Help! Is my phaser supposed to do this!?

[Drazden]

Hey guys, hopefully someone more experienced than I am with repairing effects can help me out here. I recently bought a vintage 1980 MXR Phase 100.

Now, the pedal looks fine--it's in great shape, there isn't too much noise when I hit the switch, etc. But the sound... it's buried in my rig. It just doesn't cut through--I've switched the battery, but the sound's weak. Thin. The effect just really isn't there.

Is there anything I can do to fix this? Or should I just spray contact cleaner in all the pots and jacks to see if it's a dirt problem, or... what? Or maybe it's supposed to sound like this. The effect is 'barely there' whether or not it's playing through my Marshall. I brought it into work and on the practice amp there, had the same problem. Unless I'm on the widest setting, or have the rate set really high, I can't even really tell if it's on. Maybe I'll get a little oscillation.

Who's played a Phase 100? Who can help me?! It'd be really appreciated. If you guys need clips, I can try and record some maybe tomorrow night.

[Greg Ellis]

Does it sound something like this?

http://www.youtube.com/watch?v=XHycF1a8Ptw

Or this? (fast forward to about 1:30 where he starts playing)

http://www.youtube.com/watch?v=ujci0XW_Kgc

[Drazden]

Well, both of those sound pretty subtle... but I think mine's even less pronounced.

[Emohawk]

How do you have it hooked up? Before the amp or in the FX loop?

If in the loop, is it series or parallel? Some parallel loops tend to bury pedals, regardless of how wet you set the mix. My Traynor's like that. So is my Laney in "side chain" (i.e. parallel) mode. Has to do with impedance matching & signal levels or some such thing. I'm sure there's a few cats around here who can be more technical than that description! :)

I've had no issies with pedals in insert/series FX loops, with the exception of a delay I have that's not true bypass and sucks the life out of the amp when disengaged.

[mhammer]

If you look here - http://www.generalguitargadgets.com/pdf/ggg_p100_sc.pdf - you can see that there is a trim pot on the board, labelled Center Freq on the drawing. This sets the sweep in the "sweet spot". Set it too high or too low and you can end up with very negligible and potentially inaudible sweep.

I am not suggesting this is definitely the source of your problems, but it is a possible source.

To find out if it matters, carefully mark the current setting, so that you can return to it, and twiddle the trimpot a couple of times with some contact cleaner to make sure that any dirt is removed. Now plug your guitar in, set it for a medium fast speed (the sort you could easily tell is on), and gradually adjust the trimpot to see if it results in more pronounced sweep.

Another thing to consider is the assorted electrolytic capacitors in there. It's been almost 30 years since those caps rolled off the assembly line and they may have simply crapped out on you over time. It's something that regularly happens with pedals of that vintage, and you will likely hear the recommendation to change those for new caps from more folks than just myself. What you see in the schematic as C14 and C15 are prime candidates, and both are intimately involved in determining whether the circuit provides pronounced sweep...or not.