I need a high-gain amplifier to boost my horizontal signal for vector rescanning

I’m trying to do vector rescanning, and am getting very close. The last hurdle is that my scope wants to see a really hot signal on the horizontal input. I’m getting an image that responds to input, but it’s an unrecognizably super-squeezed vertical block.

I ran the signal from VBM through both mults of a Bridge with them set to x5. That helped, but still only got me 1/10th or 1/20th towards where I need to go.

Is there some kind of amplifier that I can use here? I really don’t want to mod the scope- the horizontal gain works great for doing oscillographics with normal euro audio oscs…



You can also use the mixer on the right side of Bridge. Using a mult as the input should give you a x3 boost. However, you’ll be limited by the power rails, ultimately, so you can’t get more than +12V. I’d expect the max voltage you could get to be a little under +12V due to the limits of the circuitry (op-amps, specifically). So you really need a specialised kind of booster circuit to get a higher voltage. E.g. if your scope’s range goes as high as 60V, forget it. You won’t get anything like that from an existing module.

Fortunately, 60V range is extreme. My CRT scope, for example, only uses the 60V range internally, and boosts the Z mod input. So the range is a mere 0-10V. I’ve read the specs for other 'scopes that use a similar Z mod range. I got lucky with mine, as I got it years before I got into video. If I was looking for a 'scope today, I’d take care to check for details in the spec like this.

#1 Look for a 'scope with a Z mod input
#2 Check that the Z mod range is no higher than 10V
#3 Check if the graticule is removable. This isn’t a show stopper, but it helps for rescanning.


Thanks! That helped some- now the image is wide enough that I can see things in it, but I still need to get a lot hotter. At least 10x, judging by image width - not sure if that directly translates to voltage.

I’m kinda hesitant to say exactly which scope I have until I get it working. The Z axis seems super twitchy, and may not be capable of doing the subtle things that we like. This is the 5th scope I’ve bought on this quest so far, and I don’t want to lead anyone astray.

On a related note, if anybody wants Leader LBO-51MA scopes that have a couple of nasty holes burned in the phosphor, let me know. I have 3 of them. Do these things always have bullet holes in the phosphor?

I’d rather not ship them, but they’ll be super cheap if you’re near Chicago or want to meet up at Knobcon 2020…

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What I’m really hoping for is some kind of external box that I can run the horizontal signal through to get a bunch of gain. Bonus points if it has a nice simple knob on it.

Is there such a thing?

Doesn’t your 'scope have an attenuator for that? Ouch.

BTW, I just checked the manual for mine. Apparently the Z mod range can go up to 70V, where it “gives full blanking.”:boom:

Ahh, my 'scope has a sensitivity range of up to 20V for vertical but no such control for horizontal in the manual. I can’t check the 'scope itself ATM, its currently in storage until I can find space for it in my video rig.

Z seems to go from nothing to mid-bright instantly, and is then variable between mid and max.

Could easily be user error, and fixable. Not my biggest problem at the moment- I’ll burn that bridge when I come to it…

Just trying to get a solid screenful of happiness right now…