Hantarex us250 psu (DEAD) Help Please

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neokidgeo

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O.k guys i'm having some problem with my hantarex us250 psu, It keeps blowing the f1 fuse, I opened up the unit and found this little carbon disk that seems to have blown do you think this could be my problem and if yes what is this thing could.

I'm in the uk.
Thanks guys






 
ttooddddyy

ttooddddyy

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That looks to be a PTC thermistor for degaussing, cut it out and try running.
The monitor will work without it, but you may have colour purity errors on the crt.
 
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neokidgeo

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O.k i've remove it and it is not blowing :) anymore, Is it safe to hook it up to the monitor and hook up the pcb????
 
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neokidgeo

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Just hooked everything back up and nothings happeing, No fuses blowing but no power, The edge connector or monitor is getting no power i've just checked with multimeter.
 
ttooddddyy

ttooddddyy

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Do you have a schematic or link to one for this model ?

The psu should work without the device fitted, I would remove it again and check if there are any psu secondary voltages.
 
ttooddddyy

ttooddddyy

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Found it

http://www.cs.utah.edu/~strong/arcade/manuals/US250-300.pdf

There is a 2 amp fuse on the rectified mains supply to TR 3 collector, the smps switching (chopper) transistor. Be carefull around there as the smothing cap may be charged up if the set has been recently powered on.

Interestingly this schem does not show the thermistor for degausing, but it must be there. You can not connect the degaussing coil straight across the mains, as shown on this schem. It must be an error.
 
ttooddddyy

ttooddddyy

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stuffmonger said:
maybe that power supply just rides the short bus... ;)
Click to expand...

It will continually blow the 4 amp mains fuse at switch on if the degausing coil is wired direct to the mains with no thermistor as shown in the diagram.
 
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neokidgeo

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I have just removed it again but i am a bit lost on what and where to check sorry.
 
ttooddddyy

ttooddddyy

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Seeing as the 250 and 300 have a common schematic (without any notes on different output voltages or different component values) I would say they are interchangable.
 
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neokidgeo

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Thanks for all your help ttooddddyy i'm going to buy the psu, But i might leave the other psu as a spare or a project if i end up doing a course in electronics.
Thanks :)
 
ttooddddyy

ttooddddyy

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Just a note on the 250 vs 300 power supplies.

The 300 should have a cooling fan fitted. The 250 does not

There is a note on the schematic "US300 has a fan connected here (no other differences were found)"

The connection is just after the mains switch, connector CG.

I would say that if the 250 worked OK without overheating the 300 will be fine without this fan fitted. If it has the fan even better.

Post a piccy of the 300 when you get it.
 
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