Looking for help with an IFR 1200S

[Jay_Diddy_B]

Hi group,
I have an IFR1200s that most of the functions seem to work correctly. One thing that doesn't work is the MODULATION switch which is used to select AM-SSB-FM. I have done some investigations:

1) The switch seems o.k.

2) I have checked the logic circuit that reads the switch and it looks like the uP never reads the switch.

I would like to try new EPROMs. My unit has the 80C31 processor. This means that I need firmware versions 1.4, 1.51 or 1.7.

I currently have 1.7 installed, but I think it might be corrupt.

Later versions 3.00 and above are for 80C188 uP.

Can anybody help me?

Regards,

Jay_Diddy_B

[voltz]

Hi,
If you suspect the EPROM(s) are faulty, try pulling them out and reading them. The chips have their checksum values written on them. Compare values.

The Modulation rotary switch has a common +12 rail to it, check that its there.

See if the Modulation mode can be changed via RS232 control (see manual for command set).

The Modulation switch data is sent to the DVM/IO board and leads to U16 (74HC244) buffer. Make sure switch logic levels reach the pins of that chip. Note RN2 resistor network is used for GND logic low pull down.

Hope that helps.
PS, yes your particular CPU card will only accept versions below 3.0, cpu's were changed after that.

[Jay_Diddy_B]

If you suspect the EPROM(s) are faulty, try pulling them out and reading them. The chips have their checksum values written on them. Compare values.

I thought about. Unfortunately my EPROM doesn't have a checksum on the label. It just says version 1.7.0 maybe a field upgrade?

The Modulation rotary switch has a common +12 rail to it, check that its there.

I did check the switch, I think that the 12V is a mistake on the schematic. I did measure 5V. It seems o.k.

See if the Modulation mode can be changed via RS232 control (see manual for command set).

This is a great idea!! It will take a little time to rig up a cable and computer that 'speaks' RS232 but I do have one. I also have the manuals so I know the commands and format.

Thank you!

Regards,

Jay_Diddy_B

[voltz]

Yes, pretty sure its +5 at the switch, not 12.

Shame the Eproms have no checksums. Its usually a hand written label written in pen.

Is U16 being addressed at all? Pins 1 and 19. If not then could be address bus decoding problems at U13 etc.