[Hallicrafters] SX-117 disaster

Tue Aug 2 21:04:35 EDT 2016

I wonder if the transmitter put a high voltage down the AVC bus, which 
goes a lot of places.

That's exactly what appears to have happened.

On 8/2/2016 8:27 PM, Richard Knoppow wrote:
>     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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>>>
>>
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>