[Heathkit] Heath Hm 102 watt meter questions

[Jeramy Thibodeaux]

John,

Sometimes I get ahead of myself.  I didn't make it clear in my previous post 
that you should replace D2 and D3 together.  While you are in there you 
might as well replace all three.  They are cheap enough and it will surely 
help in getting a more consistent calibration.

Jeramy
kg4azt

----- Original Message ----- 
From: "Jeramy Thibodeaux" <kg4azt at earthlink.net>
To: "John King" <k5pgw at yahoo.com>; <heathkit at mailman.qth.net>
Sent: Wednesday, July 06, 2011 11:17 PM
Subject: Re: [Heathkit] Heath Hm 102 watt meter questions


> John,
>
> My recommendation for a replacement diode is the 1N34A.  I believe you can
> still gets these from Allied Electronics.  Buy a handful and check them 
> with
> a meter.  Use the two with the closest match for D2 and D3 as this is a
> balanced circuit.  As with all equipment this age it wouldn't hurt to 
> check
> everything in circuit and replace anything out of spec.  The circuit is
> small so it shouldn't take long.  Use a little Deoxit sparingly on the
> switches and it also wouldn't hurt to reheat and reflow the solder joints 
> to
> eliminate any intermittent joints.  Be careful on the amount of heat you
> apply to the circuit boards to prevent lifting traces.
>
> Jeramy
> kg4azt
>
>
> ----- Original Message ----- 
> From: "John King" <k5pgw at yahoo.com>
> To: <heathkit at mailman.qth.net>
> Sent: Wednesday, July 06, 2011 9:51 PM
> Subject: [Heathkit] Heath Hm 102 watt meter questions
>
>
>>
>>
>>
>>
>> I own several  Heath HM 102 watt meters and they need going through and
>> bringing
>>
>> up to specs and calibrated. Some act as if one or more of the 1N295 
>> diodes
>> might
>>
>> be bad as well as some resistors have probably changed values over the 30
>> plus
>> years they have been around. Heath's carbon resistors  often changed in
>> value
>> over the years. I have the following questions:
>>
>> If you have replaced the 1N295 diodes what number diode did you use to
>> replace
>> the 1N295 diodes with? Your recommendations, please?
>>
>> Do you know if there are any particular resistors and capacitors in the 
>> HM
>> 102
>> that historically changed value and gave trouble?
>>
>> Based on your experience and knowledge of the HM 102 watt meter do you
>> have any
>> suggestions and tips for restoring the instruments to their original
>> specs? If
>> so please share your experience and knowledge.
>>
>> Your input on restoring these meters will be greatly appreciated. Thanks
>> and 73,
>>
>> John, K5PGW
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>
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