Is the Maxon PT-909 True Bypass?
I did the battery/power test. Unpowered it passes a bypass signal. I also took an ohm reading from input jack to PCB input, but got 0's. Not sure if I was doing it correctly.
Here I think I've accurately laid out the switch configuration. I also include the schematic for the Ibanez PT-909 which I believe is the same.
Any help as to how to properly TB (if needed) would much appreciated as always.
(https://i.postimg.cc/R66vqq3f/SWITCH.jpg) (https://postimg.cc/R66vqq3f)
(https://i.postimg.cc/N57BK30N/ibanez-pt-909.jpg) (https://postimg.cc/N57BK30N)
If you can't tell, why would it matter?
Does it tone-suck?
Good question ;D
I like running all TB on my rig. And I enjoy soldering things
Also the switch is a little wonky I was going to replace anyway. I didn't know if it's TB the way it is or not. Still fairly new to the game my apologies
QuoteIs the Maxon PT-909 True Bypass?
With a DPDT switch *and* an LED it cannot be true bypass.
It will be like the older MXR pedals where the switch center contact (the pole) connects to the output socket. The switch wires the output socket either to the input socket (the zero ohms you measured) or to the output of the phaser.
The thing that makes it not true bypass is the input socket is always connected to the input of the effects pcb. That will add a permanent 510k load or so via an input cap. The input cap prevents multimeter measurement seeing the 510k to ground/Vref.
Some options:
- ditch the LED and use the other contact for true-bypass
- get a three pole foot switch and wire for true-bypass with LED.
The switch may or may not fit in the space. It will fill the battery space for sure.
- use a Millenium bypass type circuit and corresponding switch wiring.
With the low value of R138 on the Ibanez PT-909 schematic the switching click/pop will be very low with
the Millenium bypass.
FWIW, the Ibanez PT-909 circuit uses JFET switching and pushbutton switch. That era of Ibanez pedals is a little messy and I wouldn't be surprised if there's a slightly earlier Ibanez PT-909 with the exact same wiring as the Maxon. You might find an older schematic on the FSB forum. It won't help your problem though. You are pretty much stuck with the options.
Yep I was hoping to get away with a DPDT, but I'll just go with a 3PDT...I usually power Phasers with a jack anyway.
Thank you so much for answering my question!
Quote
FWIW, the Ibanez PT-909 circuit uses JFET switching and pushbutton switch. That era of Ibanez pedals is a little messy and I wouldn't be surprised if there's a slightly earlier Ibanez PT-909 with the exact same wiring as the Maxon. You might find an older schematic on the FSB forum.
Interesting. Yeah there's an Ibanez PT-909 with a switch and looks to be the exact same circuit board. I have a request for analysis on FSB. I would love to make a clone of this thing. It's a sleeper (don't tell anyone 8))
Ibanez PT-909
(https://i.postimg.cc/CZTryjdB/Ibanez-PT-909.jpg) (https://postimg.cc/CZTryjdB)
(https://i.postimg.cc/BjLZ7G1Z/images.jpg) (https://postimg.cc/BjLZ7G1Z)
Maxon Pt-909
(https://i.postimg.cc/w71w7WmR/1.jpg) (https://postimg.cc/w71w7WmR)
(https://i.postimg.cc/Y4NHT227/4.jpg) (https://postimg.cc/Y4NHT227)
QuoteInteresting. Yeah there's an Ibanez PT-909 with a switch and looks to be the exact same circuit board. I have a request for analysis on FSB. I would love to make a clone of this thing. It's a sleeper (don't tell anyone 8))
Well done finding that!
Yes, most of the early Ibanez pedals where exact replicas of the Maxon. IIRC some of the PCB's were even marked Maxon. The PCB's usually had numbers which were codes for the circuits and the Maxon and Ibanez boards had the same markings.
Your pics sparked my memory a bit. The units with the square buttons were all JFET switching. The early units like yours had the round buttons and had the old school bypass circuit. However, there were some transitional Ibanez pedals which had round button but JFET circuits. There's a whole lot of details like wide boxes, flying fingers logos, presence of LEDs, presence of DC jacks, types of knobs. I spent ages working it all out at one point but it's so confusing the memory has frayed away.
There's something puzzling about those pics.
The Ibanez (1979) has red dot JFETs whereas the Maxon (1978) has yellow dot JFETs.
I'm inclined to think the dot color means 2SK30AR and 2SK30AY which have quite different specs. If that's the case the Ibanez unit will sound different to the Maxon, well at least the pedals in the pics will sound different.
IIRC, the PT999 Phase mostly used yellow dots but I would have to check my notes.
[EDIT: The painted dots do not seem to match the JFET suffix. Ibanez have red dots on 2SK30AY parts. See reply #10 below.]
Here is my crude analysis of the Maxon. I still haven't documented the resistors. Hope this helps! In all honesty I know nothing about JFETS
(https://i.postimg.cc/kDZX0LjD/1-CB575-FE-5025-4-DAA-BD60-96-C2-CB6-D0-FF5.jpg) (https://postimg.cc/kDZX0LjD)
Btw I'm not sure my layout of the stock switch is accurate. I attempted to TB with a 3PDT but not getting effect signal.
Which technique for wiring a 3PDT using the stock LED do you recommend? I know there's more than a few ways to configure.
I used this method
(https://i.postimg.cc/F1mHNjmX/F3-C485-F4-0-A51-4-F5-D-A164-50-E5-E2-BDDB4-D.png) (https://postimg.cc/F1mHNjmX)
QuoteHere is my crude analysis of the Maxon. I still haven't documented the resistors. Hope this helps! In all honesty I know nothing about JFETS
So your unit has the 2SK30AY (and yellow dots to match the Y in the part number ... or maybe not ... ).
I had a look at my old 1975 Ibanez PT900 (PCB marked 999) and it also uses 2SK30AY. The interesting thing is the JFETs have *red* paint dots! I can only assume the paint dots are some additional sorting marks done by Ibanez/Maxon.
QuoteBtw I'm not sure my layout of the stock switch is accurate. I attempted to TB with a 3PDT but not getting effect signal.
Hmm, the way you have drawn it looks OK to me.
QuoteWhich technique for wiring a 3PDT using the stock LED do you recommend? I know there's more than a few ways to configure.
I'm in favour of shorting the input like the "better" version on this link,
http://stinkfoot.se/archives/2233
For one it prevents the need to add a de-pop resistor but I also like to short the input as a floating input can sometimes cause problems.
BTW I was referring to the photo of the stock Maxon switch I drew arrows on. Might not be labeled correctly.
And that's interesting your Ibanez uses the same JFETS. I'd be curious what the color paint coding means!
QuoteBTW I was referring to the photo of the stock Maxon switch I drew arrows on. Might not be labeled correctly.
No problem. That pic isn't for you unit is it? If so I'm very confused. I can see 4xJFETs for the phaser but there's three other transistors or two transistors and one JFET. If you look at the schematic for the PT909 there should be 4xJFETs for the phaser, three transistors and one JFET for the switch. For your unit with no JFET switching I wouldn't expect those parts at all.
That's what I was getting at early on in the thread, Ibanez/Maxon made changes through that period.
QuoteAnd that's interesting your Ibanez uses the same JFETS. I'd be curious what the color paint coding means!
Back in the early days manufacturers sorted some parts in the subcategories and marked them with a dot. For example transistors (with the same part number) were sorted by gain into ranges. Instead of using colored dots the Japanese put the sorting category in the part number using a letter and didn't use dots. The letter is the name of a color. So you might see 2SC1815Y (yellow), 2SC1815GR (green), 2SC1815O (orange). You get the same with JFETs, see the bottom of the datasheet,
https://imgv2-1-f.scribdassets.com/img/document/380787885/original/5eb14b72db/1607017630?v=1
Anyway that's what I thought dots were. However, now I don't think that's the case. Phasers need JFETs to be sorted into tighter categories than the manufacurer's category. That means some more testing. The dots might simply mean they have been sorted (and were placed in the appropriate sorted bins). Alternatively the color of the dot might be significant in that it represents some sort of sub-category within Maxon.
It's hard to work out this still without having a lot of samples to see the pattern.
Quote
No problem. That pic isn't for you unit is it? If so I'm very confused. I can see 4xJFETs for the phaser but there's three other transistors or two transistors and one JFET. If you look at the schematic for the PT909 there should be 4xJFETs for the phaser, three transistors and one JFET for the switch. For your unit with no JFET switching I wouldn't expect those parts at all.
Yep the pictures of the labelled components and the labelled switch wiring are my Maxon.
I assumed the schematic for the Ibanez was similar because of the speed/depth/feedback pots. I'm not very familiar with phase circuits yet :o
Hoping someone from FSB traces it
QuoteYep the pictures of the labelled components and the labelled switch wiring are my Maxon.
Well that puts a different light on things! It might even explain why your true bypass isn't working.
Maybe the circuit has JFET switching but the LED switching is done with the switch. That might explain
why there's one C1815 missing.
If they have done something funky with the switching it might explain why you perfectly OK true bypass wiring doesn't work in effects mode. Maybe the funky switching is disable and the effect stays off.
However, I'm very much struggling to come-up with an arrangement which matches your wiring and also somehow switches a switching circuit. The main problem being the center contact of the switch connecting to both the input and the switching circuit. Also there can't be a flip-flip circuit because the footswitch is on/off not a push button.
There's a missing piece of the puzzle somewhere!
QuoteI assumed the schematic for the Ibanez was similar because of the speed/depth/feedback pots. I'm not very familiar with phase circuits yet :o
It's not a bad assumption. I'm sure the bulk of the circuit *is* like the schematic you posted. It's the small differences that are stuffing things up.
QuoteHoping someone from FSB traces it
I'll trace it but I'll need a bit more info. Some more photos will help:
- photo of the bottom of the board
- photo of the wires to the pots, and the input/output sockets
- I can see a few part values on the Ibanez board pic you posted earlier but if you can take a few side shots
it might let me see a few more values.
I'll take some more detailed pics today...
I attempted to replace the jacks and rewired the switch so it's kind of a mess right now :icon_redface:
Here are the pics I took before
(https://i.postimg.cc/JH4yBCBj/2.jpg) (https://postimg.cc/JH4yBCBj)
(https://i.postimg.cc/rz8RHxYz/3.jpg) (https://postimg.cc/rz8RHxYz)
(https://i.postimg.cc/c6wZfbcn/1.jpg) (https://postimg.cc/c6wZfbcn)
QuoteI'll take some more detailed pics today...
I attempted to replace the jacks and rewired the switch so it's kind of a mess right now :icon_redface:
Here are the pics I took before
Cool, thanks. I actually found the pic of the bottom of the board you posted on another forum.
Those will do for now. Some pics of the part values might be helpful soon.
Already I can see the extra JFET is an input buffer, as opposed to the opamp buffer on the other schematic. I'm not seeing any weird JET switching. It's more or less looking like what we thought it was in the first place. So now I'm puzzled about what's gone wrong with your true bypass wiring. Perhaps you could hard wire the input socket to the pcb input (the old yellow wires) and wire the pcb output to the output socket. That will hard wire the effect to the sockets. It should work. The only thing you can't do is switch back to bypass. At least you know the effects part is still working. If it is then maybe there's something wrong with the switch.
Effect worked great before, although I was having problem with input jack, would have to wiggle to get sound before. So I replaced both, had to sand the holes slightly to fit newer jacks. Jacks barely fit, so might not have been the greatest idea :icon_redface:
I'm getting bypass, LED turns on, but no effect.
Output jack is now unstable. I think there is loose connection somewhere. Or maybe jack is shorting on enclosure (although not sure what material is) Might put old jacks back if they still fit. Please excuse the mess ::)
(https://i.postimg.cc/Lnm5GK9z/IMG-1409.jpg) (https://postimg.cc/Lnm5GK9z)
You might want to check the wiring of the yellow and white wires on the top row of the switch. I think they are reversed. That would stop the effects mode but not bypass.
Oh forgot to mention if the old sockets have star washers you should use them on the new jack, on the inside surface. It gives a better ground connection.
Quote
You might want to check the wiring of the yellow and white wires on the top row of the switch. I think they are reversed. That would stop the effects mode but not bypass.
oops will fix that asap thank you sir
QuoteOh forgot to mention if the old sockets have star washers you should use them on the new jack, on the inside surface. It gives a better ground connection.
Don't think I saw any star washers but may have some laying around. thanks Rob :icon_biggrin:
QuoteDon't think I saw any star washers but may have some laying around. thanks Rob
Actually I can't see any in the pics so maybe they didn't use them.
FYI, I finished tracing the unit. There's no weird JFET switching or anything like that. The switching is very straight forward like the old MXR pedals. It should be very easy to do a true-bypass mod. Everything is like we first thought.
It's not 100% like any of the other Ibanez units. It's kind of a transition between the early PT-900 (pcb marking PT999) and the latest PT-909 schematic you posted at the top of the thread.
As a very brief summary:
- Input buffer is JFET not an opamp
- The output mixer is a plain vanilla inverting mixer. That means overall the pedal inverts the signal.
- The phase stages are more like the later PT-909. No 100pF cap from what I can see.
Feedback circuit very similar except no trimmer.
- The LFO is more like the PT-900 (which is similar to the MXR Phase 90). It's not an integrator type like the later PT-909.
- The LFO has some transistor buffers added. That's where the two 2SC1815 transistors come in.
The LFO output is buffered in order that the Width control can be added.
On "the other" forum there's a thread called "Ibanez PhaseTone PT-999". Dirk Hendrik's pdf schematic is the for actual PT-999 - yet another unit. This one has JFET switching but a normal switch (probably round head). However, Bernard Duur's schematic at the end is actually for the PT-900. It could be for an earlier PT-999 as well [Actually I'm sure it is]. The confusion arises because the PCB for PT-900 is marked PT-999. The PT-900 is the earliest and is the one before the PT-909.
The PT-900 is a flat box unit (approx 1975)
http://www.effectsdatabase.com/model/ibanez/first/pt900
The early PT-999 which is like the PT-900, (approx 1976)
https://mirosol.kapsi.fi/2015/02/
Awesome Rob!
I'm not as well versed as you, so a little lost in all of the "P's" and "9's" I have a lot of homework to do tonight! ;D
I'll try and get all the resistors mapped out asap
FWIW As far as vintage phasers, I've really only had my hands on a P90, P100 and now the PT-909. And by far I dig the PT-909 over the other two. I love the sound/functionality. Still need to dig deep on what magic ingredients make up all of the different phase flavors.
I've spent a lot of time reading up on Mods for the MXR's, to basically have the functionality (Depth, Feedback) as the PT-909. That's why I think the PT-909 is worth mapping out and cloning.
So went nuts and just rehoused it. (I know I'm going to vintage pedal hell :icon_twisted:)
Stock output jack was wonky, and the new jacks were unusable in the existing enclosure unfortunately. Replaced the 9v jack and battery snap. Repurposed the pots and knobs. Doesn't look that cool but it'll do for now, needed to be boxed up!
Might spend some more time and make it fancier one day, add an LED, who knows
Pedal sounds fantastic imo, it might actually replace my long standing vibe. It's got all the psychedelic swirl I'm after with great control.
(Thank you Rob for your infinite knowledge)
(https://i.postimg.cc/jWnLKFxx/11.jpg) (https://postimg.cc/jWnLKFxx)
(https://i.postimg.cc/HcGjL9nQ/22.jpg) (https://postimg.cc/HcGjL9nQ)
QuoteI'm not as well versed as you, so a little lost in all of the "P's" and "9's" I have a lot of homework to do tonight! ;D
This site has some very good info.
https://www.tonehome.de/ibanez/narrow-box-series-w-round-switch/pt-909-phase-tone/
The only thing I don't like about the site is he gives versions from the first phaser instead of versions *within* the same model.
I think I've got 5 or 6 versions of PT-909 alone.
The site resolved a few weird versions I've seen but I still have some others that look like they shouldn't exist! Examples where
there's two features that appear together at the wrong time.
QuoteI'll try and get all the resistors mapped out asap
I'll do some final checks and start drawing it up tonight. I wanted to avoid drawing it up in Ltspice.
QuoteSo went nuts and just rehoused it. (I know I'm going to vintage pedal hell :icon_twisted:)
Yeah pretty extreme. I'd probably just source some new jacks which were like the existing ones.
QuotePedal sounds fantastic imo, it might actually replace my long standing vibe. It's got all the psychedelic swirl I'm after with great control.
Cool. Do you use the feedback at all? It's useful for copying sounds off some records but in general I tend not to use it. It does add some extra swirl if you like that.
FWIW, my old PT900 sounded a little weak. I have heard a few better ones on Youtube. It could very well depend on thre JFETs that ended up in the units. I modded mine somewhat about 25 years ago and its a much deeper phasing than it originally was. Interestingly I removed the cap between the LFO and the JFETs. Looks like that's what Maxon have done on the PT-909.
Well I've got the bulk of the schematic drawn up. I did some checks and my resistor count doesn't match up. I'll need to check it after I've had some sleep.
Quote from: Rob Strand on April 14, 2021, 10:25:35 AM
Well I've got the bulk of the schematic drawn up. I did some checks and my resistor count doesn't match up. I'll need to check it after I've had some sleep.
Sorry havin a busy week over here. I will have those resistors mapped out hopefully by the weekend. Get some sleep! ;D
QuoteSorry havin a busy week over here. I will have those resistors mapped out hopefully by the weekend. Get some sleep!
No problem. Whenever you get time. I've found a few things to clean up on the schematic anyway (always is). On the whole it's not looking too bad.
A couple of things popped-up which need checking:
- value of the big cap with the red dot.
- values on the tantalum caps
- the C1815 should have a letter like C1815GR or C1815Y
This might save some time identifying the parts. You can just write down the values for each part designator in a text list.
(Last Resistor R43, Last cap C17)
(https://i.postimg.cc/6Tp7Z8Cx/Ibanez-Maxon-pt-909-Designators-v10.png) (https://postimg.cc/6Tp7Z8Cx)
EDIT
C1 473z 25V
C2 4.7uf 25V
C3 473z 25V
C4 473z 25V
C5 473z 25V
C6 473z 25V
C7 473z 25V
C8 473z 25V
C9 473z 25V
C10 473z 25V
C11 4.7uf 25v
C12 4.7uf 25v
C13 10uf 16V
C14 33uf 10v
C15 47-35
C16 103
C17 6.8-10
Way to go! We are nearly there.
Quote
I mapped this out with the assumption the color band in attachment is "brown" - i.e. "brown black orange gold"
Any resistor with a (?) was difficult to read but fairly sure they are correct.
Yes, that's brown. It's hard to read.
Some of the ? values I am able to fix up as well as a few others where I wrote "pretty sure"
However, there's a few which need rechecking. I put the colors next to the value if it helps.
If possible, on the 2SC1815 transistor could you check if it's 2SC1815Y, 2SC1815GR, or 2SC1815BL
Part Prev Value Possible Value
R1 4K 1K Brown, Black, Red (pretty sure)
R2 4M 1M Brown Black Green (pretty sure)
R3 45K 15k Brown, Green, Orange (pretty sure)
R4 9.2K Recheck. 12k Brown, Red, Orange or 8.2k Grey, Red, Red
R5 350K Recheck. maybe 10k Brown Black Orange? or 15k Brown, Green, Orange, or 3.9k Orange, White, Red
R6 40K 10k Brown, Black, Orange (pretty sure)
R30 1.3K Recheck. maybe 30k Orange, Black, Orange ; Actually it could be 3.3k Orange, Orange, Red
R31 10K Recheck. maybe 5.1k Green, Brown, Red
R32 1K Recheck. maybe 2k Red, Black, Red
R34 9.1K Recheck maybe 910 ohm White, Brown, Brown; 9.1k White, Brown, Red still a possibility.
R40 10K Recheck Could be 10k Brown, Black, Orange but maybe 20k Red Black Orange or even 30k Orange, Black Orange
Yep some of those are wrong, not sure what happened. I'm going to redo the list today. Sorry for the delays!
QuoteYep some of those are wrong, not sure what happened. I'm going to redo the list today. Sorry for the delays!
Don't stress out about any delays, no problems at all.
It's good to check all the values but I'm fairly confident the other parts not in that second list.
Resistors:
R1 1K
R2 1M
R3 15K
R4 (white/grey) red red
R5 10k
R6 10K
R7 10K
R8 150K
R9 30K
R10 100K
R11 10K
R12 10K
R13 150K
R14 30K
R15 100K
R16 10K
R17 10K
R18 150K
R19 30K
R20 300K
R21 10K
R22 10K
R23 150K
R24 30K
R25 100K
R26 15K
R27 10K
R28 10K
R29 10K
R30 3.3K
R31 5.1K
R32 2K
R33 100K
R34 (white/grey) brown red
R35 150k
R36 470k
R37 470K
R38 4.7K
R39 10K
R40 20K
R41 1K
R42 10K
R43 100K
Quote
If possible, on the 2SC1815 transistor could you check if it's 2SC1815Y, 2SC1815GR, or 2SC1815BL
Hard to read but 99% sure it says "BL"
Side note: I ended up purchasing an additional unit as a backup (in case I blew up the first). There are slight variances in values as well as RED painted dots on the K30A - but that's for another day. We'll just focus on the original :icon_cool:
QuoteResistors:
Awesome work.
The one value I'm suspect of out of that is R20 300k. Since the all-pass filters are all the same
it's highly likely to be 100k.
QuoteHard to read but 99% sure it says "BL"
Thanks for checking as I was struggling to see how they would get this thing working reliably with a GR (and no way a Y).
QuoteSide note: I ended up purchasing an additional unit as a backup (in case I blew up the first). There are slight variances in values as well as RED painted dots on the K30A - but that's for another day. We'll just focus on the original :icon_cool:
Wow, that's dedication. I don't think you will lose out since it's a good unit!
Regarding the 2SK30A dots. Hard to believe but I've managed to work out a pattern between the position of the bias trimpot and the color of the dots. That means Maxon are sorting the JFET into four categories and putting paint dots on the JFETs. Moreover I've managed to work out that each color corresponds to a 100mV change in the JFETs VP (Vgs_off) parameter. That's the parameter which is measured when sorting JFETs.
So I think we have gone far enough to put up a schematic.
Schematic:
(https://i.postimg.cc/bSXqyFq9/Ibanez-Maxon-pt909-round-switch-sch-v10.png) (https://postimg.cc/bSXqyFq9)
Schematic PDF:
See attachment.
Part Desiginators:
(https://i.postimg.cc/w3J6fHkf/Ibanez-Maxon-pt909-round-switch-designators-v10.png) (https://postimg.cc/w3J6fHkf)
So a couple of points.
C15 I've made it 470nF (0u47) 35V as that makes a lot more sense.
C17 is probably the only thing causing grief on the schematic.
With C17 at 6.8uF 10V the speed of the LFO seems like it won't match-up with the published LFO speed of 0.2s to 14s.
If C17 is increase tod 10uF then it nearly matches. I can't imagine you reading reading 6.8uF 10V instead 10uF 6.3V and even so a 6.3V cap is quite running quite close to the limit.
One idea is you could set the unit to the slowest speed. Wait for the sweep to hit the top of the swirl then start timing/counting while it falls. Then wait for the sweep the go down then back up to the top of the swirl again and stop. If the time is 14s we have a problem if it's like 8 or 9 seconds then it's likely 6.8uF is correct.
Please check over the schematic and see if it makes sense or if you find anything wrong.
Wow Rob amazing work. I have (literally) no idea how you did that! :icon_eek:
Concerning the caps:
C15
(https://i.postimg.cc/8FHRj1Qs/C15.jpg) (https://postimg.cc/8FHRj1Qs)
C17
(https://i.postimg.cc/JDYj5PhL/C17.jpg) (https://postimg.cc/JDYj5PhL)
QuoteConcerning the caps:
For C15 I can see a small dot in front so .47uF = 470nF. That's what I put on the schematic. So all looks good.
For C17 I'm reading exactly what you read 6.8uF 10V.
So the values on the schematic match the board. I'm happy it's all good .
It's not a big deal that the unit doesn't match the published specs. The published specs of pedals don't always match the final units, maybe they did at some point but things got changed.
I guess it would be more puzzling if the unit could dial the speed out to 14 secs but the schematics look like it only goes to 8 or 9 secs. That would cause some head scratching for sure.
FYI, anyone can trace a PCB it just takes a bit of perseverance. The hard thing is not having any errors (values and connections). That takes a lot of checking. Thanks for sticking with it, this thing wouldn't be what it is without your help.
Thanks Rob for all your hard work, super impressive. Hopefully others will get some good use out of it.
I've got a couple other older pedals I'll be uploading in the near future. I'll give you a heads up might be something you'd dig. 8)
QuoteI've got a couple other older pedals I'll be uploading in the near future. I'll give you a heads up might be something you'd dig. 8)
Yep, no problem. It might be worth checking "the other forum" as many of the older pedals have been traced.
In the late 70's Ibanez/Maxon made a lot of changes over a short period so it's easy for some variants, like your PT-909, to fall between the cracks. From time to time I've found obscure schematics for a few models in this era. They tend to get lost on the web since people think there's one or two versions but there's really two or three. Dod's another one with lots of variants.
Ibanez really doesn't really "make" anything. Maxon made over 95% of the pedals for Ibanez. Hoshino Gakki, Fuji Gen Gakki, Terada and other factories make their guitars or guitar parts. TKL made Ibanez parts. Hoshino Gakki first started marketing Ibanez guitars using the name as Salvador Ibanez, which stayed on the guitars when Julvez took over Salvador's with his two sons running the shop in Spain after Salvador died in 1920. Julvez was still using the old Ibanez labels as late as 1944. In 1957 Hoshino brought back the name Ibanez. Ibanez really just markets guitars effects and amps made by other factories. Maxon has been their main pedal supplier for many years now. An Ibanez law suit guitar was as good as a Norlin made Gibson for 40%-55% the price of a Gibson. Their X series were great players for a great price. Then they had the weird USA assembled Custom Saber Series, where Fuji Gen parts were shipped to retail shops in the USA and someone bolted the part together in the back room, put strings on it and called it "custom made". Those are also killer guitars. Check the Ibanez pedal schematic if you can find it.