The official G9 help thread

[phelar]

Thanks!
I´m going to use a variac. ........maybe i messed up the phasing on the secondaries :/ there is a chance i´m afraid. If so, is this the reason for the hot(and dead) transformer.
I´ve got 230 primary winding by the way.

 

[sonolink]

Hello,
If this is not the right place where to ask for this I apologize. I'm building a G9. I'm wiring Inputs and Outputs with shielded wire. Basically I understand that Input screens are connected to the ground pins on the board and pins 1 on input xlr connectors, but Output screens are only connected to pins 1 on output xlr connectors.
Then all pins1 (inputs and outputs) are connected together to chassis and safety earth. is this correct, please?
Thanks

 

[phelar]

As far as i know you only ground the mains socket to the case. In and output xlr pin 1 to the ground pins on the pcb. Never heard that you should leave the output screen, not connected to pcb ground trace.
....but i hope to get this confirmed though

 

[MeToo2]

As far as i know you only ground the mains socket to the case. In and output xlr pin 1 to the ground pins on the pcb. Never heard that you should leave the output screen, not connected to pcb ground trace.
....but i hope to get this confirmed though

Sonolink had it right. Check the PCB layout. The screen pin (centre of the 3 pins) isn't actually connected to any PCB trace at header K3 & K103 (that connects to the XLR Out), so you don't have to do anything special there.

See http://www.rane.com/note110.html http://www.rane.com/note151.html

 

[phelar]

Oh, thanks............i´ve really messed with the wiring :/

 

[sonolink]

@MeToo2

Thanks for confirming, mate
I've finished my build now, but something is wrong.....troubleshooting.....  :-\
Cheers

 

[sonolink]

Hi everybody,
I finished my G9 build some days ago. Ch1 had no output. Ch2, massive hum. Voltages seemed ok. Left the unit on for a few hours and everything ok. Decided to go for Ch2 first, so after some chopsticking I noticed the trafo wiring was the cause for the hum. So, I redid the trafo wiring. After doing so, I noticed there was no voltage getting to the board and one of the trafos was getting VERY hot. Quickly switched the unit off and corrected the wiring. Now everything seems ok BUT, the big caps are not charging at all: 0V!!
Any ideas?
Thanks

 

[gyraf]

Sonolink,

No charge at all could indicate either no 220V ac from power transformer, wrong/broken/wrong-oriented 4007 diodes, or wrong/broken 1KOhm/2W (470?) resistor. Or some wireing fault

Take care when troubleshooting


Double check your measurements and the integrity of your voltmeter


Take care


Jakob E.

 

[sonolink]

Thanks for your answer, jakob. I'll recheck everything and report back.
Cheers
Sono

 

[sonolink]

Hi again,
To make sure I'm wiring the trafos correctly could you please confirm this is correct?


Tx1 (12V)
PRI (blue/brown) -> 220VAC socket
SEC1 black -> left pole of 15V terminal close to d8
SEC1 red  -> right pole of15V terminal close to d8
SEC2 (orange/yellow) -> 15V terminals close to d13

Tx2 (15V)
PRI (blue/brown) -> 220V terminals close to d16
SEC1 black and SEC2 orange -> left pole of15V terminal close to d8
SEC1 red and SEC2 yellow -> right pole of 15V terminal close to d8

Thanks for your time and help
Sono

 

[gyraf]

Sonolink - that looks right.

Jakob E

 

[sonolink]

Thanks for checking, jakob

This is probably a bit of a noob thing, but I checked and R33 checks 470R, and the Trafos seem to be wired fine (although on my previous post Tx1 should be 15V and Tx2 12V, but I guess this is irrelevant to the caps no charge problem). I checked D17-D20. I don't know how to check a diode really, so I used common sense and checked continuity in both directions. I consistently read 0.5 and 1 on all four diodes. Any ideas? Thanks

Cheers
Sono

 

[gyraf]

- check that you have some 210-240V AC going to the 1N4007 rectifier diodes (measured at diode legs)
- check that you have some 240-290V DC on the other side of the diodes

if you have no AC coming in, check wireing and transformer(s)
if you have AC going in, but no DC coming out, the diodes may be blown

 

[sonolink]

I apologize: the 220V terminal on the board had a bad solder joint. My bad.
I'll get to the other problems the unit has tomorrow.
Thanks for the help
cheers
Sono

 

[sonolink]

Hi again,
The caps are charging now
BUT,
I have the following problems:
Channel 1: no audio at all. Phantom ok.
Channel 2: no Phantom at all, Mic Ok (a bit rough sounding but that's probably because I'm using EH 12AX7 for testing), Line position = massive hum that increases when plugging a guitar in and when increasing gain and volume. When chopsticking the shielded cable going from the jack to the board it sounds microphonic (I don't know if you say that in english but I mean it makes noise like when you tap on a mic). I did the DI mod. I didn't have switched mono female jack sockets, so I used switched stereo female jack sockets without connecting anything to the ring. I mention it in case that could be the cause.

I have measured voltages several times with different voltmeters and. I get this:
230VAC from socket
Tip121: 50 80 50
78S12: 18 0 12
TL783: 243 244 355

I've attached some pics in case they're helpful...








All ideas and/or suggestions are very welcome
Thanks for your time and help
Cheers
Sono

 

[gyraf]

voltages are alright. Now time for checking your components, soldering and cabling

 

[sonolink]

Ok
Incidentally, is there a way I can check the audio path with a sinewave and an oscilloscope? If so, how do I do it? Thanks

Cheers
Sono

 

[sonolink]

Nobody?

Ok. Let me have a go at it. My scope is digital and has 2 channels. Basically, I guess I connect the black lead of one channel to ground and then I poke with the other end around the path I want to check, right? If this is correct, that's great but my concern is, what if I fry the scope? How do I know that?

I would appreciate some help with that pretty pretty pretty please...

Other than that, I guess it's all about checking continuity, resistors and caps, right? My God what a pain....
;-)

Thanks
Sono

 

[MeToo2]

Nobody?

Ok. Let me have a go at it. My scope is digital and has 2 channels. Basically, I guess I connect the black lead of one channel to ground and then I poke with the other end around the path I want to check, right? If this is correct, that's great but my concern is, what if I fry the scope? How do I know that?

Sono

Poking about is definitely not a good idea. Plan what you are going to test and what you think the waveform should look like: Connect up test gear: power up: check results: power down: think: repeat. Watch you don't fry your PC or scope. I use an external signal generator and don't connect up any PC kit until I'm sure the working voltages on both input and output are safe. Be sure to check out the maximum safe working voltage on your scope. I use a good old analogue Tektronix 2445B scope on tube kit for that very reason. It can easily handle 400V DC on the input. Also remember there's galvanic isolation (transformers) on the input and output. Connect your scope ground the the chassis. You may be better off measuring voltages on the outside of the transformers using 2 inputs in differential mode.

 

[redmojosteve]

It's been a while since I wrote on this thread but with the Olympics out of the way and my decorating finished I am back to my G9. Although I started on my second one I have decided to get the first sorted out. I still need to check out why I had the hot transformer problem. Looking through this thread it seems there have been a couple of other instances where this has cropped up. I need to work through it again, and in particular make sure the transformer connections are correct. I have done this so many times I can't imagine that I have ended up with the wrong configuration so many times.  On a different point, apart from the above issue, I had got the G9 working well on both channels with low noise but when I tried the inst input on the front panel (and this was the same for both channels) I still got a very small amount of the input from the XLR bleeding through. This is manageable from an operational standpoint i.e. switch off the input to the XLR! However looking at the schematic I can't figure how anything from the XLR input gets through as it is mechanically isolated by the switched INST jack input. Any hints would be much appreciated.
Cheers
Steve