Faulty R2400A

[Gordonjcp]

Hi all,
During a clearout I've just inherited a Motorola R2400A which isn't quite working. After plugging the front panel back in and checking the power supply voltages, I have the following:

PSU voltages OK going by the labels on the board, with +12V possibly a little high at 13.4V
Scope lights up and the spot can be positioned with the X and Y controls, but has no sweep
RX squelch control works in as far as the scope trace jiggles up and down when you turn the squelch down, and the red LED comes on beside the squelch/volume control
Occasionally the 1kHz tone generator works
Occasionally the buttons seem to work in that the unit beeps when they're pressed - but only if the 16-pin ribbon cable for the LCD is disconnected.
The LCDs remain blank no matter what
The lithium battery is reading about 2.9V

Anyone got any suggestions on where to start? Also, is the service manual available anywhere, either online or from Motorola?

Gordon MM0YEQ

[DJP126]

The lithium battery is okay @ 2.9 V (it's a 3 V battery). Since you checked the LVPS voltages, the next step is to check the master oscillator (located behind the scope module). You should get a 10 MHz signal out.

[Gordonjcp]

Thanks for replying.

the next step is to check the master oscillator (located behind the scope module). You should get a 10 MHz signal out.

Okay, about 800mV peak to peak on both sockets, a nice clean 10MHz sinewave. Does that sound about right?

Gordon MM0YEQ

[radio_05]

It sounds like the same fault I'm having with my 2200A. In my case, I had a spare FPI board, and found it was the cause of the failure. I replaced the module with another, and display now works well. The pots at the top wouldn't align on my problem unit, I may try alignment again, or sent it out for Module repair.

This is from Auburn:

On the front panel interface from left to right there are three adjustable pots. The first is R80 which is the 8VDC adjust. Turn unit on. Remember where the orginal setting is and adjust until front panel comes on. If this adjustment doesn't work, go to the center pot (R66) do the same. This pot is the "Mod Display Sel.". If this pot doesn't work, go to the pot on the right (R9) and do the same. This pot is the "Scope Vert. Input".


This board is very reliable and normally causes no problems except for these three adjustments.