[Heath] Heathkit VTVM model IM-13

[Ron]

On 1/12/2013 10:30 AM, Dick KF4NS wrote:
> [....]
> While on topic, I wanted to mention that I made the mod in my IM-18 replacing the battery with a custom
> DC supply. That does not work so great so I decided not to do that in the IM-13. Just have to remember to
> check the battery occasionally so I don't have the mess I  had  in the IM-18.
I've been that route myself and decided a battery eliminator wasn't
worth it. I use alkaline batteries and don't mind replacing a battery
every couple of years or so.

-- Ron



>
> Thanks for the reply my friend.
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
>
> ----- Original Message -----
> From: "Ron" <ra.ah at verizon.net>
> To: "Dick KF4NS" <kf4nsradio at verizon.net>; <heath at puck.nether.net>
> Sent: Friday, January 11, 2013 8:49 AM
> Subject: Re: [Heath] Heathkit VTVM model IM-13
>
>
> |
> | The original circuit had a 10K pot for Ohms adjustment. This gave a
> | 0 to 10K range. With the added 5.6K, the range became 5.6K to 15.6K.
> | The effect of the added resistor was a shift in the adjustment point.
> |
> | I have built and repaired a large number of Heathkit VTVMs (this
> | portion of the circuit was common to most, if not all, models) and
> | cannot remember that such a mod was ever necessary. I'll venture a
> | guess that, due to component tolerances (say, meter too sensitive
> | or an out of balance 12AU7), your VTVM could not attain correct
> | Ohms adjustment and you added this resistor to correct the problem.
> |
> | -- Ron
> |
> |
> |
> |
> | On 1/10/2013 6:55 PM, Dick KF4NS wrote:
> | > I restored this unit about 10 years ago and put it in the closet until now. The thing works great,
> even
> | > better than my nice IM-18.
> | >
> | > Now more to the point. I did something that most of us have probably done. During restoration I added
> a
> | > part and have no idea why.
> | > R13 (ohms adjust pot)  now has a 5.6K resistor on the wiper terminal. Wish I knew why I did it. Was
> there
> | > a mod somebody created?
> | >
> | > The pot has very little control from end to end but the meter needle is right on for infinity after a
> | > good warm-up. Let me know if this is a known mod and why.
> | >
> | > Thanks and 73, Dick KF4NS
> | > St Petersburg, FL 33714 USA
> | > Keep The Glow!
> | >
> | > _______________________________________________
> | > Heath mailing list
> | > Heath at puck.nether.net
> | > https://puck.nether.net/mailman/listinfo/heath
> | >
> | >
> |
> |
>
>
>