SOLVED Muroidea Distortion Very Little Volume/Gain

[KJKeul]

Hello All!

Built a Muroidea that I'm not getting very volume/gain out of.
I'm using an OP07 Op Amp instead of the LM308 called for.

I've probed some areas with an audio probe and had the following observations (Volume and Gain pots maxed):

1) No signal coming out of pin 6 of the op amp into C7

2) Signal can be heard from Op Amp Pins 1, 2, 3, 8.

3) Strong signal can be heard going into center pin of 2N5458 JFET (sounds like input signal). If looking at flat side, no change when probed on left pin. Right Pin cuts buzz, but no signal heard.

Let me know where you think I should start looking, or any additional info I can provide! THANK YOU!!!!

 

[BuddytheReow]

Clean your board with some isopropyl alcohol. You’ve probably got some bad solder joints. What are the voltage readings on the op07?

 

[KJKeul]

Clean your board with some isopropyl alcohol. You’ve probably got some bad solder joints. What are the voltage readings on the op07?

Thanks for the reply! I cleaned it up some, still struggling to find anywhere that I suspect has a bad joint. Might just reflow a bunch of the joints, maybe I'll get lucky...

The OP 07 has the following voltage readings:

Pin 1 DC: 9.15 V
Pin 2 DC: 4.6 V
Pin 3 DC: 4.12 V
Pin 4 DC: 0 V
Pin 5 DC: 40 mv (took a bit to ramp)
Pin 6 AC: 3.85 V
Pin 7 DC:9.21V
Pin 8 DC: 40 mv

Transistor Left: DC 9.21 V
Transistor Center: AC .12 V
Transistor Right: AC .86 V

Any thoughts? Thanks again!

 

[music6000]

Pin 5 has No Connection so that is normal.
Pin 8 should be around 4.6v so an issue is coming from component or solder to there.?

 

[KJKeul]

Maybe Progress?!

I reflowed solder on the pads and retested. Now signal is stronger, but never gets louder than input signal. Sounds kind of bit crushey.

Rechecked voltages around the IC and I got the following values:

1: 9.18
2: 4.13
3: 4.13
4: 0
5: 0
6: 4.6
7: 9.18
8: 9.18

I read somewhere that when you use OP07 doesn't need the 30p cap between pin 1&8. Should I try jumping it out?

Any other thoughts?

Thanks again!!

 

[KJKeul]

OK! Got this thing working. Thanks for all input guys! For those who might be curious found a few issues:
1) Had a bad solder joint
2) C9 was a bad cap
3) Had the wrong transistor in the 2n5458

I had it wrong above the OP07 does need the 30p cap.

Thanks again for all who reviewed!