someone upped this on "another" forum...worth a look!!!!!

[pinkjimiphoton]

dude, so glad we could help ya, doctor FRONKenSHTEEEEN...

[Mr Bill]

I'm so vamped up, Jimi - I don't playmuch anymore, but boy am I psyched to take this comatose entity off life support and give it the dignity of a quality life again!   

[Mr Bill]

Just a last item before hitting the sack...I have nine wires going between theupper/lower deck...you guys specify 10!  Will have to persue the interconnection signal paths, tomorrow ....

[pinkjimiphoton]

let us know, bill...it appears some of the phase II's didn't use connection # 5 (from left to right) on the console board, so you may be good!

[R.G.]

One thing to watch is that since all the wires in the originals simply slide on/off the PCBs, it's also very easy to get them replaced onto the wrong slot.

I figured that out after thinking about what *I'd* do, faced with slide-on wires like this. I would put them in a random mixture of right and wrong places, then "enjoy" a pleasant day or two trying to figure what exactly I'd done. 

[Mr Bill]

  My bad....there are ten wires in my harness.  Looks like lower console wiring is all correct.   Next break time I will get into the upper deck. That's where I expect to find the wiring errors and/or broken wires.  Just for posterity's sake I have model 9000, serial #1480.

[Mr Bill]

Into upper deck. Measuring at C11, 48.5VDC.  THERE'S NO +36VDC at pin 17!   That's the ticket!  Pretty simple series pass regulator and zener circuit to troubleshoot tomorrow.  I've got it scared!!     Of note, my xfmr wires were different colors than your's, Jimi...

[pinkjimiphoton]

wow, 48 vdc?

interesting!! gonna look at mine later, see what the serial is.

since i just finally got around to re-upping my dot com, i'm gonna put up a section on the pII, where folks can get all the resources for it, and hopefully create a registry for them.

just outta curiosity bill, does yours have the 1 meg resistor tacked on to the fall board?

could the higher voltage you're reading be a result of a failed electrolytic?

[Mr Bill]

The +48VDC is before the series-pass regulator comprised of the 36V zener diode D3 and series-pass transistor Q6.  Incidentally, I just replaced Q6 with a 2N5551 transistor and I now have my +35VDC restored!!  WOO HOO!     Will save the electrolytic cap replacements for later. Time to hook up a sweep generator and oscilloscope and check the signal paths!  As far as the bottom board is concerned, are you talking top or bottom of board?  I do have a 1.5 meg resistor across R33 on the topside of the board. I may have done that myself back in 1974 to adjust the bias on transistor Q7.  Let me know where the resistor you're talking about is in proximity to.

[Mr Bill]

The 48V is pre-regulator, Jimi.  That's normal .  Q6 and D3 then regulate down to the ~ +36VDC rail.  I've got a severe rolloff on my sweep driving from the Hi Z input to the primary out jack.  I'm now seeing the same rolloff on the stereo (dry) output jack.  Cool it's common to both.  Looks exactly like a bad dc block electrolytic cap between stages.  Damn!  I'm running out of time, gotta head home.  Will get back into this tomorrow.  It will be relatively easy to trace through the circuit to nail it......baby steps 

[Mr Bill]

To clarify the rolloff is on the low end, classic for a electrolytic or bad connection somewhere.

[R.G.]

I very much recommend just taking it by both hands, making a list of all the electro caps and replacing them all. It'll save you time later. I also recommend remelting all the solder joints with a little fresh rosin core solder.

[pinkjimiphoton]

hey bro, yah, the 1 meg IS across r33 i think...

so you did that mod? seems the factory did, too!!!

bad caps scare me bro...please replace 'em all asap. i reccomend 100v electros, as most are 65 volt anyways. originally, i thought they were lower!!

if you increase the size of the c11 on the console board it will be a little quieter.....i run 300mf on mine
.

c1 on the fall board seems to work well at 22mf

[Mr Bill]

Well, i guess i didn't do that mod in 1974!  Trying to remember what I was doing or intended to do 37 years ago and what Ludwig did to fine tune the product off the assembly line is like a dreamworld.  Incidentally , I blew the power supply when I had the upper deck slip and short out on the chassis, all those years ago..... Not to worry on the caps, being that I work in product service of an audio company, I have bins galore of parts on the wall. I 've also got the luxury of  audio sweep generators, oscilloscope, spectrum analyzer and Audio Precision analyzer at my disposal.

[Mr Bill]

Well, that was easy!  .01 uF mylar Capacitor C3 on the Hi Z input was shot.  Replaced it, now have full sweep restored. Damn, my lunch period is over, set it aside yet again.

[wavley]

Man, you guys have really been making some progress.  I've been ignoring this thread on purpose because I was really busy this summer and had to fix a few things around the studio and build some things for friends, now I'm trying to get together the rest of the parts for some API mic pre clones because I won some PCBs for them on the interwebs and the transformers are expensive.  I really want this to be my very next project.  I think I might want to try and do a layout with board mounted faders like an old Yamaha or Roland analog synth to try and cut down on all that offboard wiring.

I just wanted to check in and say GREAT JOB!!!

[Mr Bill]

MAJOR DISCOVERY!

The striped MYLARS caps on my lower board are proving to be defective, literally across the board.  I'm sweeping 20Hz -20kHz into the Hi Z input and each stage was acting like I had a HPF cornered at about 800Hz  on it!  As I changed the capacitors that would restore that stage only to find the next stage with the same predicament.  After getting to the fourth stage, I decided their ALL coming off.  I can't see how other people aren't having rampant trouble with these caps.  They're the interstage dc blocking capacitors and also used in some of the filters we switch in.  It's a well documented fact to change electrolytics in vintage products, but i wasn't expecting to find the carnage of these parts.  My particular pedal has survived being placed in a unheated basement that was literally as cold as the winter outside for a couple of years and just thrown into a corner wherever I moved.  The capacitor themselves are sticky, like they're decomposing.  The president of our company took one look at these and said they are "notorious" failure parts.  Well, that's 21 MORE parts to be changed (actually 22 with the little cap, C29).  So, Jimi, R.G., you can rest tonight because I'm doing a wholesale change of EVERY capacitor in this unit.  I'm astounded that you guys aren't experiencing this or may not know know how much  low-end balls that this machine has been slowly depriving you! 

What's very interesting is I measured one of the .1uF caps that was failing miserably in the unit and it measured dead-nuts, .1uF!  Checked to see what frequency the capacitance meter was using to measure the cap, 1 kHz!  The cap turns into a pumpkin 800Hz and down...LOL!       

[digi2t]

Hmmm... maybe explains the weakness of the fuzz to some extent. Yup, full cap job sounds good.

[R.G.]

The striped MYLARS caps on my lower board are proving to be defective, literally across the board. ...
What's very interesting is I measured one of the .1uF caps that was failing miserably in the unit and it measured dead-nuts, .1uF!  Checked to see what frequency the capacitance meter was using to measure the cap, 1 kHz!  The cap turns into a pumpkin 800Hz and down...LOL!       

It would be very interesting to capture one of these caps and do an electronic postmortem. Given that the capacitance looks right, what are the ESR and ESL?

[Mr Bill]

R.G. ,we've got a rinky dink LCR meter here, doesn't measure ESR on it. My last company, Harris, had all the high end equipment to measure those parameters, parasitics, etc.
These failures bode exactly as I saw at the company I worked before Harris where we were using .1uF SMT caps on broadband microwave amps interstage and the assembler had applied too much heat to the part.  With electrolytics drying out, you literally see may see a 100th or 1000th of the original value, all the way to just measuring a resistance when completely depleted.  I was expecting to read the parts as being a shell of their original value, very weird to have the part start behaving mid spectrum and be literally open at the low end!  I can probably query one of our cap vendors to demystify this failure mode when I get back to work on Monday.
The interstage capacitance values are interesting for the impedance of the circuit their working into, you size the interstage cap to be able to pass the lowest frequency on the BW you want to pass.  These caps are deliberately undersized as you cascade stage to stage, suspect they had monstrous instabilities in this design when they first fired them up, motorboating, etc.  My brother, who owned this originally, got fed up that when he kicked in effects on stage and it would occasionally emit a big WHELP... LOL!   
  Being that these units were built in a very short window of time, what '70 and '71, you would figure that we are sharing pretty close to the same date code lots on the caps, I would think that there MANY time bombs out there.  If I did not have the test equipment available and changed all the electrolytics I would've been dead in the water and so frustrated.