MXR PHASE 45 ISN'T PHASING (ANYMORE)

[t7mackie]

HI all,

I built the Tonepad Phase 45 and it worked great.

I plugged it in tonight and now it's not phasing. It just sounds like the plain 'off' setting when it should be phasing.

I did some troubleshooting. It works fine in off mode - regardless of plugged in or not. No signal if unplugged in 'on' mode. Normal signal when plugged back in in 'on' mode - just no phasing.

I replaced the two TL072's with freshies and still no phasing any more. Turned the trimmer all the way up and down (which used to have a big effect on the 'depth') to no effect.

All the connections look good. Nothing popped out. I just don't get it!

Any suggestions where to go from here / what to check next?

Thanks in advance,

-mac

[willienillie]

If you turn the trimmer when it's on, does it make a phasey sound?  If so, your LFO has stopped.  Well, that happened to me with a Phase 90, I'm assuming it would do the same with a 45.

[t7mackie]

No, no phasey sound when turning the trimmer.

The pedal sounds exactly the same clicking the switch on and off. Juice is getting through. It's just not doing its thing anymore. No change when I change the rate knob either.

It appears I made a clear boost (minus the boost) pedal.

[Kipper4]

Welcome Mackie

Go here and help us to help you please.
https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Rich

[t7mackie]

Welcome Mackie

Go here and help us to help you please.
https://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Rich

Will do, thank you very much! >bookmarked<

The only sketchy things I did are: I didn't have a 3M9 resistor so I connected two in parallel with a combined value within 5%. The only other thing was, I didn't have a 1N5230 so I used a (hopefully) equivalent Zener I had on hand. This may be the culprit I'm thinking. I got an assortment of really sketchy ones from Amazon. The voltage should be on spec, though.

Would a Zener of incorrect value or quality cause my issues?

I think the caps I used are overkill for this circuit. Values are correct, though. Any issues using what I had on hand? (see photo below)



I will report back after I've done all the steps from the debugging thread Rich suggested.

Thanks all!

[Rob Strand]

Would a Zener of incorrect value or quality cause my issues?

Since it worked before it's highly likely something has gone open or short.    Go over your soldering and check for solder bridges or wire-strands shorting.  Also check for broken wires.

Another option is your battery has gone flat but you would expect the trimpot to have some effect.

If you have a multimeter, measuring some voltages would be a big help.

[t7mackie]

Would a Zener of incorrect value or quality cause my issues?

Since it worked before it's highly likely something has gone open or short.    Go over your soldering and check for solder bridges or wire-strands shorting.  Also check for broken wires.

Another option is your battery has gone flat but you would expect the trimpot to have some effect.

If you have a multimeter, measuring some voltages would be a big help.

Roger that!

This is really bugging me and I'm not going to work on anything else until I get this squared away. I'm literally one component away from finishing a Disaster Transport close being finished. 

If I can't get it going I'll post all the info requested in Rich's troubleshooting thread.

FYI, I don't install the option for batteries. Only 9v pedal power.

Wish me luck...

[t7mackie]

Well, she appears to have fixed herself. I think all the probing around for voltages must've knocked an errant metal chip off of the board. I want to thank everyone who took the time to help me!

After I got her working I did a couple upgrades. I replaced the 250k trimmer with a 500k pot to have depth control. I also added a 100k double gang pot to be able to blend clean and phase tones. With the blend one can still have a real deep depth but mix in clean tone to mellow the sound out a bit. It couldn't have come out better! I'm quite content with myself at the moment.

I'd like to paint it white with spaceship panels and give it a Star Trek theme with proper font decals and call it the Forward Phaser Bank. I'm sure nobody ever thought of that before though...   



(MIX) - (RATE) - (DEPTH)

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