Capacitor code question - Page 1
Forum section: electronics / beginners

author: joelgraff
author_rank: Contributor
timestamp: April 17, 2022, 11:18:24 pm
content: I have a few capacitors I'm replacing on an Atari 2600 motherboard. They're coded and it doesn't quite match what I'm familiar with. Specifically, they look like old film caps and have ratings as follows:0.068K 100V0.22M 100VFF.1K 100VThe "100V" is fairly obvious (though I wonder about the 100VF). As for the other numbers, I would assume M and K are tolerance references, except the preceding values aren't the usual integer codes. Looking around, I get a few different possible meanings, one being the 0.68, 0.22, and 0.1 values are in an assumed unit (either micro or pico farads) and the M and K are tolerances, or they're a 0.068 Kilofarad and 0.22 microfarad capacitor, respectively. As for the preceding "F" in "F.1K", I've no clue.Anyway, I figure this is an easy one, but weirdly, I'm having no luck getting a clear answer after searching.

author: inse
author_rank: Super Contributor
timestamp: April 18, 2022, 12:18:56 am
content: Kilofarads don't exist today, so much to be said...

author: joelgraff
author_rank: Contributor
timestamp: April 18, 2022, 12:38:08 am
content: My bad. I meant thousandths... not thousands... So milifarads.

author: ledtester
author_rank: Super Contributor
timestamp: April 18, 2022, 12:44:50 am
content: I'm pretty sure they are all in microfarards. The K and M are likely tolerance codes:https://www.electronics-notes.com/articles/electronic_components/capacitors/capacitor-codes-markings.phpDo you have a way of measuring capacitance? That will give you a ballpark figure. As inse mentioned, K as in kilo as a multiplier would mean a factor of 1000, but milli- and micro- mean 10^-3 and 10^-6 -- way off in the other direction.For the ".068K" caps used in the paddle circuitry, this blog post says they are 68nF caps:https://www.skooterblog.com/en/2019/06/30/conserto-de-atari-2600-que-nao-funcionava-com-paddles-problemas-e-solucoes/#:~:text=I%20then%20decided%20to%20identify%20and%20test%20the%20capacitors.It also mentions a service manual for the 2600. I found one at manualslib.com. It's 156 pages and includes a parts list starting on page 137 of the PDF.Update: the prefix for 1/1000 is "milli-" -- using "K" wouldn't make much sense.

author: MikeK
author_rank: Super Contributor
timestamp: April 18, 2022, 12:59:07 am
content: Aren't the schematics freely available online? I would think someone was bound to do it.

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 18, 2022, 05:28:12 am
content: All numbers less than 1.0 are in microfarads (until it is stated another). When we talk about a digital device, usually there is no need to talk about tolerance (mostly).

author: joelgraff
author_rank: Contributor
timestamp: April 18, 2022, 12:44:11 pm
content: Quote from: MikeK on April 18, 2022, 12:59:07 amYes, they are. But the units aren't noted on them, either.

author: joelgraff
author_rank: Contributor
timestamp: April 18, 2022, 12:48:07 pm
content: Quote from: Vovk_Z on April 18, 2022, 05:28:12 amFrom your response, it seems most likely the letters indicate the capacitor tolerance, then.

author: joelgraff
author_rank: Contributor
timestamp: April 18, 2022, 12:58:38 pm
content: Quote from: ledtester on April 18, 2022, 12:44:50 amI seem to recall reading that "M" meant micro / millionths on older caps, so if that were the case, "K" would seem reasonable as an indicator of milli / thousandths. It's not as though anyone would confuse it with a megafarad or kilofarad cap, after all, except me.Anyway, I could see it used either way, but tolerance codes are probably the answer.Anyway, I don't have a reliable cap tester, but I'll give the one I have a try and see if maybe it gives me a clue. Thanks for the links, btw. I hadn't come across those!

author: MikeK
author_rank: Super Contributor
timestamp: April 18, 2022, 08:06:10 pm
content: Quote from: joelgraff on April 18, 2022, 12:58:38 pmAs ledtester said, K and M are almost certainly tolerance codes. K = 10%, M = 20%Post here what the schematic says. Have the knowledgeable people here make the informed guess.

author: TimFox
author_rank: Super Contributor
timestamp: April 18, 2022, 08:24:43 pm
content: Quote from: joelgraff on April 18, 2022, 12:58:38 pmMany years ago (1960s), the abbreviation "mfd" meant "microfarads" and "mmfd" (pronounced micky-mikes) meant "micro-microfarads" (pF).

author: tepalia02
author_rank: Regular Contributor
timestamp: April 20, 2022, 03:41:27 pm
content: I think it will be better if you post a schematic or a photo.

author: metrologist
author_rank: Super Contributor
timestamp: April 20, 2022, 03:48:40 pm
content: I'd like to inject a related tangent. I have SMD tantalum caps with code 10-35 N2. What does the N2 mean? I've seen N1, N2, and N3 codes, and these are the black monoliths not yellow.And who decided that a line that goes most of the way across these caps and looks like a minus sign should designate the positive pole, instead of how we designate the cathode of a diode with a line?

author: free_electron
author_rank: Super Contributor
timestamp: April 20, 2022, 04:57:55 pm
content: Quote from: inse on April 18, 2022, 12:18:56 amthey do. a bank of Maxwell caps.

author: free_electron
author_rank: Super Contributor
timestamp: April 20, 2022, 05:05:11 pm
content: Quote from: metrologist on April 20, 2022, 03:48:40 pmon tantalums the line is ALWAYS the positive. the black ones are typically made by kyocera , vishay (sprague division) and kemet. the orange ones are siemens, avx and yageo. now, since acquisitions constantly happen this boundary is now "soup"

author: tooki
author_rank: Super Contributor
timestamp: April 21, 2022, 04:22:58 pm
content: Quote from: free_electron on April 20, 2022, 05:05:11 pmYou don’t say… (Siemens spun off all its component manufacturing back in1999. So nobody is gonna be buying Siemens caps now. Those would be TDK now.)