

the three +/- keys on the right side of the UIC are the ones that do not
work

thakns
for your time in looking,
rob

[Donald[_2_]]

robb wrote:
hello here are pics of the circuit boards i amworking on

the three +/- keys on the right side of the UIC are the ones that do not
work

thakns
for your time in looking,
rob



Are you also going to share a schematic ??

How about the gerber files too.


donald

[robb]

"Donald" wrote in message
. ..
robb wrote:
hello here are pics of the circuit boards i amworking on

the three +/- keys on the right side of the UIC are the ones that do not
work

thakns
for your time in looking,
rob



Are you also going to share a schematic ??

How about the gerber files too.
donald

i can not locate a schematic , i will eventually try to draw up simple
schematic trace of the circuit in question as i decipher it.

rob

[robb]

"robb" wrote in message
...
hello here are pics of the circuit boards i amworking on

i had to remove the black button cover to follow traces and that was held
down by 16 cell VFD , so i desoldered...
rob

[Oppie[_3_]]

Any logo recognizable on the defective switches? My guess is that they are
Marquadt.

My wife got a Pfaff 2010 three years ago. Was a dog at first but has been
working wonderfully after the first year when it went in to factory service
three times. They eventually replaced the main pwb.

Oppie

"robb" wrote in message
...
hello here are pics of the circuit boards i amworking on

the three +/- keys on the right side of the UIC are the ones that do not
work

thakns
for your time in looking,
rob

[robb]

"robb" wrote in message
...
hello here are pics of the circuit boards i amworking on


the only buttons that do not work are the 3 groups of two on the right of
picture .
notice there is a ribbon connection on the right sied (10 conductor ribbon)
goes to another circuit board and those buttons all work too

thanks for looking and help,
rob

[Oppie[_3_]]

Looks like a scanned switch matrix. If you look at one side of the switch,
it should have a 1 of N scan where N is the number if scan lines. One scan
line goes active at a time and selects a switch or VFD column. The other
side of the switch is a sense that goes back somewhere else you do not show.
The 40 pin chip you show is this one
http://focus.ti.com/docs/prod/folder...t/sn75518.html
Looks like it it giving the scans while you have two sense bits returning
somewhere (the 12K resistors).


"robb" wrote in message
...

"robb" wrote in message
...
hello here are pics of the circuit boards i amworking on


the only buttons that do not work are the 3 groups of two on the right of
picture .
notice there is a ribbon connection on the right sied (10 conductor
ribbon)
goes to another circuit board and those buttons all work too

thanks for looking and help,
rob

[Ecnerwal]

In article ,
"robb" wrote:

the only buttons that do not work are the 3 groups of two on the right of
picture .

So, whatever is connected to the 12K resistors that connect to the
traces joining those buttons and the 4 on the left must work, if the 4
on the left work.

Check continuity between the 4 on the left and the 6 on the right where
those traces are - just in case there's a problem with the traces. If
that's good, then the problem is presumably either with the 3 traces
leading to the 75518, or with the 75518 itself (or something beyond it?).

Couldn't hurt to try remelting the solder on every pin in the path of
the problem, in case one was marginally cold-soldered and failed over
time, but it's not overly likely, just an easy thing to try.

A note on schematic style - rather than the semicircular jumps,
schematics are much easier to draw and clearer if you observe the
following two rules - No 4-Way junctions - if a line crosses a line, the
assumption is that it does NOT connect. If something "would look like" a
4 way junction, make it two 3-way junctions by moving the end of one
line along the intersecting line to make 2 adjacent connections. That in
itself will almost do it, but the second thing is to put a solid dot
where things _are_ connected. But don't do a 4 way with a solid dot -
that starts to beg the question "is it a connection without a dot, or is
it not connected?" with no 4 way connections, all crossings are not
connected, end of story, clarity. Not my idea - one of many useful,
simple things from Paul and Win's book.

--
Cats, coffee, chocolate...vices to live by

[robb]

"Oppie" wrote in message
...
Looks like a scanned switch matrix. If you look at one side of the switch,
it should have a 1 of N scan where N is the number if scan lines. One scan
line goes active at a time and selects a switch or VFD column. The other
side of the switch is a sense that goes back somewhere else you do not
show.
The 40 pin chip you show is this one
http://focus.ti.com/docs/prod/folder...t/sn75518.html
Looks like it it giving the scans while you have two sense bits returning
somewhere (the 12K resistors).


hello thanks for the help,

i had not gotten that far along, those 12K lines go back to main board, i
was hoping the problem was isolated to this smll circuit board. *but* now i
am doubtfull ... i think the problem is on mainboard.

those 12k lines both return directly to the I1 and I0 pins of a SN74LS251
found at
http://pdf1.alldatasheet.com/datashe...SN74LS251.html

an 8 input multiplexer w/3 state output, this chip sits near the bigg IC's
on rhe main boad.

i am having trouble understand ing the VFD chip purpose in the button
presses ? th eVFD drives the VFD as wel as sharing with some button pressing
fnction.

thnaks again for help ,
rob

[Oppie[_3_]]

The 75518 Qn outputs are a toem pole output for the VFD drive and go between
Vcc2 (up to 170V) and ground. They are most likely using extra outputs with
either diode coupling (to ignore source and only use sink output) or voltage
scaling with the 12K resistor to get the scans to a compatible voltage.

Have you tried to contact Pfaff support? I have the manual for the 2010 but
it does not go into board level schematics (iirc) that was purchased through
a Pfaff dealer. Never hurts to ask though. www.pfaff.com You might have to
go through a dealer if Pfaff won't help you direct.
Oppie

"robb" wrote in message
...

"Oppie" wrote in message
...
Looks like a scanned switch matrix. If you look at one side of the
switch,
it should have a 1 of N scan where N is the number if scan lines. One
scan
line goes active at a time and selects a switch or VFD column. The other
side of the switch is a sense that goes back somewhere else you do not
show.
The 40 pin chip you show is this one
http://focus.ti.com/docs/prod/folder...t/sn75518.html
Looks like it it giving the scans while you have two sense bits returning
somewhere (the 12K resistors).


hello thanks for the help,

i had not gotten that far along, those 12K lines go back to main board, i
was hoping the problem was isolated to this smll circuit board. *but* now
i
am doubtfull ... i think the problem is on mainboard.

those 12k lines both return directly to the I1 and I0 pins of a SN74LS251
found at
http://pdf1.alldatasheet.com/datashe...SN74LS251.html

an 8 input multiplexer w/3 state output, this chip sits near the bigg IC's
on rhe main boad.

i am having trouble understand ing the VFD chip purpose in the button
presses ? th eVFD drives the VFD as wel as sharing with some button
pressing
fnction.

thnaks again for help ,
rob

[robb]

Hi,

This repair is just for my own fun/hobby.

i thought it would just be a simple (resistor, diode, transistor) fried
component now that seems unlikely.

Yes, i was curious, so i did contact Pfaff about schematic and repair. The
machine is old, new boards are not available since mid 90's. My local
authorized dealer will look at it for $80 with no guarantee and they painted
a grim picture for it's repair ..... but did offer to recycle it for me and
encouraged me to come look at there used and new machines.

i think its the over price the old equipment to push the new stuff

This repair is more of a for fun challenge/hobby for me .
I have *tinkered* with electronics since i was a teenager have a hobbyist
collection of electronic tools soldering irons/station, meters, osciliscope
, solderless breadboards etc....

if i can not repair it i'll put it back together, it does some standard
stitches fine.... without the adjustment buttons the machine is about 1/4 as
useful but still useful.

thanks for all your help though , i mostly need some helpful
experience/guidance i think to solve this problem , what kinds of things i
need to do then i can figure out the doing part/

thanks again,
rob


"Oppie" wrote in message
...
The 75518 Qn outputs are a toem pole output for the VFD drive and go
between
Vcc2 (up to 170V) and ground. They are most likely using extra outputs
with
either diode coupling (to ignore source and only use sink output) or
voltage
scaling with the 12K resistor to get the scans to a compatible voltage.

Have you tried to contact Pfaff support? I have the manual for the 2010
but
it does not go into board level schematics (iirc) that was purchased
through
a Pfaff dealer. Never hurts to ask though. www.pfaff.com You might have to
go through a dealer if Pfaff won't help you direct.
Oppie

"robb" wrote in message
...

"Oppie" wrote in message
...
Looks like a scanned switch matrix. If you look at one side of the
switch,
it should have a 1 of N scan where N is the number if scan lines. One
scan
line goes active at a time and selects a switch or VFD column. The
other
side of the switch is a sense that goes back somewhere else you do not
show.
The 40 pin chip you show is this one
http://focus.ti.com/docs/prod/folder...t/sn75518.html
Looks like it it giving the scans while you have two sense bits
returning
somewhere (the 12K resistors).


hello thanks for the help,

i had not gotten that far along, those 12K lines go back to main board,
i
was hoping the problem was isolated to this smll circuit board. *but*
now
i
am doubtfull ... i think the problem is on mainboard.

those 12k lines both return directly to the I1 and I0 pins of a
SN74LS251
found at

http://pdf1.alldatasheet.com/datashe...SN74LS251.html

an 8 input multiplexer w/3 state output, this chip sits near the bigg
IC's
on rhe main boad.

i am having trouble understand ing the VFD chip purpose in the button
presses ? th eVFD drives the VFD as wel as sharing with some button
pressing
fnction.

thnaks again for help ,
rob

[Oppie[_3_]]

Electronics for me started as a hobby about 40 years ago. Then it became a
paying hobby (a job that was really fun). Now as my eyesight gets worse and
I have to work under at least a 3X magnifier just to see the parts, it has
become more drudgery. Used to also be fun to reverse engineer hardware by
tracing out and looking up standard chips to figure it out. Now standard
chips are in the minority and software and programmed PLDs/FPGAs predominate
making it near impossible.

I had to laugh at my wife's Pfaff. When she bought it (she is an avid
quilter) it had more computing power than my desktop computer.

Keep having fun - it keeps you young!
Oppie

"robb" wrote in message
...
Hi,

This repair is just for my own fun/hobby.

i thought it would just be a simple (resistor, diode, transistor) fried
component now that seems unlikely.

Yes, i was curious, so i did contact Pfaff about schematic and repair.
The
machine is old, new boards are not available since mid 90's. My local
authorized dealer will look at it for $80 with no guarantee and they
painted
a grim picture for it's repair ..... but did offer to recycle it for me
and
encouraged me to come look at there used and new machines.

i think its the over price the old equipment to push the new stuff

This repair is more of a for fun challenge/hobby for me .
I have *tinkered* with electronics since i was a teenager have a hobbyist
collection of electronic tools soldering irons/station, meters,
osciliscope
, solderless breadboards etc....

if i can not repair it i'll put it back together, it does some standard
stitches fine.... without the adjustment buttons the machine is about 1/4
as
useful but still useful.

thanks for all your help though , i mostly need some helpful
experience/guidance i think to solve this problem , what kinds of things i
need to do then i can figure out the doing part/

thanks again,
rob


"Oppie" wrote in message
...
The 75518 Qn outputs are a toem pole output for the VFD drive and go
between
Vcc2 (up to 170V) and ground. They are most likely using extra outputs
with
either diode coupling (to ignore source and only use sink output) or
voltage
scaling with the 12K resistor to get the scans to a compatible voltage.

Have you tried to contact Pfaff support? I have the manual for the 2010
but
it does not go into board level schematics (iirc) that was purchased
through
a Pfaff dealer. Never hurts to ask though. www.pfaff.com You might have
to
go through a dealer if Pfaff won't help you direct.
Oppie

"robb" wrote in message
...

"Oppie" wrote in message
...
Looks like a scanned switch matrix. If you look at one side of the
switch,
it should have a 1 of N scan where N is the number if scan lines. One
scan
line goes active at a time and selects a switch or VFD column. The
other
side of the switch is a sense that goes back somewhere else you do not
show.
The 40 pin chip you show is this one
http://focus.ti.com/docs/prod/folder...t/sn75518.html
Looks like it it giving the scans while you have two sense bits
returning
somewhere (the 12K resistors).


hello thanks for the help,

i had not gotten that far along, those 12K lines go back to main board,
i
was hoping the problem was isolated to this smll circuit board. *but*
now
i
am doubtfull ... i think the problem is on mainboard.

those 12k lines both return directly to the I1 and I0 pins of a
SN74LS251
found at

http://pdf1.alldatasheet.com/datashe...SN74LS251.html

an 8 input multiplexer w/3 state output, this chip sits near the bigg
IC's
on rhe main boad.

i am having trouble understand ing the VFD chip purpose in the button
presses ? th eVFD drives the VFD as wel as sharing with some button
pressing
fnction.

thnaks again for help ,
rob