Hello everyone.
Yesterday afternoon I was working on commissioning my old Apple IIc. After a few years of total disuse I decided to clean it using a degrea degreaator product. To do this I completely disassembled all the pieces of plastic so as not to wet the boards.
Unfortunately, a couple of minutes after the monitor was turned on, it happened that a polyester capacitor in the power supply part exploded. I found electrical diagrams about the monitor. My first question is this: the electrical schemes refer to an A2M4090 model monitor, but I live in Italy and for obvious reasons my monitor is a European model whose acronym is A2M4090Z. Are there substantial differences between the two models or the electrical schemes of the first are fine for the second?
The polyester capacitor exploded in the manual corresponds to the C772.
Can the fact that it exploded correspond to an age-related problem? Did the same thing happen to any of you?
Everything on the DC side of the circuit should be effectively identical; on the AC side, it isn't, as you are on 240VAC/50Hz, and the US design is 120VAC/60Hz. Exactly which cap popped on you? C771? or another of them? What are the ratings on C773 and C774 on your board?
They should be identical, and C771 should be a factor of *100 farads compared to C773/C774. Try to post photos with a lot of detail of the damaged area and of the entire power board.
It's not uncommon for the caps in any old CRT to pop after 30-40 years.
c772 3.JPG
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Hello.
Here there are some other pictures.
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Greetings to Italy !
Like already pointed out by Timelord, these RIFA capacitors often pop up after a while. They are line filters.
There are plenty of cases inside PSU (Apple II or monitors or any other equipement). You have to replace the X capacitor along with all the others RIFA filters (the two 4700pF Y capacitors).
And I don't think T1 connector is polarised since it is driven by Alternating Current.
Ciao! :-)
Just to add and emphasize what was already said: yes, it's very common for filter capacitors to fail after years of service - and they are easily replaced. However, just as a warning to anyone not familiar with those filters: make sure to replace them with a matching type. Not just considering voltage and capacity as usual for other capacitors. But also considering the respective "X2" or "Y" safety class rating - since they are connected to live voltage. Replacing with capacitor of a mismatching safety class will not make any difference at first. But it may make a major difference one day when time has come for this capacitor to fail: X2 and Y class capacitors will fail differently (and a capacitor of mismatching class results in an electrical hazard...).
Here is the part that you need.
KEMET PMR209MC6100M100R30, or equivalent.