Cosmo wire feed voltages

[Charred fingers]

Hi, the wire feed on my cosmo 130 gas/gasless
has gone in into overdrive. It is so fast it unusable
I have disconnected the feed to the motor and tested
it with a multimeter and am getting a reading of 20.2V
on the lowest setting and 34.5V on the highest, the
wire feed adjuster does nothing to alter these values
nor does adjusting the trim pot.
Any ideas anyone?
Thanks

 

[R Kraft]

Sounds like your motor drive transistor has gone short, or one leg of the control pot has gone open.

 

[Charred fingers]

Sounds like your motor drive transistor has gone short, or one leg of the control pot has gone open.

Hi thanks for the reply, to be honest electronics is not my
strong point, I'm fine with 240ac or 12v/24v automotive,
so I wouldn't recognise a motor drive transistor if it bit me
on the butt. Pots i'm ok with because of guitars.
Is it possible to test the above with a multimeter or do you
need specialist equipment.

Due to the inconsistent nature of the wire feed, lowest
setting only to be fair, I've been looking at an independant
system using a 24v switching psu a 24v PWM and a relay
which I should be able to put together for £50.00.
Would leaving whatever part is dud unrepaired have
any negative effect on the rest of the PCB

Thanks Richard

 

[R Kraft]

You could just wire around the motor drive circuit, the main relay circuit on the board is separate.
Robert

 

[Charred fingers]

You could just wire around the motor drive circuit, the main relay circuit on the board is separate.
Robert

Thanks robert you've been really helpful

 

[R Kraft]

The parts should be easy to test, do you have a schematic ?
Robert

 

[Charred fingers]

The parts should be easy to test, do you have a schematic ?
Robert

Not of the board itself all I have is the wiring diagram from the manual

Not sure it will be any use
Richard

 

[Charred fingers]

One other question does the thermal cutout
just isolate the wirefeed circuit or the whole
board I'll need to incorporate it in any independant
wire feed system.
Cheers

 

[BChild]

One other question does the thermal cutout
just isolate the wirefeed circuit or the whole
board I'll need to incorporate it in any independant
wire feed system.
Cheers

Not sure I thought just wire feed but I may be wrong

To just creep the wire out at the slowest speed possible seems to need about 1.25 Volts if that's any use

 

[Charred fingers]

Hi BC was hoping it disabled the entire board.
The massive voltages I get are due to a dead
transistor, so i've ordered one along with a
100ohm trimpot from Parnells. I should then be
able to use the output voltage from the board to
to enerise the relay on the motor drive mod i'm
going to do and still keep the thermal cutout in
line.
I gather from another post yours is still giving grief!!!

 

[BChild]

Hi BC was hoping it disabled the entire board.
The massive voltages I get are due to a dead
transistor, so i've ordered one along with a
100ohm trimpot from Parnells. I should then be
able to use the output voltage from the board to
to enerise the relay on the motor drive mod i'm
going to do and still keep the thermal cutout in
line.

OK - good luck - I really don't understand some of the stuff I've actually done

I gather from another post yours is still giving grief!!!

And then some