freestompboxes.org

hi guys,
i got one of these off fleabay the other day, it appears pretty ancient, this is the ac corded model.

the transformer is with it, but supposedly blown... can't find shit on the interwebs whatsoever unless it's one site that wants 20 bux i don't have.

does anyone have one of these potatoe bugs in their collection, that would be willing to help me figure this fucker out?

i will post gut shots etc if anyone wants 'em... thanks, i really wanna get this piggie working again!!

looks like an OTA phaser (think i spotted a 4136 in it) if that makes any diff.. the only info i've found is the fuse is .25 amp for it.

i need to know what voltage it needs to run at if i can't find a suitable transformer (i know fuck-nothing about this shit)... doesn't look like there's too much to deal with to rebuild it once i know what the power supply is.

i am too damn stupid to even know what to ask, so if someone can guide my unintelligent ass, i'd sure be in your debt!!
thanks brothers

schematic, or anything would help!!

pinkjimiphoton wrote:i will post gut shots etc if anyone wants 'em...

surely you don't need to ask?




i hope you don't mind if i call you surely?

cool beans, maybe we can add this to the collection of cool shit nobody's gotten to yet.

good news... the included transformer is GOOD!! primary reads 1.7k, secondary reads about 120r from tap to tap, and 60r to the center, no continuity between primary and secondary.

it appears (if this is the original transformer) that the ac cord broke, and somebody didn't have the balls to put a new one on.

gonna try and hook it up, and see what i get for voltage at the secondary... with a little luck, it will be repairable AND we can trace it.

i can't believe nobody seems to have one of these, are they that rare? i BIN'd this for 45 shipped, which seems like a decent deal if i can get it workin'.

all i have is my cruddy phone, i will see if my girlfriend will let me use her phone to get some better pics... expect them soon!

it's a 1458 for the opamp, and a rcn 4136 for the the transconductance amp.

i think it's a 4 stage phaser, as there's 4 identical transistors/resistors/capacitors near the rcn.

i got it wired up, didn't have any 1/4 amp fuses, so i jumpered it with some roach clips. :icon_mrgreen:

not reccomended. but, i AM insane. it worked... i pulled the board out to check voltages, and they were close enough for rock and roll, and no spirits or poltergeists flew across the house.
so i powered down and put the board back, and fired it up.

it passes signal.. BIG volume drop...but no phasing.

i took a preliminary voltage reading, and everything seems to be in the ballpark, and i think it's modulating cuz the voltage keeps moving around on some of the pins. it's 2 am here, so i don't wanna get that deep into it now...

next step, i'll write out the parts, and voltages...and see if we can't make this puppy phase again.

guts:

Cool. Thanks for the images.

FYI I believe the 4136 is a quad op amp (ie 4X 741), so the 4 transistors in a row are likely JFETS used for each of the 4 op amp stages.

I remember the 4136 from old Craig Anderton designs, yet never saw them in many pedals. (The phase shifter he did had one, though it was optically controlled, rather than JFET).

That trimpot in the corner may be for biasing the JFETs like in a Phase 90. It could be miscalibrated? (volume drop)

pinkjimiphoton wrote:it's a 1458 for the opamp, and a rcn 4136 for the the transconductance amp.

i think it's a 4 stage phaser, as there's 4 identical transistors/resistors/capacitors near the rcn.

The 4136 is just a "low noise" quad op-amp (well it was low noise for 1974). Beware - it has a funny pinout, so you can't just slap in a TL074.

If it's not phasing, has someone fiddled with the preset? Many of that type of basic phaser had a preset that mixed the filtered with the direct - you tweak for deepest phasing, and then leave it there.

I think it's time for you to get your trusty audio probe out!

BTW - how did the operation go?

hi chris,

i saw the second surgeon yesterday. i REALLY liked the guy... a long haired hippy like me, swears like a sailor, and spent an hour discussing my options.

the other guys was like... "call me, we'll hack ya up!!"

this guy's like... well, first, lets try and get the inflamation down and build up the muscles in your neck to support it, so you can play..

he feels i may be able to get thru this without surgery, so i'm (scared to death of doctors) gonna give it a shot, and see what happens. if it's not better in a couple months, he's gonna go in, and fix the two main hotspots.

the other guy was gonna only do one. fuhgeddabouddit!!! i would have ended up having to go back in for a SECOND one with him eventually. i'm no rocket scientist, but to me that sounds like a retarded half assed way to do it.

so for right now, i'm gonna keep on keeping on, i feel empowered in this again. enough about me whining.

i am gonna try and trace out the whole circuit with help from Larry (armdnready) on arons', and anyone else who's interested in helping. would love to get this thing going!!

should i adjust the trimpot so the jfets are at half voltage? it does seem to affect the voltage going to them.

also thinking i should change out the electros maybe and the two orange 10u tants in the middle of the board?

or, should i not fuck around until we get a chance to look at the circuit a little better?

today, i hope to enlarge the board shot and write all the values for the parts in, so that will get us started.

thanks guys!!

ok, here we go... first, a couple more gut shots with the board removed









and finally, the board, with all the parts labled. the 470k resistors may be 480, i couldn't tell if it was purple or gray on them.




i played with the trimmer, but i can't get the volume up, and can't get it to phase. it SEEMS like it's phasing, or at least modulating, but i'm not hearing it.

here's my notes, including voltage readings:

470K MAY BE 480, HARD TO TELL PURPLE/GRAY

TRANSFORMER:
PRIMARY 1.7K, 120V 60HZ, 5 WATTS .25 AMP
SECONDARY 120R RED TAPS, YELLOW 60 R
10-0-10 VAC

SWITCH SPDT, RED WIRE RIGHT SIDE TO INPUT JACK TIP

AND CONNECTOR 2 (LEFT TO RIGHT)

SWITCH TOP LEFT, PURPLE TO OUTPUT TIP
BOTTOM LEFT BLACK TO CONNECTOR 1

CONNECTOR:
PIN 1 BLACK WIRE TO SWITCH (CCT OUT)
PIN 2 RED WIRE TO INPUT TIP, SWITCH IN
PIN 3 220U@16V+
PIN 4 GREEN WIRE TO GROUND, INPUT JACK, BOTH NEG

PINS OF 220U'S
PIN 5 BLACK WIRE PIN 1 RATE POT
PIN 6 BLUE WIRE PIN 2 RATE POT
PIN 7 220U@16V+
PIN 8 10V TAP ON TRANSFORMER SECONDARY
PIN 9 10V TAP ON SECONDARY

CENTER TAP OF SECONDARY (YELLOW) TO INPUT JACK

RING

+ SIDE OF AC TO .25 AMP FUSE, OUTPUT OF FUSE TO

INPUT PRIMARY OF TRANSFORMER

OUTPUT PRIMARY OF TRANSFORMER

SPEED POT 2.5M

LM1458
1 4.90
2 4.90
3 4.67
4 0
5 4.50-5.25
6 4.89-5.34
7 3.60-6.60
8 10.29

RC4136
1 3.58
2 4.91
3 2.25
4 4.94
5 4.91
6 4.92
7 0
8 4.92
9 4.91
10 7.56
11 10.29
12 2.25
13 4.90
14 4.91

T1
C 4.85
B 4.31
E 4.92

J1
G 2.26-2.31
S 4.92
D 4.91

J2
G 2.26-2.31
S 4.92
D 4.91

J3
G 2.26-2.31
S 4.92
D 4.91

J4
G 2.26-2.31
S 4.92
D 4.91

http://www.datasheetdir.com/2N5952+N-Channel-JFET

http://www.datasheetdir.com/2N4126+PNP-Transistors

any ideas where to begin to look?

pinkjimiphoton wrote: any ideas where to begin to look?

Yes, at a MXR Phase 90 schematic

thanks for the advice!!
i'm a fuzz guy, don't know anything about phasers.

also...

i mis-read a couple resistors. all the 350k and th 35k resistors are actually 150k. hard to read some of 'em.
my bad.

pinkjimiphoton wrote: i mis-read a couple resistors. all the 350k and th 35k resistors are actually 150k. hard to read some of 'em.
my bad.

The MXR Phase 90 schematic would have told you so....

that's helpful monday morning quarterbacking,...lol

seriously tho, thanks... thanks to you, we've achieved phasing! well, partially you, largely larry on the other forum, but thank you anyways!!

replaced the tants and electros. removed 4136, added socket and new chip. twist trimmer. done deal!

pinkjimiphoton wrote:replaced the tants and electros. removed 4136, added socket and new chip. twist trimmer. done deal!

mictester wrote:The 4136 is just a "low noise" quad op-amp (well it was low noise for 1974). Beware - it has a funny pinout, so you can't just slap in a TL074.

what'd you replace the 4136 with?

a 4136. u still have a couple brand new in the package from the colorsound vocalizer project me and dino worked up a year or two ago.

pretty sure larry won't mind:

IT'S ALIVE ..... IT'S ALIVE!!!!!!!![/b][/color]