MXR Phase 100 late 70's block - Pulsing LED?

[ChubbuckGuitars]

Hello,

I'm interested in adding an led to an old block MXR phase 100 (late 70's I believe) and was wondering if it is possible to add an led that pulses with the setting of the speed knob? If so, would this affect the sound of the pedal? I also am installing a boss-style power jack if this matters (?).

Also, what is the standard series led resistor calculation / theory? Do a lot of you use a capacitor as well to minimize pop?

PS- This is a beat-to-hell pedal and won't affect the "collector" value. Any info would be greatly appreciated. Thank you.

[cjlectronics]

I finally got a chance to reply to your post... Hurricane Ike has set us back a few days and I finally have a chance to breathe. Whew, you don't know how much you rely on the basic essentials until they're gone!!

If you look at the schematic JD Sleep drew, http://www.schematicheaven.com/effec..._phase_100.pdf, you'll see Q1 AND Q2. I would try hanging an op amp configured as a unity gain amplifier on the collector of Q1.. Then use the output of the op amp to drive the anode of an LED. Then use the cathode to drive a 470 ohm resistor to ground. This shouldn't effect the current supplied to the LED/LDR devices, but experiment with it. If your LED is too dim, add an Rin and Rf resistor for gain. If it effects the LED/LDRs then I would move the LED circuit to the base if Q2. Report back if you do this cause I'm curious what happens.

CJ

[ChubbuckGuitars]

MXR Phase 100 late 70's true bypass led frozen sweep

Thanks for replying CJ & sorry I haven't replied back to you - I got sidetracked with other projects. Hope everything has returned to normal for you after Hurricane Ike.

I finally got around to working on the phase 100 project again adding an led, true bypass & dc jack, but the pulsing led is a little over my head with the op amps, Q's, etc .... :-(

Another problem has presented itself though - the pedal was popping pretty hard with the 3pdt & led. I increased the led resistor from 2.2k to 4.7k and this seemed to help a little. I then tried the "tiedown" resistors method to help bleed the dc that I assume is causing the pops based on information found searching around the net. My interpretation of the tiedown resistors was to use 1M resistors between the circuit inputs and outputs to ground. Not really sure if this is correct and if I applied it appropriately though.

This also seemed to help minimize the popping briefly, but now the sweep will freeze in a stationary position and I can't get it to get back to normal?

I removed the tiedown resistors and the sweep came back temporarily, but the sweep is once again stuck in a stationary position. I can't find an "obvious" loose connections or visible shorts.

I don't believe this was a preexisting condition prior to my modifications, but maybe I didn't play the pedal long enough previously for this sweep issue to present itself (I'd played it for an hour or so in a jam & a few times practicing 1/2 hour sessions).

I'm at a loss as to any solutions right now other than to scrape together some cash and see if my amp tech has time to fix it. I'd like to figure this out somehow as I have a phase 90 that I'd also like to mod.

Any suggestions out there?