Hugo,
Check all the 151-0367-00 transistors in your scope. These usually are leaky from C to E. It will test as a diode. Any of these 0367 types that have the round leads with black leads (tarnish) will be leaky and should be automatically replaced. The 465, 475 and 485 series have these in them along with some of the 7000 series plug-ins. The leakage can cause problems. Use KSP10BU. These have a BEC pinout. If you see ones that are leaky after checking a few, then the rest will be leaky and will need replacing.
Davis is right about the 1000mfd electrolytic. I used a Nichicon UHE in mine, 1000mfd 16V. These should be changed no matter the age.
In my 465, and others of the series, I raised the wattage of some resistors.
Check the 9.1V zener, VR1522. It is most likely open. Use BZX85B9V1 to replace it. The 6190 ohm resistor to this zener should be increased to 2W. A 6200 ohm will work. I put in a 1% type in mine. I have not seen any 9V zeners that are original still be good. This is the only voltage zener I have found that is always bad.
If you trace is bright when turned on and dims over 10-20 minutes without adjusting the intensity, the 22meg 1/4W carbon in the high voltage section has become too high in resistance. I replace these in the circuit to prevent this problem. This resistor is R1486. Use Vishay VR37 series to replace this resistor. These are 1/2W 1% types. This resistor and the zener are ones I keep in stock. If any of the d-c restorer diodes go bad, the trace will be too bright with no control. The replacement for those is a 1N4937.
If you find bad tantalums, raise the voltage of the new ones, e.g. 20V to 25V, 15V to 20/25V, etc.. You can use low ESR electrolytics like Nichicon ULD 47mfd 25V. The additional capacitance is fine. The raising of the value is for decoupling circuits, not any timing circuits.
If you want/need to replace any of the bridge rectifiers that are 1.5A, use 4A types. The original bridges can fail. The original voltage is 200V. If you have or want a higher voltage, fine. The current capacity is the main thing.
If you want the fan speed to increase to move more air, put a 10,000-13,000 ohm resistor in parallel with the thermistor on the fan board. The lower resistance is the higher speed.
The 1200mfd in the power supply, I put in 2200mfd because I wanted the long life, low ESR and high temperature types. That higher value was the closest available and the additional capacitance did not hurt anything. Recapping yours might make things start working. At the age it is, new caps are a good idea to necessary.
The cleaning contacts is something advised by several on this thread that is always advised. I know I have a list of things to check/replace/can happen. If you have any of these during or after operation, it will help you find the problem(s).
Mark
