TDS540 intermittent test failures

[StefanS]

Hi All,

I've just finished recapping my TDS540 (from either 91 or 92) and it continues to show two failures on startup:

FAIL ++ Acq/Proc Interface
FAIL ++ Acquisition

The odd thing is, if I run the diagnostics immediately afterwards, the unit passes. Also, on a RARE occasion, it will pass on startup. Error log only shows a previous SRAM problem at 0x7300000, which was corrected by cleaning U101.

Any thoughts?

Thanks,
Stefan

[CaptDon]

What is the condition of the battery backed ram which stores the cal data as well as
the real time clock? Sounds like the signal chain is not actually failed but the data is
getting corrupted when the unit is powered down. Very common problem as the Dallas
chips internal batteries are failing. NOTE....All dallas 1650Y and 1250Y i.c.'s on Ebay
are bad, dead or fake. Seek out the guy selling the hybrid modules with the battery
on top. The restore data is readily available on this site.

[StefanS]

Thanks, Capt’n.  The battery is probably original, but seems to be holding date & time. Additionally, the memory errors are reappearing when the unit fails. The intermittent nature of this is the worst.