Re-fitting Unidentified 25xx Project Into Payback V 1.0 - Anyone Experienced?

[luggagepro]

Hi,

Just getting into electronics. Like it. Picking up knowledge as I go along, so fundamentals are useful when appropriate.

But here's what I'm trying to do:

I picked up this funky little build for a couple bucks and let it sit. Wanted to do a loop pedal and found out it was close to what I was looking for. So what I now have is a PCB layout including an ISD2590P chip, as well as a CD74HCT147E logic gate thingy. I'm not sure what this project was used for, but I want to turn it into one of the Tone God's Payback sample looper pedals.

What I'm having a hard time doing is identifying what's going on with the pre-existing build that I contain. I know that the ISD2590P is connected to a 16-pin logic gate, that the board is full of nice caps and a couple weird things by the 9v input that part numbers won't identify, I have a nice 10-pin 10 k-ohm resistor on the board, (as the photos show) it appears to be set up to run at 3.3V, there are markings on the PCB which indicate pins 23, 24, and 27, and that they are unused.

An interesting difference: this build uses the built-in speaker outputs to a small computer speaker, with an 1/8" cable with hot and ground attached to the speaker connections presumably for plugging into an amplifier.

The build I have seems to not use any of the ISD25XX operation modes, because the 20-pin connector cable was attached to 8 SPDT switches which I assume were connected to the addressing functions.



I don't know what else to say!

This seems like a reliable forum to appeal to in time of need. Haven't tried anywhere else yet, let me know if you have any suggestions.

Thanks for taking the time to read my outdated article,

Appreciate it!

[duck_arse]

hello luggage, and welcome.

now, about these photos: I can't see em. did you ferget to post them?

[luggagepro]

Forget? Sure did!

Thanks for the welcome. I was super tired and exasperated when making the post last night. Here are the pictures!

[luggagepro]

The two adjacent leads, one of which is a green wire, went to the speaker input. The two red leads next to the round orange capacitor opposite the LED were disconnected when I got the project. The red lead next to the LED went to the 9V battery. The black lead went to a SPDT switch with Battery - in the middle, nothing on one throw pin, and the PCB ground on the other pin. This SPDT switch is labeled RECORD. Another SPDT pushbutton with a wire from the 16pin connector attached, with ground in the middle, is labeled PLAY. After the 16pin connection this runs straight to pin 23 on the ISD2590.

If clearer photos of any part of the PCB would be useful please let me know!

[Edit:] I have mapped out the functions for the CMOS Priority Encoder and as many of the ISD2590 pins as I have been able to. This and some notes on the connections for the 10-pin resistor and the 16-pin connector will be uploaded later tonight when I have access to my friend's camera again (I know I said last night that it was a 20-pin connector - I mistakenly counted pins on the cable rather than on the PCB). At this point I mostly just need help understanding what's going on with odd pins 21-27 and pin 20, and while the powering system is a bit beyond me still I should read up on it some more before I go throwing inane questions around. It just really looks like it's set to run on 3.3V and I don't like that.

That said it's safe to assume better photos of the right side of this chip and the powering circuits will soon be made available as well.

Thanks a million to anyone taking the time to look at this. I would make a joke here about how I'm lost without you all, but even without direct help to me this forum is full of information with which to find my way through the dark, and besides, if people weren't out tinkering in places where their rightful knowledge abandoned them completely there probably wouldn't be a forum full of people dedicated to sharing the valuable insight you can gain thereby, no?

So, hey: a quandary, and some philosophical musings. Hopefully sooner than later I will be able to join the ranks of those able to give advice as well as receive. [/Edit]

Thanks duck for alerting me to my lack of photos.

[luggagepro]

Here are some functional diagrams I made of the 16-pin connector, 10-pin bussed (10kohm? part # 750-101-R10K) resistor, and 10 line-to-4 line CMOS priority encoder (part # CD74HCT174), as well as a partially complete pin out/in-put diagram displaying what's going on with the ISD2590.

This is basically my way at attempting to figure out how this thing worked via understanding the components used to control this thing (whatever it was). There are a couple hot leads (at least according to wire color; attached to the PCB near the orange cap on the opposite side of the board from the LED, relative to the 2590) that go unaccounted for. Perhaps these were connected to some of the SPDT switches on the non-pictured control mount (which again consisted of 9 SPDT switches and a SPDT pushbutton).

Still though, there should definitely be something to go off of in here. More circuit tracing will be forthcoming once I get a better flashlight or more patience to trace the circuit paths.

It looks like this person was using the non-Operational Mode multiple-message addressing feature kind of circuitry, with some real primitive SPDT version of logic circuitry to go back and forth from record to play. Perhaps this implies that the previous owner frequently used the same samples and I should be glad the chip might live to provide many more. However, if this is true I need to learn a thing or two about binary numbers, as the CMOS encoder outputs address only pins 6, 7, and 8, (A5, A6, and A7, respectively). A0 through A4, as well as A9, are grounded. (A high logic state at BOTH pins A8 and A9 is necessary to enable operational modes.)

The 10-pin resistor connects 8 of the 16-pin connector pins to I 1-8 on the CMOS encoder, while a resistor pin also supplies a line to the CMOS encoder's I 9. The resistor's 10th pin seems to connect to the hot side of the bottom of the PCB.

The notes on the 16-pin connector seem hard to read, so in the simplest words I can muster:
1.) 8 pins go straight through the 10-pin resistor and into the CMOS encoder. Of the connector's two columns of eight, these 8 pins are all in the same column
2.) Of the remaining column, the top pin's hole is connected only to a blue wire which connects to the PCB on the bottom side of the hole marked "Pin 27"
3.) Of the remaining column, the next pin's hole is connected only to a blue wire which goes straight to pin 23 on the 2590
4.) The next three pins are floating, effectively making this a 13-pin connector
5.) The next two pins are grounded directly to the PCB
6.) The final pin runs (through a blue wire) to pin 9 (A8) on the 2590, which is piggybacked with a (100kOhm, I think) resistor which connects to pin 16, V_cc

The circuitry connected to the hole marked "Pin 27" seems to be optionally connected via a manual SPDT toggle where you pull off the plastic bit to change the configuration. Looks like you either manually feed pin 27, Play/Record, or it runs automatically via the output of pin 23, Chip Enable. On the opposite end of the lead running to the optional "Pin 27" configuration is a SPDT switch with the lead in a throw position and with ground at the pole, while the other throw position floats.

If it may be useful, a datasheet for the 2590 and the CMOS controller and bussed resistor:
2590 - http://pdf1.alldatasheet.com/datasheet-pdf/view/143280/ETC1/ISD2590X.html
CMOS - http://pdf.datasheetcatalog.com/datasheet2/b/0f3axek5kz87qxh66oe11door73y.pdf
Resistor - http://datasheet-found.com/Datasheet.jsp?pn=750-101-R10K

Perhaps someone familiar with these chips can now get some idea of what I'm looking at here and how extensive the work necessary would be to turn this into a Payback looper.   Either way, I keep following this little project deeper and deeper down into the rabbit hole...




http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/image-8.jpg.html?g2_imageViewsIndex=1

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/image-6.jpg.html?g2_imageViewsIndex=1

[duck_arse]

that's a real ugly mess a nice looking board you've got there. good luck.

it's hard to see clearly, but the surface mount parts near the "3.3+" seems to be regulator, up or down I can't tell. I did look at this datasheet, with some app notes, it might prove helpfull down the rabbit hole.

http://pdf.datasheetcatalog.com/datasheet_pdf/information-storage-devices/ISD25120G_to_ISD2590X.pdf

it might be easier if you pry the ic's outta the board, and insert them into something you know the works of. might be. I'm sure you've already tried the function hereabouts. I remember there's a thread on fake ISD chips, there's probably others.

and as for binary, it's fun and easy. as someone here once said, there's 10 types of people, those who can understand binary, and those who can't. the priority thing just codes a maximum ten input conditions and shoves them into 4 lines of address.