Little to no signal from EP booster clone, help?

Started by turbofeedus, March 20, 2018, 03:17:58 PM

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turbofeedus

Working on my second build here;

EP booster clone from Aion. Here are the project docs: https://www.dropbox.com/s/h5ogujjyxzbwj02/aion-ares-echoplex-preamp-documentation.pdf?dl=1

Double checked all resistor and capacitor values, looks good.

Replaced Q1 transistor (2N5952), hence the wacky wiring.

Replaced R2 resistor (1M) because I thought I used the wrong value.

Bypass works fine, so jacks and switch are good. Turning effect on, output is super low. No signal at all when FAT switch connects right terminal. Volume pot works, but very little change, like from nothing to very little.

Here are the voltages on the IC and transistors:

IC

pin 1: 1.17
pin 2: 4.84
pin 3: 0
pin 4: 0
pin 5: 0
pin 6: 2.55
pin 7: 1.42
pin 8: 8.87

Q1 2N5952

pin 1: 2.12
pin 2: 2.12
pin 3: 2.86

Q2 2N5485

pin 1: 0
pin 2: 1.86
pin 3: 14.21
For the transistors I measured left to right with the flat side facing up.

Realizing now I have no idea how they work, homework tonight. I also used that 2N5952 instead of the 2N5484 as the docs suggests, couldn't find the latter.

Any ideas?

Note: The pot was offboard wired because I drilled my enclosure incorrectly :/

vigilante397

First of all, welcome to the forum :)

Second of all, I see some red flags. The voltage on the drain (pin 3) of Q2 leads me to believe the voltage doubler might be working, but 14V is not 18V. Q1's voltages are all wrong, so there's definitely a problem there.

Questions:

- What power source are you using? 9V battery, OneSpot, etc? Can we get the voltage of that as a reference?
- Can we see pictures of your board? A picture is worth a thousand words, sometimes more when it comes to troubleshooting.

It's also worth mentioning that this isn't a clone of the Xotic EP booster, it's a clone of the Echoplex EP-3 preamp which the EP booster is based on, but this preamp isn't a boost. It says on the first page of the build doc that max volume is "slightly above unity."
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turbofeedus

Thanks for the reply, glad to be here :D

I'm using a basic Radioshack 9V DC adapter, output it ~9.08V last time I checked. Center pin negative.

Here are some photos:

https://imgur.com/a/uZRIU

Thanks for the clarification on the EP-3. That makes me curious then what the differences are between the EP booster and what I'm building.
I know my EP booster original either starts 3db above unity, or at unity depending on an internal switch.