M&K Subwoofer Amp Fault, Help Anyone?
Hi Guys,
I have bought a M&K subwoofer as faulty in the hope of repairing it, i cant find the model number because it has been removed, but the amp board inside is identical to a picture of an MX-100 board from M&K, the sub was working & suddenly stop outputting & only made popping & rumbling noises, the amp was powered & led lit, also no sound is heard now when you connect an rca lead, but was before, i opened it to inspect the board & someone had already carried out a repair(badly!) the board had heat patches, tracks lifted, capacitors of wrong value leaking, & a few capacitors with only 1 leg connected! how it worked i dont know! anyway i cant find schematics for this to try to repair any further or have a new board made up, so any help would be appreciated! i have attatched a pic of the board, i have had to remote a few components as the tracks underneath wouldnt take the solder properly, & kept unsoldering other bits around it, so looks a mess, Oh & the 12" dual voice coil driver thats installed (2x6ohms) still works fine, personally i think its an input prob, but just incase have a new STK4050v on order. Thanks.
Hi Guys,
I have bought a M&K subwoofer as faulty in the hope of repairing it, i cant find the model number because it has been removed, but the amp board inside is identical to a picture of an MX-100 board from M&K, the sub was working & suddenly stop outputting & only made popping & rumbling noises, the amp was powered & led lit, also no sound is heard now when you connect an rca lead, but was before, i opened it to inspect the board & someone had already carried out a repair(badly!) the board had heat patches, tracks lifted, capacitors of wrong value leaking, & a few capacitors with only 1 leg connected! how it worked i dont know! anyway i cant find schematics for this to try to repair any further or have a new board made up, so any help would be appreciated! i have attatched a pic of the board, i have had to remote a few components as the tracks underneath wouldnt take the solder properly, & kept unsoldering other bits around it, so looks a mess, Oh & the 12" dual voice coil driver thats installed (2x6ohms) still works fine, personally i think its an input prob, but just incase have a new STK4050v on order. Thanks.
An externally hosted image should be here but it was not working when we last tested it.
hmm well by the looks of the pic it was repaired by a 10 yr old, but if u cant find scematics i would trace the main input of the power amp, and just use your own active crossover network, like find the point where the crossover/preamp inside the unit joins to the main amp and join an input to that, or it might be easier just to install a new amplifier.
another problem is that because the preamp might b dead (as an assumption) and it is a DVC woofer it uses 2 amps, so you might need to find 2 inputs, but if it is the main amplifier you might just have to replace the output transistors, and MAYBE a few resistors.
what is the ratings of the amplifier and subwoofer?? and i have never heared of a dual 6R woofer before, what brand is it?
haydn
another problem is that because the preamp might b dead (as an assumption) and it is a DVC woofer it uses 2 amps, so you might need to find 2 inputs, but if it is the main amplifier you might just have to replace the output transistors, and MAYBE a few resistors.
what is the ratings of the amplifier and subwoofer?? and i have never heared of a dual 6R woofer before, what brand is it?
haydn
ahh i just realised after posting that message that the power amp is a power IC, here is a sight that u can purchase a new chip if needed http://www.ampslab.com/trans_stk4050v.htm
haydn
haydn
Hi, thanks for your help, i have found 2 zener diodes burnt out on the board, so replaced them with like for like & still no joy, just a voltage sound when i power up the amplifier, i have ordered a new stk4050v & it arrived this morning, so im hoping that the bad solder job had shorted out & blown the amp, so if i replace this it should work, also found 2 tracts that were broken so have repaired them, so it all relies on whether installing this new amp chip cures it, otherwise i think i've exhausted every option & will just bin it.
oh and its branded M&K, its 200w per coil from what i can find out, at 6 ohms per coil, bit of an odd impeadance but most of the time if its labelled 8 ohms it drops under certain loads or frequencies, so i base the driver on a 4 ohm load while under load, hope i can get this fixed, the bass was awesome & so deep before when it worked, its just a shame to not have it working properly.
Just finished with the amp, fitted new stk chip & new lm348 op-amps, repaired all broken track hiden under where the stk chip was & thoroughly checked everything on the board and...............Still nothing, so i gave up now & the board is in a million pieces lol. removed the 110 transformer & output capacitors from the sub box, they work fine so will keep them like all the other junk i got, just gonna buy a new plate amp, found prices around $100 so about £50 in my money, so not too expensive. Thanks for your help guys, shame the board was beyond repair but you have to give up sometime!
P.S got a stk4050v chip if anyone needs one! lol (can have for what i paid) & 2 10,000 mf at 63volt so gimme a shout if anyone needs them.
P.S got a stk4050v chip if anyone needs one! lol (can have for what i paid) & 2 10,000 mf at 63volt so gimme a shout if anyone needs them.
h3ad said:
the boards in bits mate, i had enough of it, i still have the new stk chip, the old one had some pins not connected & didnt meter out properly so binned it too, so all i have is the stk chip, cappys, transformer & the new lm348 op amps, the old op amps were fine so gonna hang on to them, would be looking for £10 plus postage to get my money back (paid £12 for the amp alone) let me know if u interested. The STK chip has been soldered onto the board & removed again so might need the pins cleaning up.
i am interested and to be fair i will give u 15pounds for it + postage. if u r thinkin of sending the transformer, because i am unsure if u are, dont worry about it, keep it as Australia uses 240v and it will just make sum pretty smoke over here. i would assume postage would be aroun the 5pound mark?? so call it $50- $55 AUD??
thanx haydn
thanx haydn
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