Bumblebee 2020 - no output

[jessenator]

Hey hey. I've reached a hole in my swiss-cheese knowledge bank.

So I've got my Bumblebee assembled, but I can't get audio when engaged (audio comes through when bypassed). I started probing, and here are the values I get vs spec (mine in sharpie):

BAH! Q3 values should be negative voltage like spec but I neglected to write them that way...

My wall wart is putting out 9.17V
I'm using P416A NOS 1980s Soviet era PNPs and an actual TC1044SCPA

No bypass boards; straight wiring to 3PDT:


Thanks for any pointers and things that fell into my massive knowledge gap!

[jimilee]

Have you looked up the pin out for the transistors to make sure those are right? Have you checked all of your component values? After that, reflowed all of your joints? After that audio probe.


Sent from my iPhone using Tapatalk

[matmosphere]

Check the values of c6 and c7 and the orientation of d3.

The connection at in the middle of the top row of the foot switch looks a little suspect as well.

[Thewintersoldier]

Voltages seem within reason. Sounds like something may be grounding out the input or output. Check for any solder briges on the back side of the board and off board wiring. Audio probe is your friend here, follow the schematic to see where the signal is dropping out.

[jessenator]

Thanks for the pointers, all!

I've done a check on the following:
As far as I can tell the transistors are standard PNP and have the correct orientation.
all diodes are oriented correctly (the 1n34a has one whole end that's black, so that's what I oriented to the band symbol)
Caps are orientated correctly, and correct values
No solder bridges on either side

However, I did find two resistors that were DEFINITELY not the correct values. I'm usually slow and methodical, but hey, I'm human. Replaced those with the proper values and I'll test it again later today and report back.

If that doesn't solve it, what is a good tool for audio probing?

[jessenator]

Something like this?
https://diy-fever.com/misc/audio-probe/

[jessenator]

Alight, I got my probe set up. I'm stuck right at the beginning it looks like :|

I get sound at R1 and its side of C1, but beyond C1 (to R3 and R2 and to Q1) I get nothing.

Replace C1 then? 100n ...should I be using ceramic caps? I have MM5104K50J01L4

[jimilee]

See if you have continuity between the north end of r3 and ground. Sounds like a short to ground after r3.


Sent from my iPhone using Tapatalk

[jessenator]

See if you have continuity between the north end of r3 and ground. Sounds like a short to ground after r3.

Yup. When it's engaged and powered I get continuity. Might be my inexperience to know if this is normal or not, but when it's not powered, I don't get any continuity engaged or bypassed.

[jimilee]

See if you have continuity between the north end of r3 and ground. Sounds like a short to ground after r3.

Yup. When it's engaged and powered I get continuity. Might be my inexperience to know if this is normal or not, but when it's not powered, I don't get any continuity engaged or bypassed.

Nope, that don't make sense. Here is a link for the pinout for those germs, from what I see when I compare it to the pic of the board on the layout, its different than the board, meaning you'd have to match the pinout.

http://diy-tubes.com/image/cache/data/germanium/E-K-B-Transistor-DRW-500x500.png


Sent from my iPhone using Tapatalk

[matmosphere]

Yeah, there's no such thing as standard pin outs. It's a pain, do you have to check every time.

[jessenator]

well bugger me!  !@#$balls, that's such a rookie move on my part


Damned commies

[jessenator]

WELL THERE's, as they say, YER PRAHBLUM

That was it. I've got signal though now! I'll have to rig it all back up in the proto holder and test it out with an actual guitar now.

Thanks again, all for guiding a rookie through it. On the plus side of my pride being wounded, I've got an audio probe built


edit: I'm just glad I didn't solder them in!

[madbean]

WELL THERE's, as they say, YER PRAHBLUM

That was it. I've got signal though now! I'll have to rig it all back up in the proto holder and test it out with an actual guitar now.

Thanks again, all for guiding a rookie through it. On the plus side of my pride being wounded, I've got an audio probe built


edit: I'm just glad I didn't solder them in!

Dude, I've been at this going on 20 years and I still make "rookie" mistakes. Just less often. Don't sweat it! Glad you got it worked out. The audio probe is second most important tool after a multimeter. You'll use it all the time.

[jimilee]

You are welcome.


Sent from my iPhone using Tapatalk