68kMLA Classic Interface
This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.
| Click here to select a new forum. | |
| Pre-SE Analog Board Capacitor and Upgrade Mouser List | |
| Posted by: superjer2000 on 2018-10-27 13:35:49 I recently revived my Mac 128k analog board by replacing all of the capacitors, doing the upgrades noted in Macintosh Repairs and Upgrade Secrets and replacing Q1 and Q2 transistors as well as U3 Optoisolator. I'm not sure what part(s) were bad, but the board fired right up after replacing these components. I'm attaching the list of Mouser Part #s I used to complete this work in the attached spreadsheet (which also includes an inventory of the pre-existing capacitors on my board. I'm attaching a few pictures as well for how I changed out CR20 and CR21. Thanks to JDW for his list as well - I referenced it when going through my board to see if I was missing anything. I couldn’t perfectly match lead spacing for some of the capacitors and I used some hot glue to ensure stability. There seems to be various schools of thought on hot glue for this type of work and I guess I’ll see if it causes any problems in the future. One change I made after this was for C5 - I had to use a radial cap as I couldn't find an axial with the right specs. I had it sticking up (as in these pictures below) and that worked great for my 512kE test unit with a Clinton CRT but it wouldn't clear my 128k's Samsung CRT so I had to remove it and resolder it laying on its side. I ordered replacement pins for the J4 connector as well so I could replace the 22 gauge wire with 18 gauge. I tried to order replacement J4 connectors but ended up with 4 pin versions so I just ended up using the pre existing connectors. I've got some new 11 pin J4 connectors. I'm working on my Classics now - I have only found one list of capacitor parts but it didn't have diameters or lead spacing so I'm measuring those out for my A and B boards and will post once they are successfully recapped. A list of Color Classic analog board capacitors would be nice if someone had but I haven't come across one so that will be an eventual project.     View attachment Pre SE Capacitor and Upgrades.xlsx | |
Posted by: Bolle on 2018-10-27 13:52:33Pos. uF V size (cm) CP34 100 25 CP35 1 50 CP39 3300 16 1,25*4 CP56 3300 16 1,25*4 CP41 1000 16 1*2,5 CP40 5600 10 2*2,5 CP42 5600 10 2*2,5 CP46 1000 10 1,25*2 CP44 470 25 0,9*1,2 CP43 470 25 0,9*1,2 CP47 1 50 CP15 100 25 CP13 1000 35 1,5*2,5 CP12 100 100 1*3 CP54 1 50 CP14 1000 16 1*2 CP9 100 25 CP10 1 50 CP55 1 50 CS4 1 50 CV39 1 50 CV40 1 50 CV21 100 25 CV20 2,2 200 0,5*1 CV17 100 25 CV19 2,2 200 CV13 10 100 CV18 2,2 200 CL19 10 250 1,25*2 CL21 100 100 1*3 CL14 47 100 1*2 CL4 100 25 CL31 1 50 CL11 1 50 CL13 2,2 200 CL24 1 50 CL23 100 6,3 CL33 2,2 100 CL34 2,2 100 CL35 0,47 100 CF9 220 25 CF8 3300 16 2*1,5 CF7 100 25 CF11 470 35 1*2 CF10 220 35 1*1,5 CF2 4,7 50 Taken from the notes I did when doing my Rev A. CC analog board. Edit: btw, did you remove the sealant from the flyback or did it come that way? I have a few flybacks where the glue is really dark and brittle and always feared it might fall off. Is it actually needed or can I get rid of it? | |
| Posted by: superjer2000 on 2018-10-27 16:41:34 Flyback came like that - In person it doesn't look too bad and seems well sealed. Thanks for the CC list - I'll be sure to xref that when I get ready to place my order. | |
Posted by: techknight on 2018-10-28 15:43:46Edit: btw, did you remove the sealant from the flyback or did it come that way? Yes, its required. Its to stop the core from vibrating. The switching frequencies can cause the core to "physically vibrate" in the audio range and it'll create a nasty ring noise. The second thing that can happen is core vibration could lead to heating in the flyback leading to premature failure. I heard that as an old "wivestale" from TV techs back in the day. A lot of old school TV techs are not with us anymore, or retired and I tried to learn as many tips and tricks as possible so not everything is lost in the grave. | |
| Posted by: JDW on 2018-10-30 02:25:35 I don't have my Mac 512k handy to shoot photos of its flyback and sealant, but the flyback on one of my SE/30's Analog Boards looks like this:  I also have another SE/30 with a flyback that looks like this:  As you can see, the sealant is darker but secure and not cracking off. The only issue is that brass colored support (whatever it's for) has snapped into two pieces.  I get fairly stable video on the CRT, so clearly that broken metal rod isn't doing much. Curious if it supplements the sealant in keeping the core from vibrating. | |
| 1 |