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Miniwatt N3 not turning on!
Miniwatt N3 not turning on!
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Old 10th February 2014, 11:36 PM   #1
vkengeri is offline vkengeri
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Default Miniwatt N3 not turning on!

Hi, I have a 2year old Miniwatt N3 that had been working quite well but just stopped working. I thought it was the fuse but the light on the switch would not work with out the fuse working. I removed the fuse and checked it and seems like it did not blow. Any one have thoughts on what may be wrong? Thanks.

- vkengeri

Last edited by vkengeri; 11th February 2014 at 12:55 AM.
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Old 11th February 2014, 07:25 AM   #2
ballpencil is offline ballpencil  Indonesia
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First, do the tubes light up, meaning that the heater works?
Can you trace voltages? The pins on the tube looks accessible to voltmeter probes without unplugging them. We need to understand how good you understand electronics before proceeding.
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Old 11th February 2014, 07:26 AM   #3
azazello is offline azazello  Bulgaria
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Is main transformer common for both channels? Are tubes light?
1. You can measure with voltmeter /in AC mode of voltmeter/ is there AC on taps of transformer - high and 6.3 v/...Is there DC +U /in DC mode/ after bridge rectifier. Maybe something is wrong in PSU?
Please, give us results. Next measuring advice - after first.
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Old 11th February 2014, 04:04 PM   #4
vkengeri is offline vkengeri
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The tubes are not lighting up or getting hot. I am not sure what I need to open to measure the voltages but will give it a try by opening the tops of the two transformers.
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Old 11th February 2014, 09:33 PM   #5
azazello is offline azazello  Bulgaria
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I can't see power transformer. Maybe +U DC and 6.3 V AC are formed direct from AC net? IMO, it's dangerous and don't open amplifier, if it is connected to the wall. Maybe something is wrong with 6.3 former and/or power diode rectifier.
IMO, You can ask some person, who understand electronic and SS rectifiers.
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Old 11th February 2014, 09:41 PM   #6
lexx21 is offline lexx21  United States
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Simplistic suggestion, though very valid.... fuses? Check the fuse with an ohm meter (not in the circuit of course)
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Old 11th February 2014, 10:05 PM   #7
azazello is offline azazello  Bulgaria
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miniwatt N3 | ???????????? - ?????
There is inside picture.....it seems something like HF impulse PS, maybe problem is here....with IC on Allum. cooler plate.
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Last edited by azazello; 11th February 2014 at 10:17 PM.
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Old 11th February 2014, 10:10 PM   #8
yagoolar is offline yagoolar  Poland
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Miniwatt N3 not turning on!
You mean SMPS. Thats odd...
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Old 12th February 2014, 12:27 AM   #9
ballpencil is offline ballpencil  Indonesia
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Tubes not lighting up means there's no heater power supply. Now the problem is whether the plates are not getting power as well. Looking at the internal pic, I think plates are supplied directly from a rectified mains while heaters gets a stepdown transformer? So.. first thing i would do is to unplug all the tubes and check if there's supply for the plates. If plates are powered, then it could be the step down transformer for the heater.
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Old 12th February 2014, 08:26 AM   #10
ishiru is offline ishiru  Indonesia
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it's SMPS supply.that's why the mains was directly rectified.(i assume SMPS used for smaller case and lighter weight )
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