Lexicon 224 problem (errors E34 and E91)

[psych60s]

Hello guys

I have a 224 in which I replaced few capacitors on the PSU card. When I power it up the remote displays two error codes, E34 OR E91, the last most of the time. I know what these codes mean, and that LEDs on the remote indicate more precisely what is faulty.
Strangely, each time there are different LEDs lit on the remote.
When I reset the unit (allowing it to run self-diagnostics again) it boots without error. I've also noticed that turning on the unit immediately after turning it off makes it start without problem.

Any idea? One of the caps I replaced is the big 47000 uF filter cap, but not with the exact same part, I've found another cap with the same value. I've never experienced such a thing but is it possible that the capacitor isn't acting "fast" enough, so the 5V power rail isn't well smoothed, so when the self-diagnostics start some chips are "seen" as not working?

I have checked with a DMM all supply rails, everything is ok, so it shouldn't be a PSU problem.

Thanks guys

 

[radardoug]

The 224 is prone to errors due to the cheap sockets that Lexicon used. That was why on the 480L they soldered most chips in!
I have found that replacing sockets with good turned pin ones is the answer. Also, look for ics with blackened pins, they are likely to be the problem ones.
Take out the logic cards one by one, move the ics in the sockets. Do it in batches of half a dozen ics. Put the card back in between batches and fire it up. If your errors have gone then the last batch was the dodgy sockets.
Or replace them all if you are keen!
Start with the DMEM card, the 90 errors can be caused by ics on this card.

 

[psych60s]

Yes I know old Lexicon such as 200 and 224 are quite tricky because of the IC sockets. I've already checked that all ICs were correctly inserted in their sockets, and I've looked for blackened pins, cleaning a few.

The errors don't show up if the unit is reset, I doubt that it is faulty socket as diagnostics would fail too when using the reset function, but I'll have a closer look.

I've also checked if these error codes were of the "show up only once and then ignore the error" kind, but if I remove the T&C card for example, the E34 and E91 and many others are displayed even if I reset the unit.  So in my case, if the errors disappeared when I reset the 224, that means the unit is working! And as I said, the remote LEDs sequence usually help you to locate the faulty IC but here there is a new sequence each time I power it up...

 

[radardoug]

No, it still could be a socket problem. I had a unit giving the E92 error, tracked it down to 3 ics on the DMEM card, changed the sockets and its been good ever since. Because there are more than 50 ics per board its a long slow trek!

 

[psych60s]

According to the service manual, E91 may mean that DMEM or T&C is bad. E34 refers to input port no. 4 error and results from "tests performed on the T&C through the ports".

EDIT : Okay I didn't see that part in the manual saying that some ports used to test the T&C board are on the DMEM. I've unplugged ARU & FPC boards as recommended in the manual, and quite logically got some errors. Among them was E91.

I'm not an expert in decoding and control bus theory, but the problem is probably on DMEM, isn't it?

 

[radardoug]

Do you have the NVS card? What software version are you running?

 

[psych60s]

This is V.4.3. I got the NVS card, but the E91 error still shows up with ou without the card plugged, I've assumed that it was not a problem to leave it in.

E91 error seems to show up with this particular LEDs sequence :
PROGRAM LEDs: 1, 2, 6, 8
REGISTER LEDs: 3, 4, 5, 8