Dirtbag Deluxe v3205 problems

[sidebernie]

Hi Guys,

Following the rules:
1. I 'm building a dirtbagdeluxe v3205 version.
2. The main problem I am having is that I only get one repeat. The circuit does not seem to self oscillate. Everything else seems to work except when I turn the delay all the way up I get a really high pitched squeal. When I biased the BBD's they seemed fine. I was able to hear the delay on both chips and got a pretty clean signal, however when I got to the gain stage setting I could not get it to self oscillate and I think this is the reason I'm only getting one repeat.
3. I used stock parts at first according to the instructions I received which are not the latest. I used the 47kfor R11/12 and the 100k for resistors for R21 and C14. That version did not work at all beyond the BBD biasing. Then I saw the new revision and finished up putting in all the new parts and reverting to the correct R21 and C14. This was not easy. However it sounds much better now and if I can get the repeats working and get rid of the high squeal on the delay I think it will sound great. It is not boxed up and I'm hoping you have heard of this problem. I guess this is what you may call not getting a wet signal??
4. The only parts substitutions are the ones for the new revision.

I am building this for my son as a present who absolutely loves the DMM. My background is in electronics and I have built other pedals so I'm not a beginner. I hope you can help me out.

[madbean]

First thing to do is figure out where your repeats are going. You need to audio probe at the junction of R62/R44, then R48/C34 and lastly C5/R7. If the signal is dying out at any of those points then look for solder bridges, cold joints or bad parts on those.

For the squealing, you probably have your Clock trimmer too high. Try dialing it back some. That should eliminate the whine at the max delay setting.

[sidebernie]

Hey Madbean thanks for the quick response. That makes sense to me. I'll let you know what I find.

[sidebernie]

Hi Madbean,
Well I finally got around to fooling with the circuit again and found the problem with the repeats and the self oscillation. It was as you said, I was losing the delays between C5 and R7. I discovered that the lead on one side of C5 was barely touching the component next to it. I carefully rectified that and now I have plenty of repeats and no problem with the self oscillation. This is something people should take note of because this is such a tight board it does not take much to create a short somewhere. I had to look very closely with an eye loupe. Now when I turn the feedback to about 3/4 of the way up it starts going into runaway mode. I'm sure you know what I mean. I do still have some distortion but I got rid of most of it by re-biasing and fooling with the gain trimmers. It could still be a little cleaner.

However I still have the probelm with the delay pot squeling at about 3/4 to full throw on the pot. I have tried to trim the balance, which is what I think you meant by the clock trimmer, but it still remains. I would really like to get rid of this since most of the delay occurs in this range. I'm making progress but if you have any other suggestions for the delay squealing I'd appreciate it. At least I'm very confident that I have built it correctly and got the mods installed right. I appreciate your support.
Bernie 

[LaceSensor]

Try swapping the clock capacitor think its c41 from memory, change it from 240pF to lower value. Start at 220 perhaps.

[sidebernie]

Well, I've tried several different vlues of capacitors from 150pf to 340pf and the only difference is that the squealing starts at a slightly different position of the delay pot.  I read in another post that the whining , or squealing, is expected and acceptable. I can't believe this to be the case. Does the DMM squeal when you turn up the delay? Has anyone built a v3205 version that does not sqeal when the delay is all the way up? Do you think that this might be minimized when put into an enclosure? Its kind of a drag when youi can't get all the delay available when maxed out without any squeal. It's definitley enough squeal that I don't think it would be drowned out when running at stage volumes. Please any suggestions from anyone are appreciated. I'd like to hear from someone who has built a v3205 without this squeal or from someone who has gotten rid of it. Other than this the pedal works fine.

[gtr2]

Are you testing unboxed?  If you are, it will squeal at the longer time pot setting.  When boxed it will no longer squeal.


Josh

[sidebernie]

Hi Josh,
Yes I am testing unboxed and that's what I would expect. I just wanted to get that verified from someone who has done it. Thanks. I will box her up and see how it goes. I appreciate your reply.