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Thread: Heathkit ol-1 oscilloscope help. Can't get solid spot during setup procedure.

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    Senior Member jasonguitar's Avatar
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    Heathkit ol-1 oscilloscope help. Can't get solid spot during setup procedure.

    My uncle gave me this cool Heathkit OL-1 scope years ago and I never used it. I obtained all the documentation, cleaned, re-capped it and fired it up and everything seems to work. Problem is that following the start up instructions I can't get a solid spot. All settings are per the instructions with the vertical and horizontal gains zero-ed of course. I get a 3/4" diagonal line like a forward slash. Anybody have a suggestion?

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    Lifetime Member Enzo's Avatar
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    OL-1 or O-11?

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by Enzo View Post
    OL-1 or O-11?
    Its an OL-1. Wish it was an O-11

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    Senior Member jasonguitar's Avatar
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    Here's a pic of what I'm getting. A nice old tech I met at the YMCA told me to adjust the astigmatism setting but this unit doesn't have one. How can I fix this?
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    Last edited by jasonguitar; 07-11-2010 at 04:37 PM.

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    Senior Member JHow's Avatar
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    Hell. Just curious, but I didn't see the attachment?

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by JHow View Post
    Hell. Just curious, but I didn't see the attachment?
    That's strange. Its showing in my browser on both my macbook and pc.

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    Better Tone thru Mathematics bob p's Avatar
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    I can't see it either. I guess that explains why you can't get a solid dot during setup.

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    Better Tone thru Mathematics bob p's Avatar
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    the problem is that you hyperlinked to an image on a secure mail server at gmail. one has to be logged into your account to see the image. notice the "https" prefix in the link.

    why not upload the image here as an attachment?

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    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

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    Senior Member jasonguitar's Avatar
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    Attached it above. Thanks.

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    Senior Member jasonguitar's Avatar
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    I assume that what would be an astgmatism control is set by a fixed resistance on this unit. I started replacing resistors which had drifted a bit in value and the problem has improved quite a bit. Guess I'm gonna have to go all the way now! Wish I knew what resistor I could replace with a pot to add the control I need? Anybody?
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    Lifetime Member Enzo's Avatar
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    The sure doesn;t look like an astigmatism problem to me. Astig is like a focus, the beam will look fat or smeared.

    SO I can;t see the whole panel, are there V and H size controls? Do they affect the image? Does turning the H and/or V gain up and down affect the image. Does slowing the sweep speed way down affect the image? And H and V position controls, what do they do?

    We don't know yet what we are looking at. For example, what if the tube is partially rotated in its holder, and that is a short horizontal line now at an angle? If the position and size controls move along the line and perpendicular to it, then we have that. If the image moves horizontally and vertically in response to the controls, then the display really is an angled line.

    If you slow the sweep speed down, then the line ought to resolve into a bright dot sweeping back and forth. Whether it does that or not is a clue.

    ANy chance there is an X-Y switch on this thing, on the back if not the front?

    If this is an actual 45 degree trace with no input, perhaps a poper supply has large ripple and we are seeing an X-Y plot of that ripple.

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    Senior Member jasonguitar's Avatar
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    Yes there are V and H gain controls which function properly. H and V position controls function properly. The H gain will stretch that line out straight across the screen and the V will raise the image straight up so the crt tube seems to be positioned correctly. As you can see from my two pics, the line has become shorter after replacing some resistors. I will have to go to the local shop tomorrow and get more replacements as I didn't have all I needed to finish the job. All electrolytics have been replaced. This image is with no input and all controls in their initial positions according to the startup procedure in the OL-1 manual. The switch on the back is int/ext sync switch.

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    Lifetime Member Enzo's Avatar
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    OK so you can get the trace to go all the way across horizontally. Still at that angle, or does the vertical dimension stay the same?

    How about that sweep speed question. Turn the sweep CCW, is it still a steady line or do you now get a spot moving back and forth?

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    Senior Member jasonguitar's Avatar
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    Yes its stays at that angle. If I just adjust the V and H position, that same shape moves around accordingly and does not change its shape. If I adjust the H gain it stretches out and becomes sort of a parrallelogram from left to right and raising the V gain just widens that shape from top to bottom. Adjusting the sweep gives a steady line unless I raise the H and V gains, then I get some movement.

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    Lifetime Member Enzo's Avatar
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    Set the sync switch on the rear to internal.

    Lower right control is the horizontal selector, where is it set?

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    So you can get a sweep, but it goes from upper left to lower right? Maybe the CRT has shifted. Some scopes have a trace rotation adjustment, but on this one maybe you just need to loosen the CRT clamp and physically rotate the CRT so the sweep is horizontal.

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by JoeM View Post
    So you can get a sweep, but it goes from upper left to lower right? Maybe the CRT has shifted. Some scopes have a trace rotation adjustment, but on this one maybe you just need to loosen the CRT clamp and physically rotate the CRT so the sweep is horizontal.
    I think I am mistaken on the sweep. Dont have the unit in front of me. The setup for initial dot indication is adjust the trace with H and V positioning, H and V gains at 0, Hor select full clockwise and Sync amp at 0. This should produce a solid dot. I get the diagonal line shown in the pics above which has improved and shrunk somewhat with partial resistor replacments. Seems like I'm heading in the right direction. The H and V gains stretch the given trace straight across the respective hor and vert lines so the CRT seems to be in correct position and if I had a solid dot it would likely make a solid line horizontaly. Since I'm not getting the dot it simply stretches the given line across instead. The H and V positioning work correctly. The Intensity and focus work correctly. When I jump the 60cyc to vert input I get some action and am able to adjust the sweep. Seems like everything is pretty much functioning.

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    Lifetime Member Enzo's Avatar
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    Find the power supply caps, ideally use another scope to look at what they are doing. Otherwise, measure the DC voltage ion them and see if it seems reasonqable, but mainly measure them for AC voltage to see how much rippple there is. Caps are suspects, at 50 years old certainly the electrolytics, but also the film caps. When you recapped it, did you replace ALL the caps, or just e-caps?

    have you tried different tubes?

    Wait, you say you have all the documentation? Like including the schematic? Geez scan that and post it.

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    Senior Member jasonguitar's Avatar
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    I only replaced the electrolytics with fresh caps and brought the unit up slowly on the variac. Haven't touched the others. I will look at the power supply. If thats not a problem, once I have replaced all out of value resistors if there is still an issue I will have to look at the other caps. Hate to touch those cool old yellow spragues. Anyone restoring tweed or brown Fenders would go nuts for em!

    I don't have the info on this computer but amazingly I found a link while scanning a forum somewhere with the full manual and schematic. Can't find it in a Google search. I will post them tomorrow. My workshop and studio are at my Dad's house just a couple miles away and that is where the gear and files are. As always thanks for your time. Hasta manana!

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    Lifetime Member Enzo's Avatar
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    I don't necessarily want you to replace them without question, but if they are leaking, that makes DC go where it is not wanted. And at 50 years, that is always a concern.

    Drifted resistors are more likely to alter performance, rather than prevent it. The voltage scales might be off, or the linearity funny so the waveform distorts, or the sweep rates cockeyed, but unless the resistors are WAAAAAY off, if everything else is OK, then the thing should function. Just like a guitar amp.

    The deflection is a pretty simple push-pull affair, but a dead tube stage can easily kill the signal.

    And while this is a visual device, if you feed some audio signal into it, you can still use a signal tracer to see if it is passing through the scope stages.

    If you google "Heathkit OL-1" you will find various references to it and the schematic, and several sources selling it. I wasn;t about to order the stuff myself.

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    Quote Originally Posted by jasonguitar View Post
    . Hate to touch those cool old yellow spragues. Anyone restoring tweed or brown Fenders would go nuts for em!...
    Some of those old spragues can be leaky. On one of the scope groups, where do you these caps go after they're removed?

    [added]

    This may not be not be anything to do with your problem, but I picked up a scope a few years back, weird display that just didnt make any sense. I posted the problem to the Tekscopes group on Yahoo. A retired Tek engineer wrote back suggesting I clean the CRT socket - that fixed it. It's common for these guys when they get an old scope to wash them. Sounds weird, but at the Tek service centers, all scopes returned for service were first washed and then dried before any service or calibration.

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    Senior Member JHow's Avatar
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    Quote Originally Posted by JoeM View Post
    ...It's common for these guys when they get an old scope to wash them. Sounds weird, but at the Tek service centers, all scopes returned for service were first washed and then dried before any service or calibration.
    Washed how? Can you elaborate?

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by Enzo View Post

    Wait, you say you have all the documentation? Like including the schematic? Geez scan that and post it.
    Here's the OL-1 manual:

    http://www.maintainband.com/AMP%20FILES/OL1_man.pdf

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    Here's a good article on the cleaning process used by Tektronix
    Attached Files Attached Files

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    Senior Member JHow's Avatar
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    Thanks for posting this link. I like the old-style mica-cap color code chart included on the cover. I had a copy from a book I have, but this is much clearer.

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    Lifetime Member Enzo's Avatar
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    Ah, terrific, schematics.

    Look lower right corner, the B+ supply. Get out your meter and check all those B+ nodes, A, B, C, D. especially A. Are all those B+ DC voltages reasonable? Now flip the meter to AC volts and remeasure. We are measuring ripple now. A little ripple might be expected on A, but the rest should be real smooth and clean. Zero VAC, that is.

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    Senior Member jasonguitar's Avatar
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    Got so busy today, didn't have time to check it. I will check tomorrow. Thanks!

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by Enzo View Post
    Ah, terrific, schematics.

    Look lower right corner, the B+ supply. Get out your meter and check all those B+ nodes, A, B, C, D. especially A. Are all those B+ DC voltages reasonable? Now flip the meter to AC volts and remeasure. We are measuring ripple now. A little ripple might be expected on A, but the rest should be real smooth and clean. Zero VAC, that is.
    Okay, here's what I got: A=412VDC, 2.4VAC B=262VDC, 0VAC C=189VDC, 0VAC D=261VDC, 0VAC

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    On page 24 of the manual, there's a voltage chart. I'd go through these first and check. Be careful, some high voltages in that thing.

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by JoeM View Post
    On page 24 of the manual, there's a voltage chart. I'd go through these first and check. Be careful, some high voltages in that thing.
    I checked all the pins on the 12au7s and the 12ax7. Most of the voltages are a slightly higher than the chart but are relatively consistant.

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    Lifetime Member Enzo's Avatar
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    Well, we have some vertical stuff with no input, right? SO pull V1. Now what is on the screen? You have four 12AU7s in this thing, two for each direction. Try swapping them around. ANything changes we kinow the tube is what made it change.

    And that couple volts of riple you had on B+ A? Try slapping another 20uf cap from A to ground. See if that smooths anything out.

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by Enzo View Post
    Well, we have some vertical stuff with no input, right? SO pull V1. Now what is on the screen? You have four 12AU7s in this thing, two for each direction. Try swapping them around. ANything changes we kinow the tube is what made it change.

    And that couple volts of riple you had on B+ A? Try slapping another 20uf cap from A to ground. See if that smooths anything out.
    Okay, so adding another 22uf cap got rid of the ripple at point A but the display didn't change.

    Removing V2(vert ctr) shifts the diagonal line to a straight vertical line(actually a very tight elipse). Swapping different tubes in this position displays the same diagonal line again.

    Removing V5(hor ctr) shift the diagonal line to a straight horizontal line(elipse). Swapping different tubes in this position displays the same diagonal line again.

    Removing both V2 & V5 gives me a solid dot! But of course I can't do anything with it!

    Removing V1(vert gain) with V2 and V5 removed, the dot remains the same.
    Removing V4(hor gain) with V2 and V5 removed and V1 in place, the dot remains the same.

    Moving tubes around and substituting other 12au7s, 12at7s, 12ax7s, produces the same diagonal line but differing lengths according to the gain of the tube.

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    Lifetime Member Enzo's Avatar
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    But the point was to remove V1 and see what happens, not to remove the V2 and V5 first and then V1. Clearly with V2 removed, V1 can;t have any effect. What we wanted to find out was if V1 was sending any odd unwanted signal to V2.

    Look at the circuit, V2 and V5 directly drive the deflection plates in the CRT (picture tube). When either is removed, then the exact same voltage is sitting on opposing plates, and you lose deflection completely in that direction. The unmoving dot as you found.

    Now V1 is the inoput amplifier tube. It takes the input signal and amplifies it for V2. And V4 does the same thing for V5.

    If you pull V1, the functions of V2 remain, so the position control should still work. What we want to know is if pulling V1 eliminates the odd vertical deflection signal you have. Just as we might remove V1 from a guitar amp to see if it removed some hum. Just exactly like that. And we are trying to isolate the problem, even if the tube itself is OK, that doesnlt mean the circuit around it is. We need to determine just where this unwanted deflection arises.

    Pulling V1 SHOULD kill any vertical movement. Pulling V4 would kill horizontal movement, but that would also include teh sweep. SO lets concentrate on the vertical for now.

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    Senior Member jasonguitar's Avatar
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    Quote Originally Posted by Enzo View Post
    But the point was to remove V1 and see what happens, not to remove the V2 and V5 first and then V1.
    Sorry, I forgot to mention that pulling V1 gives no display at all. Same with pulling V4.

    The diagonal line(or elipse) shortens a bit when I remove V3.

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    Lifetime Member Enzo's Avatar
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    Well now that is odd. Those stages are capacitance coupled to the V2 and V5 stages, there should be no DC problems there. I would have expected no deflection, not no display.

    We never did determine those other caps did we.

    Pull V1, set the vertical position control to its mid point, and measure DC voltage at pins 2 and 7 of V2. What do you get?


    And let us not forget the high voltage. Note that the voltage coming off pin 9 of V7 is NEGATIVE, as are the voltages derived from that for the CRT. Look at the voltage chart, if your meter is up to it, check them. Mainly I want to know what you get with meter set for AC volts - ripple. If the voltage at V7 is too high, just worry about the voltages going to the CRT. Ripple here can cause beam problems that can affect deflection. There is very little current in that supply, so the filtration is those two little .1uf 1200v caps.


    OH, and another check. Put V1 back in. Measur DC voltage at pin 2 of V1 as you turn the vertical gain control up and down. If it goes positive at all, then there is a problem, probably that 20uf/150v cap from pin 8. or done a different way, is there any DC voltage across either horizontal or vertical gain controls themselves?

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