Heathkit IO-4540

I’ve run across several requests in electronics forums for the schematic of this very old Heathkit IO-4540 5MHz Single-trace Oscilloscope.  The schematic in the Heathkit manual is a large foldout and is difficult to scan.  These are photographs of the four quadrants, and are better than nothing.

All four schematic photos in a single zip file (3.5Mb)

Also, selected pages from the “Illustration Booklet”:

Illustration Booklet Figures in PDF file (1.4Mb)

10 Responses to Heathkit IO-4540

  1. Bill says:

    Thank you.

  2. Robert Lyon says:

    Hi, I recently picked one of these up, and am trying to calibrate it.
    I got as far as the trigger circuit, but then the manual refers to an “Illustration booklet”
    to make various adjustments.
    Without the illustrations, I’m stuck!

    Any Ideas?



  3. Bruce says:

    I have a Heathkit IO-4540 scope and the vertical trace has disapeared, I have the horizontal trace and it works fine. How do I get the verticle trace back.?
    Thank You

    • modemhead says:

      I assume you mean that you have a flat line and no vertical deflection. Set the Volts/Div appropriately, set the coupling switch to AC or DC, and input a signal. The 1Vpp available from the front panel will do. If you still get a flat line, then there must be a fault in the vertical amp.

  4. Hunter says:

    Does anyone know what to adjust for the dc balance and plate volts on the horizontal board? The variable resistors broke and I was going to replace but have no idea what they need to set at or what to do for adjusting them.

    • modemhead says:

      I do still have the manual for this scope (Heathkit IO-4540). I’m out-of-town at the moment but when I get back I’ll see if I can dig out the horizontal board adjustment procedure.

      • Hunter says:

        I ordered another one but it broke in the mail too. Became a parts one and I got the first one working. The calibration is so far off. I pretty much just need the full manual to calibrate it. At least it works now even if the case is completely destroyed.

  5. Richard Montel says:

    Link to IO4540 schematic photos doesn’t seem to work.

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