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What's wrong with my Electrophysics Micronviewer?

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Ben321:
Today I just received the Electrophysics Micronviewer 7290A that I bought on eBay last week. The seller didn't show any screenshots of a TV with the camera's video output onscreen, but when I messaged him, he said the camera does output video. I got it today, and tried it by connectiong it to the composite video input on my TV, but no video output on my TV screen. I connected up its video output to my Picoscoope USB oscilloscope and tried to see if it at least output something, maybe a waveform with the wrong frequency (maybe it had 50hz instead of 60hz video output, so wouldn't work on a US TV I thought), or maybe I could see some increase in electronic noise when the power was on, or maybe even a single transient voltage spike at the instant the power was turned on. But NOTHING. The video output port always had the EXACT SAME 0-volts output (with a slight amount of noise of a few mV) on my Picoscope, even when the scope was set at its highest sensitivity setting (50mV per division).

I even checked, and double checked, all of the power and video cable connections, to make sure nothing was loose. I made sure the power switch on the Micronviewer was turned on. I checked everything that could result in the camera not being powered, and nothing was wrong with any of my equipment setup. So the output of this thing is DEAD!

There's a number of things that could be wrong with it, from a loose solder connection somewhere on the board, to the power supply for the camera having no voltage output (dead power supply), to possibly even a crack in the glass of the SWIR vidicon tube in the camera (which could actually have been caused by poor handling of the package by the UPS crew, and not necessarily the eBay seller's fault).

Any ideas on what is most likely wrong with it, and what things I should be checking to see if I can fix it?

By the way, one thing that could help, is if somebody could provide the pinout for the power connector. It uses a non-standard power connector with 4 pins arranged in a square and an outer screw-on ring to hold the connector in place when it's connected to the camera. That way I could verify that the power supply is working at least, by testing it with a simple multimeter.

DaJMasta:
Not output can be a lot of things.  If you power it off a bench supply (or otherwise measure current consumption), mine starts at 750-800mA at 12V and then settles into the mid/high 600mA range when in operation.  I've had one with an issue where it didn't not turning on far enough to see an image where after a few seconds of normal power consumption, it drops to below 600mA.

That said, using a USB dongle that can see either PAL or NTSC and reconfigure automatically, it still puts out a signal, it just never resolves to an image.  It will show some gray noise but will correctly output frame timing info required to get a video lock even when the tube isn't reading anything real, the output formatting electronics will do their thing fairly quickly after power on.

It's worth checking the obvious stuff though: change the gain setting knob, sometimes with some settings just a black screen is output, and listening to the slight whine of the switching electronics that drive the tube voltages - should be audible shortly after power on.

As for the power connector, if it's the 4 pin arrangement, it should be just power and ground, using a nominal 12V and connecting directly to a 7810 linear regulator on the inside for a 10V operating voltage for the boards.  There is another - I think seven pin - input connector that is for the versions with an integrated battery (which is NiCd and guaranteed to be dead), but the connections should be obvious if you take the lid off and look at the wiring on the inside face.  Maybe some of the documentation can show which pins are used.... or maybe even one of the threads?  I converted mine to a barrel jack and never looked back.

Ben321:

--- Quote from: DaJMasta on May 12, 2021, 02:17:57 am ---It's worth checking the obvious stuff though: change the gain setting knob, sometimes with some settings just a black screen is output, and listening to the slight whine of the switching electronics that drive the tube voltages - should be audible shortly after power on.

--- End quote ---
That's one of the things I'm NOT hearing.  I don't hear the high voltage high frequency tube power supply circuit running. So I suspect that either the internal HV supply is dead, or the external 12V power supply is dead, or there's a loose solder point somewhere in the power circuits in the camera somewhere between the power-input jack and the HV power supply.


--- Quote from: DaJMasta on May 12, 2021, 02:17:57 am ---As for the power connector, if it's the 4 pin arrangement, it should be just power and ground, using a nominal 12V and connecting directly to a 7810 linear regulator on the inside for a 10V operating voltage for the boards. the connections should be obvious if you take the lid off and look at the wiring on the inside face.

--- End quote ---
What are the minimum number of screws that need to be removed to open it? There's 4 screws on top, 4 screws on the back, and 8 screws on the bottom. I wish I could get a service manual for it or something, that would show exactly the right way to open it. I want to be able to put it back together again.


It would be great if Fraser could show up in this thread. He usually has info on exotic IR equipment, info that I never thought anybody outside of the companies that make the equipment even had access to. Such info would be great in this thread, as it might help me fix my Micronviewer.

DaJMasta:
I think he's got one, but I've got one on the bench beside me so I can give you at least some info  ;)  I think the only manuals and things that have turned up have been linked in the main 7290A thread.

You only need to remove the four screws on top and the filter holder if your unit has one.  If your unit has the side handle (unlikely if you don't have the internal battery) then one of the screws for the handle goes into a standoff on the board and also needs to be removed.

Fraser:
Quick observations.....

This will start as a standard ‘dead unit’ investigation. That is to say, Visual inspection for physical damage or visible component failures (including fuses!) followed by simple checks on power and control. If the basics are OK, you can then begin the fault tracing process on the PCB’s.

1. Always check for power at the connector, preferably inside the camera, to ensure that power is reaching the power input regulator board.
2. Check power output of regulator board mounted in the rear of the camera
3. Monitor current draw at a convenient point in the power supply rail.
4. Check that wiring from video connector to the PCB is intact.
5. If power is present, check for heater glow from the rear of the Vidicon tube.

If you have power at the output of the regulator board then the problem can be more complex in nature and further investigation of the PCB’s will be required.

A broken Vidicon tube will not cause a ‘no signal’ condition at the video output as other circuits produce synchronisation pulses even if the Vidicon signal is absent

WARNING : If you are not familiar with Vidicon cameras, be careful where you poke your fingers as high voltages are used for the tube and they will ‘bite’ if touched. Painful but not deadly.

Fraser

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