thumping question

Blackcloud

New Around These Parts
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Mar 9, 2019
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4
#1
New to this forum, and could use a little help. PL 700b with PL 2000 pre has begun to thump at powerup and also during playback, even with no volume. Have owned units since late 70,s (bought new) and have had serviced many times over the years. Any recommendations on what it could be?
 

orange

Veteran and General Yakker
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Jul 6, 2010
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16,697
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Broken beyond repair but highly affable
#2
IIRC It's a capacitor (or a few)...Vintage receivers do this as well, energy builds up before the signal is passed and let go.

It's really disconcerting sometimes I would bet, especially if you are really worried about your speakers going pbbbbbblllt! on you. Not a complete big deal when you only have a 15 watt Pioneer but...
 

laatsch55

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Jan 14, 2011
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Gillette, Wyo.
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Halfbiass...Electron Herder and Backass Woof
#3
Turn on/off thump is caused by the front end losing regulation as voltage drops or when powering up. If it is a recent thing matching new input differential pairs will help, but rarely will it eliminate it. White Oak has fixed that problem with the new driver boards. You can also install wattsabundants DC protect board that also provides turn on/off muting..
 

Blackcloud

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Mar 9, 2019
Messages
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#5
Looks like time to get a tune-up. Thought I solved the problem a few years ago by hooking up power conditioner and plugging in amp to the delay input. Worked until just this week. I believe the sound is a little muddy, not very crisp as usual too. Thanks for response.
 

Blackcloud

New Around These Parts
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Mar 9, 2019
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#7
No not yet but that is a good idea. I remember having trouble years ago with the push button tone controls on the pre. Thanks for the heads up.
 

Blackcloud

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Mar 9, 2019
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#8
Powered up amp without pre, very little start up and power off thump and none in between. Would you conclude the problem might be the pre?
 
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