pt909 phasetone build

[cortey]

Ive attempted this build once before with no results. This is what I have so far this time:

http://www.aronnelson.com/gallery/main.php/v/diyuser/cortey/ibanezpt909.png.html
http://www.aronnelson.com/gallery/main.php/v/diyuser/cortey/2011-12-04_02-04-10_8_Deroche.jpg.html

Component Substitutions:
IC 101-104:LM1458
Q 101-104: J113
Q 105: J111
Q 106-108: BC548C
D 101-102: 1N4148
D 103: 1N4734A
D 104: 1N5231B
D 105: 1N4007
CR1 & CR2: 100Kohm||470pF

This is the schematic I have been working from.
(I color coded the components for easier comprehension.
The red lines are where I have connections made.):

http://www.aronnelson.com/gallery/main.php/v/diyuser/cortey/pt909+markup.png.html

The troubleshooting begins.
First off, I give the pedal a 9V supply and connect the input to my guitar and the output to my amp. With the indicator LED off the clean signal goes through to my amp.
When I switch the pedal on (in my breadboard picture you see im using an (on-off) rocker whereas the circuit is designed for an (on-mom) so i just flick it on and back off real quick.) the indicator LED comes on, however I get the same clean signal through to my amp. I think the problem is that the transistor Q105 is not switching on. If that is the case, that leads me to believe transistors Q101-104 may not be switching as well. Which in turn begs the question, Am I using the correct transistors?

http://www.aronnelson.com/gallery/main.php/v/diyuser/cortey/pt909+subcircuits.png.html


At the test points I get (test conditions: indicator LED on, input and output pluged in, amp off, 9V battery supply used):
CP-1: 9.03V
CP-2: 4.86V
CP-3: 4.82V
CP-4: 4.84V
CP-5: 4.86V or ~4.2-5.3V (*depending on the width pot setting at either maximum)
CP-6: 0.03V
CP-7: 4.48V
CP-8: 4.82V

[Fender3D]

CP4, 5, 7, 8 are signal test points.
You should check with a scope what signal you get:
CP5 = LFO wave
CP4 = effect signal
CP7 = working Q105
CP8 = phase shifting

You may short Q105's D and S and check for effect, provided that Q101-104 are somewhat similar (matched is better) and you have a working LFO (IC 104 and surrounds)

[cortey]

I dont own or have access to an oscilloscope.
If I was to purchase one, what would be a low-end but decent solution?

You may short Q105's D and S and check for effect, provided that Q101-104 are somewhat similar (matched is better)

Do you mean that Q101-104 is the same as 105? (so use all J111?)

[Fender3D]

I dont own or have access to an oscilloscope.
If I was to purchase one, what would be a low-end but decent solution?

http://cgi.ebay.com.my/ATTEN-ADS1062CAL-60M-Hz-1G-Digital-Oscilloscope-7-LCD-/320626722997?pt=BI_Oscilloscopes&hash=item4aa6d788b5

this should be enough, it's a dual trace, you'll enjoy it with phasers...

Do you mean that Q101-104 is the same as 105? (so use all J111?)

nope,
Q105 behaves as a switch, any n-channel FET should work here,
Q101-104 should be matched to achieve a proper phasing effect (they work as variable resistors and matching will ensure they act the same with applied LFO voltage)

[cortey]

Q101-104 should be matched to achieve a proper phasing effect (they work as variable resistors and matching will ensure they act the same with applied LFO voltage)

Which values need to be matched? The cut-off voltage? How do I measure?

[DavenPaget]

I dont own or have access to an oscilloscope.
If I was to purchase one, what would be a low-end but decent solution?

Yeah the ATTEN is a good one , if you want a portable ARM-core DSO :
227$ ( fingers crossed. )
http://www.ebay.com.sg/itm/ARM-DSO203-Nano-V2-Quad-Pocket-Digital-Oscilloscope-/280721267553?pt=LH_DefaultDomain_0&hash=item415c4a9b61#ht_2797wt_905
59$ ( seriously low-end , but feels good to use your own DIY DSO ) ( available at amazon also )
http://www.sparkfun.com/products/9484

[cortey]

ok so i found this and made it:
http://www.geofex.com/article_folders/fetmatch/fetmatch.htm

i got 4 FETs and the Vgs are:
Q101: -2.07V
Q102: -2.07V
Q103: -2.06V
Q104: -2.05V

I plugged them in and I still have NO phasing, whether the pedal is on or off. Just the clean signal.

[cortey]

I dont own or have access to an oscilloscope.
If I was to purchase one, what would be a low-end but decent solution?

Yeah the ATTEN is a good one , if you want a portable ARM-core DSO :
227$ ( fingers crossed. )
http://www.ebay.com.sg/itm/ARM-DSO203-Nano-V2-Quad-Pocket-Digital-Oscilloscope-/280721267553?pt=LH_DefaultDomain_0&hash=item415c4a9b61#ht_2797wt_905

How good is this portable one? Is it worth the 227$ (or in my case $179 Canadian)? Are they durable?

[cortey]

Here is the full list of test voltages (with respect to ground):

   Drain   Gate   Source
Q101   4.84   4.70   4.84
Q102   4.84   4.70   4.84
Q103   4.84   4.70   4.84
Q104   4.84   4.70   4.84
Q105   4.82   0.03   4.82

   Emitter   Base   Collector
Q106   0.74   1.35   0.75
Q107   0.74   0.27   5.83
Q108   0.74   1.36   0.83

IC101
P1   4.80
P2   4.80
P3   4.56
P4   0
P5   4.81
P6   4.81
P7   4.80
P8   8.59

IC102
P1   4.89
P2   4.84
P3   4.84
P4   0
P5   4.84
P6   4.84
P7   4.80
P8   8.58

IC103
P1   4.89
P2   4.84
P3   4.84
P4   0
P5   4.84
P6   4.84
P7   4.80
P8   8.58

IC104
P1   4.81
P2   4.84
P3   4.84
P4   0
P5   4.89
P6   4.77
P7   4.54-5.15 (slow up-down)
P8   8.58

D1
ANODE   0.03
CATHODE   5.29

D2
ANODE   0.74
CATHODE   0.11

D3
ANODE   0.33
CATHODE   6.22

D4
ANODE   0
CATHODE   4.84

D5
ANODE   0
CATHODE   8.58

[DavenPaget]

I dont own or have access to an oscilloscope.
If I was to purchase one, what would be a low-end but decent solution?

Yeah the ATTEN is a good one , if you want a portable ARM-core DSO :
227$ ( fingers crossed. )
http://www.ebay.com.sg/itm/ARM-DSO203-Nano-V2-Quad-Pocket-Digital-Oscilloscope-/280721267553?pt=LH_DefaultDomain_0&hash=item415c4a9b61#ht_2797wt_905

How good is this portable one? Is it worth the 227$ (or in my case $179 Canadian)? Are they durable?

I bet a dime that it might be good .
Apparently , seeeeeeeeeeeeeeeeeedstudio carries it ,
http://www.seeedstudio.com/depot/dso-quad-4-channel-digital-storage-oscilloscope-p-736.html?cPath=174
Good if you need a portable 4 channel DSO .
other then that , it's useless .
Get the Atten , if you don't need to use a portable oscilloscope , might seem expensive but hey , it's 1st hand and it's 1GSPS* . Very worth it if you ask me .
Pre-owned scopes probably cheaper but they're huge .

[Fender3D]

...
I plugged them in and I still have NO phasing, whether the pedal is on or off. Just the clean signal.

Did you short Q105's D and S?
Did you check for signal at CP4?

[cortey]

I FIGURED IT OUT!!!!

I had a gut feeling the problem was something to do with Q101-104, due to there being no phasing. So after a long hard look at those darn transistors it came to me.

Why would a phaser not give you a phased output??
Answer... The FETs are not switching.

Why are my FETs not switching??
Answer: It could be that they are not being biased correctly.

   Drain   Gate   Source
Q101   4.84   4.70   4.84
Q102   4.84   4.70   4.84
Q103   4.84   4.70   4.84
Q104   4.84   4.70   4.84

So I take a closer look and find that i've got the 30k resistors going from Source to Gate, and not in their proper location between the Source to Drain.
Problem solved and i get a great phasing effect. Time to start designing the PCB!!

i'm so proud of myself

[cortey]

I have another question regarding the power supply. My enclosure is going to be too small to fit a 9v batt, so i was wondering how I would cancel the battery out but still have the external 9volt supply work. Im thinking i should just put a short where the battery was... am i right? Heres the schematic again
http://www.aronnelson.com/gallery/main.php/v/diyuser/cortey/ibanezpt909.png.html

[Fender3D]

Why short?
Simply trow away your battery snap

[cortey]

oh, yeah that makes sence. cause if i short out the battery i'd be shorting out the 9V from the wallwart >_<
so where the negative end of the battery is connected on the input jack. i can tie that inputjack pin to ground or leave it open?

[Fender3D]

...i can tie that inputjack pin to ground or leave it open?

Since you'll get rid of the battery snap, it's the same thing

[cortey]

Ahh, then I might as well use a mono input jack, instead of the stereo.

[jmasciswannabe]

I REALLY like this phaser and am looking forward to seeing your completed build layout. Good luck and thanks!!

[snjensen]

+1