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Posted: Thu Mar 11, 2010 10:06 am
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Congratulation.


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Posted: Thu Mar 11, 2010 3:31 pm
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Good deal, James. Glad to hear all your work turned out so well!!! Art

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Posted: Thu Mar 11, 2010 3:46 pm
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Very cool James. 8)


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Posted: Fri Mar 12, 2010 6:36 am
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One thing that was mentioned was forming the caps and you said that you turned on and hoped nothing blew....I've been there before.
:shock: In one of Weber's books he shows how to make a current limiter that uses a 100watt lamp bulb to keep the amp from getting full current in case there's something wrong inside.That way you might save valuable parts inside instead of holding your breath and keeping your fingers crossed.
I built one and it's pretty cool...maybe someone can post a diagram.
Glad it worked well for you!


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Posted: Fri Mar 12, 2010 7:09 am
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Thak you all for the encouragement. Rebelsoul. I saw the current limiter on Weber's dvd but haven't bought the book yet. I also don't have a Variac. But, I was a little anxious to just see if the cap job worked and I turned it on. I was lucky and won't do it like that again. I tried to find a diagram for the limiter online but no go. I'll do it right next time. Any speaker suggestions for a Twin Reverb? It has Pyle Drivers now and I don't know how good they are.


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Posted: Fri Mar 12, 2010 7:27 am
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I understand,believe me I know that anticipation when you're just about to flip the switch....and the relief when everything works!
Lots of people use JBL speakers,but personally I like Weber speakers...no relation to Gerald Weber.The Weber speakers sound vintage to my ears,it's hard to explain.


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Posted: Sat Mar 13, 2010 9:28 pm
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Yeah, that light bulb in series with a power cable is a very handy tool for amp work. If I was more computer savvy, I'd send a sketch. Just a tip, I found that a flat appliance extension cable worked out best for the separation of the conductors and then with the use of insulated staples. Any way, those caps are quick-formed by the manufacturer, not all amp builders are going to take the time to bed-in the caps. Art

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Posted: Wed Mar 17, 2010 7:12 am
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Art,
You kind of lost me there with the 'light bulb in series with power cable.' Maybe you could just describe what you have and how you made it. Also, what does it mean to 'bed-in' caps? Is that something I should be doing?
James


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Posted: Fri Mar 19, 2010 4:21 pm
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James, I'll see if I can come up with a clear and concise way to type that out for you. The "Bed-In" term, is just another way of saying "forming." BTW most modern caps are the "self-healing" type. So in your case, no harm-no foul. Art

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Posted: Sat Mar 20, 2010 11:10 am
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That's great. Thanks. Also, I've noticed the last couple of times I've turned the amp on, there'a a kind of hissing, sizzling sound. It's only in the vibrato channel so I'm wondering if it could be from the reverb tank. Any ideas?
James


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Posted: Sat Mar 20, 2010 8:35 pm
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James, it's highly unlikely that the noise you described could come from the reverb tank. The first suspect would be a tube, then the carbon comb plate load resistiors. I'm assuming all the new solder joints are bright and shiny, not grey and cloudy. The noise of sizziling, is arcing(electrons jumping across a space). Does the noise go away if the reverb is switched off, using the footswitch? Have you tried swapping V1 with V2? If the normal channel was quiet, we know that V1 and the power section are fine. If swapping V1 and V2 made no change, put V2 back. Swap V1 with V4, If there is no change, return those tubes to their original positions. The only other tube to test is V3, you'll need a good 12AT7. Just a note: since the power filter caps were replaced, the components are getting more current and voltage than before the change. It will take some time for the amp to stabilize, and some components may need to be replaced. This is a normal scenario. Oh man, am I getting forgetful!!! All of the tube sockets, pots, and jacks should be cleaned, first. And of course discharge the new caps before working in the chassis. Art

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Posted: Tue Mar 23, 2010 7:44 pm
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Hey Art,
Man, I'm glad to hear from you. First, all the pots and sockets were cleaned during the cap job so I'm sure they're okay. But, I was wrong before. The hiss is on BOTH channels and it gets louder as you turn the volume up. I did the tube swapping with no success, but I need to get a couple good 12AT7s. About all I can say is that when I began to pull tubes with the standby on and volumes turned up, first from V1 toward the output tubes, nothing changed. Then, I pulled the phase inverter first (are tubes supposed to make that loud pop! when you pull them?) and the hiss stopped? Is that one tube bad? Should I replace with a 12AT7 or something else? Thanks.
James


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Posted: Wed Mar 24, 2010 3:17 am
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aclempopi you are right, you know amps


And what I can say:
The hiss can also come from some resistors which have humidity inside if the amps is not use since a long time
Leave it power "on" couple hours to dry all.
The noise can't come from the vibrato tank.

If it's not better (the hiss) :
You could have to change your bypass capacitors on all 12AX7. The 25 microFarads, 50 volts. Electrolytics.
They can make also the noise


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Posted: Wed Mar 24, 2010 2:55 pm
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James, the amp must be shut "off" whenever any tube is removed or replaced!!! I should have made that clear. By removing the PI, the preamp is no longer connected to the power amp. OK, so now with the PI out of the amp and the amp switched "on", also the standby switched to the play position, is the amp quiet ? I believe you said the hiss was gone, right? OK shut it "off", both switches. Remove V1, V4, and V5 and plug V6( the PI 12AT7) back in. Turn the amp "on" (both switches) and check for hiss. If the hiss returns, you'll need a quality 12AT7 before going any further. BTW did you try putting the old PI back in the amp and testing it ? Just want to make sure nothing fried when that tube was pulled. Art

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Posted: Wed Mar 24, 2010 3:45 pm
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Art,
Ooooohhh, turn it OFF before pulling tubes. (Here's where I slap myself in the forehead) Duh. Okay, so I'm still lucking out. It plays, but with the hiss. With the PI out, no hiss. But when I pulled V1 V4 and V5 with PI in, it's still quiet. Ready for the next tests. Oh, and I broke the center plastic piece off an output tube, the guide piece right in the middle. Dumb question but could that be glued back in place with no harm? I know. Dumb!


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