Troubleshooting degauss on Hantarex MTC9000

[Nipedley]

Hi folks :-)

My Hantarex MTC9000's degauss circuit has never worked, I'm in the process of refurbishing my cab & monitor and would like to get this sorted at last

When I first got it, the degauss coil had been disconnected. I connected it up and the fuse did not blow, however also no degauss function. I've just tested the circuit from the schematic in the Hantarex MTC9000 manual and all seems well. What I am unsure how to test is the coil itself and the positor. The push button function is disabled as there's a factory link (P34 on schematic) bypassing it so that degauss is always on. It appears that this board is either power on degauss or push button degauss.

I' m getting a reading of 33 ohms between the 2 common pins of the positor (degauss button & voltage to positor, and positor to coil) and 1.7k ohms on the other side of the positor to coil & voltage. Is that normal?

Also, how do I test the degauss coil itself - should it be a dead short or should there be resistance, and if so what kind of range? As the fuse doesn't blow, I'm guessing nothing is actually making it to the coil?

Many thanks ! :-)

[ed12]

when u open p34 u are to insert a temp pushbutton
#3 in tec ref.

if the deguass coil is not open i would go after the ptc
mertering a ptc is a pain in the a&& (postive temp coeffecent)

ed

[Nipedley]

Thank you :-) so resistance between the two wires from the coil itself should be 0 ohms?

I'll check that tomorrow (left my multimeter at work.. doh) and if that's all good I'll source a replacement PTC

My cabinet came with a push button on the main service panel but as you say the chassis would need p34 open for that to work. Perhaps the monitor was replaced during it's life

Many thanks

[grantspain]

European mtc9000 chassis have 240vac for the degauss circuit,so you should have 4 wires onto the power connector-check that voltage
ptc you can get on ebay uk

[princess prin prin]

Thank you :-) so resistance between the two wires from the coil itself should be 0 ohms?

About 23-25ohm.

[Nipedley]

Thank you, my coil is fine at 28 ohms however on the power plug I'm measuring 125v on both sets of pins, so the degauss circuit is only getting 125v

From what Grant said it seems this might be the problem then? As I don't really feel like fiddling about with transformers I guess the easiest solution here is to just get a degauss wand and do it manually when required?

Incidentally I also decided to measure the B+ and it's running at 133.3v, is that okay? I know it's supposed to be around 130v but not sure how exact that should be

Many thanks

[princess prin prin]

Thank you, my coil is fine at 28 ohms however on the power plug I'm measuring 125v on both sets of pins, so the degauss circuit is only getting 125v

If it's a US one, it's normal.

Incidentally I also decided to measure the B+ and it's running at 133.3v, is that okay? I know it's supposed to be around 130v but not sure how exact that should be

It's ok.

[ed12]

i read something here today that set my mind off how the op could of stated what they did
without centering out the op
the 120/240 vac input has 0 to do with the deguass circuit
it is only used for refernce to the input voltage to the switcher power supply
ie: min-max rating,the deguass is the ptc and its switching (manual/automatic)
it is about that simple

ed

[grantspain]

I am absolutely failing to see what bit of info I gave that was wrong,mtc9000 have two sets of voltages,128vac for the chassis and 240vac for the degauss circuit-you can wire the power input in such a way that u.s voltage will work by basically linking the ac lines
please tell me what I said there is wrong

[Nipedley]

I've ordered a replacement PTC but still a bit confused about that voltage. What you guys said there went over my head

Given that the degauss circuit of my MTC9000 is being fed 125v AC from the isolation transformer should that work when I fit the new PTC?

I'm unsure what region my MTC9000 is from, it doesn't match many schematics/manuals available on the internet so it's difficult to say. However my cabinet's wiring does seem to be original. For the record I'm in the UK on 240v mains

[ed12]

please re read my statment i made it very clear i was not calling u out
just pointing out that the psu input can be either 120vac or 220 vac
thus the deguass will work either way
the governer here is the ptc and not the input voltage
that part ment 0

ed

[grantspain]

to be perfectly honest in the majority of posts you make I have serious problems understanding what the hell you are saying, it's not English  as I know it

[ed12]

thk's for the attack..........
next time u make a wrong post
I WILL CALL U OUT..ENGLISH ENOUGH FOR U ??

ed

[grantspain]

trembling

[Dave11674]

hi guys
sorry to drag up an old post
but to the OP did you fix teh degause ?
ive a mtc9110 here that does not degause when powering up

to you 2 kicking off with eachoner, made me chukkle

dave