When turned on the Display will not Show
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).
I did replace the 22 micro farad capacitors and at first it seamed to help.
Alas after reassembling the bottom and testing in normal upright position, the failure showed again.
Culprit here is the 5 V AC: if the display vanishes there is no voltage and about 28 ohm.
If the display works there is only 9 ohm.
If I apply light pressure to the pcb beneath the transformer while the display fails, it beams again.
I resoldered the 5 V AC transformer pins to no avail, so I think the transformer is kaput.
I'm unable to lift it's plastic cover. Its likely sealed.
Looking for a spare:
Pfaff 92 - 328 - 767 - 91/A
Karsten, please, read my initial answer and measure the AC voltage at the secondary of the transformer. You could do that by just plugin the main 220V connector. Be extra careful as the primary on the transformer is live and has 220 Volts!!! Do not measure resistance when there is power applied to the board, only measure AC and DC voltage. The circuit board is double-sided with holes which provide connections between the top and the bottom side. Look up for any cracked metal tracks around the transformer and re-solder its pins/legs if necessary. You may want to strip the protective layer 5 mm (green stuff) to expose the conductive tracks and add some solder or a small piece of wire from the pin to the track.
Hi- I also had the Pfaff 1475CD on which the display would not light up on power on. Oddly, if I waited about an hour or two, it would eventually come on. Anyway, after reading advice here and at one other site, I replaced the (5) 22 microfarad 16V capacitors on the circuit board. After reassembly the machine turned on normally. So far, so good! Note: you must pay attention to the polarity of the capacitors when replacing them.
Any advice on where to buy these, part number, and what they look like? Amazon? Jameco?
I got the capacitors as a set from Amazon - Tegg 120pcs Aluminum Electrolytic Capacitor Assorted Kit 0.22UF-470UF 12 Values Commonly Used Electronic Component DIY Assortment. This contained 10 of the desired 22 microfarad 16V capacitors. My son-in-law did the repair removing the 5 capacitors and replacing them with new ones. It worked! Thanks for the great advice!
Anyone have pics of the board? Genius desoldered and didn’t notate which pins were +/-…. Ugh. Rookies.
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Could be an electronic issue. Take it to your local Pfaff dealer for an estimate on repairing it. The parts may or may not be available.
Possibly a computer component malfunction/failure.
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