Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: pro_crip on October 17, 2010, 01:25:13 PM
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I finally got around to doing the voltage check on my crack, Newton's first law is a bear, and after a minor mistake (the led from a3 to center was disconnected) and fixing thereof, all the readings were to spec. So, I figured, time for some music so I fire up the cd-471 and plug in the 650's. Problem. I only got sound on one side, the right. Also, with the volume turned down it was LOUD. I swapped the inputs, no effect. I swapped out the driver tube, no effect. In frustration I started to yank out the 'phone cable but managed to only get it out halfway. Wait a sec, sound from both sides issued forth and the volume was normal (almost, I need some padding at the attenuator). I redid both of the terminals on the headphone jack leading to the output to no avail. I'm at a loss as to how to proceed. I'm tired so I'm quitting for the day. Any thoughts on how to proceed? Thanks for listening.
Rich
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This is just a generic sort of guess, since I don't know the circuit, but it sounds as if the "common" lead is in the wrong place, which of course means that at least one of the "hots" is incorrect also. My bet is that the common lead has been connected to the "ring" terminal on the headphone jack.
Your ohmeter should help you sort it out.
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I think JC's on the right track. Double check the wiring from the headphone jack and the input jacks to be sure you haven't got something connected wrong.
BTW The thing where you heard the "dead" channel come alive when you pulled out the headphone jack part way is a "red herring". Because of the "tip-ring-sleeve" construction of the male 1/4" jack, when you pull it out slowly you end up with both headphone drivers connected to the right channel momentarily (the tip bridges the left and right channel-the ring is still in contact with the right channel and the sleeve is still grounded).
It sounds like you have both left and right channels routed to the right channel somewhere.
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I followed grainger's advice from a previous post and used my dvm to track the signal from the rca's through the whole circuit last night/this morning. The right side checked out with no problems, on the left the signal went into the attenuator but didn't come out. Thanks to ironbut I'll ignore the jack for now (the first thing I did was check the wiring) and work on the attenuator tomorrow. Hopefully all it needs is a rewetting of the out terminal on that side. Just fyi, I'm using a Goldpoint stepped attenuator.
update: Re-wetting the attenuator joints had no effect. I'm putting it away until the weekend as I'm a little frustrated and I need a battery for the dvm.
Rich