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 Post subject: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 3:29 am 
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Joined: May Sat 17, 2014 2:56 am
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Location: Pocatello ID
Anyone know a source for a 10k/500k dual linear concentric pot with a 3amp 125 vac switch?
I have a tr4 with a bad audio pot.


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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 4:32 am 
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Location: Costa Mesa, California
Usually it is the switch that goes bad on these things. You may find someone with a unit that has the bad switch and with some careful disassembly, combine the two for a working control. I have searched for something that would replace the AF/RF/power switch control with no success. I do have some switches for piggy-backing onto pots, but haven't tried to add those to one of my bad units yet.

Norm

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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 4:39 am 
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Joined: May Sat 17, 2014 2:56 am
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Location: Pocatello ID
My power switch works. I do have a source for getting a new one built but it's 40 bucks. Thought I'd see if there's an alternative.


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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 3:55 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
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How bad is the audio pot? I have found WD40 worked where other cleaning stuff didn't with scratchy pots.

If the audio pot is scratchy also make sure that capacitors C122, C134, and C140 are good because depending upon the position of the mode switch leakage in any of these will put DC on the pot causing it to quickly become very noisy. Check for any DC potential at the top of the AF gain pot.

Rodger WQ9E


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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 4:27 pm 
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Joined: May Sat 17, 2014 2:56 am
Posts: 192
Location: Pocatello ID
It's beyond scratchy. I read this as open between the wiper and the other lugs. So this seems just completely open and non working.


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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 4:33 pm 
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Bridkarl wrote:
It's beyond scratchy. I read this as open between the wiper and the other lugs. So this seems just completely open and non working.


It might be worth dissecting to see if it can be repaired given it is reading open. It could be a failed mechanical/electrical connection inside the pot and it may be possible to transplant a wiper from a donor pot to this one if the spring metal wiper arm has broken.

Good luck!

Rodger WQ9E


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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 8:46 pm 
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Location: Costa Mesa, California
If you are searching the internet for one of these, don't type in "pot sales." I have had bad luck with that.

Norm

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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Fri 23, 2018 9:06 pm 
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Norm,

I suppose you would also want to be careful searching for those gender changing connectors :)

Common electronic terms can get you into trouble with non-electronics types.

I grew up calling a pair of diagonal cutters a pair of dikes for short. When I was still a fairly new prof I was in a small university meeting with one of my colleagues, whose father had been a ham and we shared a common vocabulary, and he had a spiral notebook with a bit of wire sticking out that cut his hand. I told him to stop by my office after the meeting because I had a pair of dikes there. The meeting was being run by a person I knew fairly well and she was an "out" lesbian. I got a VERY strange look from her and my awkward attempts to explain just made it worse.

Things went downhill from there because we were discussing the development of a personnel assessment tool which each department had created individually and we were attempting to come up with a single compromise usable by all. My friend objected to the amount of items one department had proposed and the lesbian leader's response was to chide him because the assessment tool created by his department had even more items which would have been OK if she hadn't stated it in the form of "your tool is the biggest one in the college." She quickly realized that didn't sound good so we had a round table of PhDs trying not to collapse into laughter like a group of elementary school students. And one of the other people at the table was involved in a gender discrimination action against the university so it was a fairly tense situation.

Often work was actually pretty fun :)

Rodger WQ9E


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 Post subject: Re: Source of Drake TR-4 audio/RF gain pot
PostPosted: Mar Sat 24, 2018 5:14 pm 
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And that is why I always called them "alternative gender cutters."

Norm

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