Checking out Hantarex MTC9300

[bigtrev2]

Hi there,
   I've started my first Cab project, and to make it a bit easier have found a generic cab which comes complete with the above monitor.  The cab was shipped from Germany (I'm in Australia) so line voltage is OK.
    I already have an I-pac and controls and stuff like that and therefore I'm a bit loathe to purchase a AVGA card and jamma harnass to connect to the cab without knowing that the existing monitor is OK.
   I plan later today to rewire the mains plug to the australian standard and then try powering up, if there are no bangs, I'll try and get something on the screen by turning up the screen control.
 
   My wife has recently upgraded her laptop, so I'm thinking of using the old one's VGA out and something like soft-15khz to try and get an image on the screen.  The Service manual for the monitor states that Video in is OK for 1.5-5V so I'm guessing that I'll be able to get an image (although not too bright)  but it is not a multisynch monitor - I'll probably use my CRO to check the horizontal frequency out of the laptop before attaching it to the monitor.

   The service manual also states that the +5Vdc supply is rated for 1Amin to 13A max.  I know that some switching supplies have a minimum current draw to guarantee regulation.  Given that there are a couple of small globes mounted on the coin door, do you think that there will be enough regulation to stop the monitors supply protection circuitry from triggering or should I add some more current draw to the circuit.  (I haven't yet worked out how to get the globes out of their holders so that I can read their ratings!!)

   can anyone see anything wrong with what I propose?  I'm confident with low voltage electronics, but am not keen at all to go delving inside a monitor to try and fix it.

Trev

[bigtrev2]

Well I've tried it out but didn't get far!!!

    When I applied power not much happened!

    There is a +5V load of about 4ohms, so I presume that I haven't tripped any protection.  All I get is a high pitched whistle, like the switcher trying to do the right thing.  No bang, no smoke, BUT no glow from the neck of the tube, no raster, no power for the game PCB (I read a few mV at most on any of the logic supplies)  As I don't have an isolation transformer and don't really know what I'm doing with the EHT, I'm going to take it to the one TV repair place that's willing to look at it.  Hopefully it's not too badly broken!!!!!

[qrz]

most smp's for gaming have internal load resistors allowing brief unloaded operation.
suggest disconnecting the 5v line  and see if still squeals upon pwr up ( measure 5v line while doing this)
keep test brief

squeal , repair supply - check diodes
no squeal, inspect game pcb for obvious damage/shorts , wiring issues...

[bigtrev2]

Where I am at the moment is that I expect there is something wrong with the switcher in the monitor.  Without a PCB, but with the coin door lights I have 4Ohms resistance on the +5V line - which I assume is the cold resistance of the two 6V globes in parallel. 

   with or without the power connectors plugged in, the monitor doesn't power up, all I get is the high pitched 'squeal' - so I assume there is something in the monitor causing the protection to kick in.   I've found someone with the appropriate tools and equipment to check it out.  Hopefully it's something simple and inexpensive!   I do have a backup plan though - a interstate supplier has a generic monitor board which is supposed to be a direct replacement for most monitors, and add a multi frequency capability which the Hantarex doesn't have. If it is beyond reasonable repair, I'll get the repairer to check out the tube to the best of his ability and put in the new control electronics.

   Thanks for the suggestion

Trev