EA Tremelo question

[powerplayj]

Anyone know if the GGG version of the EA Tremelo requires the LED to be wired (like the ROG version) for the circuit to work?  I have built it and have not added the LED yet and I have sound but no tremelo effect.  I'll post voltages for troubleshooting if someone confirms the LED is not critical to the circuit.

[rogerinIowa]

The GGG layout does not require the LED to be wired in to work. I have one working now, on the bench, but have not added the LED yet....still working out the perfect placement of the LED.

[powerplayj]

Voltages

Q          D     S     G     or     C     B     E
4          9.5   9.3   8.8       
1                                       0.1   8.0   0.0
2          0.0   0.0   0.0
3                                       7.4   0.5   0.0 

   

Checked pinouts, Voltage from adapter is 10.1, cap orientation looks correct, no obvious solder bridges or loose connections.  Sound is present but quite gated like a misbiased fuzz or distortion.  Volume works and speed seems to work as well but depth is hard to decipher due to the low and distorted signal.  Is there any one component that seems out of sorts and causing all the funny voltages?

Any help would be appreciated.



[/quote]


schematic here..........http://www.generalguitargadgets.com/diagrams/eatrem2_sc.gif

[mac dillard]

I built one and had the same problem...Q2 was bad. Yours looks to be bad also...Suggestion. Make C5, C6 and C7 about .67 uF for a little more speed out of it..I did and it made a lot of difference.

[mac dillard]

Found my old readings
dillard
Posts: 30


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   Need some help on a build.
« on: June 18, 2006, 05:42:27 PM »
   Reply with quote
Have just completed an EA Tremolo build and can not get it running. Any help would be appreciated.

The unit will power up. By pass works. Can play through the unit when it is on.  When unit is on the Volume control will control volume. When the Speed pot is turned all the way down (counter clockwise) there is a huge amount of gain. Nothing else happens with the speed and depth controls..

Project: EA Temolo from General Guitar gadgets ...Used the PCB from GGG for the build.

Don't  know how to link but the project is on WWW.generalguitargadgets.com

Improved EA Tremolo project.

Followed lay out provided

Only parts sub was 1uf non polarized  electrolytic caps for C5, C6 and C7

Transistors used are the ones on the build BOM so the Pinout is the same as the layout.

READINGS:

battey voltage un connected= 9.27

Voltage at circuit board end of the red lead = 9.26

Voltage at the circuit board end of the black batterly lead = 0

Q1- 2N3904                        Q2- 2N5457          Q3- 2N5088                         Q4- 2N5457
   C= 5.95                              D= 0                    C= varies 3.5 to 6.0+           D= 9.25
   B= 1.56                              S= 0                     B= 0.54                              S= 5.65
   E= 0.97                              G= 0                     E= 0                                   G= 4.42


I have check connections and component positions untill I am seeing them in my sleep...

[powerplayj]

Thanks for the thread reference Mac.  I have some nice small .68 caps from RDV that will fit the bill for the substitution you suggested.  I did try a different (J201) JFET for Q2 (currently 2N5457) but it did no good.  I reversed the Q2 orientation just for the hell of it as well.  I'll retouch some solder joints in the meantime to see if I can get it cooking.

[phxbass]

I'm thinking about building the EA Trem from the GGG site but I can't find the 25k log pots anywhere...where can I find them?  or can I substute?  This is my third build.  I did my first two in about a week so I am still very new to this.

[powerplayj]

Updated Voltages

Q          D     S     G     or     C     B     E
4          10.0   9.8   9.4       
1                                       8.9   8.2   0.3
2          0.0   0.0   0.0
3                                       8.4   7.6   0.0 

Obviously, Q2 is out of sorts.  How do the other voltages look and where might a trace voltages to find the source of my error?

Thanks !!!

Jason

 

[powerplayj]

just realized the GGG build notes do not show up when using Firefox

http://www.generalguitargadgets.com/index.php?option=com_wrapper&wrap=eatrem_inst

[snufkin]

you probly rialise this but you can just select the black text and it will show up i had the same problem in safari

[petemoore]

Q          D     S     G     or     C     B     E
4          10.0   9.8   9.4                             All are too near V+
1                                       8.9   8.2   0.3    Base here is near V+
2          0.0   0.0   0.0
3                                       8.4   7.6   0.0   
  1. somethings pulling the base up near V+ rail.
  2. This one doesn't look like it has connection to V+ via resistor..
  3  Again the base on this one is near collector, something in the resistor bias network is probably either not connected or misvalue ?
  4.  All pins near V+, I would use DMM in continuity mode to test continuities on board [non-continuities also], and use *Resistance tests with DMM to verify the color codes on the resistors.
  Testing resistors in circuit may show a reading of an alternate path through the circuit of a lower R Value...post the 'wierd' readings or...
  Do math and figure if it makes 'ballpark' sense
  Pull one end of the resistor and retest it's value
 

[powerplayj]

Thanks Pete....

But after lifting all those initial resistors and measuring them,  I now feel like a clod.  I ran out of the standard DC jacks that I use and found one that would only work with a cheap universal adapter.  I noticed all my previous voltage measurements were negative and then it dawned on me.....Check the adapter polarity.  For some reason I had in my head the switch should be on (-) for neg gnd but obviously the switch is for voltage type (in this case, it should be (+)).  I should have posted the voltages as negative to help the troubleshooting but I thought maybe I just reversed the meter leads accidentally.

It's funny how these things work.  A Vibe and delay can fire up on the first try and make you feel good about your work  (or at least lucky)and then you get bogged down with a less complicated circuit all for a simple bonehead mistake.  hhhhmm..... what next?