Codan 85xx Phantom Problems & Regulator Faults

Motherboard and Chassis Supply Voltages:-

Main "B" rail regulator IC1 10V  (+/-0.2V)

"C" & "B" rail voltage in RX, &  0V in TX

"D" 0V in RX, "B" voltage in TX

Main 5V regulator IC2 5V  (+/-0.4V)

RF Mixer Dual Synthesizer Board:-

+5V supply IC4 5V  (+/-0.4V)

+26V supply TP7 26V  (+/-1V)

+9V supply V1 Emitter 9V  (+/-0.25V)

If your radio is failing to lock across the band, check the voltage on Z4 on the upper microprocessor board.

The zenerdiode should give 5.8 to 6.2V, if anything other then this replace the zenerdiode with equivalent (400mW 6.2V).

This is the reset control line to the CPU on power up, this  forces the PLL it into an unlocked state.

The absolute most common problem is the IC1 10volt regulator. A factory genuine is a biscuity brown regulator on a

thin white substrate. As above the regulator has a narrow window of operation, in circuit under load voltage will fluctuate

slightly causing erroneous errors that sometimes cant be explained. NOW "if" your regulator looks like the one in the 

picture, you have 2 options. Firstly: a simple drop of superglue and 20 seconds pressure holding it back into place.

OR Secondly: fixing it properly and permanently by replacing the regulator, this will mean removing the opposite board

giving access to resolder, and this will give you years more reliable operation.

The reason for replacing is thermal runaway might have damaged the regulator because of insufficient heatsinking when the

substrate comes away from the tab heatsink and may continue to cause problems.

More problems or short stories as i remember them....!