Heathkit IG-5280 (old?) manual needed

Discussion in '"Boat Anchor" & Classic Equipment' started by W8TMT, Jun 11, 2019.

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  1. W8TMT

    W8TMT Ham Member QRZ Page

    I think I have an early version Heathkit IG-5280 RF Oscillator, serial number 00740. The 1000 Hz audio oscillator section does not have a 5.6 volt Zener or a bias adjust pot, as all manuals I have found on line show. Anyone know about this?

    Thanks,
    Terry, W8TMT
     
  2. WA2CWA

    WA2CWA Ham Member QRZ Page

    Obviously, in the early introduction of the model, the designer might have felt those components weren't necessary or didn't even consider them. Customer complaints or other "discovery" may have prompted them to add those components. If I planned on keeping the generator, I would add them along with verifying all the other components in the design.
     
  3. W8TMT

    W8TMT Ham Member QRZ Page

    Thanks, Pete. I should have stated my reason for needing the manual. The 1000 Hz oscillator is not working. All DC voltages look fine. I'd rather fix it as is, then think about modifying it later. Again, I'm looking for a manual for the correct version, with NO Zener or bias pot.
     
  4. WA2CWA

    WA2CWA Ham Member QRZ Page

    Does the board have mounting holes for the zener and the pot?
    I have two versions of the manual: 595-1957-01 and -02. Both of them have the zener and pot so most likely, if there were any additional iterations after "-02" the zener and pot would likely be there. I can't see running that oscillator accurately without them.
    SO, the manual/schematic you're looking for, or at least the Illustration Booklet (that's where the schematic is), would be 595-1957 (No "-" suffix).
     
  5. W8TMT

    W8TMT Ham Member QRZ Page

    No holes. Update: Since the DC voltages looked OK I assumed the 3 transistors were good and went poking looking for a problem in the Osc feedback area. I shunted a .001 uF cap across the existing .0022 and the oscillator took off, but at a lower frequency. Weirder yet, it would not run with the additional cap soldered in place, just when my fingers were there so I started looking for something that would put the circuit on the edge, like biasing. In place of the bias pot mine has a 22.22 K fixed resistor, so I replaced it with the later 50k pot. Tweaking this made the oscillator run at 1000 Hz. I'm going to watch it for stability but will most likely finish the mod as you suggested.

    Thanks,
    Terry W8TMT
     
  6. WA2CWA

    WA2CWA Ham Member QRZ Page

    I would also hang the zener on it too in case your AC line variations happen to run high when using the equipment.
     

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