EDIT: I replaced the microprocessor and that fixed the issue detailed below. Now need help fixing the capacitance measurement ranges starting in reply 10. Hello all,
This is a continuation of a previous thread below, starting a new one a year later in hope of repairing this poor LC102. I would VERY much like to get this useful bit of kit running. Note from previous thread I likely damaged something probing around the relays but the device was not functioning correctly even before this operator error damage.
Prior thread:
https://www.eevblog.com/forum/repair/sencore-lc102-troubles/Schematics are available here:
https://bama.edebris.com/manuals/sencore/lc102/Device Behaviors:- Device will not read capacitance. Relay will click, display remains 0000
- Device hangs/freezes when
open lead zero is attempted. It WILL zero (or acts like its zeroing)
shorted leads. - I get error 7 (component out of test range) when trying Dialectic Absorption and ESR tests.
- Device WILL present a reading for leakage 100uf/16v cap it reports 8.4ua leakage.
- Device WILL present a reading for coils/inductors both uh and rings. 220uh inductor it will present a reading of 190uh and 16 rings.
Checks:I have checked and verified power supplies, including (probably un necessary) electrolytic cap replacement.
I have probed all diodes and transistors and all seem ok, at least none sort or open.
Clues: - I have observed the 2000 board on thermal imaging, while nothing gets super hot I note that IC46, IC23, IC22, and IC27 are warm. R84 seems warmish/hot.
- When I attempt the open lead zero, TR14 gets warm fairly quickly (a clue hopefully). The device hangs/freezes once the open lead zero is initiated.
Things I have done so far:- I replaced IC 27 just because it was in proximity to my clumsy probing. No improvement.
- Replaced PSU electrolytic caps. No improvement.
Assumptions:-I assume the micro and ROM are fine, since the device will do certain readings and seems to operate at least some of the relays.
-I think I damaged a logic device somewhere. Unfortunately documentation is fairly light on this device, for instance I see NO mention of the lead zeroing process in the circuit description. In fact, the previously mentioned TR14 is not mentioned in the circuit description at all.
While I have come a long way reading schematics I am not quite up to the point where I can understand how to troubleshoot the circuit without more guidance, so I am at a dead end at this point. I would greatly appreciate assistance getting this thing going.