[Heathkit] Heathkit IM-18

[Ron]

I would check/clean/replace the zero adjust pot R1. If OK, I would check R33 

(150K), R34 (220K) and R35 (150K). If OK, check R14 (10K), R15 (100) and 

R16 (27K). Statistically, it should be fixed by now. If not, measure the voltage 

across C1 (16uF/150V) - should be 65V-80V and clean the function switch 

(unlikely, but what the heck).  

-- Ron


________________________________


>________________________________
> From: Garey Barrell <k4oah at mindspring.com>
>To: Heathkit Reflector <heathkit at mailman.qth.net> 
>Sent: Thursday, May 31, 2012 12:03 PM
>Subject: [Heathkit] Heathkit IM-18
> 
>OK, I give up.........
>
>I have an IM-18 that has been working for years.  Turned it on, and the meter pegs 'downscale' on 
>'AC'.   On 'DC-' it pegs downscale, on 'DC+' it pegs upscale.  ZERO control has no visible effect. 
>No combination of the CAL controls makes any visible effect.  Interestingly, results are identical 
>with the 12AU7 removed.  DC voltages on the power  supply capacitor are nominal.  Whoever built it 
>did a VERY nice job, beautiful solder on board and switch.  Close visual examination shows not 
>obvious shorts, bridges, etc.
>
>Open to ideas or suggestions..
>
>73, Garey - K4OAH
>Glen Allen, VA
>
>Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
>and TR-4/C Service Supplement CDs
><www.k4oah.com>
>
>
>
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