Phoenix Microsystem Model 1500A COMIT with RS232 Service manual or Schematic Needed please

[inotarobot]

Greeting all. I have a need to do some RS232 DB9 and DB25 port testing on one of my Motorola 68xxx systems.
So I have a few easy choices using more modern hardware.

However during my recent cleaning up as part of my planned downsizing I got out this Phoenix Microsystem Model 1500A COMIT.

Does anyone have a user manual and service manual with schematic please ? I cannot locate one online

Since I did not have either the manual nor the original ac power pack; and since the power input on case only says AC but no VOLTAGE value ( expect it to be somewhere between 12vac and 30vac via transformer isolated supply). I choose to open case and look for info on the PCB.

Sadly no details.

So I chose after taking heaps of photos and marking a few chips I ten withdrew all ICs on the base motherboard.

I then fed 13vac and got the following voltages for +5vdc I got +5.14dc.

I assume other voltages needed being +12vdc and -12vdc and maybe -5vc but I cannot read these values. It late and bed calls hense why I am posting this request in case some here has circuit info.

regards
David

 

[inotarobot]

Well quick update. As you can see from the last picture I removed all IC's prior to putting any low voltage AC power to the main board.

The only transformer that I had easily available and prewired gave me 13.42vAC on its secondary.

Doing an initial read of the power rails for most chips I am getting +5.05vdc on all easily measurable IC sockets. ie about 90% of them. The remaining ones I just need to use finer meter probe ends on.

So NOW for the Tricky bit.

Where are my +12vdc and -12vdc coming from that are mentioned on front panel of the Interface module 1500-250 ? There is also a mention of two other voltages EV1 and EV2 but what value are these meant to be?

Looking a little further on the main PCB near a DB25 that is marker as RS232 Control port is an IC u29. Its a LT1039 16 pin chip being RS232 Driver/Receiver with Shutdown.

Pin outs show pin 18 +5v dc power with pin 10 as the gnd for this 5v supply.

Further Pin 1 is +12vDC and pin8 is -12vDC.

So again i tried putting my 13.42vac on input .. Got +5.05dc on pin 18 and pin 9 HOWEVER on pin 1 I read +16.36vdc and on pin 8 i measured -13.72vdc.

At this point I hooked up my ac transformer to my mains voltage Variac and set it to give me 10vac on output of my small isolation transformer. After taking readings increased variac to give 1vac increments up.

AC input............+5vdc rail......+12vdc rail......-12vdc rail
9.98..................... +5.05............+12.1............. -9.68
11.01.....................+5.05............+13.64...........-11.14
12.01.....................+5.05............+15.0.............-12.04
13.02.....................+5.06............+16.36...........-13.72

The +5vdc rail is regulated and as a trimmer to adj.

But it appears the +/-12dc rails dont. They appear to be at the mercy of the input ac fluctuations.

I simply don't have the time to reverse engineer this power supply design to sort out this power issue. So for now this unit I will box back up and get another
solution to my need.

maybe someone will come up with a service manual or cct for this unit and an operating manual as well? One can hope