need advice for fixing MPC3000

hi all,

i joined this forum because a friend of mine gave me a MPC3000 to fix.
it is a 110V model and we use a 220V-110V voltage regulator to power it (we live in germany). the regulator is known to be working and not the root of the problem - the second MPC3000 he has will work with the regulator for hours upon hours.

now, the machine seems to have a thermal problem. it'll power up and run for approx. 5 minutes, then it will reset itself.
in some cases the LCD will not come back to life and all LEDs will stay lit.

i looked for a service manual on the web but couldnt find one. i did, however, find and join a yahoo group about the mpc3000. there i located a .pdf which apparently was written by a guy called rohan - it seems he is quite the mpc authority
this pdf had the voltages listed that the power supply generates (+5, GND, -12, AGND, +12, +5)
i hooked my multimeters probes to the supply and confirmed that all voltages are present.

the interesting bit is probably that when the mpc goes into "zombie mode" (all LEDs on, no display) the +5V rail on pin 1 will go down to +2V!

i would think that IC801 is the +5v regulator - could it be broken?
where else could the problem be?

any input is gratly appreciated - and if someone could post a service manual for this beast i'd be super happy. i searched the forum but all links pointing to the service manual are broken.

thanks a ton, chris

POWER SUPPLY BOARD - L4012B507B

Main 5 volt regulator ( IC801 )

It is a Sanken "SI-3052V" 5.0V / 2.0 AMP voltage regulator.

Replace it if suspect.

Repair damaged and dry joints on this board also.

Actually ...... start with repairing dry joints.

There are bound to be a few in critical locations.

From my own experience.

Re-flowing most solder on the power supply secondary board is not a bad idea.

That and replacement of any faulty parts ......

Then it should come back to life.

Rohan.

hi rohan,

thanks for the reply.
i already resoldered all of the joints on the two power supply pcbs before writing my original post - that alone didnt do the trick.
the discoloration of the pcb tells me that there is some heat problem. which makes me wonder:
why did akai use power caps rated for 85° max??? using some rated for 105° wouldnt have hurt...
the smaller heatsink (on bridge rectifier D801) gets mighty hot!

anyways:
i looked for the 3052 in my favourite german online electronic shops but couldnt find it.
the 78s05* seems to be an alternative (although not pin compatible and therefore no drop-in replacement).
it can handle a 2A load (which the 5032 can do as well) so i dont expect any problems. i'll just have to use some flying wires. not pretty, but...

i'll report back when i get the part (might be some time though, my last order came just in)




*not to be confused with the 7805, which has a max rating of 1A

creekree wrote:hi rohan,

thanks for the reply.
i already resoldered all of the joints on the two power supply pcbs before writing my original post - that alone didnt do the trick.

Ok ... a good starting point.

creekree wrote:the discoloration of the pcb tells me that there is some heat problem. which makes me wonder:
why did akai use power caps rated for 85° max??? using some rated for 105° wouldnt have hurt...
the smaller heatsink (on bridge rectifier D801) gets mighty hot!

Check the bridge rectifier for shorts circuits.

Why AKAI chose to use 85 degree and not 105 degree capacitors ? Sign of the manufacturing times.

Back in the mid 90's ... A lot of Japanese stuff was equipped with 85 degree capable capacitors.

creekree wrote:anyways:
i looked for the 3052 in my favourite german online electronic shops but couldnt find it.
the 78s05* seems to be an alternative (although not pin compatible and therefore no drop-in replacement).
it can handle a 2A load (which the 5032 can do as well) so i dont expect any problems. i'll just have to use some flying wires. not pretty, but...

Use the real part.

I can get them down here ok.

Although obsolete. New old genuine Sanken manufactured stock.

Talk to me via PM if you want to get the real part and we can work some thing out.

creekree wrote:i'll report back when i get the part (might be some time though, my last order came just in)
*not to be confused with the 7805, which has a max rating of 1A

Suggestion...

Use the genuine part.

Putting a 78S05 in place as a substitute will get you into trouble.

IE: Voltage regulator feed back components and such. All those present being set up for an SI-3052.

Not to mention the arse about wiring.

Rohan