EA tremolo – rate and depth not working

[Anonymous]

everything is from pedalpartsandkits. I can’t seem to get a secure connection with the Q4 socket, I can’t get it to stay in a spot to keep the LED flashing.

[Billy]

Try wedging in some cut off component legs to get a nice secure fit

Does the LED keep flashing when you hold Q4 in place?

If you got the kit from Bruce it’ll be top quality components

[Anonymous]

alright, I got a multimeter. where do I start? lol

[Anonymous]

I’ve tried looking online for how to troubleshoot with a multimeter, but I’m not really sure where to start with this particular build. I’m sure being able to read the schematic would be helpful, but I’m still a noob and don’t really know how to read schematics yet.

I couldn’t wedge anything in the sockets to secure Q4, and while tapping/wiggling Q4 I could only get the LED to flash a little bit then it stops. when it does flash, Im able to adjust the speed knob and it flashes accordingly.

 

[Anonymous]

That’s good news! That means the LFO is working (sometimes). It could be that a bit of precision bending of the leads to create tension might remedy that. Maybe the two outer legs slightly bent outward and the center bent slightly perpendicular? Or perhaps a slight “kink” in each leg would help. They are fragile but not brittle.

If you are planning to build more pedals, another great tool to have is an audio probe. There is probably a how-to build one on this site.

I’m just a DIYer, so please don’t assume I speak from any other capacity. Billy (and the others) know their stuff, and will get this pedal working.

[Billy]

I don’t know about knowing my stuff I’m 100% DIY too and Fig knows what’s what I’d say

Anyway using your meter to check for voltages

Set your meter to 20 VDC (symbol below solid line and dotted line = DC) black probe in the COM socket red probe in V for voltage

First thing to do is place your black probe on the ground pad and red probe on the +9v pad just to get used to it you should see what your power supply is putting in less a little voltage drop

The accuracy of your reading will depend on the meter input impedance 10M ohm being what you want for fairly accurate voltage readings that will suffice for pedal circuits if your meter has a smaller input impedance you would just take that into account so no big deal if it’s lower impedance

Then you want to check the voltage you get in and around the LFO and control parts of the circuit blue and green areas shown below, these are what voltages to expect doesn’t have to be exact just round about these voltages

All you do is place your black probe on the ground pad or any ground point if it’s in an enclosure you can put it in a screw hole giving you 2 free hands shown below and touch the component you want to check with the red probe

Check what voltage you get on Q4 collector to start with then check Q3 voltages and report them like this

Q3

D

G

S

Q4

C

B

E

If you don’t know which transistor pin is which you can google 2N5088 pinout, 2N5457 pinout etc

Then all you would do is match it to the silkscreen flat side to flat side curved to curved

I don’t want to overload with information but just as an example take Q1 we can see from the schematic the drain pin labelled with the D comes straight from +9v with no components in between 9v and drain so we’d expect around 9v on that pin so what you are basically doing is checking you get the expected voltages and if you didn’t get 9v on Q1 drain you would trace it back to see where your problem is so anything preceeding that you’d check, the DC jack, C9, R2 for value, orientation, dry solder joints etc

In your case your looking for something affecting your LFO so you’d check those areas

You will get there Bafo and hopefully learn a few things for future reference, I know I continue to learn all the time, if you’re unsure of anything just ask none of us were born making pedals!

Here’s the transistor pinouts I always double check them

 

 

[Anonymous]

Check the version number on your board. If it is V3, the updated schematic is in the build doc.

Edit: Disregard, V1 works just fine. Guess I need to read more too…move over Wilkie!

[Anonymous]

ok, first of all, I want to thank fig and billy for all the help and information. this will def be a learning experience.

here are the readings:

Q3

D-0.00

G-0.00

S-0.00

Q4

C-6.07

B-.60

E-0.00

so it seems the issue is in Q3?

I have to say, this is a lot of fun, learning all this and trying to find out what’s wrong

thanks again to everyone who is helping and guiding me

[Anonymous]

so, if I did everything correctly and Q3 is not giving any reading, would the next step be to check C4 and/or R9?

[Billy]

Yes I’m not at home at the moment check voltage on Q2 and from Q2 emitter through R8 / 9 and C4 you’re basically trying to find where you loose voltage

Do you get alternating voltages on Q4 collector

[Anonymous]

noo the readings were pretty steady, just moving like .01.. I turned the depth all the way up and the rate all the way down

[Billy]

Check with the rate about halfway

[Anonymous]

still only moves .01 with the rate halfway

[Billy]

Post what voltage is going in at the +9v and ground pad

Then all transistor voltages we need to track down where you loose voltage

[Anonymous]

voltage at the 9v and ground is 9.25

also, I didn’t have any 9v batteries, so I rigged my multimeter with a one spot and the battery snap adapter. it seems to be working fine, but I just want to know if its a really stupid idea and i’m gonna explode or its safe..

 

[Billy]

Not something I  would do but for ingenuity that’s an A+

I can’t see it doing any harm unless you short it or put too much voltage into it

Not all 9v adaptors put out exactly 9v hence why i wouldn’t do it, but yours seems fine check voltages on the anode + of D1 and the green side cathode ie when it’s switched to effects mode

[Anonymous]

lol I just try to avoid disposable batteries, they’re wasteful. I should probably get some rechargeable batteries.

D1

anode-7.97

green-6.08

red-7.20

 

[Author]

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