Philips CDI 450 repair

[Anks]

Hi I'm trying to repair my old CDI450 that was showing a black screen on the TV.

I got the service manual and followed the tests for checking clocks and such and everything is correct and present. At this point I made a null modem cable to preform the LLT(low level tests) but had a really hard time trying to get into the console by pressing space.

The console was outputting "syser" that i assume means system error. I was using termite and found that if i continuously press enter and space while turning the CDI I could get to the LLT. At this point all test pass fine apart from number 4 the DRAM test. this would get stuck testing DRAM0.

At this point I pulled the two dram chips off and soldered one back on its opposite footprint. Now the CDI would still not boot but on the console in termite I could see a message "unable to assign name table" then "system reset".

Now I retried the LLT and the DRAM0 was passing the test but of course DRAM1 was showing data lines that had issues (The LLT is actually very good).

So just to rule out any other issues I placed the other ram in the other ram position to check that I was on the right track and not just fixed a few cold solder joints. Sure enough the chip now at DRAM1 was showing the issues it did in the DRAM0 position.

Now I'm pretty confident that the drivers on the chip controlling the dram are Ok and replacing the ram would be a worth while thing to do. So now onto the next issue.

The chip used for the memory is a HM541270ATT-8 in a 44pin tsopII package I believe. This is the the package that s only 40 pins broke out with a gap in the middle. The TMS45165DGE is the equivalent part but both these as far as my google powers go are unobtainable.

There are some very close chips with 262,144 word x 16bit drams out there but these do not use the LWE (lower write enable) UWE. Instead the seem to use the more common LCAS(strobe) HCAS and hence had slightly different pin out.

I can find HM541270 on ebay in a 40pin SOJ package but obviously this wont fit on the board and I'm tempted to try and bodge one and hope for the best but wanted to know if anyone had a better idea before I go down this route.

If anyone come across this post in future and would like and help with this system just send me a PM and ill try my best to help.

Thanks Kris

I tried to attach the service manual but its too big I will try and split it into two parts or something if anyone is interested.

 

[Anks]

Just to let anyone that maybe interested I managed to dead bug the  soj40 part onto the pads of the tsopII pads and after clearing 1 short between data lines 14 and 15 the I found via the LLT terminal all is working correctly.

It looks a bit "how you doing" but its all very solid and was the best I could do with no magnification and what was lying around the lab.


And here it is working