[Hallicrafters] SX-117 disaster

Tue Aug 2 20:27:47 EDT 2016

     I assume you opened up the destroyed coil and are reporting what 
you saw.  I am not sure how running a transmitter into the input cold do 
that but maybe it can. I wonder if the transmitter put a high voltage 
down the AVC bus, which goes a lot of places. All I can suggest is to be 
sure its really as bad as it seems.

On 8/2/2016 4:30 PM, Jeff wrote:
> Thanks all for your help.  I've gone through everything, and it looks
> like the 50.75 kc system is shot.  One coil totally destroyed.
>
> Can anyone advise if any of the 50.75 KC transformers from the other
> Hallicrafters rigs will work, if I'm lucky enough to find some?  Based
> on the sounds of things, I think the 1650 KC ones are shorted out
> internally as well.
>
> These are similar to the SX-101s...
>
>
>
> I appreciate everyone's help and messages.  Totally disheartened.
>
>
> Jeff
>
> WB3JIH
>
>
>
> On 8/2/2016 2:41 AM, Richard Knoppow wrote:
>>    Check R-64 and R-63 for value.  This is a voltage divider from the
>> B+ that sets the voltage at pin-2. I don't know how this relates to
>> the RF being burned but worth checking.  Its possible the AVC is
>> partly shorted due to a fried cap in the RF but this is pretty removed
>> from there.
>>
>> On 8/1/2016 7:58 PM, Jeff wrote:
>>> Doing some voltage checks this evening, and interesting observations.
>>>
>>> I'm leading towards the AVC, as I'm not getting much fluctuation on the
>>> S-meter (meter movement seems OK...).   DC Voltage checks on all of the
>>> tubes show very close to the manual specs, with the exception of V10B,
>>> Pin 2.  My manual indicates that the voltage there should be 24 volts,
>>> and I am seeing 4.
>>>
>>> Any thoughts?
>>>
>>>
>>>
>>> On 7/31/2016 11:47 PM, Richard Knoppow wrote:
>>>>    Well, the cap is easy enough to check, a VOM will tell you if its
>>>> shorted and depending on the value may give you a kick if its OK.  My
>>>> guess is that its OK.
>>>>
>>>> On 7/31/2016 7:44 PM, K9FFK wrote:
>>>>> Jeff:
>>>>>
>>>>> C4 is also a suspect. Its a 300V mica.
>>>>>
>>>>> If it is shorted, AVC goes to ground through L5 along with V1's
>>>>> bias...red plates.
>>>>>
>>>>> If it is open, no signal. V1 is normal. Receiver is deaf.
>>>>>
>>>>> Dick, K9FFK
>>>>>
>>>>>
>>>>> On 7/31/2016 7:26 PM, Jeff wrote:
>>>>>> Thanks to all the fast responses. I've drowned my grief a bit, and I
>>>>>> did some disassembly.  The Antenna coil surely does look like it got
>>>>>> toasted.  I've included an image on my webserver:
>>>>>>
>>>>>>
>>>>>> http://www.podengo.com/sx117/L5.jpg
>>>>>>
>>>>>>
>>>>>> In looking at it, it looks as if the coil form actually deformed
>>>>>> (inside) so that the slug won't move past a certain point.  I don't
>>>>>> see any damage to rotary switches or other components. The 6DC6s test
>>>>>> OK, but I don't have any replacements in my stock to try a different
>>>>>> one.
>>>>>>
>>>>>> Anyone have any advice on the coil (or a spare you can part with?)
>>>>>>
>>>>>>
>>>>>> Jeff
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 7/31/2016 3:05 PM, Jeff wrote:
>>>>>>> Looking for some advice or consolation...
>>>>>>>
>>>>>>> Previously well working SX-117/HT-44 twins.  I hadn't run them in a
>>>>>>> long time, and many cables got messed with in the mean time.
>>>>>>> Unfortunately, in my haste to hook the pair back up again, I got the
>>>>>>> transmitter output fed into the receiver antenna input... and then
>>>>>>> hit transmit to tune up the transmitter...
>>>>>>>
>>>>>>> It's taken me a while to stop cursing about it, but now my SX-117 is
>>>>>>> deaf as a post.  A quick check of the RF amp and 1st mixer show that
>>>>>>> the tubes are OK.  A signal generator on 14.250 is barely audible,
>>>>>>> but I can no longer get a good strong peak on the preselector.  I
>>>>>>> can
>>>>>>> get a bit more of a peak on 40 meters, but it's still quite deaf.  I
>>>>>>> had the rigs in 20 meters when the mishap occurred.
>>>>>>>
>>>>>>> It's just about acting like there's no antenna at all hooked to it.
>>>>>>> I get no increase in noise whether or not it's hooked to the antenna
>>>>>>> or dummy load.
>>>>>>>
>>>>>>>
>>>>>>> I've had the courage to admit I've done something heroically stupid
>>>>>>> -- so I'm reaching out to the list for any thoughts or guidance
>>>>>>> as to
>>>>>>> how to fix this.
>>>>>>>
>>>>>>>
>>>>>>> Jeff
>>>>>>>
>>>>>>>
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>>>>>
>>>>> ______________________________________________________________
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>>>>
>>>
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>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL