Torchy's Phase 45 w/Mods.
LFO oscillates, LED blinks, speed pot works, plugging in JFETS causes audible change in tone, Bias pot does nothing, circuit does not phase.
I have tried 8 2N5458's from smallbear, none phase. They all change the sound but the bias pot has no audible effect. The mix pot causes a change in tone, but nothing other than that.
Any suggestions? I omit voltage readings, etc, because the LFO works and the sound is affected by the FETs, but I'll get them if necessary.
The IC voltages all appear to be correct. The D and S voltages on the FETS are both 3.40V. The bias knob changes the G voltage from around 3.40V to 1.8V.
3.40V across the 5V1 Zener. I'm really hoping the obvious answer isn't the correct one, i.e. buy a zillion more FETs and wait for them to arrive.
Quote from: PCS
I omit voltage readings, etc, because the LFO works and the sound is affected by the FETs, but I'll get them if necessary.
Post em', especially the zener voltage. :)
Uhh... did you match the FETs? That might make a difference. It is possible that out of eight, none of them pair up well. :x
I actually used J201s in mine, and it works great even though I've been told that they're not supposed to... :?
I tried matching them as per J.C. Maillet's instructions, but absolutely no phasing occurs with any FET at any location at any point on the Bias pot, despite the Bias pot adjusting the Gate voltage from anywhere around 1.2V to 3.40V depending on the FET.
Hmm... perhaps there is a mistake in the layout, or maybe you have a bad cap or maybe you inadvertently used a wrong cap value?
I don't think there is a mistake in Torchy's layout, as it has been built by many others. I cannot see any mistakes in my wiring, there are no shorts, all of the readings seem to be correct, sound comes through from the guitar, all of the caps are of the correct value and all seem to be working (although I don't have a capacitance meter). The bias pot changes the gate voltage, but the circuit won't phase with the LFO. Any other possible troubleshooting angles?
Checked the voltages on the opamp in the LFO section? Checked all solder joints? Have you tried using a 4.7V zener? I believe the original Phase 45 used a 4.7V zener...
If you can, try and match the FETs using the FET matcher over at Geofex (//www.geofex.com). Just search jfet and you should find it.
IC1:
1=3.33V
2=3.34V
3=3.2V
4=0.6mV
5=8.63V
6=3.45V
7=3.39V
8=3.39V
IC2:
1=~2.3-7.2V
2=~3.8-4.8V
3=~3.4-5.3V
4=0.5mV
5=8.57V
6=3.32V
7=3.38V
8=3.38V
Zener 5V:
a=0.5mV
k=3.38V
FET1:
D=3.38V
S=3.38V
G=~2.5-2.7V
FET2:
D=3.38V
S=3.38V
G=~2.5-2.7V
:x :x
Ack, on the IC pin readings, 5 6 7 8 should actually be labeled 8 7 6 5.
Any suggestions? I'm getting desperate, and I don't want to give up on this pedal. I get the feeling it's something obvious...
Torchy's layout is verified, so it's not that. I was lucky enough that mine worked first time. I bought 10 trannies from Steve at SmallBear and the first two I plugged in worked but the bias had to be at the far right of rotation. Since then, I actually went through them all and did get a few pair that did work in the center of the rotation. I'll mail you a free pair that worked for me if you need them to try? It actually sounds like everything is working right, except the phase. Here are a couple things I did notice:
-the Phase is a little subtle, but very good sounding.
-the Bias knob has a sweet spot (between 12:00 and 1:00 on mine), anything outside of that = no phasing (like yours) and within the 12:00-1:00 range, there is a definite change in the phasing sound character.
-the mix knob on mine is no effect when at minimum, darker sounding phase from 11:00 to 2:00 and the high end comes in after that
-speed knob works at the last third of the pots rotation (but I haven't installed the 500K reverse log that Phillip recommends yet). Hope you get it working, it's really good sounding from a vibe "wobble" to pulsing tremelo, phase a it also get a cool filtering sound when you put it after a fuzz with the speed slowed down (think Eddie). Good luck
I'd be thrilled if you were to send me a pair of trannies. I guess that it must be the highly unlikely scenario that none of my transistors work in the circuit... I'll PM you my address. I'll owe the forum some Karma points. :D
Well, you could always resort to building another one. I have had to do that on a couple of things that I built - even though I could not find anything wrong with the circuit, something was wrong because it didn't work. :x
Also, double check the bias pot, and pot wiring. Your initial description points to that. 4 trannies on the way in the morning that I know work. :D
Well, the 1 and 3 on the Bias pot were backwards and the phase/vibe switch was backwards, but neither of those helped. I'll wait for the trannies and report back.
It sounds like it's been narrowed down to the FETs then. 8)
Quote from: Paul MarossyIt sounds like it's been narrowed down to the FETs then. 8)
Or JFET pinout. Did you double check the pinout of jfets? What brand are they? Pinouts differ from company to company. You can look up your brand at Mouser and check the data sheets, or go to the companies web site directly.
tungngruv: The 500k rev. log pot does have a better distribution of the phase. That's what MXR originally used. I've found that whenever MXR used a 500k rev. log pot, it always is the best progressing taper to the ears.
I verified the JFET pinout with my DMM and tried all possible combinations. The 2N5458's from SmallBear are in standard pinout TO-92 cases.
If you tried them in all postions, then that eliminates the pinout question. Most all jfets use a TO-92 case, that means nothing in regards to identifying pinouts. There is no standard pinout when it comes to jfets. Even the same manufacturer will switch around the drain, source, and gate on the same part #.
After you try some jfets known to be in the right range, it will narrow your problem down.
Okay. What I meant was that with the flat side facing me, the left to right was DSG as I have typically seen.
Some JFETs have the gate in the middle - DGS...
If I understood RG correctly, the Gate would be the pin which is resistive in one direction and not in the other, while the Drain and Source are resistive both ways. Using that method, mine are DSG. But, I tried other ways.
The surest way to confirm the pinouts is to look at the data sheet for your actual JFETs. Although, if you did as RG directed, then that's another story...
I haven't the foggiest as to how to get a datasheet. The trannies are from SmallBear, and they came in a little baggie. :?
Do a search on Google.com for your FETs. For example, if you had 2N5457s, you would type in "2N5457 data sheet". You'll most likely get a manufacturer's data sheet on the first page of the results. If it's an old, obsolete type, it may not show up.
Hi guys, I have been planning to make my own phaser too, what do you think about the layout of phase 90 from tonepad ? is it fully working ? and i see that matching JFET is a kind of headache too ! what is the best way to match them ?
Quote from: PCSI haven't the foggiest as to how to get a datasheet. The trannies are from SmallBear, and they came in a little baggie. :?
Do they have any writing on them denoting the manufacturer? They should. You'd probably have to use a magnifying glass to read some of them.
They have a stylized F on them, as well as B411. I'm assuming they are Fairchild Semiconductor products, and their datasheet confirms the DSG pinout.
The stylized "F" is Fairchild, correct on the pinout. You've eliminated pinout as a problem.
Have you inspected the solder side of the board with a magnifying glass to make sure you haven't bridged any of the solder strips together. Even a sliver strand of copper or solder will cause a problem. Especially around the IC's, which are easy to bridge the traces together. Maybe I'd also double check the trace cuts. There is something like 28 spots where you have to cut the strip trace.
Quotewhat do you think about the layout of phase 90 from tonepad ? is it fully working ? and i see that matching JFET is a kind of headache too ! what is the best way to match them ?
I've built the tonepad version, and it works great. For matching JFETS, check out www.geofex.com
Well, I got tungngruv's FET's, and it still doesn't phase. :evil: :evil: But many thanks to tungngruv. I'm at a loss as to what to do now. :x
My suggestion is to take a break and build it again at a later date (few weeks maybe). I have had a few possessed circuits that worked the second time around, after some period of time went by without even thinking about it. My hunch is that I just kept glossing over the same mistake over and over, so after I took a break, mistakes became a lot more apparent... :oops:
Well, I'm going to rebuild it now. I've already waited almost a month! I have one more piece of stripboard. I'll check each component prior to soldering. Any way to test capacitors (w/out a cap meter) other than testing for for resistance indicating a dielectric breach?
Okay. Rebuild. Exact Same Thing. All components check to the best of my skills. All wiring is triple checked.
Every portion of the circuit works except the phaser. The mix has the light/dark effect, the speed changes the speed of the LED/LFO, the bias changes the voltage on the FETs. I guess the answer is to order a million fets from Mouser?
So your'e positive that the veroboard layout that you have has no errors? It shouldn't be that hard to get the Phase 45 working with JFETs that are reasonably close to eachother. Have you tried some J201s in it? I used some in my build, and it works great (even though they're not supposed to).
It's Torchy's famous layout. A bunch of people here have built it. I'm going to PCB's after this.
QuoteIt's Torchy's famous layout. A bunch of people here have built it. I'm going to PCB's after this.
I was wondering if maybe you were working off of an early version that may have had a small error or something, that's all. I know other people have built it from that layout. Reminds me of my ill-fated Boss Slow Gear clone that I built - it doesn't work with
any JFET that I have tried. :cry:
Anyhow, I built the tonepad Phase 45, and it worked great on the first try. Viva PCB! Uh, did I say that out loud?! :lol:
@PCS - please take clear photos and post (top and bottom of board). :wink: