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Chris55000 · 4th Apr 2019, 12:28 am

Hi!

This type of fault might occur if one of the vertical final amplifier transistors, or even the Y deflector plate connections to the CRT itself, are open–circuited!

A large piece of metal electrode like an unconnected CRT deflector–plate will tend to collect stray charges on account of it's being in contact with the remaining plate via the beam of electrons on it's way to the screen, and will also be very liable to being affected by the static charges that collect on the CRT envelope from simply rubbing it!

The way to deal with type of fault is to trace the leads back from the CRT base–socket to the vertical amplifier – to find out which is the vertical amp, place the positive probe of your DVM, on 1000V DC., at the main pcb end of the connector to the CRT base, negative to chassis, and rotate the "Y Shift" (vertical double – ended arrow) control – if you get no change in voltage, either you're on the horizontal (X) amplifier or the Y amp is faulty!

There will always be two fairly large w.w. or carbon resistors connected near to the deflection transistors for the CRT plates, and also the CRT connections, and this is how you locate them!

Unfortunately I have neither a Unilab scope or Manual, but I think the Unilab 031.602 is probably an updated version of the 032.601, which you can get a diagram on this Forum for – download and print the 032.601 diagram off and compare the CRT base on the diagram with the one in your '602 – almost certainly the CRT will be the same type!

Chris Williams

4th Apr 2019, 12:28 am	#2
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: Unilab 032.602 oscilloscope Hi! This type of fault might occur if one of the vertical final amplifier transistors, or even the Y deflector plate connections to the CRT itself, are open–circuited! A large piece of metal electrode like an unconnected CRT deflector–plate will tend to collect stray charges on account of it's being in contact with the remaining plate via the beam of electrons on it's way to the screen, and will also be very liable to being affected by the static charges that collect on the CRT envelope from simply rubbing it! The way to deal with type of fault is to trace the leads back from the CRT base–socket to the vertical amplifier – to find out which is the vertical amp, place the positive probe of your DVM, on 1000V DC., at the main pcb end of the connector to the CRT base, negative to chassis, and rotate the "Y Shift" (vertical double – ended arrow) control – if you get no change in voltage, either you're on the horizontal (X) amplifier or the Y amp is faulty! There will always be two fairly large w.w. or carbon resistors connected near to the deflection transistors for the CRT plates, and also the CRT connections, and this is how you locate them! Unfortunately I have neither a Unilab scope or Manual, but I think the Unilab 031.602 is probably an updated version of the 032.601, which you can get a diagram on this Forum for – download and print the 032.601 diagram off and compare the CRT base on the diagram with the one in your '602 – almost certainly the CRT will be the same type! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!