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Fender UltraChorus


StratDudeDan
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i just dug up a 1992 Fender Ultra Chorus that had been sitting in my friend's shed since about '92...

i'm looking for any and all information on this. i've looked several places already, however, and can't find much.

google: check

my two main sources of amp electronincs online: check

music store: check

search button: check

if anyone has some sort of info, awesome. i love you.

what i'm looking for mostly are wiring diagrams (there are lots of things coming off this amp and i'd like to know where they go) and schematics (so i can give this things a once-over to make sure its working right).

also, if you know of any places that would carry spare parts for this (mainly jacks), awesome. send 'em my way. i need 2 stereo input jacks, but the normal J11 style won't work. these are all mounted directly to the PC board.

thanks in advance!

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You can get a copy from Fender for 5 bucks - alternately, you can take a look at the schematic for the Ultimate Chorus over at the Mr Gearhead download Area. Opinions seem to be mixed as two whether or not these are different amps or different names for the same amp, but they should be similar enough to give you an idea of what's going on. Spare parts should be available from Fender. HTH.

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You can get a copy from Fender for 5 bucks - alternately, you can take a look at the schematic for the Ultimate Chorus over at the Mr Gearhead download Area. Opinions seem to be mixed as two whether or not these are different amps or different names for the same amp, but they should be similar enough to give you an idea of what's going on. Spare parts should be available from Fender. HTH.

the "ultimate chorus" was actually the ultra chorus i was looking for, and i found that after posting and continuing a search through fender for parts.

thanks anyway. i have the diagram as well as schematic, and i found a part dealer (fender doesn't carry those style jacks anymore oddly enough...) so it should be working once they come in.

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yes, i can indeed confirm that.

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k, i got the jacks and installed them, and now i'm having an issue with this thing i've never seen with an amp before...

i plug in the guitar, and turn on the amp. i strum the guitar. there is no sound. i get confused. open it up, check the solder joints (especially the ones i made), test the big caps and transistors, they work.

now, i know it's getting the signal through it. when i switch over to the drive channel and turn the gain way up, i hear a massive hissing (from the distortion) and very little of my guitar coming out the speakers.

i checked it with three different guitars, each with different pickup styles (single coils, humbuckers, actives), and different cables. stereo and mono (it's a stereo amp, so i didn't know if i could "trick" it).

what could be happening? how could i fix whatever could be happening or test to see if that's actually it?

thanks in advance!

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Try running a line level stereo signal into the stereo effects return (see the schematic) - if it drives the power amp, you've got a preamp problem, but if it doesn't, or comes out distorted or really quiet, the problem is in the power amp. If the power amp works, you'll simply have to trace the signal back towards the input to find out where the problem is - not a task for the uninformed or the faint of heart. You could also check the voltages at the test points on the schematic, but that may not give you any indication of where the problem lies. I think you may have discovered why it's been in the shed for 12 years.

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sounds easy enough, until i actually try it...wonderful.

k, thank you! gonna do what i can, 'cause I want to be the one to make this work, and i refuse to give in and take it to the local repairman. it's my project. poo!

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little less than an hour later, and i already feel like exploding...

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You might want to try printing out the schematic and tracing the signal path(s) from the input to the speakers with a highlighter. Then you can start injecting a signal (you can use a Walkman with a .1uF cap in series if you don't have a test probe or a signal injector), beginning with the output stages, and track back towards the input until you run into something that's not working. VoilĂ , you've found the source of the problem! Look for shorts between pc traces, broken leads, cracked or bent connectors, bad switches and anything that gets hot to the touch. Be careful - even at the lower voltages used in solid state circuits, the potential for injury is still there. HTH

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k. i've never worked on something this large scale, so i haven't seen "test points" on schematics before. for my own benefit as well as anyone following this, how does one test this?

is it one at the start one at the test point? or from like, TP-21 to TP-22?

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The test points are just for voltage references to make sure that the power circuits are working normally. The voltages marked on the schematic are from the test point to ground. Consider them a quick diagnostic check that might save you some signal tracing. If one of the test points is notably out of spec, chances are your problem is located nearby. This is a bit complicated, but that's why techs get paid fairly well to do it. :D

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