Hantarex MTC9000, shorted tube (no it wasnt) ??

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frsj8112
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Hantarex MTC9000, shorted tube (no it wasnt) ??

Post by frsj8112 »

Hi, im working on a dead Hantarex MTC9000 monitor.
When starting it up I have ~130VDC on the yoke connector (black wire), I can hear high voltage static but then quickly I can hear the tube discharging.

Replaced the chassis with a known working chassis but got the same result.

The yoke seems to be fine, 2.5 Ohms and 14 Ohms.

I the put the previous known working chassis together with another tube, but then I got the same symptom, HV static, discharge but still 130VDC at the yoke connector

Is there a short in the first tube that killed my second chassis? :(

The first chassis has an original Eldor flyback, which are prone to die.

Calling mr @grantspain and @PrincessPrinPrin
Last edited by frsj8112 on May 13th, 2021, 10:02 am, edited 1 time in total.
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Re: Hantarex MTC9000, shorted tube??

Post by PrincessPrinPrin »

Lift one side of D10 near the TDA2595 to disable the x-ray protection. If the high voltage stays on (but don't leave it on for more than a few seconds), check if the capacitance of C36 is much lower than 3.9nF and if so replace it.
Im running games with a vga to tv converter on my Shangai Novel, with composite and it looks amazing, Im not interested in RGB or Scart.

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Re: Hantarex MTC9000, shorted tube??

Post by frsj8112 »

I’ve looked a bit more at this.
I have a third working mtc9000 (named nr3) in my Operation Wolf cabinet.
I hooked it up together with the questionable tube and it’s working!
Great, tube is ok :)

However it seems like my previous repaired chassis (named nr2) had failed.

I hooked nr2 up again and desoldered D10. Chassis starts and I have high voltage and get image on the screen.

Most of the polymer caps in the power supply has been replaced previously.

TR15, TR20 is ok
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