Newbie, 532 restoration

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xcasab
Berichten: 5
Lid geworden op: wo apr 04, 2018 12:26 pm
Locatie: Lugo, Spain

Newbie, 532 restoration

Berichtdoor xcasab » wo apr 04, 2018 12:50 pm

This is my first message, hello to all!!

I have just bought a pair of 532 in reasonably good condition and found this forum looking for info about them.

After a quick test, one of the boxes appears to be in working order. Sound is clean, and no obvious problem are detected after a visual inspection of the electronics, other than a dead 6V 0,05A bulb.

The other box, however, has a lot of noise. It plays music, but with random crackling sounds, perceived more clearly on the sqweaker/tweeter. Again, nothing obvious visible on the electronics (all electrolytics appear to be healthy). The power switch is cracked in the outside, but the noise remains unchanged when I move the switch from the inside with a plastic rod.

I am planning to clean all switches and contacts with contact cleaner, but after that...

What should I check first?

Any specific component(s) suspected?

Is it possible to find a replacement for the power switch? It is mounted in a thight space, so the form factor of the replacement could be an issue.

Thank you very much in advance. I hope to be able to restore the boxes to full working order.

Regards,

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Fotohuis
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Lid geworden op: vr feb 19, 2016 5:37 pm
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Re: Newbie, 532 restoration

Berichtdoor Fotohuis » wo apr 04, 2018 3:14 pm

I am not a specialist in the 532 MFB (first serie from 1973) however a few points are very important:

1) Broken switches can be ordered via the web shop
2) Do not use a regular contact cleaner, it can affect the PCB on a longer termin. Use IPA only and lubricate the switches, relais, connectors with contact grease or Brunox.
3) Replacement of the power supply elco's will be certainly necessary.
4) Replacement of the regular elco's you can check with a good ESR in line measuring instrument (Peak) or equivalent ESR instrument. Or just replace all via the kit here in the web shop.
5) Take notice of the Philips PL code and version of your 532 MFB.
6) After restoration you have to re-adjust the offset current (bias) for the amps and the feedback-loop. Very often you have to replace the potentiometers too.

Read the instructions very carefully and I am sure some 532 specialists can give you other important hints for a successful refurbishment.
http://www.svema.info
Analoog ingesteld. Dynavox TPR-3 5670W buizen voorversterker, Dynavox ET-100 met Teufel Ultima 20 Mk2. N4504, N4450, N2521, 312, 222 draaitafels + GP401/412 MKII Shibata. CD204. NAD C352, C422, C521BEE met FB820-22RH544/79R.

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Remi
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Re: Newbie, 532 restoration

Berichtdoor Remi » wo apr 04, 2018 5:18 pm

you might also check the soldering of both input DIN terminals, or better, resolder them anyway.

The left-right switch could be the culprit, a fast series of toggle might help shortly.

I have never had to replace the power switch, but you might find something useful.
What i did encounter though was a bad contact in the voltage selector, be sure to take out the power cord before you turn this one for you might kill your transformer. It might help to turn this selector a couple of times and be careful to end in the right position, you must 'feel' were you're at so to speak :)
"Hoezo nu wel genoeg? D'r is toch nog plek!" jaja, waar dan? "Ha! d'r kan nog wat in de auto!"

xcasab
Berichten: 5
Lid geworden op: wo apr 04, 2018 12:26 pm
Locatie: Lugo, Spain

Re: Newbie, 532 restoration

Berichtdoor xcasab » do apr 05, 2018 1:34 pm

Thank you, Remi and Fotohuis for your advice. Very useful!!

Regards!!

xcasab
Berichten: 5
Lid geworden op: wo apr 04, 2018 12:26 pm
Locatie: Lugo, Spain

Re: Newbie, 532 restoration

Berichtdoor xcasab » vr apr 06, 2018 5:18 pm

Today I have tried the 532 removing the fuses, one by one (leaving the other two in situ).

If I remove the top one (Z408) I get only the higher frequencies, and the cracking noises remain.

If I remove the middle one (Z409) I get only the lower frequencies, and the cracking noises are gone.

If I remove the lower one (Z410) I get nothing ;-)

I am guessing that the defective component must be in the high frequency amplifier. Am I right?

Besides, all switches (including the voltage selector rotary switch) have been clenaned. No difference. Ditto for the fuse holders.

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Fotohuis
Berichten: 4773
Lid geworden op: vr feb 19, 2016 5:37 pm
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Re: Newbie, 532 restoration

Berichtdoor Fotohuis » vr apr 06, 2018 5:27 pm

Without an ESR meter and or scope it is going to be a mission impossible.
http://www.svema.info
Analoog ingesteld. Dynavox TPR-3 5670W buizen voorversterker, Dynavox ET-100 met Teufel Ultima 20 Mk2. N4504, N4450, N2521, 312, 222 draaitafels + GP401/412 MKII Shibata. CD204. NAD C352, C422, C521BEE met FB820-22RH544/79R.

xcasab
Berichten: 5
Lid geworden op: wo apr 04, 2018 12:26 pm
Locatie: Lugo, Spain

Re: Newbie, 532 restoration

Berichtdoor xcasab » vr apr 06, 2018 6:36 pm

No scope, yet. But I do have an ESR meter.

I guess I will have to check everything or -probably less trouble, in the end- to do a complete overhaul, electrolytics and transistors. But before commiting myself to this, I would like to know if there are some failure-prone components that should be checked first.

Regards, and thank you for all the input.

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motoindo
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Lid geworden op: do jul 01, 2010 11:04 am
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Re: Newbie, 532 restoration

Berichtdoor motoindo » vr apr 06, 2018 6:48 pm

The mid-high amp is biased into AB operation with 210mA idle current and as such operates at relatively high temperatures. I would check/swap C534 first and TS441 second.
Chris Camphuisen
mfb does to the ear what a pretty face does to the eye

xcasab
Berichten: 5
Lid geworden op: wo apr 04, 2018 12:26 pm
Locatie: Lugo, Spain

Re: Newbie, 532 restoration

Berichtdoor xcasab » vr apr 06, 2018 7:53 pm

OK, thanks!.
I'll check those first


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