RUNOFFGROOVE Tube Reamer - Debugging help needed

[akc1973]

Hi guys,

I've just built a ROG Tube Reamer on vero (my own layout), and it ain't working 

I've filled out the "what to do when it doesn't work" checklist below - any help would be much appreciated!!!

akc1973

1.What does it do, not do, and sound like?

Bypass works fine (I've used the 3pdt style layout with LED indicator as per GGG). When engaged, there's no sound at all.

2.Name of the circuit =

Runoffgroove's Tube Reamer

3.Source of the circuit (URL of schematic or project) =

http://www.runoffgroove.com/tubereamer.html

4.Any modifications to the circuit? Y or N

I've used an audio taper for the gain pot and a linear taper for the volume pot.

5.Any parts substitutions? If yes, list them.

See "4"

6.Positive ground to negative ground conversion? Y or N

N/A

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>

10.14V

Voltage at the circuit board end of the red battery lead = 9.98V
Voltage at the circuit board end of the black battery lead = 0.00V




IC1 (or U1)

P1 = 4.98V
P2 = 4.98V
P3 = 2.48V
P4 =  0.00V
P5 =  0.00V
P6 = 1.89V
P7 = 1.94V
P8 = 9.95V

[Kipper4]

First thing that strikes me is pin 5 of IC
i'd check that 22nf cap to ground and make sure its not shorting

[bluebunny]

Can you post a picture of your vero layout?

FYI, here's a verified one (in case it helps):



P.S. Agree with Rich - pin 5 shouldn't be 0V.

[akc1973]

Thanks, guys. 

I'll have a look at that 22nF cap tonight and see what's going on.

akc1973

[akc1973]

I gave my board a once-over again and found that I didn't have continuity between the output of the 1st opamp and the 1k resistor. 

Fixed that but still no cigar. No sound when engaged. I couldn't  find any shorts on that 22 nF to ground but I was debugging pretty late and my eyes were tired.

Here are my voltages now:

P1 = 0.01V
P2 = 0.01V
P3 = 2.30V
P4 =  0.00V
P5 =  0.01V
P6 = 1.75V
P7 = 1.79V
P8 = 9.17V

akc1973

[Kipper4]

your going to have to show us your layout please
theres no way those voltages are right.
It looks like you have shorted most of the pins now.

[duck_arse]

pin 3 is too low. you should have half the battery voltage at the junction of the 2 12k resistors, and very near the same voltage appearing at the far end of the 1M resistor, which is pin 3.

what voltage do you measure at your "Vref"?

[akc1973]

pin 3 is too low. you should have half the battery voltage at the junction of the 2 12k resistors, and very near the same voltage appearing at the far end of the 1M resistor, which is pin 3.

what voltage do you measure at your "Vref"?

My Vref voltage is 4.69V.

Here's what my vero looks like.

[bluebunny]

Did you zorch one or more of your diodes when you soldered them in?  With the output of the first op amp grounded, you'll get nothing coming out.  You need to sort that first.  You also have a long jumper taking ground up past the greeny on the left to your V_REF parts in the top left corner.  Any chance it's shorting against the resistor that it's going past?  You should try to use insulated wire for jumpers that long.

A picture of your layout - not your build - would also be useful.

[duck_arse]

well your Vref is correct, but something is going wrong before it gets to pin 3. solder joints/shorts/wrong links in that area.

[MrStab]

Did you zorch one or more of your diodes when you soldered them in? 

i HATE glass-encased diodes like the 1n4148, they've broken quite a few times on me. surely it would still pass signal if they were broken in this case, though? assuming they clip to the opamp's inverted input and not to ground.

i'm a sadist, i don't mind checking vero layouts - any chance you have one drawn, akc? it's hard to tell what's going on with the pic. or even if you could take a top-down photo, that could help, as your pic of the underside is quite clear.

the Tube Reamer reminds me of the one and only time i tried perfboard - i still have PTSD from it.

[akc1973]

Guys,
I haven't had much time to debug this but BlueBunny, you were right, that long jumper was shorting another component. I'll try it out tonight and see whether that was the problem.

akc1973