DM> I have a 3 channel chart recorder for repair. The problem is an error DM> '9999.9 - ADFAIL' comes up on all three channels. At the heart of each DM> is a 28 pin plcc chip. It says DM> <logo> TIP DM> 9924NCC DM> C17619 DM> 120S1355 DM> REV 01
DM> The logo is a smallish 'M' in a circle, but it's a very plain 'M', not DM> reminiscent of Motorola or Maxim, who use slightly fancy 'M' in their DM> logos. There is three of the above chips. The cpu is separate. DM> Google returns rubbish, of course. DM> It's about 5 years old, and I suspected a power supply, but all seems DM> good. It's a bit difficult to tell, because the circuit has loads of DM> little 78Lxx and low power lm317s in strange places and is inclined to DM> dissappear up it's own backside when you try and follow it ;-). All the DM> other stuff is Common enough (National/ST parts) and the transistors are DM> pro electron, so we appear safe from inscrutable Far Eastern devices. DM> The other bits on each channel (taking a variety of temp probes) are a DM> 93LC66 (serial eprom) LM324, LM393, & some optocouplers. There isn't a DM> databus going off either. Serial? DM> Nothing that looks like an a/d on the main board. A Mostek(!)48Z02 and a DM> Goldstar(That's an Irish meat company!) GM76C88AL-12 are the only things DM> beside logic, and the cpu, which is a 68HC11. If I'm not completely mistaken MOSTEK also used a circled M as logo during some time! >From the other description I would guess that the 28pin plcc is a microcontroller with built-in A/D. In the EEPROM there might be calibration data and/or configuration data for each channel. Are there separate analog and digital ground lines? Are both terminating in the central 28pin plcc? Of course one could also build a discrete dual-slope A/D just with 324/393 which could be controlled by a purely digital controller... Uwe. -- Author: Uwe Zimmermann INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
