Correction - R1101 and the emitter of Q1107 may be sufficiently low impedance that the unblanking signal does not show up well as a voltage signal. Check the collector of Q1107 or farther down the Z a

Try turning the readout off and probing R1101 on the Z axis board with one of your working scopes looking for the unblanking signal. If you don't see the unblanking, try adjusting the grid bias R1261

Colin, Can you not eliminate the mechanically operated switches eg S490 by either removing the single wire from its mating pin or solidly jumpering it to ground so that it is definitely open or defini

My comments about cathode voltage regulation were based on seeing a similar problem (and fixing it) in a much lower bandwidth scope without PDA. I hardly ever use my 7904 at low sweep speeds, but lo a

To my eye each of the shadow peaks and troughs of the sine wave lies on a straight line joining the real peak/trough to the CRT centre, but farther out. This should be very obvious at say 100msec/div.

On my 7B92A, the microswitch near the front panel is connected by a single wire to P911 on the interface board. P911 is to be found on schematic <4>, 'Delaying Sweep', near the top right corner. It is

Is the Y scaling per small division (+/- 5 within the box) or something else? Either way it doesn't look like the -5V is decaying to 0V and is Ch3 inverted? There is a very clear signal on LIMIT which

In one of your earlier posts you said you had seen spiking behaviour on pin 3 of U1624. This will drive larger spikes from the output pin via Q1614 and C1602 into the protection circuitry and can very

If you really have a short circuit from -5V to ground (eg a failed tantalum capacitor) you don't need to power up the scope, it should be obvious with a resistance measurement. Schematic <17> shows th

If the readout displays are still in the correct horizontal position then the fault is probably before the horizontal amplifier. Can't be more precise without knowing what mainframe is in use. Roger

Following on from Adrian's point, the 7B92A manual shows all the decoupling capacitors are preceded by the components labelled 'LRnnn' which are inductors wound on the body of a carbon resistor of may

When it dies does it bring down the other plugins? If they continue to work it is unlikely to be a tantalum cap across a power rail. Once tantalum caps fail they usually stay short circuit but I suppo

Glen, The ripple looks ok. The manual I am using is the 108MB file on the 475 page at w140.com/tekwiki. If you locate schematic <12> power supply, the previous schematic shows power distribution inclu

Posts crossed again! It sounds very much like you have an excessive current load on the +110V line. If you look at the power distribution diagram, schematic <11>, then the horizontal amplifier would b

I guess it is obvious out last posts crossed and also I seem to have a different board revision from you.(serial 708886, Holland, no Q1497). For some reason the series regulator Q1496 (on my schematic

OK, I understand the +105/+160V measurement problem! There is some screen printing on the 475 PCB near Q1490 that says '+105/160V' and it is printed on one of the PCB traces but that trace does NOT co

Hi, I am struggling to understand your measurements. The +105/160 is the unregulated supply to Q1496 which regulates the +110V line, so it is hard to understand why the output voltage from the series

Peter, According to the manuals on Tekwki both 2215A and 2230 use the same CRT part number 154-0861-00. It is common to a few other scopes in the 22xx range but beware that 2215 and 2215A are not quit

If you have broken glass you wouldn't expect to see any beam at all. It is quite easy to pull the CRT out, see the manual. Try swapping the tube with your 2213A but not swapping the shield, then swap

You could try swapping the A and B sweep generator hybrids U700 and U900, they are identical part numbers. There should be some recommendations here about cleaning the contacts (carefully!) if the pre