Hi all,
I hope the day sees you well.
My wife has een given a neat toy, its an older pfaff Embroidery machine a "Creative Designer 7570" with faults.
Its a pretty flash approx 15 yer old electronic sewing machine doodad made in Germany. It came with some manuals and lots of PCMCIA cards with designs on them.
I have found the self test menu and it conks out at the "button hole detector" and "syncroniser". I bought and downloaded a service manual and pulled it aprt to find that the btton hole sensor is a tiny phtot interuptor, and the syncroniser is a tiny assembly which has inside a marked transparent wheel and 3 sets of IR diodes (tiny) and 3 sets of I assume phtot transistors. They have 2 legs each and are mounted in a tiny assembly with 6 legs total.
This bit reminds me of the innards of the VL Commodore Nissan engine distributer, only way smaller.
Sorry for the ramble but on to my question.
I want to test these things so I have set up my ancient Heathkit test bed with the following:
The button hole bit first. I have 5 volts power applied via 470 ohms to the IR LED, it draws aboyt 8mA. Then as the circuit board has the postive leg of the IR diode and the phototransistor collector commoned, I have 4K7 from ground to the transistor emitter.
With this setup, I get 0.9V at the junction of the 4K7 when the transistor is illuminated, and around 170mV when the IR path is blocked.
That doesnt look to good to me, I would have assumed a more "TTL" level here like closer to 5V when illuminated.
Any suggestions greatly appreciated.
I am a retired communications tech and opto stuff is new to me, well I USED to repair Telex machines WAY back the 80's and they had optical sensors everywhere in them, but I'm getting funny in the brain box and my memory is rubbish
I am going to test the "syncroniser" bit next. I'll report how that goes
Oh and one last thing, I have searched in vain for replacement parts, and cant even find surface mount parts that LOOK like the bits inside these things.
I'll try and take some photos if anyone is interested.
Thanks,
Raff.