[BUILD] 1176 Rev A - Back to the beginning...

[baadc0de]

And indeed i'll take it. I'll scrounge around for parts and make something so I can trace this around. Thans for the advice!

 

[phishman13]

sorry if i insult your intelligence with this question, but from my rev a build, i wired it all up, plugged it in and immediately tried to run audio through it, horrible results.  Turns out my problem was.... I hadn't calibrated it yet.  After going through the full calibration procedure, worked like a charm.  So have you calibrated it yet?  Or at least do the first step to set Q-bias. 

 

[baadc0de]

I was under the impression that a unit that does not pass signal from input to output has problems that need to be resolved before calibration. Nevertheless, moving the q-bias resistor does enable me to get the meter to not be pegged left in GR mode but goes all the way right. I'm waiting for my scope to be returned to investigate further.

 

[Rob Flinn]

With the 1176 the calibration severely affects how the unit operates, as you've discovered.

 

[baadc0de]

Tracing the preamp section, I think I should check R5, R8, R11 and R15 for signal. Any other debugging tips and hints? The solder points look solid enough, so it's probably a dead component like Q1 or something.

 

[martthie_08]

if anyone could help me out, I'm building a two of mnats rev A 1176 and I got stuck finishing them off - after checking the wiring multiple times, I am unable to set the Q-Bias and thus can't calibrate the units.

Both pass audio in to out (sound great), input pad and output controls work fine. The psu voltages are correct, and the voltages in the GR control amp correspond within 5% tolerance to those posted by Jakob on http://gyraf.dk/gy_pd/1176/1176sch.gif, (this section is the same on most revisions of the 1176).

I started out using 2N3707 transistors and changed these to 2N5088 on one unit (observing pin-out), but this didn't change a thing. The two matched 2N5457 should be good (got em from hairballaudio) but I didn't check before stuffing them on the pcb.

If someone has a clue to what could be wrong, I'd appreciate it! thanks, Marten

 

[Rob Flinn]

Marten check to see if you have volatge on the Q bias preset & that it changes when you adjust it.  check to see this change also on the Gate of the fets

Baadcode you need to trace the signal through the audio side of the circuit to see where it dies. 

 

[phishman13]

From my experience,  setting the q bias adjustment is necessary to pass audio.  I guess unless it just happens to be set in the conduction range already, at which point you would pass audio but just need to fine tune it, but mine wasnt, so it didnt pass audio til i set it.  Check if you can set your q bias if you can and see if that does it.

 

[baadc0de]

Last I see signal is on R8/R9 junction that goes to Q2. Ideas?

 

[Biasrocks]

Last I see signal is on R8/R9 junction that goes to Q2. Ideas?

All the usual suspects.

Bad J309, inserted wrong, cold solder joint, shorts.

Mark

 

[baadc0de]

Resistance between S and D of Q2 J309 measures 60-80 ohms (tested out of socket). That can't be right, right?

 

[Stagefright13]

Best Idea is very close up pictures. Someone here may see something.

 

[evilcat]

Hi guys !

I'm thinking about building an 1176, that would be my 3rd built (after a S800 and an EZ1290) but I don't know which Rev I should choose between D and A. What are the sonic differences ?

Thanks for your advices.

Ben

 

[jdbakker]

I'm thinking about building an 1176, that would be my 3rd built (after a S800 and an EZ1290) but I don't know which Rev I should choose between D and A. What are the sonic differences ?

That has been discussed here approximately five million times. Please have a look at the META, or do a search.

JDB.

 

[ChrioN]

I started out using 2N3707 transistors

Where did you find those with hfe of 250+?

 

[martthie_08]

just got back from holidays, Rob thanks for your reply, will check it out later in the studio...
ChrioN, I got the 2N3707 from eBay seller 6k8, bought 30 pieces and there were lots of them over HFE 250...

 

[ChrioN]

Thanks a bunch mate

 

[martthie_08]

ok, found my mistake, the lead from the release pot to the ratio board was (incorrectly) sitting on the attack pot, no wonder I couldn't set the Q bias. After that calibration was easy with mnats great videos, got it done in about 20 minutes. This box has serious mojo, very very nice!

I now have to finish my second unit which has an original UTC input transformer and fuss around with different caps in the signal path, but really happy that its working now - thanks to everyone here!!

 

[Rob Flinn]

After that calibration was easy with mnats great videos, got it done in about 20 minutes.

Did you let the unit warm up for a good 1/2 to 1 hour before calibrating, without switching it off during the period ?    If not might be best to do it again to be sure.

 

[martthie_08]

well, I did the Q bias immediately after power on, but waited for 30 min before doing the zero adjust and GR tracking adjust, should be ok - if not, I can always come back to it...