Phase 90 pedal problems

[PRR]

> i meant D1 not the zener!!

D1 is reverse protection. If you put a battery in backward, a 1N914 may survive long enough to drain the battery flat, protecting all else. If you get a backward connection on a 9V wall-wart, the '914 will just melt open as if it was never there, no protection at all.

Considering warts come well over 1 Amp now, even a 1N400x is hardly too big. You can probably find one in an old VCR or drill-battery charger. But EVERY electronics experimenter needs a 100-bag of 1N4007.

 

[Spencerleehorton]

So are you saying it should have a 1N 4007 in there

 

[Spencerleehorton]

Now i have it working the only problem i can see if when the pedal is engaged there is a boost in the top end frequencies, what caps should i start tweaking?

 

[Spencerleehorton]

new pcb layout with link for 5v rail, which is not on the previous layout, that why it didnt work!!

ive adjusted the GND layer and the width between the layout a bit.

 

[Spencerleehorton]

where new link goes

 

[Spencerleehorton]

Ive used matched J201 which ive matched in pairs and matched the pairs as closely s possible, within 2-3%

 

[JohnRoberts]

Hi PRR,

sorry i meant D1 not the zener!!

right ive spotted my problem wand its a pcb design fault, the 22k R3,5,6 dont seem to attach to 5v rail? R4 does but the others dont?
when i attach them to 5v rail something goes down to earth?

D1 doesn't really do anything... A typical zener diode will look like a normal diode when forward biased, so D1 is in parallel with the zener that will already be conducting at roughly .5V if power is reversed.

JR 

 

[PRR]

> D1 doesn't really do anything...

I see it directly across 9V and ground, backward. It shorts-out reverse supply.

The Zener hangs on a 10K resistor to give a steady 5V bias.

That is IF he is building the plan linked in the first post of this thread. I'm not inclined to review the layouts he has posted later, since a known-good plan is available.

 

[JohnRoberts]

Never mind, there is more than one phase 90 schematic in the thread, and more than one D1.

A way to protect against reversed battery is to use a P-ch enhancement mode DMOS device (like BSS84) in series with +V (Drain to battery, Source to load, and Gate to ground).  For correct application of DC voltage the mosfet is turned on by the relatively negative gate voltage with <10 ohm on resistance. If battery voltage is reversed, it just harmlessly turns off the mosfet and goes hi Z.  The gate could also be used as an on/off switch.

I did this on my battery powered tuner so even drummers can't blow it up, since AA batteries can be installed backwards.

JR

 

[Spencerleehorton]

Just in case there is some confusion about what design I've used, the first Pcb layout in this thread doesn't work and is not correct.
The second which I've posted works correctly.

 

[Spencerleehorton]

I've now put it all in a case and I'm going to experiment with some of the components as the treble seems boosted when the pedal is engaged and adds hiss to sound.

 

[Spencerleehorton]

ive taken out IC2 and IC6 and still getting top end boost so it must be either C1 or C9 which i need to change?