Red Llama debug

James · Post by **James** » Mon Sep 15, 2008 2:02 pm

I built this recently anbd it passed signal in the effcted mode but without the effect. Going from memory, it oscillated at certain points on the volume pot, and the fuzz needed to be on maximum to pass much signal, 9 (out of 10) or less and it was very quiet. I checked and a couple of areas were getting no power but I wasn't sure what was wrong.

I came back to it yesterday and nothing is getting power. The 9v comes into the board fine. The first leg (as in the bottom one in the pic, next to the 9v in)of the R4 has power, the second doesn't. I changed the resistor for one I tested before installing and it didn't fix it. A visual check shows no problems. I would have thought the most likely component to be destroyed would be the diode, but I'm baffled as to why the power doesn't get beyond the first resistor.

This is the layout I'm using

I am confused. Does it mean the something on the same track as the seecond leg of the resistor is dumping all of the voltage to ground? All that's there are two jumper wires, so perhaps it's something at the other end of one of those?

Post by **Mike** » Mon Sep 15, 2008 2:07 pm

You need to check absolutely every one of those cuts is really cutting the track, and that you have done them all. Use a DMM either side to check for continuity.

Unfortunately the thing most likely to die is the IC.

R4 should only drop a bit of voltage, so you need to check everything else. All the cuts and all the placement of jumpers. Count the cuts and check their placement. Count the jumpers. Check the orientate of the IC (it's upside down). Check orientation of C4 and C6 against Schematic.

James · Post by **James** » Mon Sep 15, 2008 2:14 pm

I have the notch of the IC on the bottom in relation to that pic. Is that correct? I'm guessing it is based on this...

Where the notch is at the far end from the diode.

All of the cuts are good and in place. Another visual check shows one area where there is a small (but enough to cause a connection) solder joint across the tracks that I'll sort out now. It's pretty much on the diode, so it's possible I borked that or the IC. How do I check if either is working? i have the IC on a socket so if necessary I can remove it but that's a bit akward. I have plenty of spare diodes to replace it with (got a pack of 20 1n4001 from futurlec) so I'll do that if I need to.

I'm confused as to why a problem on that side of the board would cause the second leg of the resistor to not have any power though.

I'll sort out that solder now and see if it improves anything.

Post by **Mike** » Mon Sep 15, 2008 2:19 pm

If you haven't bought a multimeter you need to get one. Whenever anything doesn't work I always check for continuity between tracks that should be connected through jumpers and check that no adjacent tracks have continuity between them that shouldn't, and that cuts have been successful.

Your diode will be fine. It would never break a diode to have it backwards or short circuited. The IC is much more fragile.

I would remove the IC and check cont. between the IC socket and components that are connected to each leg.

James · Post by **James** » Mon Sep 15, 2008 2:30 pm

I have one and have been using it to find problems. I found a cold solder joint on the mammoth using it (the only problem I had with that one) but I don't know how to use it that well. It has a hfe checking thing I should start using for transistors.

How do I actually check continuity? So far all I've done is use it to check that power is getting place and to check that resistors work (I wired two in series for the fuzz factory and checked that, and check the dodgy bit on this)

I have this Multimeter.

Post by **Mike** » Mon Sep 15, 2008 2:39 pm

Set it to the diode symbol (triangle with a line on it). Tap the leads together, it should beep.

James · Post by **James** » Mon Sep 15, 2008 2:48 pm

No beep. Just lots of quickly changing numbers on the screen. Of the 3 sockets at the bottom, I have the red one in the middle and the black one on the right.

Post by **Mike** » Mon Sep 15, 2008 2:50 pm

Your multimeter sucks. You need to get one that has an audible continuity tester.

James · Post by **James** » Mon Sep 15, 2008 2:54 pm

I can't afford to buy another. It looks like 1 mean no connection and 0 means there is. So I guess I can go through liek that checking for errors.

If I can't get it working I might head to Maplin tomorrow to buy some more stripboard and desoldering braid. Then build a fresh board and hope for the best with that one.

Post by **Mike** » Mon Sep 15, 2008 2:55 pm

You really should get one with a beep, it's invaluable.

James · Post by **James** » Mon Sep 15, 2008 2:58 pm

Any idea what sort of price I'd be looking at to get the beep? I'm incredibly low on funds at the moment but want to get into this pedal building lark a bit more.

Post by **Mike** » Mon Sep 15, 2008 3:02 pm

I have this one
http://www.maplin.co.uk/Module.aspx?ModuleNo=33174

Â£29.99

James · Post by **James** » Mon Sep 15, 2008 3:05 pm

I defintely can't afford Â£30. Bollocks. I'll see what I can do with the one I have and hopefully get either this or the fuzz factory working today.

I actually feel a bit gutted about dismantling the Harmonic Percolator now. I had to do it to paint the Llama case but now the Llama doesn't work I feel a bit shit about it. I'm glad the Mammoth works and sounds great though, I planned on playing guitar for about 10 minutes last night and it turned into about 2 hours because of it.

Post by **Mike** » Mon Sep 15, 2008 3:12 pm

Don't be disheartened. We all have trouble at times. I stared at the first board I made for stewart's OCD for days before giving up. There was literally nothing wrong with it.

stewart · Post by **stewart** » Mon Sep 15, 2008 3:18 pm

Mike wrote:Don't be disheartened. We all have trouble at times. I stared at the first board I made for stewart's OCD for days before giving up. There was literally nothing wrong with it.

d'you still have that board? if so you should stick it together and try it on the 'bay. or someone here might buy it, it's a cracking pedal.

(apologies for the temporary topic hijack)

Post by **Mike** » Mon Sep 15, 2008 3:18 pm

stewart wrote:
Mike wrote:Don't be disheartened. We all have trouble at times. I stared at the first board I made for stewart's OCD for days before giving up. There was literally nothing wrong with it.
d'you still have that board? if so you should stick it together and try it on the 'bay. or someone here might buy it, it's a cracking pedal.

(apologies for the temporary topic hijack)

I still have it, but it doesn't work, so it's useless.

stewart · Post by **stewart** » Mon Sep 15, 2008 3:22 pm

Mike wrote:
stewart wrote:
Mike wrote:Don't be disheartened. We all have trouble at times. I stared at the first board I made for stewart's OCD for days before giving up. There was literally nothing wrong with it.
d'you still have that board? if so you should stick it together and try it on the 'bay. or someone here might buy it, it's a cracking pedal.

(apologies for the temporary topic hijack)
I still have it, but it doesn't work, so it's useless.

ah. i thought you'd sorted it out after you built the 2nd one, i didn't realise it was still fooked.

Post by **Mike** » Mon Sep 15, 2008 3:24 pm

Nah, I built a second one and it worked fine. Then I stared at it and the broken one and could find no differences. Proper odd. I think there was just a bad component on it.

James · Post by **James** » Mon Sep 15, 2008 4:33 pm

UPDATE

I fixed the solder point I mentioned near the diode. It passed signal as soon as I plugged it in. I actually got some fuzz tones out of it. I use a rubbish amp for testing but it sounded good.

The problem pot is actually the volume pot. It's incredibly crackly and if you have it on less than 10 it basically doesn't work. If you touch it it crackles like a bastard, and then rolls off very quickly once you go below maximum. I just checked and I have a 10k log pot there, so the taper should be fine.

I'm going to remove and then rewire the pot, hopefully it'll be fine when I put it back on.

aen · Post by **aen** » Mon Sep 15, 2008 6:11 pm

Mike wrote:Don't be disheartened. We all have trouble at times. I stared at the first board I made for stewart's OCD for days before giving up. There was literally nothing wrong with it.

fucking stripboard.