Supersoft Memory Error - 5160

[river]

Hi,

I have a 5160 which freezes often and I burnt the Supersoft diagnostic chip and fired up the machine, and it reports bit 6 of critical Memory has an issue. Many RAM chip swaps, including swapping working chips around makes no difference. It always says there is an issue with bit 6.

I checked through numerous previous posts here and it seems there is an issue with Supersoft reporting such errors?

 

[river]

I checked circuit diagram and suspect the 74LS245 at U9 could be a reason for this error, so will replace it and see how she goes.

 

[modem7]

Does the 16K CRITICAL MEMORY REGION test pass if the RAM chips are removed from the other banks (1/2/3) ?

 

[river]

Yes, just tried that and it still fails. The X comes up under Bit-6 the second it commences Critical Memory test.

 

[modem7]

Yes, just tried that and it still fails.

So, that rules out interference from a bit 6 chip in another bank.

The X comes up under Bit-6 the second it commences Critical Memory test.

Still waiting for the 74LS245 to arrive?

Do you have a logic probe ?

Have you used a multimeter to verify trace continuity between the pins of the bit 6 chip and other chips (as appropriate). Note that on the 5160 motherboard, for each data bit, pins 2 and 14 of the RAM chip (data in and data out) are connected together, but you will not see that for the parity RAM chips.

BTW. If you pay for postage, you have the option of sending the motherboard to me for (free) attempted repair.