Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

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Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

Post by Steve423 on Sun Jun 25, 2017 8:29 pm

Hello everyone, I have a Hammarlund HQ-180A with a reception problem that I am trying to diagnose. The unit powers up fine but will not receive any stations just static in all modes. Upon checking the chassis I noticed that the 410ohm 1w resistor at the V12 power tube (6AQ5) is burned and can barely be identified. It checks at 340ohms and probably still functioning but why would it run so hot? I noticed the 6BZ6 tube at V1 was not lit but fired up when I wiggled it. Would this dirty tube or any other defective tubes cause that particular resistor to operate hot?
Very Happy

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Re: Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

Post by gilpi on Tue Jul 18, 2017 6:46 am

Have you cleaned all the tube pins and sockets? Best way to do this without disturbing too much is to take a wire brush and clean the pins, then apply so deoxit or other contact cleaner to the pins as you insert them into the sockets.

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Re: Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

Post by jsweinrich on Tue Jul 18, 2017 10:51 am

Been my experience that these old carbon power resistors eventually start to burn. Probably a cathode return to ground resistor so it is probably a 20% tolerance so 340 is within limits (+- 20% = 328 to 492). I would think that reception issues are unrelated...

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Re: Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

Post by CaptainClock on Tue Jul 18, 2017 7:13 pm

I'm having a similar issue with a 1948 vintage GE model 62 AM Only Clock radio that I had replaced all of the capacitors in the unit including filter capacitors and went to power the unit on and for some reason all I get are oscillation noises from the tuner, no actual reception unless I tap on the loop antenna built into the back of the radio back and then I get some reception but then after awhile the reception goes away and goes back to the squealing and squawking of the oscillator. any ideas as to what could be causing my radio's issues? All of the tubes tested fine in the radio by the way.

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Re: Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

Post by Tony V on Tue Jul 18, 2017 10:58 pm

Captain, Why don't you start a new topic on your GE model 62 so it will get more exposure as your question might get lost in this one since we are talking about two different radio's. I'm just trying to get your question noticed by more people.
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Re: Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

Post by CaptainClock on Wed Jul 19, 2017 12:27 pm

OK thanks, sorry about that, Its just that I noticed that my radio and the OP's radio was doing the same thing so that's why I posted what I did, but yeah I guess if I post seperately from here it would get more attention.

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Re: Hammarlund HQ-180A Has Burned Resistor At Power Output Tube

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