[TenTec] 229A SWR Circuit - UPDATE

[Rick W]

Thanks for the suggestion Carl.  

The original diodes are 1N4148 as indicated on the schematic.  Since these were so plentiful in my spares I replaced the pair of diodes in the 229A circuit before my original posting.  Unfortunately that wasn't the problem 
 
73,
Rick
VE7TK


Website:  http://www.ve7tk.com


>________________________________
> From: Carl Moreschi <n4py2 at earthlink.net>
>To: Rick W <ve7tk at yahoo.ca>; Discussion of Ten-Tec Equipment <tentec at contesting.com> 
>Sent: Sunday, July 1, 2012 10:04:09 AM
>Subject: Re: [TenTec] 229A SWR Circuit - UPDATE
> 
>Also, I believe most diodes in watt meters are germanium.  If they ever 
>failed and were replaced with silicon diodes, that can mess up 
>calibration badly.
>
>Carl Moreschi N4PY
>121 Little Bell Dr.
>Hays, NC 28635
>www.n4py.com
>
>On 7/1/2012 12:44 PM, Rick W wrote:
>> I hung my DVM off the 200uA meter plug and it is completely within specs.  Fully adjustable and it seems to be working.  So it looks like the Korean made 229A meter has failed.
>>
>> I'll have to do some thinking on a replacement.
>>
>> Thanks for the bandwidth.
>>
>>
>> 73,
>> Rick
>> VE7TK
>>
>>
>> Website:  http://www.ve7tk.com
>>
>>
>>> ________________________________
>>> From: Rick W<ve7tk at yahoo.ca>
>>> To: Ten-Tec Reflector<tentec at contesting.com>
>>> Sent: Sunday, July 1, 2012 8:39:29 AM
>>> Subject: 229A SWR Circuit
>>>
>>>
>>> I have recently acquired a 229A tuner.  It needed a few repairs - mainly mechanical - but otherwise seems in good shape.  I've replaced the dial elastic cord and it tunes smoothly and consistently.
>>>
>>>
>>> I am having a problem with the SWR / Power measurement circuitry.  I can't get the meter to full scale and power measurements are way off.  Calibration is impossible.
>>>
>>>
>>> The meter is moving - albeit nowhere near the correct deflection.
>>>
>>>
>>> My guess is that the SWR circuit in the 229A is similar to the current 238.  Is there any history of problems with this circuit.  Any reports of:
>>>     1. meter movement failure;
>>>     2. leaky capacitors; or
>>>     3. open or out of tolerence resistors?
>>>   This is a pretty simple circuit and virtually all the parts (less the meter) are likely in my junk box. If there's a history of a part failure I'd like to start there.
>>>
>>>
>>> Thanks.
>>>
>>>
>>> 73,
>>> Rick
>>> VE7TK
>>>
>>>
>>> Website:  http://www.ve7tk.com
>>>
>>>
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>