MXR Dynacomp no output when sensitivity minimum

[fretzburner]

Hello what seems to be the problem with my 80's mxr dynacomp the output will fade and never comes back when sens set to min.if i will set it mid position the output comes back but low.my output setting is always between mid to full if sens knob set between 10oclock to full.Is there some kind of old component that needs replacement?

[fretzburner]

update: i noticed i powered the unit first and not engage the effect for a couple of minutes and i can use the low sens settings but very low output.With output knob to max and i dialed the sens knob to obtain unity gain and the resulting sens position is at position 3 (on 1-10 knob increment).Are compressors needs warming up or charging caps time?

[Jhouse]

Read THIS bad boy and post all the information is asks for. It will help us diagnose your problem a whole lot easier. It's almost impossible to determine what is wrong without any other specific information.

[fretzburner]

update; i was wrong when i said no output,it is working fine,the only problem is the output fades out after some time playing and have to increase the sens to make it start to sound again.the output seems to respond with the sens knob.lower sens setting =shorter duration of output,higher sens setting=longer duration of output but still fades out after some time of playing.

[fretzburner]

another update: measured voltages at Q2. Base voltage is 2v and i checked the 150k resistor it was rusted and changed it.now it is acceptable.But the output with sens to zero and output knob is full is not unity gain.I'm new to compressors,is this normal?how to increase the output sound to have unity gain when output knob is full and sensitivity knob to zero?
                                                             

[Thomeeque]

another update: measured voltages at Q2. Base voltage is 2v and i checked the 150k resistor it was rusted and changed it.now it is acceptable.But the output with sens to zero and output knob is full is not unity gain.I'm new to compressors,is this normal?how to increase the output sound to have unity gain when output knob is full and sensitivity knob to zero?

What transistors did you use?

[fretzburner]

it is stock transistors and no markings.Correction it was Q3 that i measured not Q2.It is working fine now only with volume problem low output but usable with output knob turned between 6 to 10.Sometimes the volume drops a little while playing and gained back a few seconds or minute.

[R.G.]

update; i was wrong when i said no output,it is working fine,the only problem is the output fades out after some time playing and have to increase the sens to make it start to sound again.the output seems to respond with the sens knob.lower sens setting =shorter duration of output,higher sens setting=longer duration of output but still fades out after some time of playing.

I would guess from this description that the pullup on the 10uF recovery cap is not recharging, or the transistor follower after it is not working properly. That's the only good explanation for this action.

By the way, have you read "Debugging: What to do when it doesn't work"?

[fretzburner]

I already managed that problem i measured the voltages around the transistor.the faulty component was the 150k resistor and now it works fine.just that sometimes it reduces volume while playing and seems not raising gain when played soft.will not sustain or the sustain is almost not noticeable compared to bypass but very obvious when played loud it reduces overall output or even it.

[fretzburner]

I finally found the cause of the volume drop problem,it is the 10uf electrolytic capacitor connected from Q3 base to ground.The problems are low output spmetimes no output when sens set low and while playing the output drops in volume and sometimes no output even if sens knob set 75percent.Now my dynacomp is working perfect. Thanks to all who responded my questions.