| Electronics > Repair |
| HP 3458A - Fails Slave Test - Convergence |
| << < (8/16) > >> |
| Ade911:
Hello Kleinstein, thank you for your feedback and advice. U140 was , is dead , doesn't do anything even on the breadboard so there was a problem with that one. Voltages TP112 stable at -15v TP140 stable at -13.67v TP142 stable at 0.2v If I select TARM the system samples in mV and DC_AD toggles between +10V and - 3 or so, is sampling controlled by the A/D or something else. After reading so many comments , convergence issues although the manual states the DC board can be generated by a dead A3 board is seems is this correct ? I did check the fibre links some weeks back and all seemed to toggle at some stage , no idea if the bit word was correct or not but still the 7414s changed state , should i check again how does this impact the reading of the voltage [Strange reading died when I was checking these devices maybe i turned the unit ON and OFF to many times in succession [10 second rule was applied]. |
| py-bb:
This is a standing offer for help as your last resort. I know a lot about the control/computery side of HP equipment spanning until the early 90s. Seriously. I've got a 5420A in the loft and a full set of manuals, I expect that to be similar. Indeed they share a lot (as the precursor to) with the control of the 62xx terminal stuff which is ALSO in a lot of stuff (like the HP protocol analysers from the mid 80s) IF you get nowhere I'm here and we can go through it but please last resort. I'd also like to know the sort of "blog post" story form of your issue if you solve it independently. I am not saying "I am HP Jesus" but I have spent a lot of time repairing this stuff. Standing by. |
| Ade911:
Hello py-bb thank you very much for the kind offer of support. Sure i will share any information gathered but i really need guidance to confirm if U180 is dead or not. I dont know if there is any commands that will allow me to test U180, ive ordered a GPIB interface so the system can be interrogated maybe a little better than through the front keyboard. That should arrive early next week and then I need to read the user guide to test some basic commands. At present +10 V received at DC_AD. But no signal change U140 [see above values]. TARM allows the system to sample and it registered overload in the mv range at 10V in put, if i drop the voltage to 1mv the system stops sampling and still shows overload. I understand U180 has an AC_AD maybe I need to check this to see if it samples AC voltage. Thats were I am, I need support from the people with the knowledge please. Many thanks |
| Kleinstein:
The much feared U180 failure usually starts with drift and if it get really bad causes an error message about convergance error. AFAIK this first happens for the slower conversions and I would expect the sampling to still work, just no valid result. The error described so far points more to other failures though one can not exclude that U180 is still bad. The lost CAL settings and configuration could be an issue to. Invalid content of the CAL ram and other settings could cause problems too. The need for the TARM part points in this direction. |
| Ade911:
Hello Kleinstein, thank you for your support and feedback. General questions, is it possible to carry out a full calibration with empty dallas devices or does the calibration chip need a base line [copy from another system ]? is there any manuals that give a detailed overview of how the circuitry works, I understand the sections of the circuit but for example over voltage does this stop U180 running if the input voltage is to high. Whats the maximum voltage that should be applied to the I/P of U180 , in mV I get 17V I hope this has not caused a problem. Again support and advice is most welcome. |
| Navigation |
| Message Index |
| Next page |
| Previous page |