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Topic: Session 400, Reverb Not Working |
Tim Heidner
From:
Groves, TX
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Posted 25 Dec 2010 7:11 pm |
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Brought the 400 home today, can't get the reverb to work. Looked in the tank and re-soldered one of the wires that was loose, I get the crashing sound when I shake the amp now, and I can hear a slight change in the eq when I turn the reverb knob, but no nice reverb sound. Bad cap, maybe?
I know this thing needs maintenance, new caps all around. The big cans have 7-90 written on them in sharpie, so they are 20 years old, the rest of the electrolytics look ancient. |
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Ken Fox
From:
Nashville GA USA
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Posted 25 Dec 2010 8:41 pm
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The fact that you get a crashing sound means the return side of the amp's reverb system is working. The reverb control is also on the reverb return side as well.
The problem is in the send side. If the tank is wired correctly the cable to the right (facing from the rear) should be connected to the reverb return circuit. That may be the case, but often these wires get reversed up under the chassis and the reverb tank's input may be feeding the reverb return.
A properly oriented tank in the Session 400 will be installed with the RCA connectors facing the front of the amp. The connector on the right side, facing the front is the tank's output and the connector on the other side is the tank's input. Wired backwards the reverb will still function, but not as well as it should and will have more hum in it than normal
First thing is to determine if the cables are correctly wired. Disconnect the cable on the right side of amp (facing from rear). The tank should no longer produce a splashing sound. If it still does then the wires are backwards and the input side of the tank is feeding the reverb return.
The idea here is to find which side of the tank is good and then check the other side with an ohm meter from the RCA cable all the way to the tank. You can do this with both cables disconnected and quickly find if a cable or the tank has an open circuit. If that is the case the issue lies in the tank or cable. Repair that and then properly connect the tank. The return side of the amp is the cable that makes a noise when you touch it with your finger and the reverb knobs is also turned up a bit. This cable goes to the right side (tank output). The other cable is the reverb send signal fron the amp and goes to the left side connector.
If the tanks and cables ohm out OK with a meter it is likely an issues in the amp and will require further service. |
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Tim Heidner
From:
Groves, TX
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Posted 25 Dec 2010 9:51 pm
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| Thanks, Ken, I'm considering sending this amp to you for the Intense mod. Are you still servicing the 400's? |
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Ken Fox
From:
Nashville GA USA
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Posted 26 Dec 2010 5:55 am
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| Yes we are, Tim. Glad to do it. If you send the chassis and the reverb tank and cables I can get to botom of the reverb problem. If it is a tank then we have those in stock as well. |
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David Higginbotham
From:
Lake Charles, Louisiana, USA
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Posted 26 Dec 2010 7:42 am
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Tim,
I've had two Session 400's with reverb problems. One also had a mid control not functioning. In both amps it was broken solder joints in the chassis. Easy fix in both cases! The Session's have a very good layout and plenty of working room.
Dave
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'92 GFI D-10 8&6, ‘67 Emmons Bolt-On D-10 8&7, Walker preamp, Sarno Tonic preamp, Tubefex, Stewart power amps, Carvin XT tube amp, Webb Cabinets, all vintage JBL’s! |
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