[Heathkit] IM-17 Question

[Richard M. Gillingham]

Yup!  As I recall, the 8.4 V Mercury cell was used not only as a power 
supply, but as a precision voltage reference for the IM-17.  When the 
manufacture of this cell ceased, the IM-17 became virtually worthless except 
for a collector.

Perhaps someone can come up with a practical solution.  IE a regulated 
supply maybe based on a 9v battery??

Best to all
Gil, W1RG


----- Original Message ----- 
From: "Garey Barrell" <k4oah at mindspring.com>
To: "Dennis Berry" <dennisberry at worldnet.att.net>
Cc: <heathkit at mailman.qth.net>
Sent: Tuesday, January 09, 2007 7:16 PM
Subject: Re: [Heathkit] IM-17 Question


> Dennis -
>
> What's special about a mercury cell is that it's output voltage remains 
> extremely constant at 1.35V over about 95% of it's life.  Unfortunately 
> for photographers and others who needed stable battery voltages, the 
> hysteria over mercury has all but eliminated mercury cells from the US. 
> Just in the last week or so, someone accidently broke a MERCURY 
> thermometer in their home, called 911 (!) and over 100 personnel showed up 
> with hazmat suits and decontamination equipment to handle this major 
> spill.
>
> Anyway, use of another type of battery in your meter will just result in 
> it being out of calibration each time you use it as the alkaline or other 
> battery voltage declines over time.  The closest thing available now is a 
> Silver Oxide cell, which has about a 1.5V output with a flatter discharge 
> curve than an alkaline cell.  Low dropout regulators that will regulate 
> with as little as 0.35V drop are available now that could maybe regulate 
> from a 9V battery and hold your calibration over time as the battery 
> declined.
>
> 73, Garey - K4OAH
> Atlanta
>
> Drake 2-B, 4-B & C-Line Service Supplement CDs
> <www.k4oah.com>
>
>
>
> Dennis Berry wrote:
>> Thanks for the reply Mike.  Others said the same thing actually.  I don't
>> know what was special about the 8.4v mercury's back then.  Maybe it just
>> lasted longer?
>>
>> I've attached a partial manual someone sent me in response.  Keep it or 
>> toss
>> it as you see fit.
>>
>> Thanks again for the response though Mike.  Looks like this will be a 
>> handy
>> addition to the shack.  Digital's are nice, but sometimes a good ole 
>> analog
>> is handy.
>>
>> Dennis
>>
>>
>> ----- Original Message ----- 
>> From: "Michael Tortorella" <w2iy at verizon.net>
>> To: <heathkit at mailman.qth.net>; <dennisberry at worldnet.att.net>
>> Sent: Sunday, January 07, 2007 16:24
>> Subject: Re: [Heathkit] IM-17 Question
>>
>>
>>
>>> Dennis,
>>> I have an IM-17 and simply replaced the unavailable battery with a plain
>>>
>> ol'
>>
>>> 9 volt and it works just fine as is.  You may want to recalibrate.  I've
>>> used this for years with no problems.
>>> Sorry I don't have a manual, though.
>>> 73
>>> Mike W2IY
>>>
>>>
>>>     ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> List Administrator: Duane Fischer, W8DBF        ** For Assistance: 
>>> dfischer at usol.com **         $$ See the vintage area on the HCI web 
>>> site - http://www.w9wze.org $$ Heathkit mailing list
>>> Heathkit at mailman.qth.net
>>> http://mailman.qth.net/mailman/listinfo/heathkit
>>>
> _______________________________________________
> List Administrator: Duane Fischer, W8DBF        ** For Assistance: 
> dfischer at usol.com **         $$ See the vintage area on the HCI web site - 
> http://www.w9wze.org $$ Heathkit mailing list
> Heathkit at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/heathkit