Dyna Comp Debugging

[jimladladlooklike]

Hi all.

So I've recently finished this build:



I haven't been working to a schematic, so this is my only reference. It's all the same parts as on the above layout except I've swapped the 2n5088s for 2n3904s. I firstly had no sound/when I played hard I got some distorted sound, so went straight to using an audio probe to see if I could spot the problem that way. When probing pin 6 of the IC (output) I noticed that the sound was loud but highly distorted. This was the same for 4 of the 10 ICs I purchased. I decided to measure the voltages and they are as follows:

IC (CA3080)
1: 0.1V
2: 3.7V
3: 3.7V
4: 0V
5: 0.1V
6: 6.8V
7: 9V
8: 8.2V

Q1
C: 9V
B: 1.4V
E: 2V

Q2
C: 6.2V
B: 6.8V
E: 6.2V

Q3
C: 7.8V
B: 0V
E: 0V

Q4
C: 7.8V
B: 0V
E: 0V

Q5
C: 9V
B: 7.7V
E: 8.2V

I'm a little concerned that pin 1 and 8 of the IC are measuring anything at all... I have checked the connections around the IC and the rest of the circuit multiple times now and the only thing I can think of as to why pin 8 is getting 8.2V is that there is some kind of short within the ICs. Perhaps they're fake? I've heard something about fake CA3080s before. I also tested the voltage of the socket where pin 8 goes when I had removed the IC, and it was 0V as it should be. Anyway, any insight anyone can give as to whether I have done something wrong to perhaps damage each IC I tried would be great.

Cheers.

[duck_arse]

read this thread, particularly reply #13:

https://www.diystompboxes.com/smfforum/index.php?topic=122095.0

also, please post some photos of what you have built.

[jimladladlooklike]

Thanks! I'll be sure to when I get chance

[jimladladlooklike]

Just checked all of the 3080s I have using the diode function and they're all giving the same readings. Guess I've been mugged off or perhaps been super unlucky. Oh well! I have some on the way from a British supplier so I'm hoping they will work.

Cheers again for pointing me towards that previous post.

[MaxPower]

I believe the lm13600 and lm13700 can be subbed for the ca3080. Not sure if the pinouts are the same.

[merlinb]

Should've built an Engineer's Thumb 

[jimladladlooklike]

I believe the lm13600 and lm13700 can be subbed for the ca3080. Not sure if the pinouts are the same.

Yeah they're different. Would need to redo the whole layout! I've found a working 3080 now so it's all good.

[jimladladlooklike]

Should've built an Engineer's Thumb 

You could be right! I'm gonna try and build one of those eventually. Hearing good things. However this one was for a mate who specifically requested a dyna comp