tagboardeffects Triple Wreck boost question

[m37a]

Hi, I am just about done with my 2nd build (a triple wreck clone) following this layout http://tagboardeffects.blogspot.com/2012/10/wampler-triple-wreck.html. The main board works but the boost doesn't seem to increase the volume any, or even change the tone much. I am double checking all my wiring but

Does anyone know what the correct voltages for the 2N5089 should be?

I am getting:
C = .29v
B = .76v
E =  .19v

These values seem really low? I have checked the power to the board (9v), and checked over the vero for any shorts but havent found any.

Any help would be appriciated!

[Cozybuilder]

Did you make the cut under the 2k2 current limiting resistor?

[m37a]

Yes, the voltage is 9.4v on the near side of the resister (Source) and 2.7v on the far side (LED).

[Cozybuilder]

It would be helpful if you posted clear photos of your build, both sides of the board. There is obviously a problem with the wiring or components around the Collector- maybe the collector resistor is 470K or 4M7 rather than 47K? The emitter and base voltages look about right.

[m37a]

Here are some pictures. https://imgur.com/a/svYCt

I assum that the transister would need a bias voltage about half of the supply.

When I use an audio probe the audio leaving the transister is distorted and quieter than the source.

[Cozybuilder]

The resistor values look right, go to the right holes, same with the caps, electro is right orientation. I don't see any obvious shorts, the solder joints look OK. I suspect the transistor is the problem.

[antonis]

Unsolder 2N5089, solder a 3-pin socket and try a NEW 2N5089...

(that BJT seems to be BLR..) 

[m37a]

I did try another transister. Could I have a bad batch? These are from Tayda. 

What does BLR mean?

[duck_arse]

.... and welcome to the forum.

I think your track cuts might need some attention, there seems to be some copper threads around those cut-holes, which might be shorting. get an exacto knife and a big magnifier, and clean the little copper crescents out. then measure your resistances across the cuts.

the transistor in yr 1st and 3rd pics looks like a moulding half-shot, like a manufacturer would/should reject. but then it appears okey-dokey in the other pics, so maybe a lighting trick. does your meter have a transistor tester socket on? you can throw the rest of your batch on and test for not/good.

[Cozybuilder]

I traced out your vero layout:

[m37a]

lol fair enough

I was also concerned about the tracks and the drilled holes. I traced over all of them to check for any shorts but did not find any (I had this problem on the main board so lesson learned the hard way ). I have also gone down the tracks with a sharp knife to clean up.

My DMM has a transister testing adapter, but apparently this model doesn't actually support testing transisters that way (UNI-T UT61E).

[antonis]

What does BLR mean?

Beyond Local Repair.. 

[Kipper4]

LPB with tonestack.

Probably could benefit from some power supply smoothing.

I'd stick a 20k pot wired as a variable resistor in the place of the 10k.

Just my 2pence.

Rich

[m37a]

okay, I tried recreating this boost circuit from scratch on a breadboard and am still having the same problem. There is an effect when I rotate the potentiometer, it acts almost like a presence knob, but there is a drop in volume from the original source signal. Also, the output signal sounds more distorted than the source.

I also tried swapping the 2N5089 for 2N3904 which are the only other NPN transisters I have on hand. I know these work because I used them in a tube screamer clone.

Breadboard:


The voltage on the collector has gone up from my original test. It seems to fluctuate between 2.4v and 4.5v.

Voltages:
C = 2.4v
B = .8v
E = .15v

[m37a]

okay now I am confused (not that I wasn't to begin with)...
I spent some time on the breadboard messing with this. I found that if I replaced the 47k with a 100ohm resister, and connected the circuit to the emitter instead of the collector the audio is clear and there seems to be a volume boost.

Here is an updated schematic:


New transister voltages:
C 4.9v
B 2.2v
E 1.5v

The problem is I am pretty sure I am exceeding the current rating for the 1/4w 100ohm resister.

Hopefully someone much smarter than me can shed some light on here

[Cozybuilder]

I mis-marked the polarity on the electro, the positive side should go to the collector 

[m37a]

I mis-marked the polarity on the electro, the positive side should go to the collector 

Good catch. I wired it with + towards the collector though, so that wasn't the problem.

[Cozybuilder]

okay, I tried recreating this boost circuit from scratch on a breadboard and am still having the same problem. There is an effect when I rotate the potentiometer, it acts almost like a presence knob, but there is a drop in volume from the original source signal. Also, the output signal sounds more distorted than the source.

I also tried swapping the 2N5089 for 2N3904 which are the only other NPN transisters I have on hand. I know these work because I used them in a tube screamer clone.

Breadboard:


The voltage on the collector has gone up from my original test. It seems to fluctuate between 2.4v and 4.5v.

Voltages:
C = 2.4v
B = .8v
E = .15v

Is the 1M on the base connected to +9? Its hard to tell on the BB. I would also measure the potential at each end of the power strip, some of them are split in the middle, causing all kinds of grief.

[m37a]

Apparently when I took the picture it wasn't  . But I just double checked and it is connected to 9v. I also confirmed with my voltmeter.

[antonis]

I found that if I replaced the 47k with a 100ohm resister, and connected the circuit to the emitter instead of the collector the audio is clear and there seems to be a volume boost.

Ahaaaaa... 

(you're the only person I know who managed to get boost from an Emitter follower...)

I'm pretty sure that you mismatched some items..

According to your revised scheme (Emitter follower), you should take:
about 800mV on Base
about 150mV on Emitter (resulting in 150μΑ Collector current)
about 9V on Collector (actually, about 15mV lower than your actual PS voltage)

P.S.
1/4W 100R resistor shouldn't bother you..
(with 150μΑ current it should be rated in the micro-watts area (μW)..