hi guys, i need some help. i finished assembling the circuit but it doesn't work properly. i am not expert but i could verify that the voltages on transistor mspa13 - Q12 has variable voltage values when it should have stable voltages. do you have any idea where the problem might be? thanks for any help you can give me.
Tanks
Nicola
Hey hey, welcome! We're absolutely happy to help, we just need some information please.
To get tech help, in the first post of your thread, you must include:
(1) Project Name
(2) General description of the problem
(3) Steps that you have taken to try to resolve the issue
(4) List any substitutions you used for parts/values
Clear close up in focus pictures of both sides of the board.
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Some schematics would help too, if available :@)
Hi, sorry I thought that the name of the project shown on the title of the discussion was sufficient.
1) Project name: Harbinger 1.5 (Univibe (TM) for 1590BB) - the version with 9v power supply.
2) The pedal turns on, the speed and depth controls work because the lamp responds to the two controls, but connecting the pedal to the guitar and the amplifier the pedal does not work. I try to explain myself better: in vibrato mode the sound comes out but without effect, in chorus mode the sound is distorted and is perceived as soon as the effect is very low in volume. Switching from modern / vintage mode seems to have an effect as I perceive the sound to lighten or darken.
3) What was I able to check?
a) I double checked the values of all resistors (with color codes)
b) I checked the capacitor values and polarity in the case of electrolytic capacitors.
c) I checked the diodes
d) I checked that the transistors were of the type indicated on the project and that the pinouts were correct.
e) Finally I checked the voltages of the transistors, of the IC1 LT1054 and of the LM7815 voltage regulator with the tester, with powered pedal, and compared with the voltage table of the project.
The voltage readings I have found that are suspect are as follows:
from project: Q12 (MPSA13) C = 9.2 B = 9.08 E = 8.13
detected: Q12 (MPSA13) C = varies B = varies E = varies
from project: Q14 (2n5457) D = 17.5 S = 2.77 G = 0
detected: Q14 (2n5457) D = 17.14 S = 1.47 G = 0
from project: IC1 LT1054
1 = ~ 2.1v
2 = 4.94
3 = 0
4 = 0
5 = 0
6 = 2.56
7 = 1.38
8 = 9.26
found:
1 = 1.37
2 = 5.01
3 = 0
4 = 0
5 = 0
6 = 2.57
7 = 1.42
8 = 9.11
I did not use equivalent components but those indicated in the project.
The rest seems okay to me.
Thanks, any advice or suggestion is precious !!
Can you add pictures of the top and bottom of the PCB?
Here are the pictures!
Reflow that copper side from tin dust and controll it from udesirable bridges between points. I see at picture minimally 2 sufficient places. Thats for a start.
BTW, hambiger and harbinger are two different words. For those skilled in electronics but not in possible names of projects it will be confusing and junk work to look for schema at web.
Quote from: nicotina74 on August 14, 2021, 08:57:56 AM
Here are the pictures!
Thank you, that's helpful. Checking your components is a great starting point. It looks like several solder joints are starved. Solder should flow through the board eyelets and look like little silver Hershey kisses. If you would, please go back over the board and reflow, adding solder where needed. Also, yes, watch out for solder bridges.
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Quote from: Zerro on August 14, 2021, 03:21:22 PM
BTW, hambiger and harbinger are two different words. For those skilled in electronics but not in possible names of projects it will be confusing and junk work to look for schema at web.
sorry I corrected!
Quote from: Zerro on August 14, 2021, 03:21:22 PM
Reflow that copper side from tin dust and controll it from udesirable bridges between points. I see at picture minimally 2 sufficient places. Thats for a start.
could you mark the colon on the image? I would be very grateful. Tanks
I assigned the most suspicious. But with some needle try to clear all, and from rosin rests too.