Mastodon+B’n’B Combo: sumpthin’ ain’t rite…

[Anonymous]

Greetings from Cajah’s Mt.????…

Little help plz…

I’m getting an anomalous reading at the collector on Q2. Instead of reading 2.3vdc, I’m getting 8.9 to 9.2vdc.

Also, the Volume pot doesn’t seem to affect the signal when the pedal is engaged. The sound is highly distorted.

The Blend pot does do what it’s supposed to by dialing the distortion into the clean signal.

I tried swapping out the 3904’s and reheated all the joints. I checked all the components before I put them on the board (doesn’t mean that I didn’t miss something, of course). The only anomalous part is R3, which is a 56k instead of the 51k called for in the BOM.

When I plug everything up, the lights light, the bypass bypasses, the Clean signal… is Clean…

Anybody got any ideas ?

Thanks in advance, ????

 

[Barry]

Do me a favor and contact me using the contact me link in the in menu bar on this one.

Mention your forum name, real name and the board name as well as basic issue.

 

[Cybercow]

What is the ACTUAL value of R4 mounted on the PCB?

[Anonymous]

Hey CC,

I think that I know what you are getting at,

The actual values of R4 and R5 are 22k and 2k2 as measured  ‘in situ’ on the board. To my eye, the markings look to be the same ????, although sometimes I have a hard time telling the difference between the colors on some of those suckers.

I don’t know if the resistance value is affected by them being in the circuit or not. I thought about pulling one leg loose and checking to see if that makes a difference, but haven’t done that yet, since the readings are correct for the parts.

Thanks!

[mybud]

Might be good to review some solder joints that look cold possibly, for instance the wool pot and the bottom right connection to the diode. Bear in mind also that you may need to connect S4 and S5 so that the circuit’s switched on. [In testing phase, I usually run two short wires from (S5) to (S4) and twist these together].

Then place an LED (long leg to middle of D2 and short leg to whichever other pad works) to confirm that the circuit is getting power when switched on. You can wait before soldering these until the circuit’s confirmed as functioning. FWIW I tend to wire the ground leads together with the input and output ones. If and when the circuit’s working, this saves time and energy in the final stretch of boxing up. There are a couple of boards where this is essential (choruses, vibes, and so on). Let us know if these revisions help please.

[mybud]

My suggestions above naturally apply before connecting the circuit to the buff n blend. If you verify that each circuit works before joining them, this eliminates a number of variables and then points to some problem with the off-board wiring.

[Cybercow]

Still, I’d lift one leg of each of those two resistors and re-measure them – just to be sure. In the photos I see, the colors appear identical.

[Anonymous]

Hey CC…

I did try the “leg lift” and measured the resistance for the two. Both measured correctly at 22k and 2.2k respectively.

Here’s a couple of pictures showing the color codes as depicted by the “Resistance Calculator Pro app that I use:

AAs I’m sure that you are aware, the only difference between the two is the multiplier. And, since I sometimes have difficulty distinguishing between the browns the reds on some of these resistors, it’s hard to tell them apart. I guess we’ll have to chalk this up to crappy paint choice by the manufacturer…¯\_(ツ)_/¯

I’ve been trying to be more diligent in testing all the components before putting them into a build and getting them installed correctly. There’s a bit more discipline involved in this racket than my usual: “If all else fails, read the manual” approach to things.

Carry On, and Keep On…????

[Author]

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