yes, another Ruby problem :D

[Mugshot]

i built the Ruby last night, but *sigh* i kinda borked a lot on me  . possible circuit changes caused the problem, i made plenty of substitutions though.

1.What does it do, not do, and sound like? sounds gated. picking lightly gives me clean-ish tones, a little harder and it distorts a lot, i mean unlike most touch sensitive pedals, there is a big gap between clean-ish to dirty.

2.Name of the circuit = ROG Ruby

3.Source of the circuit (URL of schematic or project) = http://www.runoffgroove.com/ruby.html

4.Any modifications to the circuit? uhm, no(?)

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

changed the 47nF Jfet cap to 120nF mylar
220uF output cap to 470uF (i had none smaller than that, well except maybe for some 33uF i had)
100uF power filter cap to 33uF
3.9K JFET source resistor to 15K trimmer (hey, the pcb still had room for a trimmer, so.. and allows me to change jfets)
JFET used is 2n5457 and MPF102 (socketed)

6.Positive ground to negative ground conversion? N

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? 9V. regulated power.

Q1
D = 9.0v
S = 0.5v
G = 0.0v


IC1 (or U1)
P1 - 1.4V
P2 - 0.00 - 0.05
P3 - 0.00 - 0.05
p4 - 0.00
P5 - 8.5V
P6 - 9.0V
P7 - 4.0V
p8 - 1.4V

do the above ring a bell? any help is much appreciated guys!

PS: i tried it on an unmarked speaker. no output, will try later with an 8ohm speaker tomorrow.

but rigged as a pedal, it sounds gated, as in you have to hit the strings softly to get clean tones, but at a certain picking strength it gets distorted, decays, and then fades to zero.

[Quackzed]

i'd try it with an 8 ohm speaker before i'd assume it was messed up.
not sure about using it without a speaker, but i think the 386 chip will have issues unless its driving some kind of load...the issues you mention could also be a result of whatever is coming after the ruby circuit reacting to the rubys output being so large due to it being designed for a speaker load...
it'll probably behave better that way..

[Top Top]

I just built a few rubies and your voltages look off to me, from memory.

I believe on mine the S pin on the Jfet read between 2.5 and 3v when working correctly... I was running off of a higher supply voltage (15v), though I still think .5v would be low (maybe someone will correct me on that, as I don't know that much about biasing).

[NPrescott]

Checked mine and the JFET source voltage off a 9v battery (~8.7v) was 2.54v.

[Mugshot]

i have a testing rig i use to hook circuits before boxing them up. to check if the jfet was busted, i tapped off lug 3 of the volume pot to my rig. there was signal coming out so im pretty sure the jfet works. like i said the Source resistor is a 15k trimmer so i can bias the source at will  also the jfet is socketed, ive tried others (MPF102, 2n5457), same thing though.

will try the 8ohm speaker later, cant find any at the moment 

im quite curious what effect does increasing/decreasing the value of the output cap (220uF) is. 

[petemoore]

  What is the resistance between the socket wiper for gate and GND. also between gate and ground with the transistor in ?
  .5v from ground leaves little room for the source to swing negative.
  Also measure source to ground resistance,

[Mugshot]

idunno, i'll check later with another multimeter, mine is an analog type, probably need a more accurate DMM.

what about my LM386 voltages, are the voltages fine? also i cannot identify the manufacturer of my LM386, the symbol it has looks like three white boxes arranged like this:

     

• 
  
• 
       
• 
  
  sort of, except the plus signs are more like four-cornered stars. ive already checked an RS catalog, didnt find the symbol from the manufacturer list. googled it, no luck. also, the 386 has 945 inscribed beneath, i dont know if that'll affect the intended purpose or what, im clueless with that one 

[Mugshot]

oops, the last post was kinda awry, the symbol didnt come out as i typed it 

well the sign looked like this:

     {+}
{+}
     {+}

sort of.  i should've hit the preview button first.

[Mugshot]

i breadboarded the ruby (after an apparent failed build), and guess what? it didnt work, it seems the bunch of 386 in my possession had a differentt pinout.

___________________
    +                           |
+            LM386          |
   +            945           |
___________________|

mine looked a lot like the above. sigh.

[Quackzed]

dont be discouraged. maybee you can just find a 386 with the right pinout? and clip/solder it into place?

[Mugshot]

haha, i bought five of them lm386. tonight i'll be socketing each to determine which of them is busted, but i doubt any is.

[Mugshot]

im starting to believe that either the 5 LM386 ICs i have on hand are busted or have a different pinout. 

i breadboarded one last night for the last time, and i noticed that there was a very VERY faint output, a whisper's even louder for chrissake. no luck. also, the IC heats up like crazy. which leads me to ask: just how varied can LM386 ICs be, i mean the pinout? i browsed the net for info about the 386 and usually they had the same pinout. but sadly, im beginning to think mine has a different pinout.

my friend here says it was manufactured by HRC, now the net has no available information about this particular manufacturer. it just says LM386
    945 is inscribed under.

[PRR]

LM386 pin 5 should be near half supply voltage.

At 9V supply, 4V or 5V is right.

8.5V says the output stage is stuck high. On raw opamps, I'd say you forgot to connect feedback. But the LM386 has it built in.

Pin 7 should be a little more than half-way between the pins 1+8 voltage (which is 1.2V or 1.4V) and B+. So more like 5V than 4V.

I don't think there are different pinouts in the 8-DIP package. Also the ~~1.4V at pins 1 and 8 agrees with the original pinout.

[Quackzed]

make sure you have a speaker connected as you test it as well. its not designed to run into an amp input or other pedal.

[Mugshot]

there is a speaker connected to my test rig, 4" 8ohms, 1wattter. all i managed was a very faint distorted tone. if only the speaker were headsphones 

8.5V says the output stage is stuck high. On raw opamps, I'd say you forgot to connect feedback. But the LM386 has it built in.

stuck high?

out of frustration last night i built another one, followed the schematic carefully, pretty sure all components are in place. same thing. VERY VERY faint output.

also i noticed that there is only a 60ohm resistance between ground and +9v supply rail, im sure there were no shorts in the traces when i began, the traces were perfectly clean.

some low-res pics i took just now,


solder side, nope they're not solder bridges or anything. i bend the leads when soldering. im certain there are no shorts. blurry pic is blurry. low-res cam, uneven color. the copper traces actually look uniform, but the pic's kinda awry. 


the LM386. notice the manufacturer symbol, havent seen anything like. maybe you guys have a clue. it's 945 inscribed below.

voltages:

Q1 (MPF102)
D = 9.0v
S = 2.5v (hey, in the ballpark)
G = 0.0v


IC1 (or U1)
P1 - 1.4V
P2 - 0.00 - 0.05
P3 - 0.00 - 0.05
p4 - 0.00
P5 - 8.5V (one IC measured 3.0 something, still not working)
P6 - 9.0V
P7 - 4.0V
p8 - 1.4V

both tranny and IC were socketed. i auditioned all 5 LM386s i had, none of them seemed to work. im not giving up. yet. 

[newfish]

Daft question, but are you sure it's the LM386 at fault?

If you have (or can easily make) an audio probe, you should get a decent signal from your JFET if all is good there.

Could be that the 386 is working well, just has a miniscule / mis-biased signal being fed into it from the 'FET.

Audio Probe making can be found here...

http://www.diystompboxes.com/smfforum/index.php?topic=68710.0

...and is one of the most valuable debug (and JFET biasing) tools you can have - at very little cost...

Good luck with your Ruby.  It's an excellent little amp that's well worth any frustrations you may be having.

[Mugshot]

Daft question, but are you sure it's the LM386 at fault?

If you have (or can easily make) an audio probe, you should get a decent signal from your JFET if all is good there.

Could be that the 386 is working well, just has a miniscule / mis-biased signal being fed into it from the 'FET.

Audio Probe making can be found here...

http://www.diystompboxes.com/smfforum/index.php?topic=68710.0

...and is one of the most valuable debug (and JFET biasing) tools you can have - at very little cost...

Good luck with your Ruby.  It's an excellent little amp that's well worth any frustrations you may be having.

audio probed it already, jfet works as it should. the 386 is driving me crazy.

of the five ICs, one overheats; i junked that one out. two of them measure 1.2V on pin5, the other two give me a reading of 8.5 on the same pin5. still no output but a very very faint distortion. jfet used is an MPF102 with 2.5V on the Source.