Nano Muff overdrive gated sound --- SOLVED !

[Steben]

Hi Guys,

Just got a nano muff overdrive as a bonus with another purchase. The red one, not the green.
Yet it sounds very gated. I will open it but is there anyone who has experience with this thing?
It is the muff fuzz circuit in a modern box. So is it known some are factory mis-biased or something?

[Steben]

Voltages! With 8V battery




Q1 seems with perfectly normal voltages.
Q2 is suspect!

Ie = 1.7/3300 = 0.5mA
URc = Rc * I = 0.5mA * 10 000 = 5V Which should be very acceptable!
I measured Rc and it def is +/- 10k.

[antonis]

Q2 (BTW you have two Q1's in your schematic.. ) is over-saturated..
(never seen a happy 2N5088 with 40mV V_CE..)
Also, never seen a happy 2N5088 with V_BE of 950mV with a working current of 500μΑ..

Conclusion: Put a new Q2..

[Steben]

Q2 (BTW you have two Q1's in your schematic.. ) is over-saturated..
(never seen a happy 2N5088 with 40mV V_CE..)
Also, never seen a happy 2N5088 with V_BE of 950mV with a working current of 500μΑ..

Conclusion: Put a new Q2..

Re measured and it's 2.21v not 2.61v    V_BE seems legit ...
I started a discussion on the facebook page. And it seems Q1 gets mentioned just as much as the culprit. Vb too low?
Somehow Q1 looks connected reversed. Tracing the pins it looks like the emitter has 2.21V

[Steben]

Swapped Q1 for a BC547B. The first I had in hands. BC547B has opposite pinout so placed the can exactly the same as the original. Circuit cleared up.
3,5V ish at collector Q2. Volume roll off. But a bit fizzy transition at decay of note.

Finally settled for a 2N3904. But I reversed the can since it has same pinout as 2N5088! collector now at 5.5V with 9.5V supply!

Why did EHX have it wrong here???