No output on M800

[JetFixxxer]

Adjusted all drains J112/PF5102 to 5v.

Looked for cold solders, bridges, and cleaned the bottom.

Verified resistor value again.

 

[JetFixxxer]

It's my attempt of two in one.. The Twill Deluxe sounds Amazing! Now I just need to get the M800 working.

I did a little more tracing from input lug to "3" of Q1 (1) to Gain Pot to Q2 (3).. etc.. everything seems fine.
The spare wiring are ground which I had to the jacks. Disconnected for t/s.

 

[JetFixxxer]

Used Signal Gen and put 440 into the input and used an old amp speaker as audio probe. I had tone up into 3 of Q1. Check Gain Pot at the 3 lug and not getting a tone.

 

[JetFixxxer]

Suggestions?

 

[music6000]

Suggestions?

Your M800 has some Pot lugs that look suspect in Solder joints.
The M800 Top Left Footswitch Lug looks like a Dry Joint.
You may need to reflow a few others.
If you look at your Build in Supersize with the + option you will see.
Make sure your transistors are Firmly in position, I'm not a fan of transistor sockets.


I use 3.5 % Glasses when doing this Pedal work.
My prescription glasses are 2.25%

Cheers music6000

 

[Robert]

Used Signal Gen and put 440 into the input and used an old amp speaker as audio probe. I had tone up into 3 of Q1. Check Gain Pot at the 3 lug and not getting a tone.

Looks like you're losing signal at the first gain stage.

Check for signal on pin 1 of Q1. If there is no signal measure the voltage on pin 1. You should have somewhere near 4.5V.

 

[JetFixxxer]

Thanks will try and report back.

Isnt PIN 1 the drain? At pin 1 I measured 9v and trimmed it down to 5v.

 

[Jiuk]

Check your J201. I bought 100's of J201 from Chinese seller on Ebay and received 100's of bipolar TR but marked J201. It's all fake.

 

[JetFixxxer]

Thanks will try and report back.

Isnt PIN 1 the drain? At pin 1 I measured 9v and trimmed it down to 5v. Unless I'm reading the pinout wrong.

 

[JetFixxxer]

Check your J201. I bought 100's of J201 from Chinese seller on Ebay and received 100's of bipolar TR but marked J201. It's all fake.

I'm using J112 and PF5102. Got them from Small Bear. I might just get the J102 with adapters if everything else checks good.

 

[JetFixxxer]

Your M800 has some Pot lugs that look suspect in Solder joints.
The M800 Top Left Footswitch Lug looks like a Dry Joint.
You may need to reflow a few others.
If you look at your Build in Supersize with the + option you will see.
Make sure your transistors are Firmly in position, I'm not a fan of transistor sockets.


I use 3.5 % Glasses when doing this Pedal work.
My prescription glasses are 2.25%

Cheers music6000

Thanks. The foot switch lug was taken care of already. I will reflow the pots

 

[Robert]

Isnt PIN 1 the drain? At pin 1 I measured 9v and trimmed it down to 5v. Unless I'm reading the pinout wrong.

Yep, Pin 1 is Drain, but also the "output" of that gain stage. So you should see signal there, preferably with higher amplitude than Pin 3.

 

[JetFixxxer]

Looks like you're losing signal at the first gain stage.

Check for signal on pin 1 of Q1. If there is no signal measure the voltage on pin 1. You should have somewhere near 4.5V.

Q1 Pin Drain = 5.98v
Q1 Pin Source = 2.4v
Q1 Pin Gate = -1.7v

I'm assuming Pin1 = Drain, Pin2 Source, Pin3 Gate

 

[JetFixxxer]

Did reflow the pots and still nothing.

Here's what I did with the Signal Gen with it set to 440ish going into the input. The Dark Green Circle is loud, the lighter green are lower volume, pink is barely audible, and the red lines no tone. Verified the no tone with scope.

Check with my scope
R2 = Sine
R3 = Triangle
Q1 = Triangle
R4 = Square

Gain Pot
Lug 1 & 2 getting square wave
Lug 3 I get nothing

Checked the rest

 

[Chuck D. Bones]

How did you manage to get a negative voltage on Q1's gate? Or is that a typo? Are you measuring everything w.r.t. GND?

Your sig gen amplitude should be set to something like 100mVp-p. Looks like you are overdriving Q1. I'll assume that you meant to type 1.7V for Q1's gate voltage. That makes Vgs = 1.7V - 2.4V = -0.7V which is correct for a J201. Drain voltage looks good too. You're getting signal on one side of R4 but not the other. A short to ground at R4, C3 or the GAIN pot would do that. Can you explain how it is possible to have no signal at the GAIN pot but have signal at Q2? Q2 gets its signal from the GAIN pot. You'd need more shorts to get signal to sneak around the GAIN pot. Possible, but not likely. You might want to re-check your measurements. We'll get lost real quick if we're troubleshooting with bad information.

 

[JetFixxxer]

Can you explain how it is possible to have no signal at the GAIN pot but have signal at Q2?.

I can't..
If I go from Q1 pin 3 to ground the reading is - (negative).. I've tried other PF5102 and J112 with the same result. I get no tone on the Gain pot.

Vp-p is set to 100mV.

If I measure from R4 to Lug 3 of the GAIN POT I get 470k

 

[music6000]

1. Is Gain pot Lug 1 going to Ground & on the PCB pad.
2 Has the Gain pot been tested.

 

[JetFixxxer]

1. Is Gain pot Lug 1 going to Ground & on the PCB pad.
2 Has the Gain pot been tested.

Lug 1 to Ground and PCB pad. yes
Testing it in the PCB getting. yes

 

[JetFixxxer]

Any other suggestions?

 

[Chuck D. Bones]

Let's recap what we saw/heard in the video. When you probe the bottom end of R3, which is supposed to be ground, you get the same signal as when you touch the input on the footswitch. How is your board grounded? I'm thinking it's not. I see a black wire dangling and another one going to a lug on the output connector, but I can't tell if it's the correct lug. Where is your audio probe grounded?