Tube Reamer V2 Debug

[ralley]

Hi there,
  I've held off posting this for as long as possible but have run into a complete dead end attempting to debug this on my own.  I've completely rebuilt this (first build was Gilles Caron layout, 2nd was RM Rivers layout),  checked and re-checked wiring, buzzed between all adjacent tracks looking for shorts, buzzed connected components checking for continuity, checked component values, tried different IC's - still no luck.

  1. Build: RunOffGroove Tube Reamer V2, RM Rivers Vero Layout
  2. Links:
       http://www.runoffgroove.com/tubereamer.html
       http://aronnelson.com/gallery/v/Toneys-Album/tube_reamerv2_333.png.html
  3. Layout followed exactly
  4. No substitutions
  5. Ground: -ve
  6. Symptoms: Works fine bypassed, no output when effect is switched in.  IC gradually warms up and gets very hot.Voltages also seem to decrease the longer power is applied.

  Voltages:   Battery (out of circuit): 8.71
                  Battery (in circuit):     8.02
                  Vref:                     3.94
 
              IC Pin:  1   5.13
                         2   4.31
                         3   0.58
                         4   0.00
                         5   2.20
                         6   1.50
                         7   1.58
                         8   7.79

              D1 A 4.27
                   K 5.06

              D2 A 5.06
                   K 4.27

              D3 A 0
                   K 7.75

              Electrolytics checked, orientation correct, more volts at +ve than -ve

  Questions:
 
  1) The IC getting very hot suggests a short to me but I can't find one (buzzed with multi-meter). Anything else to check for this symptom?  Could I have bad IC's (I've tried 2, both the same)?

  2) Are IC's typically numbered looking from the bottom?  I ask because the 4558 data sheet I've got shows pin outs as:

                         V
                        ---
                      1|   |8
                      2|   |7
                      3|   |6
                      4|   |5
                        ---

     Which corresponds with the layout shown from the track side.

Any suggestions much appreciated, thanks, Rob.

[Michael Allen]

your voltages look alright, but you're correct if the Ic is getting hot you have a short somewhere. Did you make all the approriate trace cuts?

Try making an Audio probe and trace through the circuit.

http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf

[mdh]

Plus there's a possibility that you're confused about pinout.  The IC pinout you show is correct, but viewed from above, not below.  However, if you have the IC inserted with the same orientation as the picture in the layout, it should be fine.  Hot op-amps often mean reversed power connections, which is exactly what occurs when you insert them the wrong way around.  A picture could put this theory to rest, if you have a digital camera.

[ralley]

Thanks guys, despite holding off on posting exactly what I thought would happen did - I realised my stupid error as soon as I went public.  For the second time I've managed to build something upside down, hence the confusion on pin outs.  I'm in the process of rebuilding.  Will let you know how it turns out.

Thanks, Rob.

[ralley]

Well that was the problem - rebuilt the right way up and it worked first time.   

Sounds great as well, heaps of sustain and harmonically very rich.

Two issues though - this thing is incredibly loud, I get unity volume at about 25% of the pot!  Also the gain is very high, much higher than I expected from a Tube Screamer clone (long time since I've played a genuine TS though).  I'm not sure if these are likely to be build problems or just the nature of the beast?  I'm going to look at changing the 51k resistor to a lower value to reduce gain (as suggested on another thread).  I will also look at adding a tone control, might as well do something with all that volume. 

Anything else I should consider to tame the volume and gain?  It was built with no component swaps (except the diode as noted below), as per the RunOffGroove schematic

I socketed the clipping diodes and tried a couple of different combinations.  Did'nt really here a lot of difference, currently I'm using one red Led and an 1N914.  Led lights up when playing moderately hard, looks pretty cool.

My plan was to put this on my pedal board along side my Boss OD-2 and use the Boss in turbo mode for heavier distortion and the Reamer for gentler overdrive - might have to change my idea on which pedal I use for what!  Or I might just build a second reamer to get 2 styles of overdrive (hate fiddling with knobs).

[Michael Allen]

Try a bigger volume pot...