zw-44

[guitarmonky55]

built one, having probs getting signal after the tranny.  does anyone have the voltages for the tranny and the op-amp in their working zw44?  i cant get to my multimeter until later or id post them up.

[petemoore]

The opamp pins need to be around about 1/2v.
 Except for the PS pins 4 and 8, 4 is GND and 8 is V+.
 The transistor is an Si emitter follower, without a schematic and more knowledge...the base has to be a diode drop above the emitter, which should sit higher than a gain stage to have 'room' to amplify that side of the wave, the collector...isn't it connected to V+ in this case?
 Sorry I can't be of more help right now, and hope I'm not steering you wrong about the E follower.

[jra2217]

built one, having probs getting signal after the tranny.  does anyone have the voltages for the tranny and the op-amp in their working zw44?  i cant get to my multimeter until later or id post them up.

i dont suppose you would have a schematic for the zw44, it is a project i would like to maybe take on.

Sorry to be off topic, but i hope you find the problem

[LoKi6922]

built one, having probs getting signal after the tranny.  does anyone have the voltages for the tranny and the op-amp in their working zw44?  i cant get to my multimeter until later or id post them up.

i dont suppose you would have a schematic for the zw44, it is a project i would like to maybe take on.

Sorry to be off topic, but i hope you find the problem

use the search... its definately on here.

[spudulike]

[Gringo]

You can find a project file in pdf format at Marcos' site :

http://www.geocities.com/diygescorp

[guitarmonky55]

ok well i walked away for a day and upon coming back discovered a HUGE error...i accidentally put 6 of the caps as picofarads instead of nano :oops:  :oops: .  so after fixing that im getting signal, and the tone control works and all, but the overdrive itself has a terrible gating.  when playing normally, i get a clean tone that changes with the position of the tone knob.  when i hit the strings WAY hard, i get a gated farty overdrive sound where i can hear the actual effect.

so after all this i measured my voltages, here they are.  im using a 2n5088 as the tranny right now(i had the mpsa14 and was switching around to see if any were more agreeable to the circuit, this just happens to be what was in when i measured) and a jrc4559d.

Q1
E:3.88v
B:4.06v
C:0.00v

U1
p1:6.94v
p2:4.45v
p3:4.40v
p4:0.00v
p5:6.93v
p6:6.94v
p7:6.94v
p8:8.91v

[aron]

Q1's collector is zero volts! I wonder if you made a mistake in orientation?

[guitarmonky55]

well that was a boo-boo.  i accidentally knocked the tranny out of the socket on the collector when i measured it :oops: yet another noobish mistake.  i stuffed it back in and remeasured everything, same except the collector is just under 9v.  still the same gating issue though :evil:

[aron]

Pin 5 looks too high.

Check your voltage at the junction of R8 and R9. It should be 1/2 your battery.

Hmmm. pin3 looks ok, there must be something wrong around the input to the op amp....

Are you sure R7 goes to VR (1/2 V+ i.e. 4.5V)?

Aron

[guitarmonky55]

now im just beating my head against a brick wall.  i triple checked my resistor values and found no problems.  audio probed again, with guitar in hand, found everything fine up until the opamp.  btw im using the pcb layout by pablo de luca.  

now i mentioned earlier that i boo-booed and put pf caps instead of nf caps.  well i didnt have the exact value for all the caps in nf, so i fudged them as close as possible.  being the noob that i am with only a barely basic grasp of all of this stuff...could any of these around the opamp possibly cause my gating issue?

in case it matters, heres the values i used(part numbers are according to the pcb layout)

c4-68nf
c5-47nf
c6-22nf
c7-50nf
c8-68nf
c9-10nf

thanks to anyone who will take the time to help out my noobish self :lol:

[spudulike]

Link to the pcb layout ?

[guitarmonky55]

well i got it                      

for some reason, it wasnt liking the 33k resistor by the drive pot...so for some reason i decided to try a 22k and voila! no more gating.  although i must say i expected a tad more od from it, it sounds wickedly heavy when i kick it up with amps distortion and run it in front of my yjm308(yes i like layering alot of distortions  :twisted:  :twisted: )

now for the fun part, im gonna audition the bazillion and a half different kinds of trannies and op amps that i have lying around.

[petemoore]

How's the output level when the gain and volume are maxxed ?
 Mine gets above unity when unity is guitar pickup as source [won't boost above a boosted input] seems a bit 'tepid' maybe I'm not having it working right yet ?

[guitarmonky55]

being as this is my first successful op-amp style overdrive pedal build, i dont relaly have much to compare it to so i wasnt sure what to expect.  i get a significant level boost along with some great snap to the strings from the EQ, but not as much distortion as i would expect from something with zw's name on it.  but then again its overdrive, and it sure does what i like to the amp.

when i max gain and volume i get a pretty large increase in volume, so ive been keeping the master volume a tad past halfway and the gain on full.

so far im liking a 2n3904 in it, but im waiting on some 2n5089s in the mail, i think i may like one in there from what ive messed with so far.  the jrc4559 is staying so far but i have some burr browns ive yet to audition.

[rama claproth]

If you have an SD1 boss pedal, you can convert it into MXR ZW44 specs!

1. Remove one leg of the resistor 33K (R5) that goes with 4K7 (R6) and connect to the diode's leg (D1) that goes to pin 7 at the opamp chip. Remove yellow wire # 4 at the PCB and also remove red wire # 2. Connect yellow wire at # 2, # 4 stays EMPTY. Connect red wire to where the 33K resistor's leg USED to stay that connects with the resistor 4K7 at R6, now this automatically goes to the opamp at pin 6.

2. Replace C4 with a 0.047uF capacitor.

3. Replace C5 with a 0.047uF capacitor.

4. Replace R3 with a 22K resistor.

5. Replace C7 with a 3.3uF capacitor.

6. Remove Q6, R15, R16, R17, and C10. These NO NEED jumpers. The white wire # 12 at the PCB must be removed and has to be connected into the hole where the base pin of Q6 used to stay.

7. Remove brown wire # 1 at the PCB and connect into ground.

8. Change Q5 with MPSA14 transistor. This is OPTIONAL.

DONE!