All things G1176 - the new "repost" thread.

[orson whitfield]

[quote author="kdawg"] Perimeter wire (did not attach to chassis, just a loop around ground solder points) - hum is almost completely gone! Only noticeable at really high output volume, which is louder than I'd ever go w/Chef's mod in place.[/quote]Hmmm. THis makes me wonder if the perimeter wire was connected to ground would the hum increase? Maybe I should try disconnecting my perimeter wire from ground too?

 

[kdawg]

hmm, I left two dual 1176s together and they had a kid. They make a cute family...

http://www.jnd.com/kdawg/kd_1176s_1.jpg

thank you everyone. I'm finally at peace, resting at more than a 1:4 ratio now

 

[orson whitfield]

[quote author="orson whitfield"][quote author="kdawg"] Perimeter wire (did not attach to chassis, just a loop around ground solder points) - hum is almost completely gone! Only noticeable at really high output volume, which is louder than I'd ever go w/Chef's mod in place.[/quote]Hmmm. THis makes me wonder if the perimeter wire was connected to ground would the hum increase? Maybe I should try disconnecting my perimeter wire from ground too?[/quote]

Well, I answered my own question. I tacked a 12 AWG wire around the perimeter and connected it to my ground scheme and the hum got worse. :evil: Well, at least I know that won't help. Now I am wondering if I should eliminate my scheme altogether and come up with a simpler plan.

 

[orson whitfield]

OK Hum is way better now that I completely disconnected the perimeter ground wire from my grounding scheme. So for me, kdawg's technique worked. There is still a slight hum when the output volume is all the way down. However, once I turn up the output volume knob, it's not really noticable. :grin: I realize there should be no hum at all but at this point I don't know what else to try.

 

[Apache5]

Hi all, I just builded a g1176 with a Gustav board. The voltages on signal line amp all all very close to schem values. But I have problems in GR control amp. the 30.3V are ok but the other values on Q12 Q13 Q14 and Q15 are wrong, all are slower. The 27.8V next to 30.3V is 17.7v only, and the voltage next to C17 (next point 22) is only 3.1. I test the NPNs with diode function and they seems to be ok, I checked the values of Resistences, the color codes, and they are all ok too (I think). Can a transistor be broken? o a res burn out?... argggghh!! oks... I continue testing it...

That post its cool :grin: , but i cant find a similar problem
Thanks

Arnau

 

[Apache5]

sorry... looking at board i find that i put C18 (47uF) reversed.... I changed it and now im looking for voltages, but they seem to be ok for the moment... im very happy for the moment
Thanks

Arnau

 

[SSLtech]

Gnaaaaaargh!

-My first 1176 is kicking my butt...! Q3 is saturating. If I remove it, the collector goes up tp 19V or so. If I put it in then it goes down to about 1.1V. It drops below the Base voltage!

I've removed Q4, still the same. -If everything was working correctly (as I read it) I should be able to remove Q4 and see a correct waveform at the base... -is that correct?

(This is a Purple Audio MC76 board, but the circuit is esentially the same in this region)

The voltages are:

..B...|..C...|...E...
0.8V 1.6V 0.3V (Q2)
1.6V 1.1V 0.9V (Q3)

Obviously, Q3 is saturating, with about 0.65V from base-to-emitter. All the resistors on the base end look correct though. I'm baffled! I can't see why this is the case... :?:

Keith

 

[SSLtech]

Problem solved. there was a wrong value resistor in one place... shoulda been 180 ohms... 108K will reallly mess things up!
:wink:

keith

 

[heybluez]

Gosh!! Those picky resistors...i mean 180 and 108 both have a "1","0" and an "8"...what more could it want?! hehehe I crack myself up.

Glad you fixed that issue. I cannot wait to see it completed!!

Lata,
Michael

P.S. Tighten down the hatches...Charley is on his way...

 

[Apache5]

Hi all, my 1176 clone is builded... all seems to be ok, now i must calibrate it and for the moment i havent the sifam AL29 VU meters. I supose that I can calibrate it with a osciloscope, cant I? But i dont remember the equivalences of 0Vu, 1Vu and voltage amplitude with a signal generator. Can I calibrate with a sin generator and a 2ch osc, can somebody tell me how?
and... would be more precise an osciloscope calibration than one with the vu meter?
:?:
thanks :grin:

Arnau

 

[romeojesus]

hi!

i just completed a g1176 with one of gustavs boards

and roundabout everything seems to be working...

but since I never worked with one of the originals
here are some questions :

( i have no meter , so I have not done the calibration process yet!)

1)
in bypass mode I have to open the input and output pot
so that the unit passes audio, is that correct?
(unit does not pass audio with in/output pots counterclockwise!)

2) in compression mode when switching from 4:1 to 8:1
output level drops a little (as I would expect it to do)

but when switching from 8:1 to 12:1 or 20:1
my output increases about 6-8dB
(and i think it does not compress in those modes!!?? no noticable difference when switching to bypass during 12:1 or 20:1 mode)

so iam guessing that maybe i programmed the ratio switch lorlin wrong??!! would that explain that behaviour???)


i finished an ssl clone so far and it worked right from the
bench, my electronics knowledge is limited to none
so i cant follow the ratio switch schematic...sorry


the hum issue:

well there is hum down there, but i have not added the
extra groundplane reinforcement thing yet.

the hum absolutely disappears at 12´o clock setting
of the output pot on my unit.

it is the loudest CW!


christian

 

[romeojesus]

ooops!

i just saw, that I forgot two solder joints on the ratio switch board
connecting the 12:1 and 20:1 lorlin connection to the board
itself....

hmm
second project seems to be finished and working right
off the bench, i am amazed
metalwork coming up (hate it)

thanks jakob for those diy projects.

hope I can decrease the hum a little...

thanks

christian

 

[SSLtech]

The 'bypass' in the original does not bypass the audio circuitry, it merely disables the gain reduction. I think that the Gyraf version is similar in this respect, so your 'bypass' description sounds normal.

Keith

 

[al_p]

regarding the hum/ground problems on the gyraf layout. has anyone tried cutting the ground trace at one point so that it is not a continuous loop around the perimeter as per mnats layout?

i'm anxious to get started on my G1176, but i was hoping/waiting to see if Gustav would get the gerbers for mnats' layout, as it seems to address many of the problems builders are having...including the BD135/136 pinout flip. has anyone etched one?

also, i got some of the parts in today. i ordered some orange drops for the polyprops to try out and the 1uF is quite big. i test fit it on the layout and it seems to be ok. what are most others using? i've seen some parts list with panasonic ECG series. any comments as to sonic characteristics of the options for the polyprops?

i also decided to try out a BUD case. i think it's great. a simple no nonsense product and the front panel seems like it will be easily workable. :thumb:

 

[romeojesus]

>regarding the hum/ground problems on the gyraf layout. has anyone tried cutting the ground trace at one point so that it is not a continuous loop....


thought about the same thing
and it´ s the first thing i am going to check out this weekend

 

[jrmintz]

I'm confused about the power transformer - the parts list has a 12-0-12V transformer listed, unless I misread it, and the board calls for 24-0-24V. Which do you use in the 120V part of the world? Also, how many VA does it need to be rated for?

Thanks

 

[orson whitfield]

[quote author="romeojesus"]>regarding the hum/ground problems on the gyraf layout. has anyone tried cutting the ground trace at one point so that it is not a continuous loop....


thought about the same thing
and it´ s the first thing i am going to check out this weekend[/quote]

Let us know how that turns out, Romeojesus. I am thinking about trying this too. In the other thread regarding the updated version of the G1176 PCB, this was posted:

" Another is adding additional grounding pads to accommodate the shields of the various wires going from the board to the controls (part of the reason why my clone has virtually no audible hum at any reasonable levels also has to do with the wiring, I believe)".

I bought a roll of shielded multicable for all of my projects. Inside of it there is metal braided wire without wrapping. I assume this is the "shield/ground"? I should connect this to the grounding pads from the pot. Am I understanding this correctly?

 

[gyraf]

Romeojesus, Al_p, and Orson,

Yes, cutting the ground at one point will probably help a lot. Only haven't I had the time to find the right spot for the surgery yet.

My guess would be to cut just after the output stage (when seeing it from the PSU section:

EDIT: This is now pointing to Christian's suggested cut...

EDIT: This is now pointing to Christian's suggested cut...

Please let me know what you find out!

Jakob E.

 

[romeojesus]

ok, just cut the ground plane on jakob´ suggested position....

this turns down the hum A LOT...really

there still is some hum down there
but now increasing the output
pot hasn´ impact on the volume of the hum anymore (like it did before)

maybe the rest of the hum comes from the fact that my unit
has no case yet. it is sitting on a record sleeve and the iec
power connection is not grounded yet etc etc


christian

 

[gyraf]

Thanks Christian,

It seems that this is a good way to go. Would be interesting to know how your unit behaves when cased and grounded.

Do you have enforced ground around the board as well?

Jakob E.