Author Topic: Jamo sub 300 amp board repair  (Read 9107 times)

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Offline N1TRO

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Jamo sub 300 amp board repair
« on: October 21, 2015, 10:13:23 am »
Hi,

I have a Jamo Sub 300 here that I bought off a friend for $20 due to it not working.
I have taken it apart and I have heard from research that the brown goop goes conductive and causes problems. There are also a few suspect caps and the yellow 104k resistor looks to be burnt or something. I would like some opinions from those more advanced than me on what they think is wrong as this is my first attempt at a repair. Any thoughts are appreciated and if needed I can do some measurements for you. I have checked the fuse and it is fine but I don't fancy turning it on. I will also replace all the electrolytics.

Here are some pictures:







Thanks.
« Last Edit: November 08, 2015, 07:52:03 am by N1TRO »
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Offline singapol

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Re: Jamo sub 300 amp board repair
« Reply #1 on: October 21, 2015, 06:21:12 pm »
Nothing out of the ordinary from the pictures. Do some resistance measurements first for shorts but make sure you discharge the caps with a 1K ohm 5 watt resistor or better yet a 10 watter. Check the output power transistors at oppoisite sides of the heatsink and the driver transistors. Then the caps. Test first before any cap replacement. it may not be necessary. If all checks out now time to power up and measure the power supply voltages. There should be plus and minus voltages. I don't think the glues are conductive.
 

Offline station240

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Re: Jamo sub 300 amp board repair
« Reply #2 on: October 21, 2015, 08:41:25 pm »
The glue certain is a massive problem, and for this device in particular.
see: http://forums.whirlpool.net.au/archive/1889470

Carefully clean the brown glue from the main filter caps, bridge rectifier, 240/120V selection (pic 2)
Then the same for the power diodes and filter caps on the other side (pic 5)
You may need to unsolder these capacitors to check for corrosion underneath.

measure the resistors you mentioned with a multimeter, to check the values against the colour bands.
 

Offline Joule Thief

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Re: Jamo sub 300 amp board repair
« Reply #3 on: October 22, 2015, 08:57:08 am »






The leads on the 160K resistor look a little suspicious, and maybe a cold solder joint on the resistor above that one (470 ohm?).


« Last Edit: October 22, 2015, 10:38:45 am by Joule Thief »
Perturb and observe.
 

Offline singapol

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Re: Jamo sub 300 amp board repair
« Reply #4 on: October 22, 2015, 10:13:28 am »
One end of 160k ohm seems to be corroded and touching the trace below? The other resistor should be 470 ohm.
 

Offline N1TRO

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Re: Jamo sub 300 amp board repair
« Reply #5 on: November 08, 2015, 07:40:50 am »
thank you all for your advice, it has confirmed more or less what i initially thought  :). One thing that has me confused is as to whether the yellow passives are resistor or capacitors, the resistance is all over and i though they could be x/y caps but the capacitance is only brief. The other thing i wanted to ask is what the blue passives are. I assume they are ceramic or mica caps. Thanks.
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Offline N1TRO

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Re: Jamo sub 300 amp board repair
« Reply #6 on: November 08, 2015, 07:50:52 am »
ok so im pretty sure that the blue passives are emi/rmi suppression x/y caps and the yellow devices are caps.
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