No video on Performa 450 (LC III) after re-cap

[avadondragon]

I've been doing quite a few component level repair jobs over the past couple of months.  Only had two failures so far.  One was the Centris 610 I mentioned in another thread the other is this Performa 450.  Before the re-cap the system made chimes of death when powered up now it makes happy Mac noises but never outputs any video.  I have no SIMMs in the machine whatsoever.  Does this model require a VRAM SIMM to function?  Is there anything else I might be overlooking?  I have my VGA converter set to 640x480@66Hz.

I also made sure to use a non-polarized ceramic cap on C22 since, according to what I've read on these forums, the polarity is probably labeled wrong on the PCB.

 

[Elfen]

The LC I/II/III needs a VRAM SIMM for video. The LC475 is the only LC Series that does not need VRAM because it has some onboard, and adding to it gives more color options and resolutions.

Sounds like you got everything else OK.

 

[360alaska]

The LC I/II/III needs a VRAM SIMM for video. The LC475 is the only LC Series that does not need VRAM because it has some onboard, and adding to it gives more color options and resolutions.

Sounds like you got everything else OK.

Not trying to be contrary but the lciii does not need a vram simm, I would suggest trying some different settings on your adapter. Does it chime?

Oh, and I should add the the 475 has no onboard vram which is probably why it has two slots...

 

[Elfen]

D'OH! You're right, 360Alaska, on both counts. I had to look at my LC III and LC 475 boards to verify this (which I should have done first).

If the adapter worked before and the settings did not changed, then they should be working now. If not, the usual settings that work for me is:

640 X 400 or 480

H-Sync and V-Sync = On

Composite On Green = On.

 

[Elfen]

... the other is this Performa 450.  Before the re-cap the system made chimes of death when powered up now it makes happy Mac noises but never outputs any video.  I have no SIMMs in the machine whatsoever.  Does this model require a VRAM SIMM to function?  Is there anything else I might be overlooking? 

Q: Does the hard drive or floppy drive tries to boot a system? After a while of leaving it on does the chips get warm?

I have the same exact issue with my LC 475 after a recap, with no attempt to boot from the floppy or HD.

 

[avadondragon]

No it doesn't try to boot off of either Hard Drive or Floppy.  And after putting an extra stick of RAM in just for the heck of it the system made the chime of death again.  I'm going to inspect my work under the microscope and see if there's a cold solder joint somewhere.

 

[MJ313]

Hi-rez pics are helpful in that some the experts around here (not me!) can help spot trouble areas for you. One thing... how's your power supply? Is it a TDK? Have you recapped that as well?

 

[register]

Once I configured a LC 475 as a print server, accessible from my PowerBook via LocalTalk. After setting everything on the LC 475 to work without any user interaction it was stuffed away without any keyboard, mouse and display attached. Later I noticed you even could remove the VRAM modules and the machine remained fully operational. Only if a display is connected to such machine the screen stays empty. A screenshot (cmd-shift-3) will reveal why: the output is just one black pixel. This might be useful to tweak headless applications to maximum performance, as redrawing plain black will be even snappier than even low resolution black and white.

 

[Elfen]

That is interesting to know, Register. But to me both Avadondragron and I have similar situations on recapped machines being totally dead after a Happy Mac Chime. All that Chime says it that the Mac passed a minimal RAM Test and a ROM CheckSum Test before proceeding to the next steps in the boot process.

In the boot process, after it does this Chime, the Mac is supposed to move the ROM's address to a higher place in its memory through some Logic Gate Magic and RAM is then fully tested from there before it attempts to boot. I believe this is where it is failing, thus it begs the question - where is these gates are at to be checked? I hope it is not inside the Eagle Chip. At best its a broken trace. At worst it's a dead or broken Eagle Chip.

 

[register]

Hello, Elfen, I would assume a false seated or incompatible RAM or VRAM unit in the first place, a bad trace in the second place (only after reworking a damaged board), improper ESD protection or applying excessive heat to solenoids during service only in the third place. This third, less likely type of damage might be caused by the use of cheap meters. Years ago I killed one PowerBook 180 just by checking traces. Many ICs from that time do not have any overvoltage protection of their MOS components. You could destroy them by simply taking them out of the box (what happened often enough). Applying a voltage to measure resistance might irreversibly overload the MO barrier. Be sure to take some ESD measures and use proper meters when reworking PCBs. i use a damp towel as a tablecloth, a soldering iron with a grounded tip, and a high quality meter applying low measuring voltage to check traces.

Hint → With regard to _compatibility of VRAMs_ you might check if you probably swapped VRAMs between machines or if you overclocked the computer while servicing. Some slow VRAMs will simply not work in the same machine after overclocking.

 

[MJ313]

I'm just going to add something to this thread that may help the .0001% of people with the same issue (recapped, but no video). I had an LCIII board, worked great, recapped, awesome. I sold it to a fellow, shipped it across the country. He gets back to me saying it sounds great, but no video appears on his monitor. After some troubleshooting, he realized the video connector had a cold solder joint. Probably just the act of attaching it to his monitor cable was enough to break the connection. He touched up the solder joint and it works fine again. In any event, it's worth checking the video connector solder joints if everything else seems A+. Those joints can experience a lot of stress when people jam on the cable and screw it in.