[DMcMahon]

Tried to clean up Board 3 in-situ but too difficult, so removed it completely. The manual says the wires and the terminal posts on the board are identified but they are not on this one.

Cleaned the board up, really messy and sticky. First thing noticed that the board part number of 14009003 is different from the manual documentation which lists it as 14009103.

Also could see that the board has had some attention before with soldering being disturbed. One of the two K8/50 HV Selenium rectifier diodes has been replaced by an ITT TV20-16K80V dated 1972. Could not get any resistance or diode readings using normal methods for both of the HV rectifier diodes.

Resistor R302 (10k) is a fairly modern looking resistor so has been replaced at some stage. It is on the output of the -780 volt voltage Tripler for use on the CRT electrodes.

Basically the board is the same as the documentation but there are technical differences. The schematic and parts list show a CRT Sense Balance potentiometer RV 304 but it is not shown in the Board Component Location drawing. This pot is not fitted but there are two 24k fixed resistors in its place. These resistors look fairly modern. Also resistors R309 & R315 are shown as 390k on the schematic and 330k on the parts list but 150k resistors are fitted.

The replacement HV rectifier diode TV20-16K80V has one broken leg, looks like it may be repairable by soldering.

The three EHT capacitors C306/C312/C313 (0.07uF, 2kV) are in a right mess with very sticky wax. One (C306) is totally shot and does not measure any capacitance just measures 200 ohms.

C312 measures 114nF and 0.8 ohm ESR and 50Mohm insulation resistance at 1,000V
C313 measures 210nF and 2.1 ohm ESR and 4Mohm insulation resistance at 1,000V

So at least C306 needs replacing and probably C313. Would like to replace them all, may not be easy to find suitable replacements.

Resistors R307 & R314 (47k) are open circuit, these feed the Focus pots so would explain why Focus is not working.

Resistor R312 (27K, 2 watt) is open circuit, this connects the Set BA (Beam alignment), the Set I.P.S. (Inter Plate Shield) & the Astig potentiometers to ground.

Resistor R304 is also open circuit, this one is a bit of a mystery. It is not shown on the schematic and on the part list is listed as "Not fitted" with * note that "Fitted on early models only". Unlike some of the other "Not fitted" components references this one does not state what the value was on early units. It is completely burnt out with no sign of colour codes. One side connects to terminal post # 15, which on the drawing is cross hatched which also means "Fitted only on early models".

I will have to trace the wire that connects to post 15 to see what it connects to and then try and work out if a resistor is required (and what value).

Yet to test the 10 x 8uF 450 volt capacitors on the board.