Heathkit IM-103 Line Voltage Monitor

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Heathkit IM-103 Line Voltage Monitor

Post by QualityGuy on Sun Oct 22, 2017 6:30 pm

Greetings TRF Members;

I'm rebuilding a Heathkit IM-103 Line Voltage Monitor. I purchased a pre-packaged "rebuild" kit which contains the items most needed for the repair of this line voltage monitor.

The kit includes a 33 mfd 350 volt capacitor, rather than the original value of 70 mfd, for C1. This is quite a decrease in capacitance. Is it OK to use this new lower value cap? What affect, if any, might it have on the performance of the monitor?

Here's the schematic:

https://elektrotanya.com/PREVIEWS/38933510/23432455/heathkit/heathkit_im103_line_volt_monitor_sch.pdf_1.png

I appreciate your help!


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Re: Heathkit IM-103 Line Voltage Monitor

Post by Chas on Mon Oct 23, 2017 11:12 pm

The 33mf "may" introduce a small amount of ripple voltage. However, the power supply consisting of D1, R1, C1 does not need to provide much current.

If you have another identical 33mf ,connect in parallel. Check the calibration with either the 66 mf and the 33 mf. If there is little or no difference the 33 will be fine...

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Re: Heathkit IM-103 Line Voltage Monitor

Post by QualityGuy on Tue Oct 24, 2017 7:16 pm

Great, thanks for the input. I do have an additional capacitor and I plan on trying it in parallel.

BTW, the provider of the rebuild kit told me the change in value of the capacitor was "intentional," although he didn't go into the reasons why.

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Re: Heathkit IM-103 Line Voltage Monitor

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