C101 on CPC464

[Vyper68]

Hi
There is a Electrolytic capacitor on my board and is listed as C101 the one fitted is a 16v 47uf one but the spec is 10V. Is the capacitor part of the start-up circuit. It is the only Electrolytic capacitor on my mainboard and i would imagine it could do with changing.

Board: PT NO Z70374, MC0044B

[tjohnson]

I'm sure someone will better be able to answer but using a higher rated cap is not an issue.  I had a look at the mainboard picture and is near the 5v power socket but can't see where it connects, the circuit diagram in the service manual I have doesn't cover this board but has a similar cap that appears to feed the cassette drive could be filtering that.  Tbh unless you are seeing any sort of issues I would leave it and not replace it.

[Bryce]

C101 is the main (only) smoothing capacitor on the 464. Yes, it's worth replacing, but the value isn't all that important. I usually use 100µf capacitors as replacements. As for the voltage, any value from 10V to 25V is fine. The voltage value on a capacitor is what it can handle, not something it produces, so as long as you don't use some silly value (4kV capacitor for example ) you are fine.
In this case (not in all cases!) the capacitance value can also vary. I wouldn't go below 47µf (that was a bit optomistic from Amstrad), but anything up to 120µf would be fine too.
C101 is connected directly across the 5V input and it's polarity is very important. Make sure you solder it in the correct way around.

Bryce.

[Vyper68]

C101 is the main (only) smoothing capacitor on the 464. Yes, it's worth replacing, but the value isn't all that important. I usually use 100µf capacitors as replacements. As for the voltage, any value from 10V to 25V is fine. The voltage value on a capacitor is what it can handle, not something it produces, so as long as you don't use some silly value (4kV capacitor for example ) you are fine.
In this case (not in all cases!) the capacitance value can also vary. I wouldn't go below 47µf (that was a bit optomistic from Amstrad), but anything up to 120µf would be fine too.
C101 is connected directly across the 5V input and it's polarity is very important. Make sure you solder it in the correct way around.

Bryce.

I used to have an Oric Atmos and there was only a couple on there too but the was one C9 which if shot would make the machine very flaky as i think it helped get the Reset circuit get up to speed. If you had a duff Atmos and power cycled it there would be a small residual charge in the Capacitor that would when powered up again be enough to get the Atmos to boot. It was a very basic machine under the hood and some of the circuits were belt & braces, nothing like the CPC.

I'm waiting on a new solder sucker anyway before i try. The shakes in my hands have got better for the last few days so i want to make hay while the sun is shining before i relapse.

[Bryce]

The reset circuitry in the 464 (and most retro computers) is a simple discrete circuit. In the 464 it's made up of: R101, D101, C102, R102 and IC110. C102 was originally designed to be an electrolytic capacitor (according to the schematics, but I've only ever seen ceramic caps in real machines for this) See pic below. There are also a few electrolytic capacitors in the tape and audio section, but they are mainly for DC filtering, so their importance is quite a bit lower and the system usually continues working even if they have drifted way off value.

Bryce.

The bits (in the two red boxes) that reset a CPC464 MC0044B:

[tjohnson]

C101 is the main (only) smoothing capacitor on the 464. Yes, it's worth replacing, but the value isn't all that important. I usually use 100µf capacitors as replacements. As for the voltage, any value from 10V to 25V is fine. The voltage value on a capacitor is what it can handle, not something it produces, so as long as you don't use some silly value (4kV capacitor for example ) you are fine.
In this case (not in all cases!) the capacitance value can also vary. I wouldn't go below 47µf (that was a bit optomistic from Amstrad), but anything up to 120µf would be fine too.
C101 is connected directly across the 5V input and it's polarity is very important. Make sure you solder it in the correct way around.

Bryce.

47uF seems low for a smoothing cap?

[Vyper68]

I bought some 47uf's for this but i have some 100uf in my "Toolkit" so i might use one of those instead.

[mr_lou]

The voltage value on a capacitor is what it can handle, not something it produces, so as long as you don't use some silly value (4kV capacitor for example ) you are fine.

Someone forgot to give Samsung that memo, when they put 9v capacitors in their 12v PSU's in a lot of their TV's.

We can't go expect a big electronic company like Samsung to know such things if no one tells them.

[Bryce]

Someone forgot to give Samsung that memo, when they put 9v capacitors in their 12v PSU's in a lot of their TV's.

We can't go expect a big electronic company like Samsung to know such things if no one tells them.

Never heard of a 9V capacitor. Do you have a picture of this? The lowest value I know of are 10V parts.
Also, just because the PSU supplies 12V doesn't mean that that point in the circuit has 12V, it may be on a 5V rail?

Bryce.

[mr_lou]

Never heard of a 9V capacitor. Do you have a picture of this? The lowest value I know of are 10V parts.
Also, just because the PSU supplies 12V doesn't mean that that point in the circuit has 12V, it may be on a 5V rail?

Well, if it wasn't the wrong size capacitor, the story wouldn't have made it to the main news channel here in Denmark a few years back. A ton of Samsung TV's all have this problem: Capacitors on the PSU gives up after only 2 years.
Easy and cheap to replace of course - but we all know that manufacturers knows that people rarely fix stuff. They instead goes out and buys a new TV, which of course is why they do it.

Or are you really gonna tell me that Samsung just made an honest mistake?.....

[Bryce]

I did some research. They accidentally used 10V capacitors. I say accidentally, because there is no way they would have done this deliberately because (A) There's an extremely high chance that they would have failed within the warranty time and cost Samsung a huge amount of money (B) They wouldn't have passed most of the emmissions tests.
Things like this shouldn't but do happen. Usually in the component ordering or BOM process. The schematics etc were most likely correct, just the production got it wrong. Also, according to the reports I found, it was only a certain batch of TVs that had this problem. Other identical TVs had the correct capacitors, which also point at a manufacturing problem. Financially it also wouldn't make sense for Samsung to do this, there's no price difference between 10V and 35V caps at those volumes.

Bryce.