Power Supply Repair, a Tale of Hope and Despair . Numark Dj Mixer DM3002X Internal Power

step by step account of how i resurrected my old mixer. (iv been trolled before for liking this mixer)

• i tried two methods of repair, the first one was expensive,stressful and took a long time,
• the second one was successful ,inexpensive and quick.a little circuit knowledge can go a long way.

i should recommend Big Clive 's youtube channel as general info in his videos helped me recognize diagram parts also thanks to numark uk support for kindly sending me a hard to find schematic for no longer supported hardware.

i had a newer mixer DXM09 with lots of fun effects. ,after reviewing old mixes, i decided i preferred the sound of the old mixer. less digital limiting. after a short play on the old one i got distracted and started doing something else, i forgot to turn it off ,when i returned something was wrong.....

it was lit up like a Christmas tree, without any signal going in. there was no sound coming out apart from a quiet buzz.

non-method 1 materials etc

• Internet /phone
• professional* services- - - - - - - - - - - - - - - £120.00
• packing materials
• phone credit
• car
• plenty of petrol - - - - - - - - - - - - - - - - - - - - - -£40.00
• sat nav
• two months minimum

O transition cost of going from method 1 to 2

O spare identical mixer (i now have 2) - - - - - - - £48.00

method 2 materials etc

• Internet
• printer
• transistors off ebay - - - - - - - - - - - - - - - - - - - -£2.58
• solder pump
• solder iron
• screwdriver
• 15 mins ,2 days for parts delivery, learning time.

there was very little information on this mixer online apart from a user manual that could be downloaded for a fee. at this time the only identical mixer on ebay was priced at about £300.

• i stumbled upon 123 djequipment (cant personally recommend ) the site looks legit as a specialist site for this type of equipment repair, there faq section described the problem as likely to be a power supply problem.
• so i fill out the inquiry form with the relevant information.

the next day i get a call back, saying its a standard repair and that they can " fit a new internal power supply and give the device a full service replacing any faders or pots as necessary, for the price of £100", plus £20 or £25 (cant remember which) for a currier to collect and return , and all this will be completed in about 5 working days.all sounds good to get my mixer good as new , paid by card over the phone and they email the collection label,

• the email i get comes from this Gadgetdoctors site. (alarm bells)
• i pack it in foam and what cardboard i have handy,and its collected.

1. one week later i contact them, "our technician team are very busy and need more time,we will call you back in a couple of days" they did not.
2. another week later i contact them "have you got a reference number"
3. another week later i contact them " out technicians thinks its a faulty component in the power supply we may need more money " no your not having any more money " ok we will fix the power but will not service it"
4. another week later a ask whats happening? " its in a queue , we have ordered parts for the power supply and are trying to get to the root of the problem, this may take some time."

i decide that "some time" is a month. so in the meantime i email numark to ask some questions

will numark supply parts or repair this mixer. "Further to your comments below, parts for this product are no longer available. You will be better off finding a replacement unit second hand on ebay or gumtree. I hope that this helps and should you have any further inquiries please don’t hesitate to ask and we will be more than happy to help."

can numark supply a service manual"Please accept our apologies for the delay in our correspondence. With regards to your previous message, I have attached the service manual for the unit. I hope this is of value to you. Should you have any further questions, please do not hesitate to contact us."

another month later i call, " the technician is not in today , i will get them to phone you tomorrow morning "

tomorrow morning .. the phone and email is very quiet. at 12:10 i gas up the car and drive to Bristol. twinned with middle earth (my car has a tiny engine, good gas mileage in town but is terrible on motorways @80to100mph)

i park outside the citizens advice bureau (a charitable organization that helps people in bureaucratic legal matters )

in the window they have large colorful budget looking speakers, inside a nearly empty glass cabinet with some scruffy early 90s games consoles, on the dirty carpet a couple of guitars and a drum kit, in the corner a stack of early flat screen tv's, some CRT tv's, and other obsolete vcr's and cassette players, in the middle was a man who looked homeless trying to sell a couple of dumpster grade tvs to the lad running the shop.who is saying "erm ,we haven't any money in the shop today",

on the counter piles of leaflets for local events and services for customers to help themselves to, and my mixer in a pile of many parts, no exaggeration , every panel was removed ,every board was unplugged and disconnected, all the screws and knobs were mixed up in spray can lids , the face plate was being used as a paperweight for the leaflets. and my packing materials were there too. relieved that i could see my equipment but dismayed at how i was seeing it.

"can i help you sir" the lad says,

"im here for that" pointing at the mess on the counter ,his face changes to that of a person who just realized they forgot their trouser and simultaneously suffered a bowel prolapse.

"erm ,the technician is not here today ,maybe you could try tomorrow"

"iv just driven from east london" i start stacking up the pieces of my mixer so that i can carry them , "any chance of getting my money back?"

" erm if you go through the channels maybe...."

"thats a no then"

assessing the damage, missing parts.

• everything is disconnected,putting it back together wrong may cause damage.
• one of the transform button mechanisms was broken open, contacts were exposed and bent, with powerful glasses tweezers and a magnifying glass i put it back together.
• one of the dust guards for the kill switches was missing.
• 2 of the counter sunk screws for the face plate were missing.

• the past couple of months while waiting iv been searching for the same mixer on ebay at a reasonable price, finally one for £48 was listed and it was fairly local to me, described as well used with cosmetic issues but working.
• I can reference this one to reassemble my one. as a quick fix i put my clean face panel on this one to give me something to use, i can fix my one at my leisure ,(more of a winter hobby)
• I wait to see if im offered a refund for the repair fail.

to access the power board does not require tearing the thing to many many pieces.

there are four screws on each side and five on the bottom, the power board is attached to plastic peg clips

the board that needs attention simply unclips and unplugs, most of the wires that need to disconnect to free the power board only fit in one place, take pictures to reference when putting it back together.

• i printed a big version of the circuit diagram to see if i could make sense of it. and googled the numbers on the chips.
• one half of the board is an amplifier for the headphones and maybe the master output? google told me the number on the big chip identified it as an audio amplifier thing,
• , the other half first takes the ac voltage from the transformer coil and turns it into a dc voltage with some diodes and capacitors, i recognized the pattern for this function on the circuit diagram and saw how the capacitor values match on the board.
• secondly it regulates it to remove any leftover ripple or noise from the ac source or capacitors. the two transistors do this,i googled their numbers one is for regulating negative voltage ,the other is for positive voltage.
• i put this board from the good mixer into the broken mixer,while hoping that i dont end up with two broken mixers.it lit up normally, not lit up like a mental broken Christmas tree mixer, so i hypothesize that the problem is more than likely defiantly on this board. none of the caps looked blown up, power was getting through the lights were nice and bright,but it was not working.my first step is now to replace the voltage regulators.(i dont own an oscilloscope,and wouldn't know what to do with one anyway.)

having identified the voltage regulators, it has one for the negative and one for the positive,i make a note of their numbers and search ebay.

iv ordered two pairs for the princely sum of £2.58,they can die of their own accord but having spares seems a good idea if a leaky cap is killing them. to buy them singularly is £0.99p each.

• de-solder the old ones ,a de-solder sucker iron makes it easy.
• solder in the new ones , i kept the legs long to help air circulation .
• repair took about ten mins, i had to fix my desolder thing half way.
• video of the soldering. i sped it up to make viewing easier.

• Below is test it to see if my repair works.
• i disconnect my spare mixer and connect the repaired mixer.
• master audio sounds good,headphones good, no obvious hums or buzzes.
• transform switch works after reassembly, middle fader is still dirty.