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Old 03-28-2013, 10:05 PM
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Question on a Hickok 505A oscilloscope

Trying to do some work with my scope, which has up until this point, never been used for, well, really anything.

It seems to function decently well, with one exception that I'll get to in a moment. I changed out all of the wax caps that were left in there....it seems that someone worked over this unit at some point and put mostly Spragues in it, and JAN tubes. I'll get to the Spragues at my next capacitor order. Tubes tested good.

Problem is, the vertical gain control does nothing. I can move the dot, or sweep line, all the way around the screen with the controls, but I just can't get a heck of a lot of height out of it.....maybe just shy of an inch at best.

Now I realize that I'm going to have to end up replacing the caps, but before I chase a ghost, there are 8 screws on the back, with jumper wires between them. The attached wires seem out of place. Numbers on them are D1 through D4. I've found a copy of the manual online, but it doesn't refer to the proper positioning of these wires, much less what they're for.

Can anyone shed some light on this? Thanks!
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Old 03-29-2013, 12:28 AM
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Those jumpers connect the horizontal and vertical amplifiers to the deflection plates of the (electrostatic) CRT. So there would be four deflection plate connections, two vertical and so on. The other 4 are the amplifier outputs.

If any jumpers are missing you won't get proper performance.

The reason the connections are brought out is for use of the CRT directly, such as in a transmitter modulation measurement.
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Old 03-29-2013, 01:22 AM
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With you so far. On the scope, D1 and D2 are horizontal. D3 and D4 are vertical. Each pair of connectors has a vertical connection, D1 up and down. D2 up and down. And so on. Makes sense with what you're saying.

BUT, the part that makes NO sense is that there is a jumper from the top of D2 (horizontal) to the bottom of D3 (vertical). Remove said jumper, though, and lose everything on screen.

I just need to make sure that it's not either missing one other jumper, or this one's not connected right. Good possibility that it's been monkeyed with....or perhaps not.

I'm trying to get the scope into X-Y mode. I've studied the manual, and I'm not completely certain how to set it up
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Old 03-29-2013, 12:18 PM
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It's possible that there is no XY mode available. If so, you'd have to disconnect the appropriate jumpers in the rear and connect your own X amplifier. Or perhaps you could modify the unit by adding a switch internally so as to retain the positioning control and maybe get some gain.

As for the renegade jumper I have no clue. The diagram would show that but it seems you don't have one.
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Old 04-24-2013, 02:25 PM
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In order to lean how to use this scope, I need to find out what the controls actually *do*.

Would anyone be willing to explain the functions of the various controls, and what they are used for? The positioning, focus, etc, are self explanatory
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Old 04-24-2013, 10:27 PM
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An oscilloscope plots a graph. In order to have it visible, the graph must be refreshed regularly.

The dot moves across the screen at a rate determined by the sweep circuit; in old units it was calibrated in sweeps per second but modern units are calibrated in time per division. It's controlled by the sweep circuit controls.

To get a steady pattern you need to synchronize the sweep with the signal. You can use the signal itself as a synchronizing source, an external signal, or the power line frequency.

This particular unit also has a detector for RF, called a demodulator. That extends its usefulness a bit, but there is no substitute for looking at the signal itself rather than just its modulation.
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Old 04-25-2013, 05:17 AM
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Would you be willing to give me a test example on how to use the scope? Sure, I can hook it up to an audio device and watch the neat graph of the pattern, but I'd really like to learn how to use this in an actual application.
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Old 04-25-2013, 11:16 AM
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If you have an audio signal generator, connect it to the vertical input. Then fiddle with the controls until you see the waveform. Once you have that, fuss with the amplitude and frequency and discover how to make it look the way you want.
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Old 04-25-2013, 11:55 AM
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Just so I'm understanding this, the lower left section labeled "Radio Frequency" is not a built in signal generator, correct?
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Old 04-25-2013, 12:33 PM
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It is a built-in signal generator operating at either 1 MHz or 50 MHZ. You can download the manuals here: http://bama.edebris.com/manuals/hickok/505a/
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Old 04-25-2013, 12:41 PM
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I've got the manuals, they just don't tell you how to actually use it. I guess they rightly assumed that whoever would buy it would already know

The online things I've found regarding scopes seem to point to newer models, with different configurations. Maybe there's a good book someone could recommend?
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Old 04-25-2013, 01:06 PM
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Something to keep in mind is that the 505A is not a typical oscilloscope. It appears to be meant for use with external sweep and RF generators for alignment work.
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Old 04-25-2013, 02:00 PM
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So, as it is, other than looking purty, it's good for.....?

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Old 04-25-2013, 05:44 PM
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Frankly, I think the best use for your oscilloscope is, as you suggest, looking purty. Contemporary designs are much more useful and certainly not expensive. I own four very nice oscilloscopes, each of which puts the HIckok to shame. Two were free. But the bandwidth and measurement capabilities of high performance units make them a piece of cake to use, and you can have confidence in them. And all are solid state except for the CRT.
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Old 05-11-2013, 04:20 PM
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Your scope is pretty old, and non standard by many modern scopes. But it looks like you could still use it for learning about tv and radio. The most important thing I remember about old, and new scopes is before you do anything with an old radio or tv, is to be sure both your scope and test item both are using the same ground. Put a volt meter between the scope ground and whatever you are planning on looking at, or working on. If 0v you should be safe to hoop it up,(ground to ground) just be careful if you unplug anything, remember ac plug polarity, on many sets one side is ground, and if not polarized, and you unplug, and then plug it in again, you may get a spark show.

Your scope lets you choose "sweep circuit osc." from the horoz. on the left. That will set your horiz scan rate. And there are sync select knobs too. Use int. sync. You have a signal source there called the radio frequency osc.

You can take the output of the RFO and put it into the vertical and keep all gain and output settings at min. slowly increase till you see something. Then play with the sync. to get the picture to lock.

You have a neato free-bee learning thing there. I'm pretty sure the one thing you will not be able to see on that scope is a signal with a DC offset. To learn more about how a scope works ask the great wizard of oz... He knows everything (google)

"how do I use an oscilloscope" and other words to that effect. On that one, you can begin just using clip leads to and from the various things on the scope itself. And besides if you get a more modern scope and overload it or connect something the wrong way, you'll be then needing to replace transistors or other stuff inside. That old 505 will be very forgiving, and a great scope to learn on.

Once you learn a little about it, start poking around inside a transistor radio, plenty of good stuff to see there.

And that scope is fully an X-Y mode scope, just put both vert. and horiz. inputs at the top left and right to ext. and then attach something to those inputs and you have X-Y display. (Again be careful with the grounds!) Some of those things might even have a Z cutoff. I have one like that made by one of Tektronix's little brothers.
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Last edited by Username1; 05-11-2013 at 04:26 PM.
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