Author Topic: Built it, works, but.....  (Read 9698 times)

jplebre

Built it, works, but.....
« on: May 06, 2011, 06:24:26 PM »
There are some issues:

My guitar level knob pops (have an active Schecter (2 seymour duncan hums) only when boost is engaged
4.7k lin pot produces a white noise - like sound when turned up and down.

Am I right to assume these 2 could be a DC issue? checked all caps and they all proved fine (22uF cap read 20uF. It could be normal tolerance drift?)
Caps right uF, right way around for the e-lytics. No visible shorts

Also, there is a boost straight from the top, not even half way trough, the bust becomes a nasty fuzz.

I'm following the vero layout on this forum (had to do 1 mod though - I'm using a WIMA cap for input (spaced 3 copper strips) so I had to add an extra strip at the top. Cool thing is, didn't had to "cut" the copper strip at the input.

Using an 2n2222 and my readings are:
Battery - 9.22v

tranny
C - 4.65v
B - 2.83v
E - 2.23v

before 47k resistor 2.86v

I know they are not the same as in the layout, but could the drift be inside "tolerance"? and it seems somewhat proportional but perhaps it's not how it works...
One thing I'm finding strange I cannot take readings of the 100k ohms resistors (just the "how many ohms?" whilst in the circuit. Popped them out, they look fine!

Used a knife to clear the grooves even more and cut any bridges that might have been there. Appart from one intrusive blob, I really can't see any short.

Any thing you can't think it might help?
Also tried a fresh 2n2222 and a BC184L. The latter would do next to nothing or a lot of noise and the pot would work on the opposite fashion (depending on how it was inserted in the slot).

jplebre

Re: Built it, works, but.....
« Reply #1 on: May 07, 2011, 04:51:14 AM »
On a veroboard, if the blobs come together on the same track by the "wetness" following the "heath" it should matter, right?
It should be like the constructions where components are soldered to the next component, no?

jplebre

Re: Built it, works, but.....
« Reply #2 on: May 07, 2011, 05:04:13 PM »
I meant *shouldn't

(can't edit my post)

anyone? please? :)

jplebre

Re: Built it, works, but.....
« Reply #3 on: May 09, 2011, 05:25:41 PM »
hmmm another cry for help...

Decided to breadboard this guy. Exactly the same sympthoms.
Fresh components, all measured before putting on the breadboard.

Voltages the same as above (9.22v for the battery, 4.5+ ish v for the collector, 2.83v for the base and 2.23v for the emiter).
It meets the same voltages except for the collector.... why is this?

The 2n2222 is in a metal case which I found it'll short if touching components around, which makes it hard on breadboard but wasn't a problem on vero.

Only the pot+cap are the same ones from the previous experience. Same scratching, and half way through boost this really nasty od kicks in followed by a "fuzz" :P I just wanted the "clean boost" as posted! xD

Anyone can suggest something?

Cheers
J

.Mike

Re: Built it, works, but.....
« Reply #4 on: May 09, 2011, 07:00:34 PM »
I'm not quite sure what you are asking.

Can you boil your question down to a sentence or two, and post pictures of your build if relevant?

Thanks,

Mike
If you're not doing it for yourself, it's not DIY. ;)

My effects site: Just one more build... | My website: America's Debate.

aron

Re: Built it, works, but.....
« Reply #5 on: May 09, 2011, 07:10:07 PM »
It's not a clean boost. The amount of distortion/fuzz is based upon the transistor. This booster is somewhat clean until it runs out of headroom.

jplebre

Re: Built it, works, but.....
« Reply #6 on: May 10, 2011, 03:12:03 AM »
Hey Guys

@Aron Yeah I borrowed a passive guitar and realised the distortion was mainly headroom.

So i guess now my main issue is:
1 - the boost pot is making a scratchy sound.
2 - both my active and passive guitar make a pop on the volume pot (on the guitar) when the effect is engaged, not present when in bypass.

Thanks :)

.Mike

Re: Built it, works, but.....
« Reply #7 on: May 10, 2011, 03:54:40 AM »
1 - the boost pot is making a scratchy sound.

There is only scratching when turning the pot, right? It may be expected behavior. If I recall correctly, a lot of people have had this issue.

Quote
2 - both my active and passive guitar make a pop on the volume pot (on the guitar) when the effect is engaged, not present when in bypass.

That makes me think there could be DC leaking out of the effect and to your guitar. It is supposed to be blocked by the 0.1uF input capacitor. Can you check for voltage on the guitar side of the 0.1uF cap?

Mike
If you're not doing it for yourself, it's not DIY. ;)

My effects site: Just one more build... | My website: America's Debate.

jplebre

Re: Built it, works, but.....
« Reply #8 on: May 10, 2011, 04:24:15 PM »
0.5mV apparently (guitar side of cap to ground, right?)

jplebre

Re: Built it, works, but.....
« Reply #9 on: May 10, 2011, 04:27:54 PM »
1 - the boost pot is making a scratchy sound.

There is only scratching when turning the pot, right? It may be expected behavior. If I recall correctly, a lot of people have had this issue.

Mike

should i try another pot? it could have been the odd sheep in the flock?

aron

Re: Built it, works, but.....
« Reply #10 on: May 10, 2011, 09:18:08 PM »
Try another pot. Yes, there might be a little scratch, but usually not a lot.

jplebre

Re: Built it, works, but.....
« Reply #11 on: May 11, 2011, 03:54:17 PM »
Cool! will try!

I like the way it sounds punchy! I guess I'll have to live with the distortion from 1 o'clock ish forward for my active guitar.

Any other boost that would sound punchy but a bit cleaner?


aron

Re: Built it, works, but.....
« Reply #12 on: May 11, 2011, 09:34:42 PM »
> Any other boost that would sound punchy but a bit cleaner?

Well, you have an active guitar already so you really don't need a preamp. You could try something like the Shaka Boost.
http://diystompboxes.com/pedals/schems/shakaboost.jpg

With 2 batteries, it will be plenty loud with headroom!

Aron

jplebre

Re: Built it, works, but.....
« Reply #13 on: May 12, 2011, 03:15:32 AM »
Well, you have an active guitar already so you really don't need a preamp. You could try something like the Shaka Boost.

True... it was to use it as a solo "volume up" really! hence wanting it  a bit cleaner than the beginner!

Shaka Boost.
http://diystompboxes.com/pedals/schems/shakaboost.jpg

With 2 batteries, it will be plenty loud with headroom!

Couple of questions:
- Do I insert the battery in series then? negative to positive of the battery?
- Which other IC could do the job? for instance the TL072 is also rated at 18v (supply voltage) - think it's time to start browsing the forum for IC info! :P

aron

Re: Built it, works, but.....
« Reply #14 on: May 12, 2011, 06:58:04 PM »
Yes, in series to get 18V. The TL072 will handle it fine. You can use any common DIP8 op amp. You can use Burr Brown op amps if you want to get fancy.

Aron

jplebre

Re: Built it, works, but.....
« Reply #15 on: May 13, 2011, 04:21:53 AM »
Cool! ordered the really really small caps for your Shaka.

Btw, a new pot fixed 90% of the scratching. Only does so between 2 - 3 o'clock hmm!
Works like a charm with a bit of distortion

aron

Re: Built it, works, but.....
« Reply #16 on: May 13, 2011, 04:21:12 PM »
The thing that's great about an op amp circuit is that it's really easy to debug (to me). It's really repeatable too. Easy to mod.

jplebre

Re: Built it, works, but.....
« Reply #17 on: May 13, 2011, 04:36:14 PM »
is it because the power supply is a single number that you can expect? :D

aron

Re: Built it, works, but.....
« Reply #18 on: May 13, 2011, 08:07:03 PM »
An op amp circuit is just so easy to debug, use, mod. I like them actually.