Heathkit IO-4530

[John]

Hi guys, got this off the ebay for cheap because it did not power up. I wish I could say did something supremely clever to fix it, but all I did was check for continuity, pulled the fuse and put back in, and it fired up. Maybe it just needed to feel the love. 

Anyway, a few questions: it came with a calibrator that was tucked inside. It's just a circuit board with various resistors, 2 e-caps, and a pigtail with a connector that I assume gets hooked up to the scope somewhere for a couple volts of power. I say that because after searching I found the calibrator in a Heathkit catalog file (which is the only reason I know what it is) with a short description. However, I see nowhere to connect that little pigtail. It also had the shielded alligator clip leads as well, for the calibrator. Anyway, how do I hook that up correctly, and what's the procedure for calibrating/checking that it's close enough. I have searched extensively, but maybe someone has a link to a manual?

The other question is, it has a nice bright dot on the screen, I can move the dot around, and when I hooked it up to as semi-functional oscillator it jumps up and down as expected. However, I don't get a trace, or solid line, just the dot. Is that just how this scope functions?

If you need some pics I will take and post. At "work" (dead slow right now) so will have to wait.
I realize that this is probably just a boat anchor by today's standards, but I just like tinkering with this stuff, I'm not trying to use it in a working shop or anything like that.... I'm just having fun!

Thanks for any ideas or info, as always.

[eleventeen]

Here is the best (that I know of) archive of heath schematics. Doesn't appear to have your model, but it has perhaps a different one, may have your calibrator as an appendix or something.

http://www.vintage-radio.info/heathkit/

If all you are getting is a spot, you have no horizontal sweep going on, which is generally considered a requirement of normal scope use and probably the default condition of such a simple scope. That's a problem. maybe you can fix it.

If what you want is a functioning larval scope, I would recommend instead that you abandon that scope and look for one on Craigslist. I have seen perfectly usable 10 and 20 MHz scopes (insanely obsolete but delightfully adequate for audio) that are dual trace, for $20 and $25 and $40. You can test them at the user's place, no incoming freight, and importantly PROBES (perhaps) included. You gotta have probe(s).  

You could also make a simple, simple supply with a 7805 regulator that would give you a fairly accurate 5 volt DC level.

But regardless...my honest suggestion is to chuck that scope. Not that it wouldn't be usable (if it worked) but if your time is worth anything...

The above (no sweep present) applies if you still get (only) a dot with the H triggering set to either "line" or "int".

[sluckey]

Forget about the calibrator for now. You gotta get a horizontal sweep (horizontal line) on it first. Does turning the HORIZ POS knob move the dot right and left? If so, the horizontal deflection amp is working. But the horizontal sweep oscillator is not working or is simply not being triggered. Try this...

1. Set the black TIME/CM knob to .2mS.
2. Set the black X-VOLTS/CM knob to LINE.
3. Turn the red VARIABLE TRIGGER LEVEL knob back an forth.

Does this give you a horizontal sweep? If so, you just need some basic scope training. If not, you need a schematic. There's one on ebay right now.

[John]

Does this give you a horizontal sweep? If so, you just need some basic scope training.

   Sluckey, you are the master of dry, blunt humor.  I like it!!  

Thanks both of your for your replies. I'll mess with a little more, but I am thinking it's an anchor. Always fun though.

*edit* yes, horiz knob does move the dot.

[sluckey]

Sluckey, you are the master of dry, blunt humor.  I like it!!

I'm glad you get it. Many people don't. My ass stays in a crack most of the time because of little pokes like that. 

Did you get a sweep yet?

[John]

No, I'm at work. Scope is at home. I ain't like you retirees. 

[eleventeen]

With probes & manual. These are all over the place.

[PRR]

Don't leave that dot in the center for long. It will burn the phosphor. While fiddling, turn INTensity down so you can just barely see the spot, and dink the POS knobs every few minutes.

AFTER you get it sweeping.

Calibration.

Don't worry. The calibration is probably fine. That's why the calibrator is a loose board. You trim a couple trims when you *build* it, and it won't go "out" unless something breaks.

Get a FRESH 1.5V battery. Check it with a good volt-meter. Typically 1.56V.

Put the V input in GND mode. Adjust INT and FOCus (and ASTig if you had one) for a small precise line. Use V pos to get the line exactly on a graticule line. Set V V/cm for 0.5V (they say 500mV). Now switch V input to DC. Put the V input red knob in the CAL "click". Tap both probe ends on the battery ends. It should jump 3 divisions (3*0.5V= 1.5V). If you look real sharp it should be a bit more, 3.12 divisions. 3.12*0.5= 1.56V, as expected.

But realy, 3-some divisions is always close-enough. O'scope is for shape, not exact measures (at least not in this class of 'scope).

Time-base: pick up some hum from wall-wire fields. It should read 1/60 seconds or 16.67mS per cycle. If it is sorta-close it is plenty close enough. There's better tools for precision frequency reading.

[John]

With fiddling, I do get a sweep. Not a great one, but enough to tell me I need basic scope training.

PRR, just printed out your instructions, I'll trot out there, and follow up later.

11teen, thanks for your advice too, I know it's good advice! This is just a hobby thing for me, I like tinkering with obsolete stuff.

[John]

Well I'll be ding danged. It works! Since this time around I wasn't starving, I took more time to fiddle, and got a very nice sweep indeed. Following PRR's instructions, it works just like it should. I got a slightly skewed trace when holding the probe against the power cord. The only adjustment that doesn't work is the INT, which IIRC correctly there's a resistor across the lugs on that pot, so perhaps there's a bad solder joint or resistor?

I think I read that the  assembly manual  does not have the schematic in it, but now that I know the thing works I won't mind hunting and paying for one that does. I think the operator's manual is the one with the schem, although you'd think it would be the other way 'round.

Thanks everyone, again!

[PRR]

Mug shot for reference:

[PRR]

Volts/cm is your "volume" control. Makes the picture taller.

Time/cm is your time-warp. Turn to the left (bigger values) to see bass waves, to the right (smaller values) to space-out treble waves.

Hook it up to your hi-fi (iPod?) and fiddle.

[Willabe]

Well I'll be ding danged. It works!

Nice!     

[HotBluePlates]

Hi guys, got this off the ebay for cheap because it did not power up.

With fiddling, I do get a sweep.

You may have figured out Ebay sellers try to avoid negative feedback and sell things they know are broken/questionable by saying "powers up, unable to test" or some such. Bottom-line is whatever they say generally is meaningless unless you see the device hooked to some kind of meter/calibrator/etc to show via pictures that it works properly.

Though it's a crapshoot, I've fared well with items that the seller sold for parts or wanted to remain non-committal about functioning.

[John]

You're right, I've seldom struck out on eBay. The funny thing is, when I got this it really did NOT power up. When I took off the case I found the calibrator, test leads for cal., and some spare relays or transistors (or something, I dunno what) in their boxes. The only thing I can figure is that there was the slightest oxidation somewhere, and me messing with it knocked it loose.