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

[Echo North]

You could see if you're getting DC at the GR fet gate.  You should be getting a DC bias with a signal and compression in enabled.  Like 1V-2V DC.

You most likely are not seeing any DC here other than the q bias voltage (or you'd have compression).  From there you can try tracing back.

See if you have DC at the cathode of CR2/CR3.
See if you have AC and the Anode of CR2/CR3.
See if you have AC at the Base of Q10 the  Q9 then Q8 then Q7.

The rev D voltage chart for the GR section should be the same or close:
http://mnats.net/files/1176REVD_VOLTS.pdf

 

[MatthisD]

I am reading 47 Ohms at the output transformer(EA-5002) secondaries, if not too much trouble could someone measure their XLR +/- output for comparison?


I have healthy signal on the blue wire and nothing, other than a tiny(0.12v), distorted signal on the red wire which is unaltered by the output pot. Orange and yellow wired together. Tested with XLR to meter board connected and disconnected.


I have read through both rev A and D threads with ChrioN's problem most similar to mine albeit my problem is with a Rev D and with only the output transformer secondary. From following the posts there didn't seem to be a positive outcome to the issue below.

Feeding a signal through the whole PCB, from the input transformer secondary to the output transformer primary shows a perfectly fine unit.
But as soon as I'm going through either of the transformers, things gets strange.
As seen from recent photos, the output transformer is correctly wired.
As seen from a drawing I posted some time ago, the input circuit (pad & transformer) is correctly wired.
what gives..
When going through the output transformer, I get a 400hz high pass filter. And only signal present on -. No signal at all on +.

 

[Echo North]

I am reading 47 Ohms at the output transformer(EA-5002) secondaries, if not too much trouble could someone measure their XLR +/- output for comparison?

Yes that is the right DCR for the secondaries.

 

[Harpo]

I have healthy signal on the blue wire and nothing, other than a tiny(0.12v), distorted signal on the red wire which is unaltered by the output pot. Orange and yellow wired together. Tested with XLR to meter board connected and disconnected.

Output is floating, not ground referenced from balancing transformer. Measure/connect between blue/red.

 

[MatthisD]

Both replies appreciated. I wasn't aware of the different forms of balanced outputs. Signal is present on pins 2 and 3 so output circuit is working as it should.

 

[mjproc]

I hope someone can help me with a small error in my build.

I've completed two units (rev a), both passing audio, compresses and sound great!  Both sucessfully calibrated.

On one of the units the vu meter acts a bit strange,

Ratio set to 20:1, Vu set for GR.  Needle correcly @ 0:
If I select 4:1 ratio , the vu increase approx +2, the same for 8:1 and a bit less @ 12:1

This does not happen on the first unit.

I've checked the obvious things and compared the two units with a dmm, Both resistors and voltages match quite fairly.

I'm soooo close now, just need a helping hand the last mile ;-)

Pleease..

Brgds
Ole Peder

 

[mjproc]

I'll anser my own q.... Problem solvd

I doble checked my voltages and found 2 volts difference between the two units on collector voltage Q3.  Swapped C5 and rotated C21  :-X (I'd trippel checked the components.... 1 mistake... Doh)

Thnx to Hairball & Mnats for puuure joy.  The easiest build so far!!!

Brgds
Ole Peder

 

[GuitarTown]

Hello folks,
I´m building my first pair of revA´s  and I´ve noticed for R11:

BOM says 9.1k (Both mnats and Hairball)
Overlay says 10k

Which is the correct one?
Does it make a big difference?

Thanx and happy building ¡

 

[mnats]

Hello folks,
I´m building my first pair of revA´s  and I´ve noticed for R11:

BOM says 9.1k (Both mnats and Hairball)
Overlay says 10k

Which is the correct one?

When in doubt, refer to the original schematic.

Does it make a big difference?

No.

 

[jmp72]

Hello folks,
I´m building my first pair of revA´s  and I´ve noticed for R11:

BOM says 9.1k (Both mnats and Hairball)
Overlay says 10k

Which is the correct one?
Does it make a big difference?

Thanx and happy building ¡

Finished mine yesterday, i noticed this too and I confirmed that it's 9.1k


Received my board yesterday morning, at 5 pm my compressor was working without any troubleshooting and calibrated even with q7-q10 at 170HFE, I have a bunch of 5088 in the mail, what will be the difference of having HFE over 250?

Thanks
-Benoit

 

[steve_h]

You could see if you're getting DC at the GR fet gate.  You should be getting a DC bias with a signal and compression in enabled.  Like 1V-2V DC.

Thanks Mike. Finally got around to trying this and upon testing DC voltage at the gate of Q11, I get a reading of -.775v and the needle pegs. This is with compression engaged and a 1k sine wave signal going into it. Wondering what your thoughts are before I go further with your other steps. Anyone else?

 

[mikerl]

So i just put in an order for the BOM (revA 1176, Hairball Audio), and there was one part backordered, looks like its the AC plug/fuse holder:

http://www.mouser.com/Search/ProductDetail.aspx?R=719W-00%2f02virtualkey56210000virtualkey562-719W-00%2f02

Any idea where i can score one of these before the backorder comes through?

Thanks,

Mike

 

[mikerl]

ok, looks like DigiKey has it.. sorry to crowd the thread with something like this!

Mike

 

[germoju]

hi guys,

I'm looking for a Carbon Film Fixed Resistor 15M ohms 5% 1/4W for my futur Rev A... on mouser I can just buy 40,000 pieces at once !!
I can't find it on Digikey, farnell, conrad, or awatronic...

Do you know where I can search ?

Hummm, maybe this one is good ? http://www.digikey.fr/product-detail/fr/CF14JT15M0/CF14JT15M0-ND/1741300

 

[BPJ]

Hi Germoju,

Try this >>>

http://www.mouser.com/ProductDetail/KOA-Speer/CF1-4C156J/?qs=9U0s%2f%252bXNmApDDV2lup04b2bmJwcMGbtsWAhT3O%252bPFqM%3d

 

[germoju]

Hi Germoju,

Try this >>>

http://www.mouser.com/ProductDetail/KOA-Speer/CF1-4C156J/?qs=9U0s%2f%252bXNmApDDV2lup04b2bmJwcMGbtsWAhT3O%252bPFqM%3d

Thank you very much  

 

[germoju]

Arffff !!!
it's not available ! ( I have to wait 11 weeks !

This one is OK ? => http://www.digikey.fr/product-detail/fr/CF14JT15M0/CF14JT15M0-ND/1741300

:'(

 

[MontgomeryAudio]

Hello everyone!
I am beginning my build and am missing a pair of 3.9MOhm Resistors and mouser is still out of stock... can I substitute with 3.74Mohm like this:  603-MFR-25FBF52-3M74?

Also, for some reason I got 1N4004 instead of 1N4003.  Looks like everything is identical except for the 4003 are 200 and these 4004 are 400V... is that going to be a problem at all?  I wouldn't think so, but thought I'd double-check here.

Thank you!

 

[AMaziad]

Hello everyone!
I am beginning my build and am missing a pair of 3.9MOhm Resistors and mouser is still out of stock... can I substitute with 3.74Mohm like this:  603-MFR-25FBF52-3M74?

Also, for some reason I got 1N4004 instead of 1N4003.  Looks like everything is identical except for the 4003 are 200 and these 4004 are 400V... is that going to be a problem at all?  I wouldn't think so, but thought I'd double-check here.

Thank you!

I can't answer the first question, but your 1N4004s will work just fine. 

Good luck!

 

[steve_h]

You could see if you're getting DC at the GR fet gate.  You should be getting a DC bias with a signal and compression in enabled.  Like 1V-2V DC.

Thanks Mike. Finally got around to trying this and upon testing DC voltage at the gate of Q11, I get a reading of -.775v and the needle pegs. This is with compression engaged and a 1k sine wave signal going into it. Wondering what your thoughts are before I go further with your other steps. Anyone else?

Hoping someone can help with this..