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.
LC III - No video, no sound, and weird schematic
Posted by: jajan547 on 2022-09-01 21:45:27 Hi there, I also have a LC III that was working but had leaky caps. I bought a tantalum kit from console5 and recapped. As far as I can tell everything looks good. Except now I have a system that powers on but no chime or video. No sound through the headphone jack either. I saw -2.8v on the -5v rail so I recapped the TDK power supply too. -5v only came back after reversing C22. However, still nothing. Anything else I can check? Is there a solution to this issue? Thanks! Hey there can you take some photos, specifically the whole board and close pictures to chips in leaky areas?
Posted by: timmcross on 2022-09-02 04:59:41 Let me know if this helps.
Posted by: bibilit on 2022-09-02 06:14:20 EGRET issue ? Problem with LCs is that video is often missing, so no FC can be seen.
Posted by: timmcross on 2022-09-02 08:06:55 So a little update. I was reading on other forums that some people have an issue with the Mac taking several minutes to start up. I powered on my LC III with no hard drive, just the floppy connected and boot disk inserted. After a while, I came back to it and it booted successfully. Do the other caps need to be replaced now? What does a delayed start indicate?
Posted by: joshc on 2022-09-02 10:43:52 Delay before flashing floppy or the boot process starts? How much memory is in there? The memory check can take a while with more RAM. How delayed is it exactly?
Posted by: timmcross on 2022-09-02 10:56:03 A delay before the startup chime. With 1x16MB module in there, it took just over 4 minutes to chime after the switch was thrown. I can try it without the module as well but I am pretty sure it started up within seconds before I recapped it.
Posted by: jajan547 on 2022-09-03 13:50:27 Hey C22 is the wrong way around
Posted by: timmcross on 2022-09-04 21:10:38 I originally had C22 as silk screened and as the previous cap was mounted. However, while troubleshooting, I noticed that the -5v rail was around -2.91v. I found this thread which states it should be reversed: https://68kmla.org/bb/index.php?threads/lciii-recap-apple-design-fault-47uf-reversed.27834/ After reversing C22, now -5 is around -4.91v. Makes sense to me?
Posted by: indibil on 2023-01-20 01:13:41 Hello, I am writing to you from Spain, sorry if my English is incorrect. I recently purchased an LCIII with a faulty power supply. I was able to repair it by changing caps but when turning on the equipment no sound was heard. I connected headphones and the chime was heard followed by the "Chime of death". I decided to recap all the capacitors and just when I got to C13 I saw that there was a raised pad, just the cap that carries the sound to the speaker. I fixed the track and just changed the caps. I turned it on and it was already heard through the speaker, but with the same result, first the chime, and followed by the chime of death, without video on the screen. I left the equipment off for a few hours and when I turn it back on, it doesn't sound, neither through the speaker nor through the headphones, I don't have an image or anything at all. I didn't make any other changes, all previous boot attempts gave the same result, chime followed by chime of death, but now nothing. Always tested with all unnecessary hardware disconnected, only power supply, fan, speaker and nothing else. What can be happening? resetting the PRAM does nothing, neither sound nor any effect. P.s. C22 recap with correct side, + to grownd and - to "-5v"
Posted by: jajan547 on 2023-01-20 01:23:10 Hello, I am writing to you from Spain, sorry if my English is incorrect. I recently purchased an LCIII with a faulty power supply. I was able to repair it by changing caps but when turning on the equipment no sound was heard. I connected headphones and the chime was heard followed by the "Chime of death". I decided to recap all the capacitors and just when I got to C13 I saw that there was a raised pad, just the cap that carries the sound to the speaker. I fixed the track and just changed the caps. I turned it on and it was already heard through the speaker, but with the same result, first the chime, and followed by the chime of death, without video on the screen. I left the equipment off for a few hours and when I turn it back on, it doesn't sound, neither through the speaker nor through the headphones, I don't have an image or anything at all. I didn't make any other changes, all previous boot attempts gave the same result, chime followed by chime of death, but now nothing. Always tested with all unnecessary hardware disconnected, only power supply, fan, speaker and nothing else. What can be happening? resetting the PRAM does nothing, neither sound nor any effect. P.s. C22 recap with correct side, + to grownd and - to "-5v" Sounds like to me cap goo may be under your sound chip I would advise removing it and cleaning under it or if you do not feel comfortable doing that really try and clean that area with alcohol. Another thing that could be causing the chimes of death would be a a bad RAM chip it's very common, oh just to make sure do you have a VRAM and RAM Simms in place? Also another thing that could be causing sound issues is it could be the audio jack is gummed up which is another thing not too uncommon but I would look at this last. What happened is the pins contact each other without a speaker cable inserted and as a result the Mac thinks there is sound meant to go out externally but because of these pins contacting you'll get no sound at all, but like I said again this is the least likely out of the bunch and more than likely a result of cap goo.
Posted by: indibil on 2023-01-20 10:15:45 Sounds like to me cap goo may be under your sound chip I would advise removing it and cleaning under it or if you do not feel comfortable doing that really try and clean that area with alcohol. Another thing that could be causing the chimes of death would be a a bad RAM chip it's very common, oh just to make sure do you have a VRAM and RAM Simms in place? Also another thing that could be causing sound issues is it could be the audio jack is gummed up which is another thing not too uncommon but I would look at this last. What happened is the pins contact each other without a speaker cable inserted and as a result the Mac thinks there is sound meant to go out externally but because of these pins contacting you'll get no sound at all, but like I said again this is the least likely out of the bunch and more than likely a result of cap goo. Thanks for reply. Finally i have removed the audio chip, clean pads and resoldered and the sound is back!!! thanks!!!!!! But i have the chime and the chime of death. I don't see any for the screen, but i use a VGA adapter without jumpers. This adapter works great with an LC475, and i can change different resolutions, but with this LC3 i only have black screen. This LC3 don't are compatible with VGA adapters without jumpers? This motherboard have RAM and VRAM soldered, i have test it without any stick of memory. What can be the cause of the chime of death?
Posted by: imactheknife on 2023-01-20 16:31:37 Thanks for reply. Finally i have removed the audio chip, clean pads and resoldered and the sound is back!!! thanks!!!!!! But i have the chime and the chime of death. I don't see any for the screen, but i use a VGA adapter without jumpers. This adapter works great with an LC475, and i can change different resolutions, but with this LC3 i only have black screen. This LC3 don't are compatible with VGA adapters without jumpers? This motherboard have RAM and VRAM soldered, i have test it without any stick of memory. What can be the cause of the chime of death? Usually bad ram. A broken trace around the onboard ram is possible too
Posted by: indibil on 2023-01-20 22:26:45 Well, I sang victory too soon. This morning it is again without sound. There may be some cold solder around the sound chip. Yesterday when warming up it made contact, but today it fails again. I will apply flux and heat the surrounding chips, to see if it fixes. I'll check the RAM later, but I still can't see anything on the screen. Can someone tell me if the VGA adapter without jumpers works in the LC3 as well as in the LC475?
Posted by: Plasticoat on 2023-01-20 22:56:47 A vga adaptor without switches on the LC. III will work fine. Remove the egret chip in exactly the same way as you did to the sound chip, clean and resolder
Posted by: indibil on 2023-01-20 23:08:10 A vga adaptor without switches on the LC. III will work fine. Remove the egret chip in exactly the same way as you did to the sound chip, clean and resolder Thanks. Can you tell me where the egret chip is? The one near the RAM?
Posted by: Plasticoat on 2023-01-21 03:56:47 In red
Posted by: indibil on 2023-01-21 10:54:49 In red That photo is of an LC475, I am repairing an LCIII, it is not the same motherboard. I will tell you the progress. The audio chip stops working when it gets cold. If I warm it up again with the air heater, it beeps again, after an hour or two passes and it cools down it stops beeping. I guess the chip is faulty right? And there is no "modern" replacement either? About the chime of death. It only stopped playing when I removed the 8 RAM chips, but when I inserted a RAM stick the Chime of Death reappeared. I have again soldered 8 compatible RAM chips from a stick and it also sounds the Chime of Death. What chip controls the RAM? could it be the cause? Next to the RAM and the crystal there is a square chip, I have desoldered it, cleaned it and soldered it again but nothing has changed. I'm going crazy. Maybe the board is dead.
Posted by: imactheknife on 2023-01-21 12:45:51 Have you checked all traces to ram, rom chip? I have a iisi that had two broken traces under a 47 uf 16v cap..
Posted by: indibil on 2023-01-22 23:04:40 Have you checked all traces to ram, rom chip? I have a iisi that had two broken traces under a 47 uf 16v cap.. Traces are ok around the capacitors, except C13, that i have repaired and the internal speaker receives sound.
Posted by: jajan547 on 2023-01-23 04:48:34 Traces are ok around the capacitors, except C13, that i have repaired and the internal speaker receives sound If you can take some photos I can provide better help and circle some areas I think you should look at.
< 2 >