Rail cap problem ? HELP!

[Carlo]

Dear All,

I was using one of my d8b's and unexpectidly i heared a blast on the monitors and a constant hum. The faders started moving slowly on their own and the pan pots moving on their own as well.

Well i though it was the rail cap problem on the mainboard that everyone talks about. I had a spare mainboard and replaced the one on board the d8b and...THE PROBLEM PERSISTED. I changed the Distribution board with another spare one and also changed some ribbon cables (since i had some spare). Well the problem persisted. I removed all cards and also replaced my APOGEE clock with the stock clock card and the problem persisted.
i swapped the PSU's computers as well and the problem persisted.

Is it possible that there is something wrong on other boards like the DSP, JACKFIELD, CARD CAGE etc? Someone on the Forum mentioned that he had a blown capacitor on the board under the mainboard metal plate...it seems that it is the one that controls the switches/buttons and pots...

Fortunately i have another d8b and i can continue working however i want to solve this problem. Im seeing it too far fetched that both main boards are dead especially the spare one.

Any HELP?

Thanks

Carlo

[Carlo]

Any HELP please?

[Carlo]

is it possible that the DSP BOARD give the same symptoms like when the brainboard has a blown railcap?

[munkustrap]

Hi

you hear a 100Hz noise?

try this
check the real BIG capacitors (Elkos) on the PCB where the big connector for Powersuppl is mounted.
there are a couple of big black cylinders. The top of them has to be FLAT. If one of it has blown you will see it on the top.

see this: in the beginning of the video two elkos are shown. the left one is defect the right one OK
http://www.youtube.com/watch?v=JEuPP6FKNMc

[Bruce Graham]

Hi Carlos;

The capacitor issues appears to be on the Brain Board. I have the same. yet different, issue.

Can I assume when you said "Main" Board you meant Brain Board?

I have 3 d8b (2 working CPU's), and the problem exists on all my d8b's. The capacitors need to be changed.

It may be possible that the problem is else where but it seems that it would be a good place to start.

If you are handy with a soldering iron they are not too difficult to change. Google "replacing or changing SMT capacitors" and there are examples.

It is very well documented in the FAQ's on the d8b

Let me know what you find or discover.

Good luck and I hope this helps.
Bruce

[Carlo]

Dear munkustrap,

Thanks for replying.

I swapped the power distributor board you mentioned (with big black caps) with my 2nd d8b and the problem is still there. The power distribution board of the faulty mackie is now installed on my 2nd d8b and works fine so its not the culprit i must say...

carlo

[Carlo]

Dear Bruce,

Thanks for your reply... and info re SMT

i swapped the mainboard of the faulty d8b and installed it on my 2nd working d8b and it works without any issues. So the mainboard is fine....... i mean i managed to boot my other d8b with the bainboard of the faulty d8b.
Its getting frustrating now.....is it possible the DSP board is faulty?

[Carlo]

I tried to trace down the problem by disconnecting various ribbon cables from various boards leaving ONLY the brainboard, faders and DSP plus CODEC cards connected. The problem persisted and im suspecting that the problem is coming from the DSP card. Could it be possible that a blown rail cap or any other components on the DSP boards causes similar problems like faulty rail caps on the brainboard ?

It seems that the if you leave the ribbon and power cables connected to the brainboard, DSP board and backplane board (with the clock card) you will manage to boot the d8b.

So since the brainboard is not faulty (since it was tested on another d8b) and likewise the clock card was swapped with the one of my 2nd d8b.....the DSP board remains the suspect.

Any help on this?

[Carlo]

So guys....be aware that symptoms normally related to the railcap problem is not restricted to the brainboard only. The following symptoms were experienced:

The symptoms can be all or one or any combination of the following:

All leds on the desk flashing of their own volition
V-pots swirling back and forth
Faders dancing to their own tune
Thumps of about 2 per second emanating from the speakers
All meters pulsing in sync with the thumps
A low constant hum emanating from the speakers

...and the culprit was an 8-fader board (in my case 9-16). Replacing this board solved all the problem. The issue was similar to a brainboard problem so be aware of this. ITs possible that this 8 fader board shorted out and provoked to the brainboard similar symptoms found when a rail cap is blown.

So if i were you i would add this to the database especially for those who think that a similar problem is coming from the mainboard. BEFORE jumping into drastic conclusions and point your finger to a railcap problem on the mainboard...disconnect the ribbon cables of all fader boards (both 8 fader boards and the 9 fader board) and reboot the mackie. If the problem stops this means that one of your fader boards or more are defective/ shorted out. If the problem persists even after disconnecting the ribbon cables of the fader boards its probably the mainboard rail cap shitty thing.

Hope this helps. And thanks for those who replied to my query. Once it used to be different here....i used to get more help from more people. well at least i will do my best to contribute a little.

Carlo

[anyhorizon]

Once it used to be different here....i used to get more help from more people. well at least i will do my best to contribute a little.

With all due respect, Carlo, all that info is in the database, which is why it's there.

Peter