Capacitor Help - UK Vintage Radio Repair and Restoration Discussion Forum

MeanDumpsterCat · 16th Mar 2015, 3:34 pm

Hello!
I'm currently in the process of re-capping my Commodore PET in the hope that it will fix a few problems.

Unfortunately, given my limited understanding of electronics I struggle to decode the numbers on some of the tantalum caps. If you guys can help me i'll be very very grateful! Here are some pictures

AC/HL · 16th Mar 2015, 3:51 pm

The last three photos are of ceramic disc capacitors, and they are highly unlikely to cause any problems. Assuming there's a V after the 16 in photo 1, yes you're right.
PS none of them are Tantalum.

Edit: This site is helpful here: http://wiki.xtronics.com/index.php/Capacitor_Codes

MeanDumpsterCat · 16th Mar 2015, 4:06 pm

D'oh. I knew id name something wrong. Those electrolytic caps are the internal power supply line so i'll replace those first. Thanks for helping

jay_oldstuff · 16th Mar 2015, 7:36 pm

Yes most of those are disk ceramics and are very reliable. That electrolytic on the power rail is a very likely suspect. I'm working on an atom at the moment which is similar vintage to your PET and I had to change every electrolytic in it. You can generally recognise a tantalum cap as they are usually sort of teardrop shape and shiny also they are polarised like a standard electrolytic so one leg will be marked positive or negative.

Jay

Oldcodger · 17th Mar 2015, 12:19 am

looking at the link AC/HL gave, reminded me of C&G Radio and Line Transmission A, but without the tip/spot etc variations. Tempted to say "When I was a lad", but I won't. But one other very useful source of capacitor identification is OLD ( more than 5 yrs) Maplin catalogues. but in my experience ,(apart from on the factory floor,where myopic production line operatives could fit Tants in in reverse polarity ) ,if the tant is within voltage limit. it seldom fails. As Jay says- even if you have to get out an eyeglass/magnifying glass ,you'll recognise a Tant as it will have a value ( e.g 10u), with a voltage(e.g. 16v)and beside one leg a +. A lot of the slab yellow polyester types ,usually around .1 uf can have leg problems with heat, but usually only if you try to look for dry joints by heating them up .

crudmeister · 22nd Mar 2015, 8:24 pm

I agree with Jay, just replace the electrolytic capacitors as any ceramic disk caps, or film caps are very unlikely to be faulty.
All the best with your restoration/repair!

16th Mar 2015, 3:34 pm	#1
MeanDumpsterCat Pentode Join Date: Oct 2014 Location: Selsey, West Sussex, UK. Posts: 204	Capacitor Help Hello! I'm currently in the process of re-capping my Commodore PET in the hope that it will fix a few problems. Unfortunately, given my limited understanding of electronics I struggle to decode the numbers on some of the tantalum caps. If you guys can help me i'll be very very grateful! Here are some pictures Attached Thumbnails

16th Mar 2015, 3:51 pm	#2
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Capacitor Help The last three photos are of ceramic disc capacitors, and they are highly unlikely to cause any problems. Assuming there's a V after the 16 in photo 1, yes you're right. PS none of them are Tantalum. Edit: This site is helpful here: http://wiki.xtronics.com/index.php/Capacitor_Codes

16th Mar 2015, 4:06 pm	#3
MeanDumpsterCat Pentode Join Date: Oct 2014 Location: Selsey, West Sussex, UK. Posts: 204	Re: Capacitor Help D'oh. I knew id name something wrong. Those electrolytic caps are the internal power supply line so i'll replace those first. Thanks for helping

16th Mar 2015, 7:36 pm	#4
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Yes most of those are disk ceramics and are very reliable. That electrolytic on the power rail is a very likely suspect. I'm working on an atom at the moment which is similar vintage to your PET and I had to change every electrolytic in it. You can generally recognise a tantalum cap as they are usually sort of teardrop shape and shiny also they are polarised like a standard electrolytic so one leg will be marked positive or negative. Jay __________________ The light at the end of the tunnel is probably the headlight of an oncoming train

17th Mar 2015, 12:19 am	#5
Oldcodger Nonode Join Date: Oct 2014 Location: West Midlands, UK. Posts: 2,181	Re: Capacitor Help looking at the link AC/HL gave, reminded me of C&G Radio and Line Transmission A, but without the tip/spot etc variations. Tempted to say "When I was a lad", but I won't. But one other very useful source of capacitor identification is OLD ( more than 5 yrs) Maplin catalogues. but in my experience ,(apart from on the factory floor,where myopic production line operatives could fit Tants in in reverse polarity ) ,if the tant is within voltage limit. it seldom fails. As Jay says- even if you have to get out an eyeglass/magnifying glass ,you'll recognise a Tant as it will have a value ( e.g 10u), with a voltage(e.g. 16v)and beside one leg a +. A lot of the slab yellow polyester types ,usually around .1 uf can have leg problems with heat, but usually only if you try to look for dry joints by heating them up .

22nd Mar 2015, 8:24 pm	#6
crudmeister Retired Dormant Member Join Date: Jan 2012 Location: Middlewich, Cheshire, UK. Posts: 237	Re: Capacitor Help I agree with Jay, just replace the electrolytic capacitors as any ceramic disk caps, or film caps are very unlikely to be faulty. All the best with your restoration/repair!