PRR-176 REV 4 Build Thread ***Manual up!***1/16/14 - (chk 1st post)

[e.oelberg]

so now I'm stuck. No sound on output, meter move sidechain is working. I use Lundahl ll1540 on second interstage.
I traced the signal with a headphone connected to a 0.1mF cap as probe in lack of a scope. Could trace signal after second tx anymore ???


.

 

[abechap024]

so now I'm stuck. No sound on output, meter move sidechain is working. I use Lundahl ll1540 on second interstage.
I traced the signal with a headphone connected to a 0.1mF cap as probe in lack of a scope. Could trace signal after second tx anymore ???


.

Hmmm you said the sidechain is working? Well that is post the second interstage transfomer....It splits after the second discrete opamp to the sidechain and the output stage. So maybe the problem is the last output gainstage?

hi abe

is it necessary to ground the sidechain at the bypass position of the switch ?

nicholas

I have it setup that way, but no...you don't really have to I guess.

 

[e.oelberg]

Actually I'm not sure sidechain is working. Meters are moving  but no signal at first u11 gainstaige
I'll check the secondary load resistor..

Thank you

 

[abechap024]

Actually I'm not sure sidechain is working. Meters are moving  but no signal at first u11 gainstaige
I'll check the secondary load resistor..

Thank you

Are your tube glowing? 100v rail measure well? also, you probably know this but worth a mention, if your using headphone you might not hear it because it gets very quiet until the output gainstage...

Hmm checked that it passed through your input tx ok...a scope is nice for stuff like this.

 

[e.oelberg]

abe !

are you sure the middle jumper (above the UM  in JUMPERS) in your sketch is correct ?

 

[ilfungo]

Hi e.oelberg
are you talking about this link?

 

[ilfungo]

On second channel is like this....

 

[e.oelberg]

right..thats what I'm talking about

 

[ilfungo]

I think it was an error...
Are you using 1Ma meter or VU?
now your 176 is working?

 

[e.oelberg]

no it passes audio but distorts like crazy. The jumper is wrong it should go from lundahl out to secondary load transistor to buffer.

I think there are other things wrong than just the jumper. I just didn't have time to dive more deep into it right now

 

[e.oelberg]

I use VU

 

[ilfungo]

Sorry like in second image I've posted?
Thanks

 

[e.oelberg]

that one is wrong

 

[ilfungo]

e.oelberg have you tried to set the threshold trimmer?
I've build rev 2 and if I remember correctly, if the trimmer is all the way the sound was distorted...

 

[mrdarwin]

sorry guys, no time these last days to experiment rev4 with you...
I will fire up my unit on friday or saturday and tell you
Abe do you confirm the new jumper?

 

[abechap024]

On second channel is like this....

Yes this is the right way. Gah! Sorry. Yea I'll update the build manual.

Also nicer manual on the way...

 

[ilfungo]

I have around 2 x opa275
can operate in the sidechain in place of TL072?
Thanks

 

[abechap024]

I have around 2 x opa275
can operate in the sidechain in place of TL072?
Thanks

Yes, should be fine. Just keep on eye on stability problems, but if everything functions as normal then you are most likey ok.

 

[ilfungo]

today I've powered up my 176 and nothing is exploded!
I've seen 2 strange things:
My tension instead 100v is 125v
Can create some problemS??
The first tube is more bright than the second,
between point A/B is 6.7V
Between point B/C is 5.8V
???
I only hear low sound and no bass
I tried to follow the signal and to the primary of T1 there is full signal,
on the secondary signal goes down as described above ...
is there any other link necessary?
Thanks

 

[e.oelberg]

today I've powered up my 176 and nothing is expz
I only hear low sound and no bass
I tried to follow the signal and to the primary of T1 there is full signal,
on the secondary signal goes down as described above ...
is there any other link necessary?
Thanks

Here we go..  welcome in the club we are at the same place
Thin distorted sound...sounds mire like leakage to me