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Post subject: Strange sound developing in my TRRI...
Posted: Thu Feb 09, 2012 3:55 pm
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Aspiring Musician
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So for a while (3 months or so), when heating up, my TRRI would pop a few times and then once it was warm, it'd stop. Now, for the last few days... when the volume is much above 3 and when a low note is played, it sometimes sounds like something is kind of vibrating... the sound seems to be isolated up near the tubes and I'm wondering if it is in fact a bad tube... Any thoughts? I've had the amp for about 6 years... it gets played nearly every day for at least an hour or so but no serious rocking out... the volume is usually at right around 3 for home use (which is all it's getting these days) Cheers, JG


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Post subject: Re: Strange sound developing in my TRRI...
Posted: Thu Feb 09, 2012 4:47 pm
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Rock Star
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If you have had the amp for 6 years and never changed the tubes, that would be a good place to start.

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Post subject: Re: Strange sound developing in my TRRI...
Posted: Thu Feb 09, 2012 5:38 pm
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probably wouldn't hurt but alas... problem solved. I think one of the tilt back legs was the culprit. I moved it back and forth, tightened the screw and that seemed to do it, at least for now. I should probably change the tubes one of these days... if I just replace them with the same color matched GT's that are in there do I need to get the amp rebiased?


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Post subject: Re: Strange sound developing in my TRRI...
Posted: Thu Feb 09, 2012 6:10 pm
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Rock Star
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JamGuy wrote:
probably wouldn't hurt but alas... problem solved. I think one of the tilt back legs was the culprit. I moved it back and forth, tightened the screw and that seemed to do it, at least for now.


I've had to deal with many a cabinet vibration problem :lol:

JamGuy wrote:
I should probably change the tubes one of these days... if I just replace them with the same color matched GT's that are in there do I need to get the amp rebiased?


Theoretically, you do not. But it is always a good idea to have it checked and adjusted if necessary. The TRRI has adjustable fixed bias, but no test point that I can find. You would either have to have a tech do it or buy a bias probe

http://www.amp-head.com/product_info.ph ... ucts_id=70

and digital voltmeter to do it yourself. It is not hard as long as you exercise caution and not stick your fingers into the amp.

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Post subject: Re: Strange sound developing in my TRRI...
Posted: Thu Feb 09, 2012 8:45 pm
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Rock Star
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+1 I would always check the bias after a power tube change. Don't believe the Groove Tube hype.They may be close, but why chance it? Twins need a matched quad set. Properly biased sound better. Tubes biased too hot won't last long, biased too cold, they'll last a long time but sound like arse.

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Post subject: Re: Strange sound developing in my TRRI...
Posted: Sun Feb 12, 2012 6:47 am
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Have the same thing going on with my TRRI. Warm-up noise and vibration on certain notes. I also (finally)pegged the culprit as the legs, and that seemed to work for a bit. Recently I've found that I can get the noise by tapping on the top of the case with the amp off. So I've got something loose in the chassis. Finding this thread was really a coincidence since I came here to find out (again-I'm getting forgetful) how do you discharge the capacitors to safely remove the guts of the amp to work on it? The chassis is going into a new head case I've just built. I'm sure this question has been answered a bazillion times but any help would be appreciated. I'll get back on any gremlins I find in the process.


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Post subject: Re: Strange sound developing in my TRRI...
Posted: Sun Feb 12, 2012 9:47 am
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Rock Star
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" how do you discharge the capacitors "

Make a draining resistor. I use a 500-ohm, 5-watt "sandbox" wire-wound resistor with two 3 inch leads and an alligator clip on each end. You can use any size resistor, the larger the resistance, the slower the draining process. Try to use a resistor above 100-ohms, just to avoid sparking. I use a 5-watt resistor, for those amps that have very large filtering caps, like big 250-500 watt solid-state units. A 2-watt for most tube amps is fine.

Turn off amp & unplug power cord out of wall. Remove amp from chassis. Flip chassis over so the trannies and tubes are facing upwards. Remove the four screws hold the top of the power supply cap cover. Carefully remove cover, so that it doesn't touch any components or wiring. Clip the draining resistor to chassis ground on one end and to the (+) side of the cap connection on the other. All of the caps are tied together, so the entire cap assembly will be drained, at the same time. If the amp has a standby switch, turn it to the "on" position, so that downstream caps will be drained.

Be sure to remove the draining resistor before bench testing or placing the amp back into the cab.


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Post subject: Re: Strange sound developing in my TRRI...
Posted: Sun Feb 12, 2012 11:35 am
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Thanks BMW. Little trickier than I thought. Is that resistor a Radio Shack item? Secondly, was planning on removing tubes before taking chassis out of the cab. Do they need to be back in for draining? I know you're probably scared that you gave advice to a knucklehead, but I'll get clear on this before doin' it.


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Post subject: Re: Strange sound developing in my TRRI...
Posted: Sun Feb 12, 2012 11:54 am
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Good idea to remove tubes before removing amp chassis, just to prevent tube damage. Nope, you don't need tubes in amp to discharge caps.

I chose this method, as it works on most all amps. Guitar, hi-fi, and car types. I've seen MANY techs use a screwdriver blade to discharge caps. With one BIG zap and spark! I would not recommend this. For safety issues as well as cap life issues.

But then again, I've seen mechanics smoke while working around cars and bikes with open gas systems. I've even seen mechanics toss lit cigarettes into open gas tanks. Nothing will explode, as long as the cigarette goes directly into the tank. But, if it misses...

Let's just say, I have also seen mechanics with new "suntans" and missing eyebrows... :lol:


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Post subject: Re: Strange sound developing in my TRRI...
Posted: Sun Feb 12, 2012 12:51 pm
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A.K.A. The "Hold my beer and watch this file"


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