Help identifying capacitor type

[justacruzr2]

Can any of you electronics experts out there identify what type of capacitor is shown in this photo. This is the main board in the floppy drive I'm repairing and I would like to replace it with the correct type. I know it's not ceramic disc, electrolytic or tantalum. I believe it's some kind of film type....but which? And it's clear to see that the cap in the lower right corner is blown. The others may be compromised as well. Thanks for any help you can provide.

[Stuart]

Looks like a polystyrene type to me. https://www.google.co.uk/search?q=capacitor+polystyrene&source=lnms&tbm=isch&sa=X&ved=0ahUKEwihxa_cvZfRAhWIrxoKHcUEB5MQ_AUICSgC&biw=1215&bih=965

 

The marking "302G" is I believe 3000pF +/-2%.

[Keatah]

Yup. That's a polystyrene laminated film cap alright.

[mister35mm]

polystyrene

[+Ksarul]

Polystyrene, and you may want to check them all,, as they do have a somewhat limited lifespan.

[CC Clarke]

For DC applications, Polystyrene has been largely eliminated by polyester (Mylar) film capacitors. One bonus is the Mylar caps are a lot easier to find.

 

CC

[justacruzr2]

A BIG thanks to all of you. And it's great to see 100% concensus.

@ Stuart

Thanks for answering what was to be my next question. I do understand how to translate the markings to the value but was not sure if it was expressed as micro farads (uf) or pico farads (pf). Thanks for clearing that up.

@ Ksarul

Definitely is my intention and the ones in this photo too (even though they don't look bad) which DigiKey identified as polyester film caps. DigiKey was unsure about the ones that all of you identified. Probably because as CC Clarke says they have been largely eliminated so they don't see them anymore. These drives are 31 years old and need some freshening up as long as I'm working on them. Actually I'm working on 2 drives. They both took a spike from a static discharge along with the disk controller. The controller I already repaired and tested with a known good drive and it's OK (the CC9900 we were talking about months ago).

@ CC Clarke

Thanks and if I can't get polystyrene from DigiKey I'll go with the polyester (mylar) as you suggest.

Edited December 29, 2016 by justacruzr2

[RickyDean]

A BIG thanks to all of you. And it's great to see 100% concensus.

 

@ Stuart

 

Thanks for answering what was to be my next question. I do understand how to translate the markings to the value but was not sure if it was expressed as micro farads (uf) or pico farads (pf). Thanks for clearing that up.

 

@ Ksarul

 

Definitely is my intention and the ones in this photo too (even though they don't look bad) which DigiKey identified as polyester film caps. DigiKey was unsure about the ones that all of you identified. Probably because as CC Clarke says they have been largely eliminated so they don't see them anymore. These drives are 31 years old and need some freshening up as long as I'm working on them. Actually I'm working on 2 drives. They both took a spike from a static discharge along with the disk controller. The controller I already repaired and tested with a known good drive and it's OK (the CC9900 we were talking about months ago).

 

@ CC Clarke

 

Thanks and if I can't get polystyrene from DigiKey I'll go with the polyester (mylar) as you suggest.

Can you elaborate on what was spiked on it and how you fixed it, I haven't had much time to work on mine, but when I do I want t cover all bases. Thanks

[justacruzr2]

Can you elaborate on what was spiked on it and how you fixed it, I haven't had much time to work on mine, but when I do I want t cover all bases. Thanks

 

Not sure if you're talking about the disk controller card or the floppy drive so I'm going to assume you mean the disk controller card which we discussed months ago. All I did was just rebuild the card since I don't have any technical equipment, other than an ohm meter, to track problems down. I thought that was what you were doing too with your CC9900.

[RickyDean]

 

Not sure if you're talking about the disk controller card or the floppy drive so I'm going to assume you mean the disk controller card which we discussed months ago. All I did was just rebuild the card since I don't have any technical equipment, other than an ohm meter, to track problems down. I thought that was what you were doing too with your CC9900.

Yes, I am and was, till I got pulled into other directions, just thought you may have some more insight.

[justacruzr2]

Yes, I am and was, till I got pulled into other directions, just thought you may have some more insight.

 

I can add a little about the details of what I did and what I found. I replaced all the chips on the card except the ROMs and the PALs. They were OK. I replaced the 9901 although I'm sure it was OK as I had tested it with another known good 9901. I know the 7406 was bad and maybe the one next to it (can't remember it's number...maybe 7438). I also found several caps that were bad. They had dark brown spots on them that suggested they overheated and weren't noticeable until I looked at them with a magnifier. I replaced all the caps just to be sure. Also all the resistors, diodes and transistors. I didn't replace the crystal or the LED. That's about it...hope that helps.

[RickyDean]

 

I can add a little about the details of what I did and what I found. I replaced all the chips on the card except the ROMs and the PALs. They were OK. I replaced the 9901 although I'm sure it was OK as I had tested it with another known good 9901. I know the 7406 was bad and maybe the one next to it (can't remember it's number...maybe 7438). I also found several caps that were bad. They had dark brown spots on them that suggested they overheated and weren't noticeable until I looked at them with a magnifier. I replaced all the caps just to be sure. Also all the resistors, diodes and transistors. I didn't replace the crystal or the LED. That's about it...hope that helps.

Thanks, any info can possibly help. I will be getting back to mine during rainy days. i have been working on my car projects, especially a Suburban and a diesel Silverado, that have taken up a lot of my free time, trying to get ready for the holiday trip we took. I have several hardware projects to finish for the TI and Geneve, IDE, SAM, Corcomp repair, Geneve repair, and so forth.

 

 

BTW: Did you happen to have a BOM for ordering, I have ordered some of the parts but not all and if there is a BOM available, I would just order all from one source to have everything there on hand. Thanks.

Edited January 4, 2017 by RickyDean

[justacruzr2]

Thanks, any info can possibly help. I will be getting back to mine during rainy days. i have been working on my car projects, especially a Suburban and a diesel Silverado, that have taken up a lot of my free time, trying to get ready for the holiday trip we took. I have several hardware projects to finish for the TI and Geneve, IDE, SAM, Corcomp repair, Geneve repair, and so forth.

 

 

BTW: Did you happen to have a BOM for ordering, I have ordered some of the parts but not all and if there is a BOM available, I would just order all from one source to have everything there on hand. Thanks.

 

Sounds like your repair list overfloweth. Good luck with all of it. All the general purpose ICs and transistors I got from DigiKey. Some of the caps and resistors I had on hand. The rest I got from various sellers on eBay. There wasn't one source for everything and it probably cost me close to $100 to rebuild the card. Not cheap but what's the alternative? A good CC9900 on eBay, when one comes up, sells for much more than that. No real good solution I'm afraid.

[RickyDean]

 

Sounds like your repair list overfloweth. Good luck with all of it. All the general purpose ICs and transistors I got from DigiKey. Some of the caps and resistors I had on hand. The rest I got from various sellers on eBay. There wasn't one source for everything and it probably cost me close to $100 to rebuild the card. Not cheap but what's the alternative? A good CC9900 on eBay, when one comes up, sells for much more than that. No real good solution I'm afraid.

Yep, it is lengthy, I'm always working on something. I just thought that maybe you had kept a list of all the parts that you bought for the card, and I do intend to get it working, as well as all of my TI equipment, even the ones I've put together, that seem not to work, like the SAMS and IDE, had to take some time off from those, but not giving up.

[justacruzr2]

Yep, it is lengthy, I'm always working on something. I just thought that maybe you had kept a list of all the parts that you bought for the card, and I do intend to get it working, as well as all of my TI equipment, even the ones I've put together, that seem not to work, like the SAMS and IDE, had to take some time off from those, but not giving up.

 

Same here. Currently working on a vintage cassette deck. Anyway, the CC9900 I was talking about was the Rev A model. I also have the first model and rebuilt it also but I haven't adjusted the trim pots yet. Still have the readings you took on yours before you disassembled your card so I have the specs to do that when I get around to it. Was more interested in getting the Rev A card working first so I could start repairing the floppy drives. Need a working card first before I can determine whether repairs to the floppies were successful. Keep at it....you'll get it done.

[RickyDean]

 

Same here. Currently working on a vintage cassette deck. Anyway, the CC9900 I was talking about was the Rev A model. I also have the first model and rebuilt it also but I haven't adjusted the trim pots yet. Still have the readings you took on yours before you disassembled your card so I have the specs to do that when I get around to it. Was more interested in getting the Rev A card working first so I could start repairing the floppy drives. Need a working card first before I can determine whether repairs to the floppies were successful. Keep at it....you'll get it done.

The journey to repair a 1000 disk controllers, begins with the first capacitor, I understand, oh wise one.