Minor issue after installing new power supply

[ahaigh01]

I installed the MeanWell T60-C power supply in My EII along with an HxC.  It's been working very well.  One thing that has changed is when I first turn on the EII there is a new noise (not the typical "pop").  It is a low tone, like a sine wave, that starts very low and begins to rise in pitch.  Then it stops after a couple seconds when the boot up starts.  I am wondering what is causing it, now that there is the new power supply installed.  Or maybe the HxC is causing it, but I am guessing it is the PSU.  Anyone know?

Thanks

[Gregory]

That's interesting. I have recently changed the PSU as well (the new PSU is not a Meanwell though) and everything seemed to work great. However, after a couple of weeks I've got exactly the same symptom you're describing.

I was able to fix it by replacing a circuit in IC86 socket on the Digital Board.

Actually, I replaced several curcuits on the Digital Board that day (I still have a replacements list if you're interested), but the problem only disappeared after replacing the circuit in IC86. Perhaps you should try to replace this circuit as well - it is inexpensive anyway..

[ahaigh01]

Hey Gregory,

How did you happen to know it was IC86 - trial and error?  I have some replacement ICs so I tried one.  Although it fits the socket it is the wrong type and the boot up stops.  Thanks for your input.

[ahaigh01]

Gregory - I am interested in the replacements list - thanks

[Gregory]

Please, only replace the circuits of the same type. Otherwise you are at risk to damage your EII. The circuit in the Digital Board socket IC86 is 74LS138.

I was told that this symptom most probably caused by something dealing with reset process. Since I'm not a tech, I decided to just replace several circuits "in question" - and it worked.

[Gregory]

Gregory - I am interested in the replacements list - thanks

Sure, I have sent you the list.

[ahaigh01]

Good news - replacing that IC fixed the problem!  Thanks for the great info.

[Gregory]

I'm glad it fixed the problem!

And I wonder if it's a coincident that this particular circuit failed in two different Emulators after replacing the Power Supplies..

[ahaigh01]

It could be.  I bought 10 of those ICs so I can replace it again if needed, but I hope it doesn't fail again.

[alka]

Old post, I know, but I wanted to add on to the notes here in case anyone else experiences this issue. Replacing IC86 did not solve the issue for me. I have had this issue twice before - one fix was to swap the 2 Z80 CPUs. The other was to replace the MC3400P and/or the AD7524 on the Output board.