Author Topic: maintaining cpcs  (Read 2631 times)

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Offline amstrad_user_aust

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maintaining cpcs
« on: 07:57, 20 April 16 »
i have a 664, 464, and a 6128, apart from the normal replacements of drive belts, and keeping a machine clean is there any issues with caps like with my amigas?

Offline Audronic

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Re: maintaining cpcs
« Reply #1 on: 09:29, 20 April 16 »
@amstrad_user_aust

Welcome on board from a fellow Australian (Williamstown, Victoria).

I have repaired a couple of machines 464/6128 i have not found any cap problems (Yet).

Welcome    Ray

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Offline ||C|-|E||

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Re: maintaining cpcs
« Reply #2 on: 10:56, 20 April 16 »
Hello!

The other day I asked Bryce about this same question and he told me that he never needed to change the caps of a CPC since they are well over-speced and never run hot. This, as far as I know, applies to the Plus range as well :) They should be fine.


Offline amstrad_user_aust

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Re: maintaining cpcs
« Reply #3 on: 10:59, 20 April 16 »
sounds good!


my next mission is getting the drives working in my 6128 and 664


Offline amstrad_user_aust

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Re: maintaining cpcs
« Reply #4 on: 11:00, 20 April 16 »
good to see more aussie amstrad fans ray!

Offline Dizrythmia

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Re: maintaining cpcs
« Reply #5 on: 04:08, 25 April 16 »
My PC Engine portables, the LT & GT have a serious case of needing the caps replaced, as does my Gamegear. I don't think they're ever been a problem for the Amstrad CPC series.


Does this spacing apply to later revisions of the board, which have the parts closer together? Again, I would assume so...


Oh & Adelaide, South Australia here!

Offline 1024MAK

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Re: maintaining cpcs
« Reply #6 on: 10:50, 25 April 16 »
I don't think "spacing" was what was meant. I think "speced" is short for specified, as in the specification.

In any event, in most electronic devices, it is one of the following types that fail: the 250V AC paper interference suppression capacitors (like in the Acorn BBC Micro plus various other computers and devices) in the mains section of the power supply. Or the electrolytic capacitors in the power supply (mainly in switch mode power supply units, but also some conventional power supplies where they are mounted near to a hot transformer or heatsink). Or occasionally the Tantalum capacitors in either the power supply or on the main board. There is and has been a lack of understanding on the voltage rating of this type, which means some fail due to being underrated for the task they are being used for.

The CPC computers of course don't have an internal power supply.
And Tantalum capacitors are not used on in any of the CPC computers that I have (at least, not that I have seen).

However, electrolytic capacitors do have a limited life, so may need replacing one day. But I would not worry about them until you see symptoms.

Mark
Looking forward to summer in Somerset :-)

Offline Kris

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Re: maintaining cpcs
« Reply #7 on: 11:32, 25 April 16 »
To complete the answers given up to now, I have reworked several CPCs (old & Plus) and never need to change the capacitors (even if I already do it on mine just "for fun").
However, I already have to change capacitors in the power supply circuitry of the monitor (especially the big capacitor link to the flyback) and some other around which are more sought then capacitors into the CPC itself.






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Re: maintaining cpcs
« Reply #8 on: 12:17, 25 April 16 »
The monitor is a different beast, for sure... I recently had to recap the board of my screen as well. It took some time but it was all good fun  :)

What I found in my Plus board, and was pointed by some other members of the forum when they checked the pics I took, is that some of the soldering points are starting to dry and should be reflowed. I will actually do it during the next weekend, but I will probably let the capacitors be (I think). Sometimes I think: well, I have the caps already at home and since I am going to reflow, I can change them as well and forget about the little guys. Some other times I think: since they did not fail, maybe it would be better not to touch them at all  :D :D .
« Last Edit: 12:21, 25 April 16 by ||C|-|E|| »

Offline chinnyhill10

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Re: maintaining cpcs
« Reply #9 on: 12:41, 25 April 16 »
I sat and watched Future Was 8 Bit recap my Amiga 1200 the other week. Opened her up and to the naked eye looked fine. Thankfully we decided to recap anyway and thank goodness we did. Once he got the surface mount caps off you could see underneath that a couple of them had just started to bulge and leak. Not at all visible while attached to the board. We'd caught them in time!


Just because a cap isn't leaking or bluging doesn't mean it's not in spec. The only way to be sure is to measure its capacitance. No good just saying it's fine and leaving it be, measure it then you will know.
« Last Edit: 12:44, 25 April 16 by chinnyhill10 »
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Re: maintaining cpcs
« Reply #10 on: 13:06, 25 April 16 »
Problem is that to measure the capacitance in a proper way you need to remove the cap from the board... and if you do this then is not worth putting the old cap back, even in the case that it is OK in capacitance terms. Recapping a computer that works well, on the other hand, is always a bit risky, even in easy machines.

Offline Bryce

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Re: maintaining cpcs
« Reply #11 on: 13:33, 25 April 16 »
There are meters that can measure Capacitance, ESR and Q-Factor without removing the capacitor.

Bryce.

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Re: maintaining cpcs
« Reply #12 on: 13:41, 25 April 16 »
It would be great to have one of those then, do you have a reference of the meter Bryce? Mine, surely cannot do it and in case the others are not extremely expensive it would be really great to have one  :)

Offline Bryce

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Re: maintaining cpcs
« Reply #13 on: 14:07, 25 April 16 »
The Peak Atlas ESR 70: Peak Electronic Design Limited - Atlas ESR PLUS - Equivalent Series Resistance is relatively cheap. It can do ESR but not Capacitance in-circuit. The ones that can do all in-circuit measurements (where possible), start at about 7 times the price of this. The peak also discharges the capacitor for you :)

Bryce.

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Re: maintaining cpcs
« Reply #14 on: 14:14, 25 April 16 »
I am screwed then, but thank you! No on-board capacitance measurement for me  ;D

Offline Bryce

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Re: maintaining cpcs
« Reply #15 on: 14:18, 25 April 16 »
In circuit capacitance measuring is very limited anyway. As soon as you have other capacitors in parallel it gives you inaccurate readings and that's almost always when it comes to Electrolytics on power rails, as is the case here.

Bryce.

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Re: maintaining cpcs
« Reply #16 on: 14:38, 25 April 16 »
That is was I thought but I was hoping to find a short of miracle reader, it would have been great!  :D

Offline Bryce

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Re: maintaining cpcs
« Reply #17 on: 14:47, 25 April 16 »
No, it can't isolate the DUT from all the other capacitors on the PCB. So on a normal computer power rail you'll have several electrolytics and sometimes hundreds of ceramic decoupling capacitors all in parallel and looking like one big capacitor as far as the meter is concerned. In-circuit capacitance testing usually only works in amplifier stages, where electrolytics are being used as filters and couplers and have no parallel capacitors.

Bryce.

Offline chinnyhill10

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Re: maintaining cpcs
« Reply #18 on: 14:54, 25 April 16 »
Recapping a computer that works well, on the other hand, is always a bit risky, even in easy machines.


It's a measure of risk. You find someone who is good to do the repair and you take into account that if it's an Amiga 600 or 1200 it's not a question of if the caps will go, but when. And when they do go it isn't always with a puff of smoke but with the contents of the cap slowly eating away at the board.


The guy who did mine said my A1200 was the best he'd seen and he's repaired loads, yet the signs were still there. Presumably Commodore using cheap parts or they got hot.
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Offline chinnyhill10

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Re: maintaining cpcs
« Reply #19 on: 15:00, 25 April 16 »
At the end of the day the CPC is only through hole technology and is a fairly simple board. How many electrolytic caps on there? 10 or so? I still have my A600 ones in a bag on my desk at home (had that done as well) and that had about 20 IIRC. As many of those are surface mount you have to heat the board which has its own risks.
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Offline Bryce

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Re: maintaining cpcs
« Reply #20 on: 15:12, 25 April 16 »
It wasn't really the fact that the A600 / A1200 caps were cheap, more the fact that SMD Electrolytic caps were a very new technology at the time and they hadn't quite got the formula right. Electrolytic caps can live a very long time depending on their function and environment. If they are working close to their specified voltage, having to deal with regular spikes and (worst of all) in a hot environment, their life is majorly reduced.

Bryce.