@Khron I measured the thermistor with the transistor tester and it gave me the value of 12.7 ohms (attached photo), the one I bought is 5 ohms could it be a problem?Di solito è contrassegnato su un lato, ma considerando che non è una cosa ad alta potenza, qualcosa come uno da 10 ohm di diametro simile dovrebbe andare bene.
https://en.wikipedia.org/wiki/Thermistor#NTC
(Secondo punto elenco in quella lista)
Hi. Was just dropping by and saw your post. We just repaired one of these at my shop. Why not save your solder and just drop in a new PSU:for all of you guys who had trouble with lexicon pcm-90/91/80/81
i bought a pcm-91 with a faulty power supply, needless to say for a small amount of money ;-)
thought this couldn't be so complicated to fix. i wasn't so easy in the end....
at first i noticed the hi voltage cap which has a bulge, it has a voltage about 270 V dc (main ac is 230 v here in germany, so it has to 310 or sth. like that).
so i changed it; wasn't so easy to get a replacement because the height of the 100µ/400V el-cap is only 2,5 cm. finally i found a replacement....
because of known problem with electrolytic caps and smps i changed all other el-caps to 105° low esr types with same or greater voltage (red dotted)
next change was the switching mos, a IRF830 which has a low resistance from one pin to another, don't ask me which one...
after that and some looking at the other components i thought the ps should be able to work now. unfortunately it doesn't....
there are 310 V dc at the bulk cap but it seems like the copper-circuit doesn't start :-(
i changed the 2 small driver transistors, no success
after few days break i checked the rectifier diodes at the output side which were ok
at last i measured every resistor and capacitor on the hi voltage / mains side.
i found the r2, a 750kOhm / 0,5W has no resistance.
after replacing this beast my lex awake to new life
i saved 50 bucks a new smps would cost from the german lex service ;-)
maybe this helps some of you guys with faulty lexicon device...
thanks a lot to svart for the tc wizard ps & general switch mode power supply thread!!!
now i have a tc power supply with a more complicated failure on the bench :-/
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