35-40 year old PCB boards - Page 1
Forum section: electronics / beginners

author: KenS.
author_rank: Newbie
timestamp: December 19, 2023, 11:28:57 am
content: I have some old Commodore 64 Printer Interface boards that I am thinking about replacing some of the components, but what about the PCB boards themselves . They look like they have separation on the traces. If they are bad, I thought about learning to use Kicad and have some new boards made. I wish there were some test and repair data on the Cardco Card Print B and Microgragix MW-350 boards. P.S need specs on power adapter for MW-350. Take care.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 19, 2023, 11:34:51 am
content: Looks pretty normal to me. The texture is due to SMOTC (Solder Mask Over Tinned Copper), as opposed to SMOBC (bare Cu) that is standard today. The mask lifts a bit as solder infiltrates under it during wave soldering, hence the wrinkled appearance.Tim

author: KenS.
author_rank: Newbie
timestamp: December 19, 2023, 01:27:15 pm
content: Thanks, I guess I will replace some capacitors (old brown round and big ceramic capacitor), one of them is black on top, kind of looks like paint. Take care.

author: forrestc
author_rank: Unknown
timestamp: December 19, 2023, 01:32:03 pm
content: Quote from: KenS. on December 19, 2023, 01:27:15 pmFor old ceramics like that I probably wouldn't bother unless there is a reason you suspect or know them to be bad.Electrolytics and Tantalums are a different story (although tantalum caps are generally good until they're not).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 19, 2023, 02:34:26 pm
content: This line...Quote from: KenS. on December 19, 2023, 11:28:57 am...Are you looking for problems that don't exist? Components are fine as they are, unless proven otherwise. I don't see anything wrong with any of the components shown; the ceramic cap has a somewhat kinked lead, but that's highly unlikely to cause a failure, at least from what I can tell from that angle.Tim

author: rdl
author_rank: Super Contributor
timestamp: December 19, 2023, 03:36:01 pm
content: The black paint mark at the top indicates the capacitor is rated for the Industrial Temperature Range.

author: Bud
author_rank: Super Contributor
timestamp: December 19, 2023, 03:40:32 pm
content: Quote from: KenS. on December 19, 2023, 01:27:15 pmDoes it have a cut on top in the middle of the black paint? Hard to see. If so then it is a spark gap component for board protection, leave it alone.

author: Gyro
author_rank: Super Contributor
timestamp: December 19, 2023, 04:31:06 pm
content: No, it's a superficial scratch in the cement. It's a 82pF 5%, probably NPO/C0G. It will be part of an RF filter or timing circuit. It's been nudged at some time but a bit of a kink on the leg isn't an issue.

author: srb1954
author_rank: Super Contributor
timestamp: December 19, 2023, 07:09:46 pm
content: Quote from: rdl on December 19, 2023, 03:36:01 pmThe black paint means it is nominally zero temperature coefficient i.e. a NP0/C0G type capacitor

author: srb1954
author_rank: Super Contributor
timestamp: December 19, 2023, 07:22:30 pm
content: Quote from: KenS. on December 19, 2023, 01:27:15 pmCheck if there is a short in that capacitor before replacing. Otherwise, I wouldn't bother replacing this capacitor for what is probably just a cosmetic defect.I would check that all of the socketed ICs are making reliable connection as some brands of IC socket are notorious for becoming unreliable with age, especially the types that make contact on the edges of the IC pins rather than on the face of the pin.Depending on the storage environment the pins of an IC can also become oxidised over time and can make poor contact with the socket. Just removing and replacing the socketed ICs is quite often sufficient to scrape any oxidation of the IC pins.

author: temperance
author_rank: Super Contributor
timestamp: December 19, 2023, 10:37:19 pm
content: Just the world wide re-capping pandemic.

author: shapirus
author_rank: Super Contributor
timestamp: December 19, 2023, 11:32:45 pm
content: Quote from: temperance on December 19, 2023, 10:37:19 pmor rather cargo cult re-capping.

author: KenS.
author_rank: Newbie
timestamp: December 21, 2023, 03:09:24 am
content: Thanks for the replies. Three of the printer interface boards are in black plastic cases. Two of the cases have a opening to where you can change the 6 switch positions depending on the printer you are using. So I guess the coponents should be OK, unless proven otherwise. One of the ROM IC's, I put some Elecronic cleaner (auto store) in the lid of a plastic box and set the IC in it, hoping it would do some good. Had a bad pin connection with a EEPROM Programmer. The cleaner seemed to help. This EPROM had almost of of the marking removed. You could see the very tip of the letter "I" and the dot. Then a "D27". And after looking at pictures of other Eprom's, I think it most likely a Intel D2764 EPROM. The other end of the IC, had a thin brownish material sticking out from the chip, and I notice one of the pictures, it appeared to have the same thing. This is the first time I have seen a Intel IC on a Commodore product. I should be getting another Micrografix MW-350 Printer Interface tomorrow. Will compare it to this one. Take care.

author: forrestc
author_rank: Unknown
timestamp: December 22, 2023, 10:24:23 am
content: Quote from: KenS. on December 21, 2023, 03:09:24 amIf this is from the mid-80's (would be curious about date codes on any of the IC's), it probably was manufactured during one of the periods where EPROM's were hard to get. You never knew what brand or size of EPROM you might find in a device. I know it wasn't uncommon to see a design to take a range of EPROM sizes depending on what the manufacturer could get.