SHEcho debug

[dstahl]

It feels like a while since I built a pedal and it just worked. Thank god for this board and the helpful people on it.
Anyway. Here goes.
I built a shecho via the GGG site http://www.generalguitargadgets.com/index.php?option=content&task=view&id=219&Itemid=244

http://216.220.98.25/david/cheddar/shechoback.jpg

At this point I think there is something funky with my voltages . With the negative lead of my meter on the ground lug, and touching the positive lead to where + voltage comes into the board I get 1.24 v instead of something closer to 9v.
  My readings for Q1 and U1 are as follows.
Q1
C 1.24
B -1.03
E -1.76

U1
1  .002
2  -.25
3  -.59
4  0
5  -.37
6  .58
7  .59
8  1.24

I will send some pics in a sec. I barely get any audible sound and it is not effected.
So does anybody have any suggestions where this voltage could be being drained from and where to start diagnosing the problem? or any other data I should send along to the forum for troubleshooting.

[Dean Hazelwanter]

You are right. Pin 8 of U1 and pin 3 of 'Q1' (which is a voltage regulator - pinout OUT, COMMON, IN) should be at +9 volts (assuming that is what you have connected to the board). Are you using a battery or power supply? Check the voltage of the battery or power supply with the board disconnected. If it's close to 9v, connect it to the board. If it drops to the 1.24v, something on the board is dragging down the supply. Check for solder bridges or other shorts. If that doesn't do it, remove all the ICs and see if your 9v supply comes back.

Let me know how you make out.

[dstahl]

I let this one sit for a bit, while I finished up a small clone project and did the final tweaking to my great cheddar and tremulus lune projects. Now this is the only one left undone.
  Any per Dean Hazelwaters recommendation I checked for solder bridges (and continuity) as well as rechecking all components. I also have now removed all the ic's including U1, u2, u3, u4, and Q1. I still get a voltage drain with these removed. now when hooking up a 9 volt that reads 8.76,  I show a voltage of .92 . This is being done with the black lead on the ground lug of the input jack and the red lead directly to the positive terminal on the battery , or at the +9v on the board.
  I am pretty sure that I should be seeing something closer to 9 volts here.
  Any thoughts on how I can narrow down where the problem is?
-D

[dstahl]

bump

[Dean Hazelwanter]

Hi,

If you haven't removed U5 (78L05) already, remove it and recheck your voltages. If the voltages are still low, you have a short on the board somewhere. Find a magnifier and check over the solder side of the board for solder bridges, shorting traces etc.

The cap on the far right side, with electrical tape under it - is there a chance that soldering has melted through the tape, causing a lead to short? Can you take some updated pictures now that the ICs are removed, especially of the bottom (solder side) of the board?

[dstahl]

ok. I just removed the 78L05. The voltage started out jumping down to roughly 1/2. 4.10 and then started to keep getting lower at first quickly and then slowly. going all the way down to 2.80 and then going down a tenth every second or so.
  I left my camera at home so won't be able to take pics until tomorrow. I looked for solder bridges and tested any place that looked remotely suspect with continuity to see if they were contacting. so far I haven't found anything that shorting. I will keep looking though.
 

[dstahl]

Got my camera. and here are some pics of the board with the ic's removed. Still losing voltage and I can't find any shorts. Any areas of board where you would like to see very close up pics?

[Dean Hazelwanter]

I don't see any obvious shorts in the pictures, but either a) there is a short (could even be a component gone bad) we haven't found yet, b) a component of the wrong value (e.g. 10 ohm resistors for the VRef bias instead of 10K), c) your battery is crapping out with this minimal load.

There are 3 jumpers (all connected directly to the +9v rail) you can try cutting to isolate where the problem is. With the board aligned so the 9v connector is on top, power up the circuit and monitor the voltage. Cut the jumper on the far right side, feeding the delay chip and RAM. No change in the voltage? Cut the jumper directly under C26. Still no change? Cut the diagonal jumper above U1. Still no change? Disconnect one side of R25 and R26. Still no change? Gotta be something very local to the area where the power comes in. If the voltage comes back to where it should be after cutting one of the jumpers, you have isolated an area to look closer.

Let me know how you make out.

[dstahl]

cool. I'm gonna try that tomorrow morning. Thanks Dean.

[dstahl]

ok I did all the jumper cuts. no change. Then I removed r26 and r25, then my reading was 0. I noticed that there was no way negative voltage would reach ground lug on input jack if I removed r26. So I soldered back r26, leaving r25 out, and then I was reading closer to 9 volts. Like 8.4 or something.
  So hopefully that helps localize the problem. Now I am wondering what I should be looking for and where. It seems it could be anywhere along the upper left quadrant of the board (before it reaches the jumper above u1). Anythoughts on how I should narrow it down from here?
Thanks
-D

[Zultan]

Hi!
I'm also building the Shecho, but can't get it to work. I'm a newbie:)
I amost gave it up because I couldn't find to much info about it.

Do you have any pictures of the connections to jacks and pots? not shure if I did the connections and grounding correctly. I just connected to the outputs on the board. I think I soldered the board correctly, but can't get any sound out of it:)

If you have some more pictures of your connections it would help me a lot.

Thanx!
Best Regards
Willy, newbie from Norway looking forward to get som juicy echo...

[Dean Hazelwanter]

Ok dstahl (for lack of a first name)  I think we're on to something here. You shouldn't need R25 or R26 in to still have your voltages. There is (or should be) a track connecting the top of C26 (with the power connector on the top of the board) to ground. In the 4th picture it looks like this trace has been scratched away. Try jumpering it.

Willie, don't give up. I think you will be happy with the sound once you get this working. I'll post some pictures in the next day or so. Do you have a multi-meter to measure key voltages with? Can you post pictures of your build?

[Zultan]

Hi!
Yes, I have a multimeter.
My biggest concernes are:
Are the boxed caps polarized or can hey go in either way?
Are the rest of my ic's and components put in the right way?
I'm not shure how to connect pots and jacks.
I'm not shure if my grounding is correct.
I think that my soldering is ok, and that the values of th components are correct. (not shure of course:)
How do i measure the ic's to make shure they work like they should?
Here are some shots of my shecho board:

[Zultan]

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[Zultan]

Hi!
I have measured all the resistors.
They are all some small desimals below the values: (the 10K's reads between 9,7K and 9,9K)

Some resistors have some strange values:

R13 should be 10K but reads 6,45K
R19 should be 1M but reads 983K
R24 should be 5600K but reads 025 when i put my meter to 2000K. (the meter doesn't go higher)
R26 should be 10K but reads 8,55K

The rest of the values are correct.
Best Regards
Willy

[Zultan]

I have some problems uploading pics, how do I do it in here?
but here is a link:
http://server4.pictiger.com/albums/2775/shecho/

[Dean Hazelwanter]

Hi Willie,

I have some problems uploading pics, how do I do it in here?

I saw all the pictures without any problems.

Yes, I have a multimeter.

Good. Can you measure the correct power supply voltages (+9, +4.5v, +5v, all referenced to ground) at the ICs, as per the schematic?

Are the boxed caps polarized or can hey go in either way?

Either way.

Are the rest of my ic's and components put in the right way?

Yes.

R13 should be 10K but reads 6,45K
R19 should be 1M but reads 983K
R24 should be 5600K but reads 025 when i put my meter to 2000K. (the meter doesn't go higher)
R26 should be 10K but reads 8,55K

Did you measure these resistances with the ICs out? If not, try it. Your resistors appear to be +/-5%, so the vale could be 5% more or less than the labeled value. R24 should be 560K not 5600K. Try disconnecting 1 end and measuring it's resistance, since it is in parallel with a capacitor.

I'm not shure how to connect pots and jacks.
I'm not shure if my grounding is correct.

Take a look here: http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ

I think that my soldering is ok

For the most part they look ok. If in doubt, get some isopropyl alcohol (99%, available at drug stores, often behind the counter) and a paint brush (about 1"). Cut the bristles so they only stick out ~ 1/2", and use the alcohol to clean the board. Then use a magnifier to check your connections.

How do i measure the ic's to make shure they work like they should?

The best way is to put them in a working board and see if they do what they are supposed to. 

Start with the voltages, and work through the above list. You are definitely on the right path - stick with it. Let me (us) know how you make out!

[Zultan]

Hi!
I'll try to do the measurements you suggest.
I think there is a type-error in the "parts ordered by name"-section in the project-file. It says that R24 is 5600K, but in the schematics it says 560K.
http://www.generalguitargadgets.com/pdf/ggg_shecho.pdf

Do you think this could be the reason why my board doesn't work? (if i put in 5600K instead of 560K) Will check later today.
Maybe i only have to change R24:) (optimist...)

Thanx for the good help Dean!
Willy
PS: do yo have any pictures of the connections? (pots, jacks,switch etc.)

[dstahl]

I think that "5600k" thing is a typo. if you look on the schematic it is listed as 560k as well as on the bill of parts. So I think you are good there. As much as I feel your pain in having a non-working shecho, I do like having company
  As well as having Dean's pics posted is a plus too. Hopefully we will both get this project sorted out.

[dstahl]

Got it working.  See next post.