AMZ Mosfet Booster not working

schnarf · February 27, 2007, 08:08:58 PM

I built an AMZ mosfet booster: http://www.muzique.com/schem/mosfet.htm
I used the GGG pcb: http://www.generalguitargadgets.com/diagrams/ge_boost_lo_amz_mosfet.gif

There is absolutely no output regardless of the potentiometer position. If I connect the battery when it's attached to the amp, it does make typical loud popping kind of sound but that's expected. I turned the amp way up to make sure it wasn't a case of very very quiet output -- there's actually no output. There is also a hiss which becomes slightly quieter when the potentiometer is turned up. I checked the resistance between the tip and rings on the jacks and the places were they connect on the board, no problem there.

My R5 is actually 2.35k instead of 2.7k because I was missing a 2.7k resistor and I put two 4.7k in parallel, and measured the resistance to make sure it was wired right. I don't have the switch or led wired up because of testing. However, everything does go to the proper place in the schematic. Here are the voltages I measured:

battery voltage out of clip: 9.39 volts
in clip and on board: 9.38 volts

bs170:
d: 8.56
g: 2.62
s: 0.69

9.1v zener:
stripe: 2.63
other side: 0.69

Vr: 5.74

db · February 27, 2007, 08:16:55 PM

Sounds like your drain isn't connected to Vsupply through the drain resistor.

schnarf · February 27, 2007, 08:20:49 PM

Yeah I just noticed I was missing a jumper. I connected it and updated the values above. Still not working.

markm · February 27, 2007, 09:06:10 PM

Pinout problem perhaps?

schnarf · February 28, 2007, 03:05:31 AM

Pinout of what?

Auke Haarsma · February 28, 2007, 03:40:29 AM

pinout of the mosfet?

Auke Haarsma · February 28, 2007, 03:41:39 AM

Can you use an audioprobe to see if the signal enters the Mosfet at all?

Also, try swapping in a different mosfet. I had a problem like this too with a mosfet boost..it appeared I had fried the mosfet. Swapping in a new one did the trick for me.

schnarf · February 28, 2007, 02:47:03 PM

The pinout should be fine; I used the same mosfet as recommended by AMZ and oriented it as shown in the GGG layout. I have no audioprobe and no extra mosfets. Any way to test it?

markm · February 28, 2007, 02:52:52 PM

Quote from: schnarf on February 28, 2007, 02:47:03 PM
The pinout should be fine; I used the same mosfet as recommended by AMZ and oriented it as shown in the GGG layout. I have no audioprobe and no extra mosfets. Any way to test it?

Understood.
However, AMZ suggests different mosfets that can be used but not all have the same pinout.
It could be as simple as that......what device are you using....BS170?

schnarf · February 28, 2007, 03:29:07 PM

Actually, I did order a BS170, but the mosfet I was sent says BC169B.

markm · February 28, 2007, 05:46:45 PM

Quote from: schnarf on February 28, 2007, 03:29:07 PM
Actually, I did order a BS170, but the mosfet I was sent says BC169B.

Well, that's a problem.
BC169B is not a MosFet.

Here's the info;

Part Number = BC169
Manufacturer Name = Various
Description = Low Power, Low Noise, General PurposeLow Power, Low Noise, General Purpose
BC169
Si
npn
300mW
20V
20V
5V
100mA
150>C
85MHz
5
240MIN
TFK
TO92

schnarf · February 28, 2007, 06:00:05 PM

Hahahahahahahaha. Well thanks for all the help. I'll be sending off an email and see if I can't get that BS170.

markm · February 28, 2007, 06:44:27 PM

Quote from: schnarf on February 28, 2007, 06:00:05 PM
Hahahahahahahaha. Well thanks for all the help. I'll be sending off an email and see if I can't get that BS170.

Yes, do that, then we'll talk!!

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AMZ Mosfet Booster not working

db