I’m trying to fix a board with a cap kit. All of the caps have specs except there are 16 little blue tab looking ones labelled only “104”. What does 104 mean, and how do I order more of them?
Also I am using LM1881 chips for video sync stripping, but this question goes for any chip really: How the heck do you order sockets for chips and know that they will fit? The descriptions on mouser and digikey (what I use for parts ordering) might as well be koine greek, I always worry when ordering that I will order the wrong thing.
As far as the chip socket goes, assuming you are using a DIP (Dual-Inline Package), they are pretty standard. They generally have a lead spacing of 100 mils, and a package width of 300 mils. Just order a socket with the right number of pins. DO NOT order the surface-mount version of the chip - you won’t be able to solder it or socket it.
It’s strange because I want to order 7 different types of caps to do a complete cap of the board, but neither mouser or digikey both have every kind of cap that I want, I think I would rather pay more to go to Radioshack (GAH) then spend another minute fooling around with online catalogs trying to figure out how to get a complete cap kit between these two sites…
Why do you want to shotgun-replace all the caps? Unless the board was in some sort of severe over-voltage situation, those little ceramic / tantalum caps last pretty well forever. Especially TTL decoupling caps, which is what I’m assuming your gang of 14 is - they’re immediately at one end or the other of the chips, right? IIRC, they’re either good, or if they’re “blown” they’re truly blown, detonated, and visibly damaged.
As far as the socket goes, I prefer round machined pins verses the cheaper stamped pins. The former is more expensive, but worth it IMO.
Also, if the lead finish on the chip’s pins is tin or solder, do not use a socket with gold-plated contacts. Use a socket with tin or solder plated contacts.
This is my first cap kit ever, and you are right that these caps are all at the end of chips, and one is visibly damaged.
The reason I am shotgunning is because the board is a bootleg chinese tetris arcade board and I don’t have any faith in the quality of the caps, so I would rather just repair it once and never again.
I would agree with you and **beowulff **here. The only exception I *might *make is with tantalum caps. They’re not as reliable as ceramics. Plus they tend to short when they go, which can cause expensive damage upstream.
I’ve never seen a fried ceramic cap that’s used for decoupling PS noise for digital circuits. It may mean the cap was subjected to a fairly high voltage for a few milliseconds. If so, I would expect other things to be fried. Like logic chips.
And to be more specific about “why” I want to replace the caps, pretty much all arcade enthusiasts recommend replacing all the caps when they go out because one usually is followed by others… but I can see the point of just replacing the visibly damaged one first since it is a ceramic. But if they have the electrolytic ones I need at Radioshack after work today, might as well replace those while I am at it, the board is probably almost 20 years old. edit: It’s a bootleg of a game from 1988, so it’s even older than that!
Logic chips are fine, the game works fine, the only problem is dim video. I’m hoping it’s the cap instead of something custom that I can’t replace.
I’m not exactly sure what you’re working on here - sounds like a full-size arcade game?
Are you able to pull video out of the game and see it on a known-good monitor? (Can of worms time - is the video NTSC, PAL, SVGA or unknown?) Conversely, can you inject a known-good video signal into the display? Either of these should help determine if dim video is a signal problem or a display problem.
Apparently, replacing all the caps on the boards is a typical recommended procedure for these things, so I won’t argue with the existing knowledgebase. Caps are about the only electronic component that will go bad solely as a function of time - electrolytics, in particular, can go bad just sitting on the shelf. If this thing is from the 80’s, you’re hopefully at least before the counterfeit capacitor calamity that led to exploding caps and dead computers.
But if the problem is dim (and how? low brightness or low contrast?) video, I’d be looking at the display section rather than logic chips and their power supply decoupling caps - those things just keep high frequency garbage out of your DC power to prevent noise in the power from becoming a signal and randomly triggering things.
It’s just the board for the game in a generic cabinet that I can test with other boards and has always worked fine, I bought the board as non-working.
Video is 15khz analog RGB and the monitor is working fine.
Yeah I only had time to replace the one bad looking decoupling cap last night and it didn’t help, there is a bigger non-decoupling cap that looks a little warped so I will try to replace that tonight.
In case you haven’t gotten a full answer yet. Yes, those are most likely conformal coated ceramic caps.
104=0.1µF
Most common voltage=50v
There’s no way to tell the dielectric from what you posted, but if I was guessing, I’d take a look at something like the AVX SR215C104KAR
Caps are about the only electronic component that will go bad solely as a function of time - electrolytics, in particular, can go bad just sitting on the shelf. If this thing is from the 80’s, you’re hopefully at least before the counterfeit capacitor calamity that led to exploding caps and dead computers.