Hantarex MTC900 (Dark Picture)

[DarkSide]

Hi!

Ive got a few problems with an old, almost fixed MTC900 monitor.

The previous owner connected the powercable to the brightness/contrast header and blew out the following parts:

The TDA3501, 7812, and a few diodes.

After replacing the parts and adding a cap kit the monitor works again, or that will say almost works, the problem is, that the picture is very dark, even with brightness/contrast and G2 turned all the way up.

Im not sure where the fault could be, even with G2 on full power i get no retrace lines, the picture is still dark.

Any ideas ?

Regards
DarkSide

[Ken Layton]

Test the tube on a rejuvenator.

[DarkSide]

Test the tube on a rejuvenator.

Dont got access to one here in denmark.

Any other ideas?

If i understand the service manual correct, there should be around 10-11 volts between TP4 and TP5, and it should be possible to adjust it with the pot RV4

Here is my problem, ive only got 6 volts between TP4 and TP5, did i misunderstood the service guide, or is that's what wrong with my monitor ?

[qrz]

if c18 ( 22uF/16v) shorts, TP5 would likely be around 6v.....
 this is part of the abl line (automatic brightness limiter) . also check d26 (ba159) and r118 ( 10k).

qrz

[DarkSide]

if c18 ( 22uF/16v) shorts, TP5 would likely be around 6v.....
 this is part of the abl line (automatic brightness limiter) . also check d26 (ba159) and r118 ( 10k).

qrz

c18 is brand new, d26 checks out ok, and so does r118.

Other ideas ?

[qrz]

new doesn't always mean good
i've had a few times where a new component was defective....AND wasted time looking elsewhere...
a quick res check will rule out a short there .

also check r42,75,142,143

qrz

[grantspain]

C205 10uf 200v,R216 0.33ohm and RV7 220k trimmer caused all sorts of brightness problem on this chassis

[DarkSide]

Are you sure that's on the MTC900, and not on the MTC900E ?

Cant find any of those parts in my schematic.

[grantspain]

yeah i'm a nob,thats for a mtc9000
check C51 4.7uf 250v,R144 2.7ohm and 115vdc at sp15

[grantspain]

actually i just read the entire post again and would say forget about this chassis,if some someone stuck high voltage ac up the signal lines so many components could be fries its not worth bothering

[DarkSide]

I did check all the resistors, and diodes, on both pcb's, no dead parts..

Could it be the flyback ?

If i can get my Kortek monitor working, im gonna scrap that Hantarex

[SirPeale]

I have an MTC-900 I never could get working.  There's a problem in the brightness circuit somewhere I never could chase down.  These monitors are a PITA.  I would also suggest getting rid of it.

[DarkSide]

i Would, if my Kortek would work in my Sega Hang on