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need some help repairing a Jamo SW 3015 active sub please

khalidlib

Sep 10, 2021
1
Joined
Sep 10, 2021
Messages
1
hello everyone i am new to this forum, came here as per the advice of some friends, hoping to find some help repairing an active sub woofer i have for more than 10 years now, it is the Jamo SW 3015 active sub woofer with THX dedicated input , it was in storage for about 3 years since i moved to a new place, and i decided it is time to put my home theater back up ,however after bulging it in the sub and hooking it up to the amplifier pre out it did not make any sound , the on standby light came on but no sound with a faint buzzing sound coming from the amplifier plate, i turned it off and back on again and same story, then the on indicator light went off still the buzzing noise is their, like a small running fan blade hitting a small wire, i took the plate off but there was no fan and the noise is coming from the preamp board or the power supply unit , can't tell for sure but if i disconnect the power from the supply to the amplifier unit the buzz stops, all caps look ok and no burn marks anywhere, after asking around it appeared it was the capacitors at the hi voltage mains input , changed one and the buzz went away, i ordered a better quality and i will put them in when they arrive, sadly that did not fix the subwoofer
still no sound and the indicator led would not come on, i left no stone unturned, looked everywhere for schematics and could not find anything as far as my knowledge goes apparently it does not go very far.
i made a crude sketch of the connections and ics on the board for reference and i noticed a few things
1- the 084C ICs on the small board get hot
2- in the small board the continuity test between column A and column B is + except for the signal line there is no continuity
3- it is printed in stencil on the board that Red line in column A is 12v but i could only mesure 6v
4- the led terminal on the control board measure 2.6v when it is floating but when i connect the led to measure 0.6v
so i am asking for help again please


i am hoping someone with some knowledge or had a similar problem and fixed it could help me out no how to proceed to troubleshoot and fix the problem
 

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Patchneck

Oct 30, 2021
1
Joined
Oct 30, 2021
Messages
1
Hi, I have 2 of those subs not being rude but if you don’t manage to fix it I would be willing to purchase it off you as spares… thanks
 

73's de Edd

Aug 21, 2015
3,433
Joined
Aug 21, 2015
Messages
3,433
Sir khalidlib . . . . .

In using your mark up . . . .
Top right corner at the power supply board, you see that it basically just develops a very STOUT +- 22VDC AMP supply and also your centrally designated + and -12 vdc to feed over to the "liddle-middle-board" at then it also exits down to the bottoms C&S board.
Are those +12 and -12 voltages holding to spec at at both "liddle-middle-board" and the bottoms C&S board power inputs ?

Next we can assume that the top left corner AMP board is receiving those +-22 V DC supplies from the PSU unit, and that they are holding at spec. Then we see that some of the +22 is getting relieved of a bit of its power to supply that KA7812 12 VDC regulator, that then ends up supplying the AMP right side terminals +12VDC.
That 12VDC comes in Terminal strip A to feed 12VDC power into that "liddle-middle-board" and supposedly to loop out and connect to Terminal strip B to feed 12VDC w a a a a y on down to the bottom C&S board for its 12VDC supply.
NOW . . . . .are you reading a full 12 VDC at that AMP board +12VDC terminal
You say . . . .
2- in the small board the continuity test between column A and column B is + (add comma) except for the signal line (add comma) there is no continuity.
" I did not FULLY "apprehend" what you are saying there . . .?

MY first thoughts, is of that KA7812, and if it is putting out +12V. . . . . along with the " capacitance health " of both its input and output E-lectrolytic caps.
My second thought is a TL084 IC's internal fault just PULLING their supply voltage down, if being solely fed from that +12 supply . . . .BUT . . . . is if their supply voltage is being acquired from that separate +- 12 VDC supplies coming down from the PSU board. . . .a different situation.

Fill me in . . . . . . from whence doth the TL084's get their power ?

ON POST . . . . . IMAGE SUPPLICATION . . . .for more convenient referencing
c1-jpg.52899



ASIDE THOUGHT . . .

Reference from above . . . .less than a 15 inch speaker size is being a WOFER . . . . .15 or larger is being a WOOFER.


73's de Edd . . . . .



Hm m m m m m m ?
My computer screen just displayed

. . . . . . . . . . . . . .THIS DOES NOT SEEM TO BE A VALID HOT LINK . . . . . . . . . . . . . . . . . .

with an ensuing raspberry and audio clip of . . . . . nyah nyah na nyah . . . . nyah nyah!



.
 
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