Originally posted by ivconic
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yes, happened also to me... sometimes. I use often 1.20 meters screened cable... not more... cause I know that the cable the more problems there. Used longer cables on other kind of stuff never on TGS or TGSL. Also... about TGSL that I've realized... but not completely tested till now I have also more instability... and I think is related to different PCB and components disposition on TGSL.
TGS exposed wild behaviour in paste cause of other problems but cable appears at source of them , from time to time, when on field.
I also wound it spiral on the pole and leave always last 20-25 to coil straight, using some pastic fixing, same kind used to keep wires tight together in complex wirings. I usually made first fixing at 20-25cm from search head and then other 2 , one at middle and one near connector and control box.
Is better keeping cable well fixed on pole and prevent movements there.
The erratic behaviour happens in some particular conditions I think... but cannot understand till now what to look for in circuit. If cable is well fixed I think problem is not from it.
I noticed that device warm-up is around 4-5 minutes for good operations and then it goes really good (at least my first TGS assembled with pole and everything) apart spot randomic that happens after 20-30 minutes BUT NOT ALWAYS... sometimes it's rock solid for 2 hours also.
I think real problem is heat/cold climate : there are parts that , after warm-up, react very bad at large temperature transients. I noticed that if climate is cold (like early in the morning) and then Sun become stronger and stronger the increase warm-up of device could lead to instability.
I think the problem could be located at fet sampler stages as 1st , and at comparator as 2nd factor.
The fets are really unstable devices to me... and commutation characteristic change (like e.g. RDSon) a lot even if temperature change just of some 0.5-0.8 °C inside the control box. So large (many) degrees variations can lead instability cause of disturbed simmetry of samplers action.
When I say "change a lot" I mean... change is relatively few thing... but we have so hi amplification and edge conditions that any little asimmetry will result in unbalance and erratic behaviour. And comparators the same story... not perfect simmetry and any channel signal asymmetry will be a problem at comparators on TGS.
An easy way to test for fet instability is heating up them with fingertip or a low power soldering iron (e.g. 20W, without touching them but just heating up air near them at few mm distance).
Best regards,
Max
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