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Post subject: Help me Diagnose a Fender I bought at a pwan Shop.
Posted: Tue Mar 03, 2009 4:23 pm
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I got a 1984 Fender concert Head model. I got it for real cheap but with a catch; some of the features don't work. This is my only tube amp and so I don't know exactly what each "malfunction" means, but I do know they are malfunctions.

Okay for example, the gain channel does not activate but rather produces another clean channel (this is a 2 channel amp), with settings I have for the gain channel?!?!....

2ndly someone tried to Lee Jackson mod this amp but only succeeded in changing the reverb knob to where the 2nd input would normally be. The Lee Jackson mod boasts sweeter distortion and a 6 position mid selector switch the switch does not do anything so I think it might have been a failed attempt and may be why the gain channel doesn't work

Also I suspect these are old tubes, but another problem is that after a few minutes of playing the sound will go very quiet, and even fizzy, is this cause of old tubes? You tell me!

Ohh another thing the effect loops on this is $@!&*% also...

I just wanted to get an idea of as to what might be wrong with it before i spend a few more hundred dollars on repairs.

So yah let me know so i can start jamming away on this beast!!!


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Fender Play Winter Sale 2020
Post subject:
Posted: Wed Mar 04, 2009 12:23 pm
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Location: In the pocket north of Washington D.C.
Get new tubes and have it checked out by a good tech.
A cheap diagnostic is to swap similiar tubes between tube sockets. Often different sections of an amp use dif. portions of a tube.
It is amazing how well this works when you try swapping between V1 and V2.

Read up on the Fender Field Guide for more amp info.

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Posted: Sun Nov 01, 2009 10:56 pm
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Did you get a huge discount for all of these problems, or did you discover them after you bought it?

With used amps, it's critical to find ones with the least amount of "mods," as most of these mods range from beneficial updates (filter caps, 3 prong mod) to hacks from people trying to turn a Fender into a Marshall or a Mesa.


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Posted: Mon Nov 02, 2009 6:56 am
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Yes friend,
It's going to be impossible to give you much without seeing how far these ugly mods go into the signal path.
You'll need a tech!

But just as a thought -
Have you looked inside?

Just a warning as a first-time tube amp owner:
Be careful in there - voltages higher than 400v are not uncommon.
A tube amp MUST have a load attached.

But I'm not asking you to go poking around on a live amp - just take a look to see if the Jackson mod had it's own circuit board and how it is mounted.

Fender amps are well-documented.

BillyVee


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Posted: Mon Nov 02, 2009 7:04 am
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Tubes are generally 90% of the problems in tube amps. Poorly done mods are another problem.


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Posted: Mon Nov 02, 2009 8:03 am
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This guy has some great stuff:
http://www.geofex.com/ampdbug/ampdebug.htm


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Post subject:
Posted: Tue Nov 03, 2009 12:50 am
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Hey ST, if you really want to keep this amp, I'd have a tech look it over. The tube swap is a fine idea and you could certainly wail away on it, but ultimately the maintenance and inspection should be done. I think this was the last of the Paul Rivera influenced Fenders. Neat amps ! ART

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