PfaFF Sewing Machines - Recent Questions, Troubleshooting & Support
Display does not light up on PFAFF 1475 CD
These instructions apply to PFAFF 1475 CD. They may also work for other machines.
If you have some advanced electronic repair skills and tools, check the following:
For 220 Volts models - there is a fuse next to the power input, make sure it is good. There is no such a fuse for 120 Volts model.
If the fuse is Okay, you have to get access to the main circuit board by removing the bottom cover.
Check the primary on the transformer for 120 V AC (220 V AC respectively). Check the secondary side for 5 V AC (luminescent display), 9 V AC (turns to 5 V DC by rectifier, 4700 micro farads capacitor and a 5 V regulator STI L387A) and 28 V AC (turns to 35 V DC by rectifier and 2200 micro farads capacitor.
Pay attention to two soldered round fuses in series with the secondary 9 V and 28 V - both should be good. On the big capacitors you should have 9 V DC and 35 V DC.
Common symptoms for bad small 22 micro farads capacitors next to the some of the IC's - there are 5 of these: These capacitors are in parallel with 5 V DC.
## All of the LEDs light up but the display is blank
## All of the LEDs light up, the display is blank, and after a minute no LEDs at all
## No LEDs nor display.
Replace ALL five 22 micro farads capacitors using a good desoldering pump or desoldering station!.
Enjoy your resurrected PFAFF 1475 CD machine!!!
I just did this procedure on my aunt's one (Made in West Germany around 1990).
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