Sequential circuits samplers

Sounds like the main CPU is dead.





On Monday, 6 January 2014, 19:08, "wgpena@..." <wgpena@...> wrote:
 
  
Hello everyone,

  I got hold of a p2000 with 512KB of RAM, but i get no sound out of it. When I turn it on with no floppy in the drive I just get a dash/hyphen on the right most part of the display. When I boot with a floppy it appears to load fine because the drive gets accessed and the first 5 patch lights turn on from left right but i still dont get sound. The only disk that I have is the a restored image of the disk in the file section of this user group. I did test to see if the midi out is sending out signal and it is. When i disconnect the front panel cable the p2000 doesnt access the drive and it appears not to boot up at all, is this correct?

How can I check it the issue is with the front panel multiplexer/control chips? I do have a multimeter and oscilloscope but am not an expert using it?

Thanks is advance!

:-) Ignore what I just said. I've only just woken up :-)





On Monday, 6 January 2014, 19:08, "wgpena@..." <wgpena@...> wrote:
 
  
Hello everyone,

  I got hold of a p2000 with 512KB of RAM, but i get no sound out of it. When I turn it on with no floppy in the drive I just get a dash/hyphen on the right most part of the display. When I boot with a floppy it appears to load fine because the drive gets accessed and the first 5 patch lights turn on from left right but i still dont get sound. The only disk that I have is the a restored image of the disk in the file section of this user group. I did test to see if the midi out is sending out signal and it is. When i disconnect the front panel cable the p2000 doesnt access the drive and it appears not to boot up at all, is this correct?

How can I check it the issue is with the front panel multiplexer/control chips? I do have a multimeter and oscilloscope but am not an expert using it?

Thanks is advance!

So you have disconnected the floppy drive cable and powered up without the floppy connected?
(take a photo first because it is very easy to plug the floppy cable in the wrong way round and you may forget which way round it is)







On Monday, 6 January 2014, 19:08, "wgpena@..." <wgpena@yahoo.com> wrote:
 
  
Hello everyone,

  I got hold of a p2000 with 512KB of RAM, but i get no sound out of it. When I turn it on with no floppy in the drive I just get a dash/hyphen on the right most part of the display. When I boot with a floppy it appears to load fine because the drive gets accessed and the first 5 patch lights turn on from left right but i still dont get sound. The only disk that I have is the a restored image of the disk in the file section of this user group. I did test to see if the midi out is sending out signal and it is. When i disconnect the front panel cable the p2000 doesnt access the drive and it appears not to boot up at all, is this correct?

How can I check it the issue is with the front panel multiplexer/control chips? I do have a multimeter and oscilloscope but am not an expert using it?

Thanks is advance!

Did you buy this broken?

Is the OS 3.0 or 4.3b?

Make sure all the voltages are good. It's easy to test this because the jumper wires between the two circuit boards have all this labelled.

Then make sure that the ribbon cable that goes to front panel board is good. Pin 1 needs to line up with pin 1. It's quite easy to plug the cable in wrong, also they seem to break a lot so check continuity of the ribbon cable with your multimeter to make sure all the wires inside are connected between the connectors.

Check for cracks in the solder joints for the front panel switches and cracks in the pcb, check for continuity of the switches to make sure that they actually work when you press them.

I would check that the main CPU is all working and that you can see things happening on nearly all the pins especially the interrupts (refer to the service manual, I think it's uploaded to the group somewhere).

Then the memory chips, then the eprom. Make sure you read the service manual as you may spot something that you want to check first yourself.





On Thursday, 9 January 2014, 3:21, "wgpena@..." <wgpena@yahoo.com> wrote:
 
  
Yes, I tried it without the floppy drive plugged in and it does the same thing. I will take a picture, but It seems to load of the floppy ok. But no sound or response from the front panel controls.

I'm not 100% certain but I think it can sometimes be very difficult to measure the voltage of a transformer. First of all the voltage of the transformer will (I think) go down while it's under load and connected in a circuit and also that there is some small inductance inside because they are coils (which can work like or is like capacitance?) You can get false readings because of this or these combinations of factors?

I learn new things all the time and am only really a beginner myself anyway. As long as you are getting the correct voltages out of the regulators then it most likely means that your transformer is fine.

(Sometimes a logic probe can simplify testing. An oscilloscope quite often confuses me because I'm not looking in the correct place (timebase/voltage etc) to find the things I need and if you are not referencing it all to the correct GND then you will probably get nothing in the first place.

A logic probe can give a simple yes/no to something working like an individual IC pin especially on older digital electronics like that used in the P2K. I used mine to find a non operating interrupt on the main CPU. They are not usually expensive and you just hook it up to GND and +5v and you're off.)





On Friday, 10 January 2014, 23:22, "wgpena@yahoo.com" <wgpena@...> wrote:
 
  
I tested the voltages at the regulators and at the power cables that go from the CPU board to the Analog/Audio board and they are ok, but the voltages coming out of the transformer are low. If I remember correctly the service manual says 16VCT and 31VCT but i get like 9 V and 19V? Is that normal?

  I'll check the continuity on the ribbon cable that goes to the front panel, i know its connected correctly because the display does show stuff sometime when i press the sample button or the execute but it works randomly. Sometimes it react to key presses but most of the time it doesn't.
  Ill take my scope out of storage and see if I can test the clock and other things, but I'm not and expert in repairing music instruments. I got the scope to do simple stuff for school.

thanks