Cross over problem.

.one. · 25 Aug 2020 at 00:17

Hi this is picture of a crossover from one of my MONITOR AUDIO MA4 MKI speakers, sound great but today after an hour of use there was a fuzzy noise coming from the base driver.

As shown in the picture I think it is a resister not sure ? which looks like crystal build up would this be the problem.

Thanks Jamie.

hornetstinger · 25 Aug 2020 at 18:59

No image

sad099 · 25 Aug 2020 at 20:57

That capacitor end looks damaged too and needs replacing

.one. · 25 Aug 2020 at 21:14

sad099 said:
That capacitor end looks damaged too and needs replacing

Yea your right did not see in the picture before:

I found out the problem because of the of age of the speakers 45 years old the driver cones sag ,some one said it is a common problem on older speakers so rotated the driver 180 degrees and sorted speakers happy again.

But some attention is needed on the crossover.

james.miller · 25 Aug 2020 at 22:36

that fuzzy looking component i suspect is a cemented wirewound resistor. I cant see the markings from there but you should be able to look at the crossover in the other speaker to identify it's exact value. As they are old, i would personally replace all the caps and resistors in both crossovers.

Kei · 26 Aug 2020 at 00:06

The two components with purple coloured wire are actually inductors with iron cores. (the purple colour to the wire is varnish used to insulate the coils) The white block to the right is an air core inductor. The small black items are wire wound resistors and the orange and yellow objects are dipped capacitors. The capacitors are probably polyester, they look like the really old ones that sometimes get referred to as "tropical fish" as they have the colour bands to denote their value instead of just text.

The only thing that would benefit from replacement in there are the capacitors as the resistors are wirewound which are as tough as you can get and don't tend to suffer from ageing. Inductors are even tougher and it's obvious if they've gone wrong as they will usually look very discoloured or burnt.

.one. · 26 Aug 2020 at 01:12

Kei said:
The two components with purple coloured wire are actually inductors with iron cores. (the purple colour to the wire is varnish used to insulate the coils) The white block to the right is an air core inductor. The small black items are wire wound resistors and the orange and yellow objects are dipped capacitors. The capacitors are probably polyester, they look like the really old ones that sometimes get referred to as "tropical fish" as they have the colour bands to denote their value instead of just text.

The only thing that would benefit from replacement in there are the capacitors as the resistors are wirewound which are as tough as you can get and don't tend to suffer from ageing. Inductors are even tougher and it's obvious if they've gone wrong as they will usually look very discoloured or burnt.

Thanks for your reply very helpful,I guess I will have to replace the capacitors with modern equivalent at the moment I love the sound from them.

Edit:
James miller yes good idea on the comparisons.

.one. · 4 Sep 2020 at 20:54

Hi looking for replacement for below any help would be very grateful.

Tropical fish capacitors:

Caps1:

UF/4.7
Tolerance %10
Voltage 100 v
Max UF/5.17
Min UF/4.23

Caps2:

UF/3.3
Tolerance %10
Voltage 100 v
Max UF/3.6
Min UF/2.97

I declare I don't know much on the subject but would like to replace as speakers are 45 years old.
Friend of mine will solider them in for me.

I did order the caps below but messed up on the voltage because I am a idiot.

(ECAP70-050) - 3.3uF 70V Mundorf ECap AC PLAIN electrolytic capacitor.
(ECAP70-070) - 4.7uF 70V Mundorf ECap AC PLAIN electrolytic capacitor.

Thanks Jamie.

Kei · 5 Sep 2020 at 08:47

That’s a downgrade as you are going from plastic film type capacitors to electrolytic. You want MKP parts, aka, polypropylene film. If you want Mundorf, they do produce them but they will be quite expensive and are usually a lot larger than necessary due to their voltage ratings. I’d look at wima, Panasonic, kemet and Vishay from an electronics supplier like RS, Farnell, Digikey or Mouser. The box or dipped style radial type with a 100-250Vdc rating should be pretty similarly sized. Choosing based on size and lead spacing should give you a drop in replacement.

Just as an example, these would be pretty good for the job provided the lead spacing and dimensions tie in with what you already have. I've used them previously in an amplifier to replace some electrolytic coupling capacitors and they did a fine job. (albeit they were a bit big)
https://uk.rs-online.com/web/p/polypropylene-film-capacitors/7270039/
https://uk.rs-online.com/web/p/polypropylene-film-capacitors/7270041/

Having had a look at mundorf, you might be able to get away with these 250V rated MKP parts as they are 28mm long and not ridiculously expensive.
https://www.hificollective.co.uk/catalog/mkp070-47uf-250v-mcap-polypropylene-capacitor-p-8504.html
https://www.hificollective.co.uk/catalog/mkp050-33uf-250v-mcap-polypropylene-capacitor-p-8502.html

.one. · 6 Sep 2020 at 22:11

Kei said:
That’s a downgrade as you are going from plastic film type capacitors to electrolytic. You want MKP parts, aka, polypropylene film. If you want Mundorf, they do produce them but they will be quite expensive and are usually a lot larger than necessary due to their voltage ratings. I’d look at wima, Panasonic, kemet and Vishay from an electronics supplier like RS, Farnell, Digikey or Mouser. The box or dipped style radial type with a 100-250Vdc rating should be pretty similarly sized. Choosing based on size and lead spacing should give you a drop in replacement.

Just as an example, these would be pretty good for the job provided the lead spacing and dimensions tie in with what you already have. I've used them previously in an amplifier to replace some electrolytic coupling capacitors and they did a fine job. (albeit they were a bit big)
https://uk.rs-online.com/web/p/polypropylene-film-capacitors/7270039/
https://uk.rs-online.com/web/p/polypropylene-film-capacitors/7270041/

Having had a look at mundorf, you might be able to get away with these 250V rated MKP parts as they are 28mm long and not ridiculously expensive.
https://www.hificollective.co.uk/catalog/mkp070-47uf-250v-mcap-polypropylene-capacitor-p-8504.html
https://www.hificollective.co.uk/catalog/mkp050-33uf-250v-mcap-polypropylene-capacitor-p-8502.html

Cheers Kei just the information I needed, will be going with the mundorfs they should fit nicely.

Thanks.