Datron/Wavetek 4600 strange behavior

[nikonoid]

I have this Datron 4600 that now seems to work fairly well. I am using it with Datron 4808, but in the Solo mode for now. So 4808 is just supplying a voltage to the input jacks of 4600.

If I turn Datron 4600 ON and turn it's output ON before applying anything to the input of 4600 then it works like a charm. However if I apply more than 300mV to the input while the output is off, the 4600 would frequently throw "PSU" error (red PSU LED) and lock up.

Is this a normal/common behavior? Can someone please check their 4600? Thanks a lot.

[jfphp]

Did you leave the analog cable between 4600 and 4808 ? Solo mode is only without any rear connection : front panel only for entry.

[nikonoid]

So far I do not have a good source for LEMO connectors for analog cable, so nothing is connected at the back.

Therefore Solo mode. Voltage output and ground of 4808 is connected to input and ground of 4600. Output of 4600 goes to current shunt.

Basically if I press output ON button on 4808 before 4600 I get a PSU fail, if in 4600 before 4808 it is fine...

[ap]

I checked this on one of my 4600/4808 @ 5A with 4600 output off and the behavior you mention seems incorrect (as one would expect).

[nikonoid]

AP, thanks for checking. This is sort of what I was expecting.

The repair project lives on. Since under load everything works correctly, I think SMPS and it’s control circuit is less of a suspect.

It sounds like a fault diagnostics is at fault
The manual said that PSU fault signal is driven by one of U319 inputs going high, yet for me all 3 of them stay low when PSU led goes red.

I checked this on one of my 4600/4808 @ 5A with 4600 output off and the behavior you mention seems incorrect (as one would expect).

[SilverSolder]

It sounds like a fault diagnostics is at fault

Quis custodiet ipsos custodes?

[pelule]

Quis custodiet ipsos custodes?

Quod esset demonstrandum...
Quis leget haec?
But - I prefer english - to make it more common understandable 

[nikonoid]

Quis custodiet ipsos custodes?

I guess in this case I do. 

[nikonoid]

This Datron appears to be definitely broken. I have done some progress though.

Switch Mode Power Supply in good 4600 should be off when output is off (SMPS or PSU). In mine it is always on and that is causing my issue. When input is applied with output off this is causing the PSU error.

SMPS is controlled by PSUEN_H line (5th pin of connector going from Sense PCB for SMPS). PSUEN_H line is controlled through optical isolator by Pin 18 of U206. (By the way my arrangement and chips for isolator are different from manual available, so I am attaching a photo).



U206 is a custom logic chip for Datron. My best guess is that it is ATF16V   GAL chip.

I shorted input jacks and also output jacks for a predictable Solo configuration of 4600. It is my understanding that Pin 18 should be going from low to high as I toggle from Output off to Output on and back. It is always stuck in low and PSUEN_H is always high.

Since I do not know the logic behind (inside) U206, is it kind of hard to understand what is causing it to behave the way it does. I attached voltage chart of U206 pins with Output On and Off. Can someone please compare it with a working unit? U206 is very easy to get to. It only requires undoing 4 screws in the top cover to get to it.

 

[doktor pyta]

I have really bad experience with optocouplers inside Datron stuff (especially MCT6). Try replacing all of them. They are cheap.

[DC1MC]

I have really bad experience with optocouplers inside Datron stuff (especially MCT6). Try replacing all of them. They are cheap.

^^^^^ This 100x

[nikonoid]

Thanks. I just ordered replacements. MTC6 and also CNY174, as a substitute for IS201 from ISOCOM.

Since they are all socketed, it is a really easy experiment.

I have really bad experience with optocouplers inside Datron stuff (especially MCT6). Try replacing all of them. They are cheap.

^^^^^ This 100x

Sent from my iPhone using Tapatalk

[nikonoid]

Just changed all 6 optocouplers. No luck. Still the same result: for some reason my 4600 turns SMPS right away even if output is off.

Any ideas what to try next?

[syau]

Just test it out on my 4600 and it behave exactly like this 

The psu trip when the output is off and the input voltage is above 600mV

[seebeck]

Hi nikonoid,

I have the manual and schematic for Datron 4600 transconductor amplifier, please tell me your E-mail address if you need it.

With best regards.
From Seebeck.