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Giant hogweed needs volume help

Started by TGP39, March 19, 2015, 10:13:06 AM

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TGP39

Hi guys. I just spent half an hour writing up a nice build report / tech help problem that suddenly disappeared. So this one will be shorter.
Just finished the giant hogweed by David. Has some really cool sounds, but I'm having a problem with the volume levels. When the octaves switch is off, I barely reach unity. When I turn the octaves switch on, I get a big jump in volume.  The only snafu I had building this was with T7. I used a BC549, but I had it soldered in the wrong direction. So I attempted to desolder it (huge disaster) and I eventually wound up resoldering a new BC549 via point to point using the schematic (see pics).



Here are the voltages I took.
t1 e-156mv, b-737mv, c-2.1v
T2 e-1.51v, b-2.1v, c-7.9v
T3 d-5.8v, g-2.53v, s-730mv
T4 e-440mv, b-355mv, c-9.4v
T5 e-0, b-348mv, c-350mv
T6 e-0, b-335mv, c-350mv
T7 e-1.13v, b-1.63v, c-6.9v

U1 1    2    3    4    5    6     7    8 (in volts)
    8.8 6.6 6.5  0    0  .175  9.5  6.6

U2   1     2     3      4      5      6      7      8 (in volts)
      4.7  4.7  4.7    0    4.3    1.4   4.7   9.5

U1 is LM308n, U2 is TL072

supply voltage is 9.66 volts



I will post more pictures. Any help is greatly appreciated. I have the build on my workbench so I can take any other readings if needed. Thanks guys.

Steve.
     
Follow me on Instagram under PharmerFx.

TGP39

Follow me on Instagram under PharmerFx.

drolo

The voltage for the collector of T7 looks weird.

Not sue for e and b but c should be around 5V for T7

pin 6 on the Tl072 looks too low.
It should be at half supply normally but I will need to check the voltages this evening when I get home.

I suspect that there is something weird around T7. can you try to audio probe your signal after T7? It should be a bit over unity, maybe twice as loud, in any case not less than unity.


drolo

If nothing helps, I will send you another board. It's my fault you soldered the transistor in reverse in the first place ...

TGP39

Hi David. I will audio probe around T7 when I get a chance today. Thank you for the help.  Honestly, it's not your fault. I should have looked at the schematic before soldering all the transistors. I really appreciate it though. Does my T7 point to point job look correct?  I double checked the schematic and I thought that would do the trick. Thanks again.

Steve.
Follow me on Instagram under PharmerFx.

drolo

It's not easy to see but it seems like you soldered the collector to the junction of R13/R32/C18 instead of the junction of R32/R29.

the best spot would be here :


TGP39

I'll try that. Should I solder it so that R29 and r32 have a solder bridge between them?

Steve.
Follow me on Instagram under PharmerFx.

drolo

they are already connected together. You can connect the collector to either resistor on the spot shown above

TGP39

Ok. I understand now. Will give it a try.

Steve.
Follow me on Instagram under PharmerFx.

TGP39

Hi David. I repositioned the collector as you mentioned above. My new voltages for T7 are c=5.55 , b=1.35 and e=0.84. I'm going to test and see if this did the trick.

Thank you for your help. Steve.
Follow me on Instagram under PharmerFx.

TGP39

Well David,  your suggestion about re-routing T7 worked!  After looking at the schematic again, I have no freakin clue why it worked.  Lol, but it worked. I am going to test everything later today, but I think this did the trick. Thank you for your help David.

Steve.
Follow me on Instagram under PharmerFx.

drolo