Help - trying to restore C1PMF

[lowrybt1]

After 30 years, I'm trying to get my C1PMF up and running and I am hoping members of the forum might help with some troubleshooting. Here's the scoop:

* A visual inspection of the 600 Rev B and 610 board finds no gross defects or broken traces or missing IC's. Cables are firmly seated. Power connections between the transformer and 600 board are intact.
* RCA video and cassette wiring conforms to standard and the wiring/solder connections between the 600 board and RCA ports looks good.
* When powered on, the fan activates.
* There is no detectable video image. The TV screen is blank.

I have the SAMS C1P manual and will begin testing various key points using a scope in the next day or two. The diagnostic flow I'm going to follow is something like this:

* What output levels are being produced by the transformer?
* Check waveforms at the X1 crystal, 02 Clock, J6 video jack?
* Conduct a much closer inspection of the 600 board, checking the condition of each socket, IC and other components

One question I have is this: is it possible the hookup to my HDTV is not appropriate? What I've done simply is run a composite cable between the RCA video out connector on the C1P to the RCA composite video port on my HDTV. I have made certain that the HDTV is looking at the composite input for signal. The TV indicates no signal when the C1P is powered on. Am I missing something in terms of the connection between the C1P and HDTV?

Finally, the disk drive is in poor shape. The drive motor is not turning the spindle/head assembly which may have something to do with belt tension (if I'm lucky). Does anyone know of a source for old MPI B51 parts or repairs?? Need to figure out if the drive's logic\controller is working. When I power on the 600\610 board, the drive's LED activity light goes solid red. When power is removed from the 600\610, the drive light goes out. A best, some indication that some kind of signal is reaching the drive's logic board from the 610. But if the drive cannot be refurbished, has anyone created a simple way to interface the 610 to a more conventional 5.25 drive?

This is fun!

Would appreciate any and all comments.

Tom

[nama]

Hi,
This is what I'd do, and again, there are people here far more qualified to answer than I am.
Firstly. I'd put the drive to one side and concentrate on getting some kind of image, on some kind of screen. The drive can wait for later.

Firstly check the output of the PSU. +5V.
Then I'd test for 5V in various places on the board itself.
Then I'd test to see what state the CPU is in. Are the busses pulsing? What happens after pressing BREAK?

Just the basic stuff to find out what state the machine is in.

I would certainly suspect the modern TV. I have various OSI machines, and some work ok with newer equipment, and some don't at all. On the ones that don't, I get no picture, similar to you.

Phil

[Klyball]

Nama is correct about leaving the drive alone, go one more step and unplug the 610.

Most monitors with comp in should work, but not all can sync with the video rate.

reseat all socketed chips, and watch out for bad ram.

several members have interfaces to modern drive's like the one below

the red light on drive is good
there is couple of MPI B-92 drives I have been eyeing for ages on ebay each one would give 80 tracks x 2 sides period correct 1 mpi-b92= 4 x mpi b-51's.
also the data separator on your drive should plug right in but would need a jumper or cut trace (need to check schematic for drive)
I use a old full height toshibia 3 1/2 that's mid to late 80's

good luck!! keep us posted

[Jeff]

This might sound silly, but I recently set up my C4P and for at least 15 minutes it had me fooled because I plugged the monitor into the wrong RCA jack.

/Jeff

[lowrybt1]

Thanks all for the guidance. I've checked all the RCA ports and no joy. Testing with an oscilloscope shows no video signal being generated. I'll be checking for waveforms all day tomorrow.

Here's one follow-up question.... I'd like to replace the old PSU with a modern switched power supply. Does anyone know what specs would be best? Obviously 5V/3A out but what wattage?

Tom

[Klyball]

the 600 and 610 should have 3A each at least so 5v 10A would be best that's 50w

[MK14HAK]

U70 7403 commonly faulty.

Nice DataSep Grant!

[nama]

U70 7403 commonly faulty.

Nice DataSep Grant!

Very.

[Jeff]

I replaced two of the OSI power supplies in my C4P with one of these:
http://www.ebay.ca/itm/350851562926?ssP ... 1439.l2649

I used one of these to power my Superboard II:
http://www.ebay.ca/itm/5V-5A-25W-DC-Uni ... 1044037764

Cheers
/Jeff

[dave]

Hi Tom,

There are some good suggestions already. I assume you have the OSI 600 schematics on hand. I think the OSI schematics are easier to follow than the SAMS drawings.

With no video out at all, you should start with the main oscillator circuit and check that out. Start with pin 1 of U29, then pin 2 of U30, input to the video counter chain. This should be near 4 MHz (~3.932 MHz). That will confirm you have a clock. Check out the output of the video shift register, U42 pin 9. Assuming the clock is good and SR output is bad, start following the timing chain (U30,U59,U60,U61), and the character generator. If there is data at the SR output, look at the Hsync and Vsync outputs.

Since video doesn't require a working CPU and since it's a nice window onto system operation once it works, I'd get the video working first.

Good luck,

Dave