Mxr Carbon Copy J177 voltages

[teknoman2]

I just got from a friend a dead carbon copy, and I believe it's version 2 since it has the diodes near by the transistors.
My main issue is that when I engage the effect I have no delay or modulation, only dry signal appears,
bypass led is on and modulation led is on.
Also I measured ic voltages and the are looking fine.
I checked all over the net and usually carbon copy main issue are Q10, Q11, Q13 and Q14 ( there are j177), they stop working from static electricity.
Can someone post his transistor voltages to compare them with mine.?

[jimilee]

Have any idea how it died or what happened before it quit working?

[teknoman2]

I don't have any idea why it died.
My friend said that it was working just fine and one day nothing.
As I said before ic voltages are looking fine but when I measure the j177's something strange is going on.
All the transistors have the same gate voltage 4.5v but drain and source are different.
Do you want to upload transistor voltages?

[jimilee]

Well I'm at work right now and then have rehearsal after so it will be a while, and I'll have to check to see if I have anything with those in it too.

[teknoman2]

Thanx mate, while working I will post most of the voltages
so we can find which component is faulty.

[Scruffie]

Might be obvious just from yours, post them up.

[teknoman2]

My transistor voltages are:
Q10: G=5.19v, D=0v, S=0v.
Q11: G=5.19v, D=3.0v, S=0v.
Q12: G=5.19v, D=0v, S=0v.
Q13: G=5.19v, D=0v, S=0v.
Q14: G=8.7v, D=0v, S=2.8v.
with dc power supply 9.01v.
Also I have all ic voltages,
would you like to post them too?   

[Scruffie]

My transistor voltages are:
Q10: G=5.19v, D=0v, S=0v.
Q11: G=5.19v, D=3.0v, S=0v.
Q12: G=5.19v, D=0v, S=0v.
Q13: G=5.19v, D=0v, S=0v.
Q14: G=8.7v, D=0v, S=2.8v.
with dc power supply 9.01v.
Also I have all ic voltages,
would you like to post them too?   

I dunno exactly what these are doing but if I had to guess, Q14 and 11 might be alright, the rest look dead if they only have voltage on their Gates.

I'd just swap 'em all, can't hurt.

[teknoman2]

I agree, something is not right when drain and source are 0v.
From my experience jfet (j201) gate usually is matched to 4.5v and its my first time to meet both D and S equal to zero.

Can someone owner of carbon copy bother to measure his transistor voltages, so we can verify them?

[Pedro]

Hello, I am new to the forum, ask permission to ask for help.
I have a carbon copy of the mxr. the led on the mod connects normally.
the main effect and the LED does not work.
is version 1, I believe that is prblema transistors Q10, 12, q13.
they are smd. would like to know which components can use to replace them?
sorry English (by google translator)

Peter

[Pedro]

Hello, I am new to the forum, ask permission to ask for help.
I have a carbon copy of the mxr. the led on the mod connects normally.
the main effect and the LED does not work.
is version 1, I believe that is prblema transistors Q10, 12, q13.
they are smd. would like to know which components can use to replace them?
sorry English (by google translator)

Peter

[teknoman2]

They are j177

http://uk.farnell.com/fairchild-semiconductor/mmbfj177/transistor-jfet-30v-20ma-sot-23/dp/2323149

[ataro]

Hi, I know this is an old thread, but I have a Carbon Copy on my bench that has the same problem, no wet signal, only dry signal either in bypass and engaged.

This are my voltage readings:

Q10: G=7.1v, D=0v, S=0v.
Q11: G=7.1v, D=2.6v, S=0v.
Q12: G=7.1v, D=0v, S=0v.
Q13: G=7.1v, D=0v, S=0v.
Q14: G=8.7v, D=4.1v, S=3.5v

Do these readings point to dead transistors? I'm about to order some J177, but I'm still in time to throw another component in the basket.
Thanks!

[teknoman2]

Just saw your post.
I haven't find any solution yet for mine also.
I will measure my voltages also and let you know, but for my experience on other bbd analog delays that symptom indicates that there is something wrong with the compander.
Those j177 I believe are for the filtering only.

Panos