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Author Topic: Drake SPR-4  (Read 1412 times)
HANSON
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Posts: 4




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« on: November 25, 2017, 08:08:43 AM »

I'm an SWL who recently got the bug for classic receivers. I picked up a Drake SPR-4 a few days ago on a face to face purchase and was able to test it with everything sounding a-ok. Today is the first day I ran it for more than an hour or so, and it developed a buzzing coming from inside the chassis (not audio output). Now if I turn it off and let it sit for a while, it will be quiet for about 5 minutes when I turn it back on, and then start buzzing again.

I'm hoping someone might have an idea of where I should start looking for the cause. Any suggestions are greatly appreciated!

Best regards,

Scott
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WB4SPT
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Posts: 502




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« Reply #1 on: November 25, 2017, 10:41:14 AM »

Nice Rx, I had one.   Likely to be the power transformer; you could verify by running off of 12V.   The Dc power cords are hard to find. 
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KD8IIC
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« Reply #2 on: November 25, 2017, 01:45:54 PM »

  Might be able to shim up the transformer with a piece of wood like a matchstick, something non conductive, between the chassis and the mid part. It's only a rattle and won't effect much other than being annoying...
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HANSON
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« Reply #3 on: November 25, 2017, 02:15:10 PM »

Thanks to you both for the replies and suggestions.  I kind of figured that the power transformer might be the culprit.
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KM1H
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« Reply #4 on: November 26, 2017, 03:15:56 PM »

Something that old should have the PS electrolytics replaced before the transformer really lets loose.

Carl
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HANSON
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« Reply #5 on: November 26, 2017, 06:12:20 PM »

Hey Carl, thanks for the reply.  So if I understand, the first step if it's an electrical hum and not a vibration, I should replace the electrolytic capacitors?
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KD8IIC
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« Reply #6 on: November 26, 2017, 06:55:22 PM »

 Try and tighten the screws on the transformer and mount first, might do the trick.
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HANSON
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« Reply #7 on: November 26, 2017, 07:03:51 PM »

Thanks for the reply.  Much obliged to you and everyone else checking in to help.
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KM1H
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« Reply #8 on: November 27, 2017, 11:05:08 AM »

Quote
Hey Carl, thanks for the reply.  So if I understand, the first step if it's an electrical hum and not a vibration, I should replace the electrolytic capacitors?

Not necessary to have hum but an overworked transformer can vibrate while it is overheating.

Carl
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N3KO
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« Reply #9 on: December 01, 2017, 04:25:42 PM »

I have three SPR-4’s and suggest recapping while you have the energy and before winter sets in.
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