No volume

[ptempel]

First of all happy father's day to all.  I just finished a build of a new quickie pre yesterday.  After powering it on for testing, I got no volume.  I literally had to turn the pot up to 100% to hear a faint sound.  Let me know if you have any recommended troubleshooting steps.  Will check the power supply circuits first.  The only changes I made are the Obbligato output caps (2.2uF) and an Audio Note 100K ohm pot.  There is also a rather large thump after using the power switch.  Is that normal?  Below are two photos I took of it:

http://www.flickr.com/photos/25479025@N05/7387404744/
http://www.flickr.com/photos/25479025@N05/7387404314/

Thanks,
Philippe

 

[coca]

I trust you had the quickie working before you installed the constant current source.

Bernie.

 

[ptempel]

No I didn't run it without the PJCCS.  Only thing different in the regular build was omitting the 4.07K ohm resistors, IIRC.

 

[Paul Joppa]

A thump is normal. Do the resistances and voltages match the expected values?

 

[ptempel]

Ok, will check the voltage and resistance after work.

 

[ptempel]

Ok, I measured the following voltages:

T3 bottom and power switch center lug (row 2 middle): 37.6V
Power switch row 2 right and A7/A1: 1.607V
Power switch row 2 left and B7/B1: 1.607V
two center most 9V battery terminals: 37.61V

So the battery connections look ok.  Further down the circuit:

Power switch center lug and A6: 36.7V
Power switch center lug and B6: 36.7V
Power switch center lug and A5: 37.6V
Power switch center lug and B5: 37.6V

Seems like the PJCCS is ok?  Let me know what other measurements to take.  Thought I saw a post with a bunch of measurements in it but perhaps it was for another amp.

 

[ptempel]

Was looking at the schematic and it doesn't show the 220 ohm carbon resistors between the pot and tube pin 3.  Were they added later on?

 

[ptempel]

I found the problem.  Went back to the original manual and saw that the 4K ohm resistor I omitted went to both A6 and A4.  When I soldered the PJCCS, I only connected A6.  So I desoldered A6 and stripped the wire back a little more.  Then I was able to solder it to both A6 and A4.  Did the same for the other side (B6 and B4) and that was it.  Sounds great so far.  I hear more "presence" or the musicians seem to be more "in the room" if I can describe it correctly.  Big thumbs up for the quickie!

 

[Grainger49]

Was looking at the schematic and it doesn't show the 220 ohm carbon resistors between the pot and tube pin 3.  Were they added later on?

You are right on both counts.  Yes, the stopper resistors are missing.  They were either missed by whoever cadded the schematic or added soon after.

Glad you found the problem. 

Enjoy the music!

 

[ptempel]

You are right on both counts.  Yes, the stopper resistors are missing.  They were either missed by whoever cadded the schematic or added soon after.

Glad you found the problem. 

Enjoy the music!

There are other errors on the schematic as well.  IIRC, it didn't show the connections I just did above.  No biggie but it should be updated.  Will definately enjoy after I finish staining the base.

 

[Grainger49]

Philippe,

The Quickie schematic I have shows pins 6 and 4 being connected.  It is dated 9/1/2009.