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Hantarex MTC 9000 image squashed vertically
grantspain:
check
mains filter cap and TR19
i doubt regulator is bad otherwise you would have b+ too high
be77amyX:
Update: By 'mains filter cap' I guess your talking about c53? replaced that. TR19 looks good, shows as NPN transistor on my ESR meter and looks OK on the multimeter ( I believe it's a Darlington pair so tests out slightly different from a normal transistor? ) I took a look at TR20 too. Not sure if it's the correct part or equivalent? Its marked as ST F441 29009 which I can't find any info on online. It tests out OK though and my spare chassis which does have a TIPL762 in that location but shows a short from B-C!
Took some more voltage readings 165Vdc with the chassis disconnected, 152Vdc with the yoke disconnected, 115Vdc with everything connected.
Strange how the monitor drawings show AC input but the power supply gives you DC!
grantspain:
--- Quote from: be77amyX on August 29, 2019, 04:00:31 pm ---Update: By 'mains filter cap' I guess your talking about c53? replaced that. TR19 looks good, shows as NPN transistor on my ESR meter and looks OK on the multimeter ( I believe it's a Darlington pair so tests out slightly different from a normal transistor? ) I took a look at TR20 too. Not sure if it's the correct part or equivalent? Its marked as ST F441 29009 which I can't find any info on online. It tests out OK though and my spare chassis which does have a TIPL762 in that location but shows a short from B-C!
Took some more voltage readings 165Vdc with the chassis disconnected, 152Vdc with the yoke disconnected, 115Vdc with everything connected.
Strange how the monitor drawings show AC input but the power supply gives you DC!
--- End quote ---
it goes through a bridge rec circuit
be77amyX:
Yeah sorry I see that. What I meant was the power supply from the US250 is DC before it goes through the rectfier ie. measured at the 4 pin power plug. I checked the power supply drawings and its supposed to be like that. just find it odd the monitor has a rectifier at all when the hantarex power supply is supplying DC
grantspain:
the dc power from a u250 should be around 138-140v btw
i have used b508a to replace the tipl762 in the past, works fine