All things G1176 - the new "repost" thread.

[adoucette]

Hey Everyone,

I powered up my first DIY to find a couple errors. While it didnt blow up, thankfully, i noticed there is no sound whatsover, only a low hum at around 50-60 cycles is my guess. I dont think there is anything wrong with my grounds, i checked them again and they are fine.

next my VU meter moves when I turn it on and swtich between bypass, GR and +4, but doesnt move when signal goes into the input, nor does it set itself to zero when adjusting the zero adjust, moves a bit but hardly enough and mostly sits at around -15db

Any ideas?

Thanks in advance

Andre

 

[gswan]

Why were you trying to pass signal through it without first performing the basic checks, tests and calibration? I'd suggest you start at the beginning rather than at the end.

Don't bother with the metering until you get your signal chain working correctly.

 

[3nity]

Hey Geoff.
I verify all my voltages and they seem to be good enough.
i did checked all your scope shots against mines and they are very near the same.

Now...i cant make my meter sits at zero...? its stops at 7db! i'm using a Pm1000 VU meter.
I cant got trough the calibration!

What do you sugest?

Thanks...

 

[gswan]

I'm assuming that this behaviour is only for the GR metering setting. The +4dB setting should show no deflection if there is no signal present, since they are connected directly to the output of the transformer.

There is an offset adjustment for the GR metering (R56 - zero adj) which can be used to zero the GR meter during the GR metering setup procedure.

You should be able to use the VU meter on the +4dB setting to perform Qbias adjustment before doing the GR metering setup procedure.

 

[adoucette]

Ok so in a method to trouble shoot, I felt the voltage going into the unit was weak, so I tried another method of wiring the transformer that another member suggested, I rewired so that rather than

Blue (green+blue) Green

I wired

Blue (green+green) Blue

I know, it was probably stupid.. but I felt I needed to try it. Now I'm learning here so Im expecting things to go wrong and to make mistakes..haha.. so what happened was I fired it up, no VU lights went on, I heard a faint buzzing which sounded like the area of the toroidal transformer. So i turned it off. Then turned back on again, and it was dead.

I checked the fuse and it doesn't appear to be damaged, there is the tiniest of markings on it, but I cant tell if its a break or just a piece of dust or something.. Im gonna try swapping out the fuses tomorrow when I pick some more up, but does anyone have any other theories in the mean time?

Thanks

 

[adoucette]

Ok so in a method to trouble shoot, I felt the voltage going into the unit was weak, so I tried another method of wiring the transformer that another member suggested, I rewired so that rather than

Blue (green+blue) Green

I wired

Blue (green+green) Blue

I know, it was probably stupid.. but I felt I needed to try it. Now I'm learning here so Im expecting things to go wrong and to make mistakes..haha.. so what happened was I fired it up, no VU lights went on, I heard a faint buzzing which sounded like the area of the toroidal transformer. So i turned it off. Then turned back on again, and it was dead.

I checked the fuse and it doesn't appear to be damaged, there is the tiniest of markings on it, but I cant tell if its a break or just a piece of dust or something.. Im gonna try swapping out the fuses tomorrow when I pick some more up, but does anyone have any other theories in the mean time?

Thanks

 

[adoucette]

Ok so in a method to trouble shoot, I felt the voltage going into the unit was weak, so I tried another method of wiring the transformer that another member suggested, I rewired so that rather than

Blue (green+blue) Green

I wired

Blue (green+green) Blue

I know, it was probably stupid.. but I felt I needed to try it. Now I'm learning here so Im expecting things to go wrong and to make mistakes..haha.. so what happened was I fired it up, no VU lights went on, I heard a faint buzzing which sounded like the area of the toroidal transformer. So i turned it off. Then turned back on again, and it was dead.

I checked the fuse and it doesn't appear to be damaged, there is the tiniest of markings on it, but I cant tell if its a break or just a piece of dust or something.. Im gonna try swapping out the fuses tomorrow when I pick some more up, but does anyone have any other theories in the mean time?

Thanks

 

[adoucette]

shoot sorry about that, my browser was lagging so I hit submit a couple times, didnt know it posted 3 times.. :?

 

[gswan]

[quote author="adoucette"]Ok so in a method to trouble shoot, I felt the voltage going into the unit was weak, so I tried another method of wiring the transformer that another member suggested, [/quote]

How did you 'feel' this voltage? What do you mean by 'weak'? Is something 'cosmic' going on here?

[quote author="adoucette"]I rewired so that rather than

Blue (green+blue) Green

I wired

Blue (green+green) Blue

I know, it was probably stupid.. but I felt I needed to try it. Now I'm learning here so Im expecting things to go wrong and to make mistakes..haha.. so what happened was I fired it up, no VU lights went on, I heard a faint buzzing which sounded like the area of the toroidal transformer. So i turned it off. Then turned back on again, and it was dead.[/quote]

Not probably stupid. Definitely stupid.
You have no idea what you are doing, so you re-wire it short circuit. That's smart.
If you didn't blow the fuse then you probably popped the transformer primary thermal link, which means that you'll need to chuck the transformer and buy another one, since the fuselink is buried under the insulation and protects the transformer against a fault which could cause insulation meltdown and hazardous voltages on the secondary.

[quote author="adoucette"]does anyone have any other theories in the mean time?[/quote]

Yes. Don't try to re-wire anything electrical in your house...

 

[adoucette]

Didn't mean to step on any toes man.. its an 11 dollar transformer, not the end of the world. Im learning, and yes your right I have no idea what I'm doing, which I'm sure at one point in your life, neither did you.

 

[gswan]

Except you chose to ignore the advice given to you earlier, based on references to the manufacturer's data sheets, and decided the voltage "felt weak". I'm only adopting the stern tone so you remember not to try something like this without rationale again.

The first thing I learnt was to read the manufacturer's data, double check everything and make useful measurements to verify what you expect.

Be careful and methodical and you will end up with a useful piece of audio gear. Otherwise it will just contribute to the landfill problem.

 

[adoucette]

Perhaps I mistook your tone a little personally without realizing your true intentions.. You are right, I regretfully chose to ignore your advice and ignorantly made an error to my machine. It was a lesson which I don't plan on ever repeating. Its my understanding that you are on this forum alot, helping alot of people with alot of problems and I should have had more confidence in your advice.

Thank you for your help thus far, hopefully I resolve this error shortly so I can continue on with the project :thumb:

 

[3nity]

One more question: +4 means bypassed?
1st position in the rotary is bypassed, next is Gain reduction and 3rd is VU is that it?

When setting Q Bias should i see the needle move? up to +1??? it doesnt even move!!
I'm completely lost.......if i cant get it to work next week i;m done i;ll trhow it out!

I'm out gotta go to bed...and its just 9pm!!

 

[gswan]

+4dB means metering the output signal.
Whether the GR circuit is activated or not depends on your wiring.

You should see the meter measuring your output signal directly in +4dB setting.

 

[kenrinc]

Finished the other channel of my 1176. Thanks for all your help Geoff! You rock :thumb: Took me 6 months to build the first side and 3 days to do the second :green: Everything checked out and worked first time on the 2nd channel. Sounds amazing and works well too. Now, I've got one small issue and that is very low noise with output cranked. Both channels have it. After an evening of troubleshooting I've found that if I disconnect the power ground (unit off) from the incoming IEC connection the problem goes away. Dead silence and wonderful sound. Not your typical ground loop in that I don't hear a loud buzz like I'm used to. Ch1 input is grounded at XLR same with ch2. IEC is grounded at it's location. Obviously, there must be a better way.

3nity: Input a 250hz signal at a nominal level, set the meter switch to +4 or VU (all the way to the right). This puts the meter across the output allowing you read it directly. Adjust input and output so that the meter shows +1db and adjust the Qbias until the meter drops to 0db. Done. It's touchy, especially with some types of trimmer pots. Takes a steady hand.

Ken-

 

[adoucette]

what sort of fuse should I use in my IEC? I used a 15amp 250v, just want to double check thats right

 

[gswan]

1 Amp slow-blow should be ample.

 

[3nity]

http://www.geocities.com/m_natsume/1176_revision_d.html#videos
Guys you think this video applies to non D revisions boards too?

Maybe i need to short the GR without affecting the meter?

Excuse me at this time i'll start asking stupid questions!

Thanks.

 

[kenrinc]

3nity,

The Qbias (first) video works with either unit. The discrete meter circuit video does not work with the G1176. Mnats already answered that question a few pages back.

I'm assuming your setting Qbias? It's very simple. See my previous post above this one. You don't need to short the GR at this point. It's not needed.

Ken-

 

[3nity]

i'm following this:http://www.axtsystems.com/index.php...7:1176lnproblems&option=com_content&Itemid=62

all the voltages are good altough not identical but nearly the same.

Now with the scope i cant get a signal at Q2....but if i turn the 2n5457 like its a BF245 i got the signal!
:roll: ???

I'm confused!