Philips PM2535 - Page 1
Forum section: electronics / beginners

author: david69
author_rank: Regular Contributor
timestamp: October 17, 2014, 11:30:46 am
content: Hi, I would like to ask something about multimeter PhilipsPM2535, I tested EPROM, SRAM, battery, its OK, but I can`tcalibrate multimeter, I don`t have null and corect voltage,0> 6mV, 60V > 58V, at DC in NC mode, is there analog hardware problem? Switches seem right? Thank You for any idea..

author: david69
author_rank: Regular Contributor
timestamp: October 17, 2014, 12:50:03 pm
content: I found broken zener diode in reference circuit for DAC ..

author: EEVblog
author_rank: Unknown
timestamp: October 17, 2014, 01:06:36 pm
content: Quote from: david69 on October 17, 2014, 12:50:03 pmThat'll do it.So it's the actual reference zener itself?In that case it will need careful selection on a replacement.

author: david69
author_rank: Regular Contributor
timestamp: October 17, 2014, 05:17:45 pm
content: Now I have +/-5V reference for DAC, I have short circuiton input multimeter, but integrator and slope amplifier with comparator still continue generate signal, but I have now smaller value mV on displayI dont know right functionof multiplexer 4051 with TEST probe clips, I dont have thereany voltage nor signal?

author: david69
author_rank: Regular Contributor
timestamp: October 17, 2014, 07:09:20 pm
content: I removed MUX 4051, and output Z conected to analog ground. Multimeter shows zero in AC modes, 0.19mA,0.19mV, 0.19Ohm/2W in DC modes, broken power supply??

author: david69
author_rank: Regular Contributor
timestamp: October 18, 2014, 01:51:43 pm
content: I will replace MUX 4051 and switch 4066, +-REF is OKin front of integrator ... power supply is OK

author: david69
author_rank: Regular Contributor
timestamp: October 20, 2014, 07:57:56 am
content: MUX4051 improved DC range voltage :-) but LTC1052is noise??

author: david69
author_rank: Regular Contributor
timestamp: October 21, 2014, 02:10:08 pm
content: The power analog voltage is +8V, -8V and digital +6V, -6V, There are stabilisators 78L05 and 79L05 with zenersin collectors, 3V3 and 3V9, and stabistor 1V5. I playedwith zeners, and changing voltage has big influence onmeasurement, mainly analog voltage, What right value should I have on output power supply?

author: Simon123
author_rank: Regular Contributor
timestamp: October 21, 2014, 03:20:50 pm
content: You mean zeners on ground lead?The output voltage should be voltage of zener + voltage of regulator.http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm2534_PM2535.pdfpage 66 for psu

author: david69
author_rank: Regular Contributor
timestamp: October 21, 2014, 03:48:22 pm
content: depends on output current and current via collectors7805 and 7905, there will be difference with types of use zener diodes.

author: david69
author_rank: Regular Contributor
timestamp: October 22, 2014, 03:43:29 pm
content: I have understand PM2535 yet, Calibration DC,AC voltage is OK :-) I think that multimeter is functious :-) AutoZero workswell...

author: david69
author_rank: Regular Contributor
timestamp: November 04, 2014, 12:56:50 pm
content: it is good to replace watchdog 7705, MUX 4051,switch 4066, chopper LTC1502, zener diodes in power, and capacitors :-)