Repair of an EG&G 5113 with stuck display + firmware upload [FIXED]

[_Wim_]

Hi All,

Yesterday I finally managed to repair my EG&G 5113 preamp, and figured I would make a short documentation what was wrong with it.

Symptoms where as follows:
- after boot-up, display is stuck on the display shown in the picture (unless buttons where pressed during power-on, then it was stuck on a different display used for encoder test purposes)

Cause:
- broken trace under the socket of the Dallas 1225 sram chip

Repair however did take me quite a while, as this broken trace was not visible without removing the socket, and no schematics are available. I first replaced almost all the 74-series logic chips, the micro, the Dallas sram chip and eprom, and then convinced myself the firmware was corrupt (as it had a blank section in the middle of the filled area). The firmware was not available online, and Ametek asked 2500€ for a repair (as was not willing to provide a copy of the firmware). I basically had given up, but thanks to a forum member, I did receive a firmware copy. To my surprise & disappointment, this had the same blank section. It did gave me new courage to continue the repair, finally finding the broken trace.

Attached is also the firmware, should anybody be looking for this in the future.
 

[CorporateReference]

Great thank you for your contribution.  Do you know what data is in the Dallas ram chip? Did you adjust any of the trimmers after all the part replacements?

[_Wim_]

Great thank you for your contribution.  Do you know what data is in the Dallas ram chip? Did you adjust any of the trimmers after all the part replacements?

I did not adjust any trimmers during the repair, as the issue was clearly digital in nature (I did chip power supply rails off coarse). All the parts I replaced were digital logic IC's, I stayed away from replacing any analog chips.

I do not think there is any calibration data in the ram chip, as the image I received from another forum member was exactly my image. It seems like the dallas chip is only used to store the user settings and to buffer the text strings for the display.