Hey all, I am somewhat new to the stompbox building thing, but I have done a couple (TS-808 clone, fOXX tone machine, Jawari, EA Tremolo, and most recently R.G. Keen's tube based wah pedal, with which I am currently in love) with pretty good success. Reading through posts in the archive has been really helpful in all this. I have also built a Dynacomp clone from R.G's layout as found on GGG, but that has some issues. I built it and it worked very well for a while, but then it stopped. It lets out a heavily attenuated, un-compressed signal when it's on. I checked all the solder joints and couldn't find anything busted. The only modification I made was a 1k trimpot instead of the 2k, for supply reasons, and I am wondering if this could have fried the op-amp? I'd rather not order another CA3080E and trimmer without some indication that I'm on the right track. If I'm not, then I'll go and check voltages.
Thanks much,
Carl Tappan
Meh, I don't imagine 1k would make too much difference, lets seen some voltages any way. Never can tell if we can't "see" the circuit operating.
Alright, here's the voltages I get. I don't know enough about the theory make much sense of them; the thing that really confuses me is that it worked and then broke down. That seems like it would be a bad solder or something of the sort, but I have checked twice and found nothing. Thanks in advance for any advice.
Carl
Edit: It might be helpful to post voltages!
Q1:
C-9V
B-2.05V
E-1.69V
Q2:
C-8.84V
B-0.70V
E-175mV
Q3:
C-8.68V
B-0V
E-0V
Q4:
C-.56V
B-.1mV
E-.1mV
Q5:
C-9V
B-8.68V
E-8.28V
IC1:
pin 1-0V
pin 2-4.02V
pin 3-4.02V
pin 4-0V
pin 5-.70V
pin 6-.70V
pin 7-9V
pin 8-0V
http://www.generalguitargadgets.com/diagrams/geo_d&r_comp.pdf is the schematic, I am building the dynacomp as opposed to the Ross.
Carl
Comparing your voltages with the ones posted for this project on Fuzz Central shows that your
Q4 collector reading is off - should show around 9V.
Q2 emitter and base are low.
IC1 pin 6 is low.
That's all I can say with any degree of certainty.
A wild guess would be that the 3080 chip is damaged, and if it is you need to find out why it got damaged before putting in another one.
Hope someone else can zero in on the problem a little better for you. Good Luck.
From now until whenever my whim dictates it to be someone else, you are my favorite person :icon_biggrin: I looked for a while for voltages on the circuit and couldn't find them anywhere! It was actually Q5 that was fried, I replaced it and the bugger works perfectly. Thank you!!!!
Carl
:icon_biggrin: :icon_cool: