Impression II Boot Trouble

I bet you  a beer it's the power supply.

I bet you  a beer it's the power supply.

I would bet the same thing.  Carefully measure the voltages coming out of the supply.  You should get a good +5, +12 and - 12.  In fact, if the voltages are a little high, that would be good.  If they are low, there's a pot on the power supply to bring this up.  If I remember correctly, you turn the pot counter clockwise to bring up the voltage.  If the voltage is low, it may not boot or run the drive.

While you're in there, check the pins on the harness on the low voltage side of the power supply.  If the pins are burnt or brown, the harness needs to be replaced as you are losing power there.  If they are silver or tin in color, they are ok.

Hope this helps.  Let us know what you find.  Bruce has access to good beer.

David

Voltage is a no joy.  The psu fan seems much happier though (it cranked right up)

Starting Values:  4.97; -11.81; 11.95

Ending Values: 5.30; -11.93; 12.1;

I turned the pot back down to 5.10 volts when it didn't boot after being at 5.3 v

The drive is clicking; but no spin on the fdd.  If I unplug it; will the boot bypass the drive? (Don't know if the drive may be bad?)

It's so frustrating because  there are so many indicator lights blinking and on; looks like it's working just fine, but it's stalled somewhere in the boot process.

 It would probably be helpful if you could get a hold of a floppy drive and try and reload software. If you can get the floppy drive working, it should be possible to run some more diagnostics.

 With the console unplugged, disconnect each cable and plug it back in individually, then try booting up. This will clear any corrosion off the connectors that might be causing a voltage drop. And don't forget the one that plugs into the power supply.

 Also reseat the DRAM memory stick if you haven't already. Does the corrosion you see look white and powdery, or light green/blue? If it looks white, it's probably just some detergent from when the PCB was made. If the board isn't corroded, you probably just have a bad oscillator clock, but you will need an oscilloscope to see which one is bad.

 You can always just send it in for repair and request an estimate before any work is done ;-) so you could get it checked out, but you would be on the hook for an hour of labor and shipping.

 And don't worry about the blinking LEDs, they are mostly there for RnD purposes and they aren't super useful for problems like this.

 Just stay calm and resist the urge to smash it to bits and toss it  =D

I have a FDD, and it is working.  I pulled the main board and tried it in another Impression light board at another theatre.  Did the exact same thing, so I'm pretty sure that the problem is on the motherboard.

The floppy is now clicking when I boot, so I may be able to get something going there. what are these diagnostics you speak of?

If I had to describe the problem now, I'd say this.  It's like the board software is crashing.  I was wondering if there's a way to wipe the SRAM and force the boot loader to reload everything for the board. (the 4-5-6) keys down on load seem to do nothing

The other thing I was wondering about was if that is the checksum printed on the boot rom.  I could throw the chip in to a programmer and see if the boot rom check sum is bad.  The chip i have is EX2X-V2.0/SBOOT U47/ETC- 65FB

I know about the estimate, but with the budget cuts we have had, I'm having trouble getting them to spend 100.00 to buy a usb dmx dongle so i have a backup in case the backup board goes down :(  a round trip shipping and hour of labor would make them howl.  Would you need the whole light board or could I just send the CPU assembly?  That might make shipping more reasonable.

Thanks for all your help in tracking this down.

 Well you were close, the buttons are 7-8-9 to clear memory, but SRAM doesn't usually cause a console to hang up like this. If the floppy drive is a different brand, double check that your pin 1 lines up with the triangle marker on the mother board.

 The boot EPROM that you're talking about(on top of the small stack?) is pretty reliable, but it can be erased by UV light if the label is torn or missing. I guess it wouldn't hurt to run the check sum. I didn't know anybody still had equipment for that kind of stuff  =o

 You can try to reseat the floppy drive controller chip(U28? depending on version) If you have a tool to remove it from the square socket. Otherwise it is really easy to crack that kind of socket by just prying on a corner.

 If you send in just that board, yes it can be tested, but if there aren't problems found with it then you're still in the dark on what the actual problem is when you get it back.

Yeah I have a bunch of stuff around.  Love working on old Arcade games, and enjoy restoring old Pac Man games.

Unfortunately, No Joy.  I think the problem may be the FDD controller.  My O-scope showed some activity on all the main crystals, but I can't scope all of them because it's just a 10 MHz one.  I'm thinking that it might be somewhere around the FDD or U23/U24 the custom PAL Chip.  I can't get the diagnostics to load from the FDD, so there is something going on with the bus over to those chips.

Could a newer FDD cause any damage to the board? (I don't see how) But we had to replace the FDD with a newer one when the old motor crapped out about two years ago.

Second; do I need to go through a dealer to shoot the CPU to you, or can I send it direct for repair/quote? and what are the rates?  I know when I'm going outside what I can do, and there are enough PAL chips on the board that without the code and programmer, I'm not going to be able to continue to troubleshoot.

A Few more follow up questions here If you guys are still following.

The Checksum on the chip is wrong.  I get a checksum of OC30 instead of 65FB.  Secondly, The EEPROM in U78 seems to be toasted.  (My reader is throwing chip not recgonized/inserted wrong errors while the other three come up just fine.

Any thoughts on worth repair, or is it time for the dumpster for this bad boy?

 Please give Tech Support a call (608-831-4116) to set up the shipping details, and Ill see what I can dig up for chips. I might have to dust off the old DOS chip programmer =) Is your board 4031B5001 Rev A?

 What was the location of the first chip you were referring too, U69? Also, U78 is actually a counter(74HCT40103), if I'm looking at the correct revision. You should be able to see a 4MHz signal on pin 1, and pins 9 and 14 are used by PAL U71 and GAL U72.

 It looks like you just got a mislabeled EPROM. The Impression 2 board uses a different EPROM with a checksum of 0C30, so that is correct. The Expression 2 board has an EPROM with a checksum of 65FB. They use different firmware boot chips and face panel chips. So I'm guessing you might want to look into the corrosion on the board. Or just toss it, and get a nice shiny new element?