aion vintage sigma

[grotex]

Hi all, I built the Aion Sigma to use as a tone /booster. At any gain / volume setting there is a low volume, spitty, distorted,  sound. Very ugly. Unplugging the guitar and touching the cord tip going to the sigma there is the distortion that soon fades to no sound. I let go of the cord tip then touch it again and the distortion comes back and fades again.The tone, volume, and gain controls are all working. Wired to a 9vt battery did not help either. The diodes, transistors, IC, and caps are correctly oriented.
The Aion Chephus  and the Eclipse builds were no problem. Any advice please. Thank you.

[antonis]

Hi & Welcome..

As a starting point, take measurements on all VA, VB, VC & VD marked points as well as on +9V one..

[ElectricDruid]

Welcome!

Also please post some nice clear photos of your PCB, both sides, so we can see what you've done.

Thanks!

[grotex]

Thanks for the reply but I found the problem. The Mouser parts listing called for BC58C and Mouser sent the equivalent 2n5088 Had I read the instructions I would have known the 2n5088 has a reverse pinout. My error totally! Thanks again.

[grotex]

 I thought I had it sorted out but Mouser did send the 549c transistors after all. After screwing up the tracings I decided to start over and reorder a new pcb and get all new parts from Mouser. I still get that constricted ,spitty, blatty sound.To the best of my noob abilities I measured the indicated points from the schematic. I hope they make sense. From top left:
VC at C22 220uf   11.46
VA                11.33
VD at C23 100uf    11.42
VB at C25 22uf    5.6
 Q1               11.73
 Q2               11.40
 Q3               11.48  ( 0 at other side of R16 120k ) 
 Q4               11.42  ( 11.42 at other side of R21 1.8k)
 Q5               11.45  ( 4.87  at other side of R30 1.8k)
 IC #7            11.44
 IC #3             5.71   ( 5.71 at other side of R33 5.1k)
   
   Thank you for your time

[idy]

Those voltages are odd. How are you powering it? Some kind of 12v supply? We see lots of numbers over 11v.

Then, when we ask for voltages, we mean all three legs of each transistor, labeled E, B, C.

And the IC, we want to see all 8 pins. Good luck on your second try.

[grotex]

Thanks, I'm using a 9vt 700ma. adapter and it reads 12.71v
All BC549c transistors are CBE in order.
Q1 11.93
    7.02
    6.53
Q2 11.6
    7.03
    6.32
Q3   2.23
     2.13
     1.55
Q4   11.58
      2.15
      1.98
Q5    4.95
      1.89
      1.23
IC #1   .14
   #2  5.77
   #3   5.77
   #4   0
   #5   .14
   #6  11.61
   #7  11.65
   #8  0

Thank you

[ElectricDruid]

Are you sure it's a DC adaptor? If it were 9V AC, you might get symptoms like you describe. Maybe.

[duck_arse]

Welcome!

Also please post some nice clear photos of your PCB, both sides, so we can see what you've done.

Thanks!

so, now, we really want to see those photos. and a pic of the adaptor included. thanks also.

[idy]

Do make sure your adapter is DC and not AC. If it says 9v on the label but your effect is getting almost 12, that means it is not regulated. Not a deal-breaker, but not the best.

But your numbers on the '071 opamp show a problem: 6 and 7 show supply voltage. 7 should, that is V+. 6 should not, that is the output and should be the same mid-voltage as 2 and 3, 5.77v. Check for solder bridge there. Check, with power off, for continuity between those two pins.

[grotex]

Hi, the adapter is DC. I reheated the 6 and 7 pins of the IC and now with the power on:
2 - 5.9
3 - 5.9
6 - 5.8
7 - 11.6
with the power off there is 0 continuity between 6 and 7.
I just tried it out and I still get that bad sound.
 Tanks for the support all.

[grotex]

I just wired it to a 9v battery and got the same bad sound. Thanks

[PRR]

> I just wired it to a 9v battery and got the same bad sound.

Also please post some nice clear photos of your PCB, both sides, so we can see what you've done.

so, now, we really want to see those photos. and a pic of the adaptor included.

[grotex]

[aion]

Definitely unregulated, but probably fine. The Power Booster runs at 18V and is largely the same circuit as the Overdriver (which the ST-2 is based on, though with some additions like the op-amp).

As idy said, you've got to solve the voltage issue on the IC. I recommend pulling the op-amp out of the socket and seeing if you still get +V on pin 6. If so, there's a short someplace, probably to pin 7 but definitely nearby. If not, then the IC is bad.

[duck_arse]

when asking for help, please be so kind as to include a link to your build docs.


also please be testing the value of the arrowed part. its colour bands suggest it is not 680R.

[grotex]

Looks like I'll be reordering soon - that resistor is 680k!
 Thanks for the time everyone I'll be back with the results.

[idy]

So you solved the IC voltage. 2, 3 and 6 are properly biased.

Does any one else think that input buffer looks funny? I would expect that 4.7us cap to go to ground, stabilizing the bias voltage? But no, it goes to the emitter. And that 1n cap, that would look more normal going to ground...instead of through that other cap to the bias? what am I missing?

The first boost stage is the same...

[antonis]

Does any one else think that input buffer looks funny? I would expect that 4.7us cap to go to ground, stabilizing the bias voltage? But no, it goes to the emitter. And that 1n cap, that would look more normal going to ground...instead of through that other cap to the bias? what am I missing?

No funny at all..

4.7μF caps (C2 & C7) are used to bootstrap (via R3 & R11 ) respective bias configurations impedances..
Figure 2.4

1nF caps DO need to be placed between B and E for effective RF rectification prevention..
(they completely bypass B-E junction at RF frequencies..)
1nF cap

P.S.
You can also search the forum for various threads concerning Cornish buffer respective items utility..

[grotex]

Looks like I'll be reordering soon - that resistor is 680k!
 Thanks for the time everyone I'll be back with the results.

I installed the correct 680r resistor and all is well.Sounds great.
Thank you for your time and patience !