Tonepad BMP questions.

[stuznu]

Output jack is wired as per Tonepad diagram - black from ground to sheild, white to jack tip.

[duck_arse]

really, until you get those transistor voltages in the right areas, you can forget about all the off board wiring, except for the power supply, of course.

unless your in/out interstage caps are all shorted? something doesn't make sense at the component level, because of the way the fault is seemingly repeated in each isolated section.

I put 'a transistor' on the bb with your resistor values, and measured the resistances. all but the 100k at the base were VERY different to yours, and very close to the colour-band indicated values.

[stuznu]

Hi Duck

The wiring response was to another poster who suggested the output was wired incorrectly. Apologies for the confusion.

In response to your posts I have cleaned pcb and removed some solder web and remeasured resistances between Q1 legs and ground

Collector to ground=389.9ohms

Base to ground=84.81k

Emitter to ground=1.83k

[stuznu]

Base to collector= 140k

Base to +ve =135.2k

[antonis]

Collector to ground=389.9ohms

Oopssssssss...

[duck_arse]

something is wrong. is that too much of an understatement?

with 470k base to collector, and another 12k collector to supply, base to collector resistance should (did on my test) measure more than 400k. and then base to supply should be more (at least 10k) again, not less. and if you have a 390R resistor emitter to ground, then ground to emitter should not measure 2k, or thereabouts.

[straw_grasping] can you disconnect power, clip black lead to ground, then measure the resistance to both ends of the Q1 emitter resistor on the component side of the board (ie on the resistor leads)? and then measure resistance to the transistor emitter lead. otherwise, remove the transistor or the resistor and measure the resistor resistances. and yes, I know you've measured them a thousand times, but it still doesn't work. [/straw_grasping]

[stuznu]

Disconnected power and measured resistance to both ends of Q1 emitter resistor on component side of board: = 389.9R,
resistance across resistor to Emitter lead=390.0R.
Emitter resistor removed from pcb and measured both ways=388.8R

[stuznu]

High res pics of BMP pcb solder side posted here, hope they help.  http://imgur.com/a/rMI22

[bloxstompboxes]

That solder joint next to the capital E in El looks highly suspicious to me. But the other suggestions above might be more pertinent at the moment.

[stuznu]

Checked it out an nothing reportable there.
Thanks

[duck_arse]

I'm all out of straws, I'm afraid.

[stuznu]

Thanks for the time and effort.

I have removed each component and tested resistors, caps and diodes. According to Francisco Pena of Tonepad/Gran Mango (Green Russian BMP) there shouldn't be a problem with the voltages?!? So I am back to square one. Maybe purchase a pcb on line and start a new build.

Thanks again.

[plexi12000]

just wanted to chime in....so pardon my 'unrelated' comment please!   Thanks duck-arse for the hosting website info.   that's something i've been wanting to do as well.

Also.....  i have a question about the links to the older forum post started by "carboncomp"??

he has a pic of his PCB.....i 've been wondering about the wiring of that type of board.    you have 3 leads from the pcb that go to each pot.....but also an "out" solder pad

on the board.  do you run a lead from the "out" pad to your 3pdt switch...... as opposed to what i am familiar with?   that is, the "out" usually being from the wiper of the

"volume" pot?

[hymenoptera]

also an "out" solder pad

on the board.

Should be easy to follow the trace from that wiper pad to the out pad. If there's a direct connection, nothing else between here and there, no LED return trace or anything, then you can wire it up either way.

[stuznu]

Hi again,

After checking almost every component individually, I finally got to the transistors only to find that in response to my order for 2n5088 transistors the supplier provided BC550s!!!!!!!!!!!!

a quick referral to BC550s data sheet informed me of the need to reverse all transistors. This was suggested by one response, however, I overlooked that suggestion being under the misconception I had 2N5088s.

Voltages at transistor pins are now measuring at:
Q1    C=4.799v B=0.739v  E=0.133v

Q2     C=4.814v  B=0.740v  E=0.6v

Q3     C=4.173v   B=0.729v    E=0.124v 

Q4    C=4.796v      B=1.446v  E=0.842v

Thanks to all who assisted in the trouble shooting. All advice and suggestions are appreciated. I will do further tests before boxing.

Watch this space.

[duck_arse]

excellent! I thought you was going to toss it and start again.

also, finally!

[antonis]

I don't like Q2 Vbe but let it be...

[stuznu]

Thanks to all the kind people who so patiently contributed.