[Hammarlund] HQ-170 A smokin-culprits found

[Bob Camp]

Hi

Ok, so now the trick is to go back in a week or so and look for more 0.047 uf caps from the same batch ….

Bob

> On Nov 7, 2014, at 10:44 PM, Robert Sauvan <rsauvan at beyondbb.com> wrote:
> 
> 
> Thanks for the replies I received. After posting the email, I went back down to the test bench and turned the radio on and believe it or not, it started up as usual. So, I took the time, what little I might have had, and started poking some caps with my wood stick. I found 2-.047 caps that when poked would make the radio act up a bit. These were connected to the V7 tube where I felt the problematic area was. I had a few new ones so I replaced both of the caps and voila, no more smoke, pops or crackles. Now, how lucky was that? I would assume they were  getting hot and when the radio quit working, they were at their limit. After a cooling off period, they would work again but not sure for how long. But, it was long enough to find them. Just in time for the SKCC Weekend Sprint.
> 
> Thanks to all-Bob-W0YBS
> 
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> 
> On 11/7/2014 7:47 PM, Bob Camp wrote:
>> HI
>> 
>> HQ-170’s are pretty rugged beasts. We proved that one field day back in 1971 when somebody didn’t check to see if the generator was set to 120V or 220V. Being a bunch of kids it took us a bit longer than it should have to figure out what was going wrong. All of the HQ-170 made it through ok.
>> 
>> Resistance checks are your friend in this case. A known good / working radio is ideal as a comparison standard. If one is not available, a bit of quality time with a schematic is the alternative. The tube sockets are a start. It’s as you work down into the radio that the other stuff really helps.
>> 
>> Before I went that route, I’d get some good light and a lot of magnification. Parts rarely smoke without leaving a trace. It sounds like you probably have at least two resistors to swap out before you get to whatever the real problem is.
>> 
>> Bob
>> 
>>> On Nov 7, 2014, at 9:33 PM, Robert Sauvan <rsauvan at beyondbb.com> wrote:
>>> 
>>> Hi all,
>>> After I feel everything is going well, another radio decides to take a dive on me. My HQ-170A started getting a hissing/crackling sound minutes after turning it on. I decided to try to find the culprit. So I put it on the test bench, turned it on and it started smoking. I couldnt find the exact spot but it was in the area of the V7 tube socket. After turning it off and then on again to see if I could find where it was smoking from, it decided not to act up in that way anymore, but the S meter no longer climbs as it always did as it warmed up. Decided to do some resistance checks. I started at the V7 tube pins and found some really high resistances at pin 5 and 6.Pin 5 is supposed to have 8.5K and it has a 500K reading. Pin 6 is supposed to be 68K and it has 800K reading. All other pins on that tube look to be OK. Both of these pins have wiring going to the wafer switch.There are numerous caps in this wafer switch. What would I do to continue finding the possible bad part? Any ideas?
>>> 
>>> Any suggestions would be greatly appreciated.
>>> 
>>> Thanks-Bob-W0YBS
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