Crashing & locking up >> Power supply calibration

[dvdborn]

At one point my EIII started acting up again. This time the whole machine would crash. There were 3 kinds of crashes:
1. The EIII would lock up, the display would read "SCSI Hardware failure"
2. The EIII would just lock up. The screen showed junk characters and a random number of led's on the front panel would be active
3. The Hard Disk would shut down, but the EIII kept working. Sometimes the hard disk started spinning again. But most of the time the EIII would lock up.

At first I thought that the hard disk was failing but replacing the hard disk didn't solve the problem.

All the above problems were caused by one thing: The voltages on the power supply output were erraticly changing. Meaning that most of the time it was giving 11.00 Volt on a 12 Volt line (Orange wire), but sometimes the voltage would drop below 11 Volt causing the EIII to crash and the hard disk to shut down.

Solution: cleaning the trimpot on the power supply PCB and adjusting the voltage to the correct level (+12 V).

There's only 1 trimpot on the power supply so you can't go wrong.

I suggest you disconnect everything from the power supply, except the fans and/or the hard disk, when you adjust the voltage. Otherwise you migth fry something when the voltage peaks.

I used one of the fan connectors to read out the voltages.

Here's the complete procedure to calibrate the power supply. Kindly provided by Dr C. (http://mapage.noos.fr/g.cerdan/)
READ CAREFULLY AND COMPLETELY BEFORE ATTEMPTING ANYTHING !!!

IF SOMETHING IS NOT CLEAR OF EVEN OBVIOUS IN THIS EXPLANATION, JUST STOP !

Required equipment :

a) - Small isolated crewdriver compatible with the power supply adjustable
b) - Digital voltmeter with correct batteries (to be sure the voltage
reading is accurate)
c) - PCB cleaner (KF-F2 for example)
d) - Black permanent marker (the kind to be used to write in CDs)
e) - EXTREME PRUDENCE, TAKING YOUR TIME AND THINKING OVER WHAT YOU DO.

PREPARATION

Put the Emu in a very stable position and well lighted

TAKE AWAY THE MAINS PLUG (220V), THE METAL PARTS OF THE POWER SUPPLY ARE ON LIVE, EVEN IF THE POWER SWITCH IS OFF, AND THESE ARE LETHAL VOLTAGES.

Take off the top cover.

See the adjustable on the power supply.

Using the permanent marker, trace a mark to be sure to find how it was adjusted.

Verify if the screwdriver is compatible.

Set the voltmeter to voltage measurement, continuous current, at 20 V caliber (for example).
Put a probe on one of the yellow cables of the card cage connector (not on the power supply connector, see picture) and the other on the chassis, for example.

Put the power plug on and put the machine on.

You must see a voltage around +5 V on your voltmeter. If not, something is wrong. Verify where you have plugged the voltmeter and retry.

If yes, shut the machine down and take the power plug off the machine.

STATUS : Machine "OFF" and power plug away.

Put some PCB cleaning product on the adjustable and turn the adjustment around with the screwdriver (to clean the inside of the adjustable).

Put the adjustable completely leftwise (anti clockwise) or more : like a volume potentiometer to the minimum.

Go have a beer for 15 minutes, the time it dries.

Put now the cursor of the adjustable half way from the minimum and the trace you have made with the marker.

Check everything, voltmeter probes in place, cat away, etc...

ADJUSTMENT

Power the Emu. You must read quite a low voltage (around 3 V) and the hard disk doesn't even start.

This is normal

Gently turn the adjustment, clockwise, and the voltage should climb. If not, something is WRONG.
As well, if you get to the trace you have done and the voltage is still low, DO NOT OVERPASS THIS TRACE !!!!

The hard disk should start spinning around 4 - 4,5 V

Increase the adjustment until you read : 5,05 V. Not 5,5V, I say : 5,05 V.

Once you are at it, shut the machine down, do not attempt to perform any bank load or anything else, the machine didn't start accurately whit its normal sequence, so it will be crappy and you may even crash everything, datas and hardware.

Take the screwdriver away, the voltmeter, put the cover and restart your machine.

[rokuez]

List of devices connected to the PSU

Card Cage with the four boards
Hard-drive
3.5 Floppy
Front Panel
2 Fans

I am attempting to calibrate the PSU on both of my EIII racks.

I read through the instruction but I'm still a bit confused.

1.  From the list of devices that are connected to the PSU I assume that I should leave everything connected to the PSU with the exception of the floppy.

The Front Panel should stay connected so the EIII can be powered on.
The Hard-Drive and Fans should be connected to the PSU because of this statement

I suggest you disconnect everything from the power supply, except the fans and/or the hard disk, when you adjust the voltage. Otherwise you migth fry something when the voltage peaks.

The reason why I think I should leave the card cage attached to the PSU is because of this statement when you are taking your first voltage measurement, at least that is what I think you are doing?

Set the voltmeter to voltage measurement, continuous current, at 20 V caliber (for example).
Put a probe on one of the yellow cables of the card cage connector (not on the power supply connector, see picture) and the other on the chassis, for example.

The above statement was confusing for me because I at first read

I used one of the fan connectors to read out the voltages.

To me it seems like in your instructions you are taking a voltage reading from the molex connector that goes to the card cage, but then before this you state that you are using a voltage reading from the molex connector that goes to the fan?  Or are you doing two separate voltage measurements?

I'm unsure what precisely to leave connected to the PSU should it be ?

Card Cage with the four boards
Hard-drive
Front Panel
2 Fans

or

Hard-drive
Front Panel
2 Fans

2. When you take your voltage measurement with the volt meter and you say the following

Put a probe on one of the yellow cables of the card cage connector (not on the power supply connector, see picture) and the other on the chassis, for example.

I haven't taken any voltage readings with a volt meter so excuse my ignorance on the matter.  When you are saying to take a voltage reading by putting a probe on one of the yellow cables, isn't that insulation and it wouldn't yield a voltage value?  Or do you slip the probe along the yellow cable following the path that the yellow insulated wire takes as it goes into the molex connector to get a voltage measurement?  I guess I'm just confused on how to take a voltage measurement from the molex connector that goes to the card cage, if the molex connector is connected to the card cage.  I would figure that I would have to unplug the molex connector from the card cage and then stick the probe into the female side of the molex connector to get a voltage reading?


3.  Let me summarize what I think is a general break down of what is going on to calibrate the PSU .

Unplug the EIII

Open up the EIII and mark a small dot or line to indicate the original position of the PSU pot which adjust the voltage, so that you can use this positioning pointer as a original reference of where the pot was before adjustments are to be made.

Touch the black probe of the volt meter to the EIII chassis, and the red probe to the card cage's molex connector (confused on how this works to get a voltage reading)

Take a voltage reading of the molex connector that goes to the card cage by plugging the power cord back into the EIII and powering it on.

Verifying the volt meter reads + 5 Volts for the card cage molex connector

Turning the machine off and unplugging the EIII. 

Cleaning the adjustable/pot on the PSU.  (why is this done or is this only done if it feels dirty when adjusting the pot with the screwdriver?  Also can  you provide a link for this pcb cleaner kf-f2 or something equivalent I can buy in the USA I googled pcb cleaner kf-f2 and nothing came up from the search results)

After turning the pot all the way to the left and having let it dry from the cleaning, turn the pot so it is halfway between the absolute minimum value and the original reference line/mark made with the sharpie marker.

Plug the power cable back into the EIII, and turn on the EIII making sure to have the volt meter in place (at this point am I taking a reading off of the card cage molex or the fan molex?)

Increase the pot until the voltage is equal to 5.05 volts. (why shouldn't one pass the original reference mark/line if the voltage is still below 5.05 volts?  I'm also assuming that once the EIII is properly calibrated to 5.05 volts the orange wire coming from the PSU will be at 12 volts?)

Turn off machine once 5.05 volts is reached, place the top back on and power up the EIII again.

[rokuez]

nevermind i suppose i found out how to do it.  just put/shoved the probe into the molex connector along with the wire traveling into the molex connector


EIII rack from E-mu HQ voltage = 4.85 volts

First EIII rack E-mu voltage - 4.45

[karlscott]

That's what mine roughly (4.45 volts) get that s*** upto 5.5v and you should be flying!!! (sorry 5,05v)

[rokuez]

That's what mine roughly (4.45 volts) get that s*** upto 5.5v and you should be flying!!!

5.05 according to dvdborn :p

[dr.c]

Hi !

Look at the Molex connectors on both ends (power supply and cards backpannel) they may have bad contacts and may be oxydized by the heat.

Shut the machine down, UNPLUG IT FROM THE MAINS, take off the Molex connectors, put some contact cleaning spay, put the connectors back, anke them away and put them back again a few times.

It should work bette.