Re: RM15/515 Vertical Problem


ditter2
 

Sorry about the incorrect reply - there are two troubleshooting threads currently open - a 532 with no sweep, and the 515 vertical. I am contributing to both and replied to this one incorrectly)
Steve

--- In TekScopes@..., "Steve" <ditter2@...> wrote:

--- In TekScopes@..., "Tom Miller" <tmiller11147@> wrote:

I would use an ohmmeter to check all the resistors in the vertical amp stages. Just measure them and see if they match the value on the resistors. If for example you measure 12 K across a 10 k resistor, you know it is bad. If it measures 5 k, you need to consider how it is used in the circuit. Most of the time, the carbon comp resistors go high in value, even open circuit.

The fact that the position control works narrows things down to just the four tubes. Also, you can take some voltage readings on all four tubes with the controls set to normal positions.

Good luck, you are off to a good start.


Regards,
Tom
With all due respect, I would not start here. Vertical and horizontal amp both work in XY mode, so unlikely to be a vertical problem.

The sawtooth test as suggested would verify unblanking, but unblanking is not likely to be the problem, Power supplies are good, so I would focus on trigger or time base.

If you have another scope, set the trigger to one of the Line positions (+ or -), with the trigger level knob near the center and stabilty set to auto. Set the time base to a medium to fast sweep (1 ms/div or faster) This should rearm the trigger before each new trigger pulse.

look at pin 6 on V306 (trigger comparator), then pin 1 of V320 (trigger shaper). Should see something like a square wave at V306, then a sharper pulse at V320 with a period of 16.6 ms (60 Hz power). If this is good move on to the time base. If not try swapping one of these tubes (where you don't see the signal).

If you only have a volt meter, go back to the slow sweep and look at pin 5 of V460. You should see a sawtooth here, which most likely you won't (as that would indicate it is only unblanking).

If you have a good trigger pulse but no sweep, it gets a bit more complicated. My schematics don't show waveforms, and the 532 circuit is a bit different than other 53x or 54x circuits. I would need to figure out what some of these waveforms should look like. Perhaps another member who has a working 532 can probe around and report what they see.

Let us know what the trigger circuit shows

- Steve

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