Crybaby mods (Catmandue's requested)

I'm doing alright guys. I was able to take care of my issue I had going. Even though things are more complex right now, I will manage to put it all together. I'm not wacked out in my brain anymore.
 
I worked on the JH-1 wah yesterday. The transistors are hooked up correct, I made sure of that. I changed out the sweep cap for another one. I have a good strong tone when I engage the wah but, it is not wah-ing. I'm setting it down for a while. I'll look at it again in the future. I got my "Q" adjusted to 1 K ohm.
 
Hope you get it sorted Cman. Some suggested reading that may help, if you go to the GEOFX homepage, at the upper left of the page click on FX TECHNOLOGY The Technology of the,,,, then click on Wah pedal. Quite an in depth study & scattered through quite early in are transistor voltages, to check that the transistors are biasing up correctly. I don't have time right at the moment to check on them, but can tonight & list them here (probably a good idea anyway). R G Keen goes right into the circuit workings in detail, & in circuit segments, which may well prove helpful. Hope this helps. Cheers
 
Hi Cman, sorry I haven't been here, I've had a lot on the last few days & haven't had much free time. Ok, these are "theoretical" transistor voltages given by R G Keen in his excellent study of the wah, so wont be exact, but should be ballpark.
Q1's Collector 4.5V, but anywhere between 3V & 5V will do. He measured an actual at 4.14V
Q1's Base 0.6V
Q1's Emitter 0.1V

Q2's Collector will be at (or right near) the supply voltage.
Q2's Base should be greater than 3.4V & less than 4.5V. He measured an actual at 3.64V.
Q2's Emitter should be around 4.5V.

Again, these are "theoretical" voltages & will vary a little in each wah due to differences in transistor gains, resistor tolerance etc. I will have time this afternoon (1/2 day off, cool), so will measure actual voltages in my ZW-45 that has the transistors changed out for NOS types called for in the original VOX patent & get back to. Cheers
 
ivan H said:
Hi Cman, sorry I haven't been here, I've had a lot on the last few days & haven't had much free time. Ok, these are "theoretical" transistor voltages given by R G Keen in his excellent study of the wah, so wont be exact, but should be ballpark.
Q1's Collector 4.5V, but anywhere between 3V & 5V will do. He measured an actual at 4.14V
Q1's Base 0.6V
Q1's Emitter 0.1V

Q2's Collector will be at (or right near) the supply voltage.
Q2's Base should be greater than 3.4V & less than 4.5V. He measured an actual at 3.64V.
Q2's Emitter should be around 4.5V.

Again, these are "theoretical" voltages & will vary a little in each wah due to differences in transistor gains, resistor tolerance etc. I will have time this afternoon (1/2 day off, cool), so will measure actual voltages in my ZW-45 that has the transistors changed out for NOS types called for in the original VOX patent & get back to. Cheers
Click to expand...

Thanks! I got to get back to messing with the pedal. I have not given up. I'm sure I'll figure out what is going on with it. I've been busy with other stuff also lately. The climate is starting to cool off over here. I do all my soldering in the garage so that is one of the factors which comes into play with me working on the wah. After I changed out the .01 sweep cap to a different one, I got the good tone without wah back but, I still need to get it to wah again. I will find the solution in the near future I'm predicting. At one point it seemed like I had wah but it was not very strong. That went away to just a bit of a decent boost to the tone, with the toe down.
 
Ok, I measured my transistor voltages as follows.
Battery Voltage; 9.37V
Q1;
Collector; 4.59V
Base; 0.63V
Emitter; 0.05V
Q2;
Collector; 8.34V
Base; 3.65V
Emitter; 3.21V

Ok, the circuit makes use of the feedback loop between the Emitter of Q2 & the Base of Q1 to create the wah effect. C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_cry-baby-wah-gcb-95-bias.jpg
The feedback loop comprises the 0.01uf capactitor attacked to the juction of Q2's Emitter & the 10k resistor (to ground). The other end of the 0.01uf cap is in series with a 1k5 resistor that goes to the Base of Q1. This 0.01uf cap & 1k5 resistor complete the feedback loop. You can see that the inductor & 33k resistor also connect to the junction of the 0.01uf cap & 1k5 resistor. This is the part of the circuit that is utilized to make it wah, so if all your transistor voltages are in the ballpark maybe look in this area. I should have checked my voltage at the junction of the 470k/82k(voltage divider)/4.7uf/33k/inductor for you, so I'll do this arvo & post for you. Another good read on Crybaby circuit workings can be found at ElectroSmash - Dunlop Crybaby GCB-95 Circuit Analysis.
Hope this helps. Cheers
 
Hi again C man. I hadn't noticed before but there are some voltages shown on the schematic I posted in my last post. I did take the voltage at the multiple junction on mine as I said I would. It read 0.63V, the schematic shows 0.6V. I'll post a pic of where the voltage can be taken without removing the boardWP_20170916_005.jpg
Hopefully you can see the red probe (EZ clamp) attached to the lower side of the 33k resistor beside the inductor, the end of the resistor furtherest from the top edge of the board. Hope this is of help. Cheers
 
Thanks Ivan, I think you're on to something with the .01 cap going to the resistor in series. I will look into this. I feel I may need to look at and clean up at least one or two spots I soldered. I'm pretty sure the transistors are alright but, I will further check those is needed. I'll probably mess with it today or tomorrow. As a matter of fact, later on in a bit I will check to see what kind of reading I'm getting from that resistor. I'm glad I changed out the sweep cap again. Now it is giving me the proper reading .01, even installed. I'll have this handled eventually.
 
Yes, I'm glad I changed that cap out on mine too, the sweep was too "lower frequency" focused for my liking before I did. One thing I noticed is that the PC board's copper foil tracks are very fragile, easily damaged. I had to repair one of mine while doing the modifications. A pad lifted off taking some of the track with it. Had to repair with fine wire. Hope you get it up running soon. Cheers
 
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