The official G9 help thread

yeah !!!! it's good... i think the problem is solved.
strange noises appear sometimes... like used tube in a guitar amplifier !!!

That's exactly what I expected you would find.

Glad you got it sorted out! You should try DI'ing some bass through it. It sounds great.

What are the strange noises?

Oh and welcome to the wonderful world of DIY audio. You will be completely hooked from here on in!

Rob

Strange noises...
a high-pitched noise which hold and disappears...

That's probably oscilation-which is why the person did that mod...

what can i do ?
i have not oscillator ...

Hi,
i closed the box. All is ok !!!
but i have always this noise... a little like a whistle
when I pat the box,a noise appears. And disappears in the same way.

can be that the tubes start to vibrate ?

i don't know

hi everybody...i started a topic in the lab by mistake...so here i am where i belong.....but it  should be said that thanks to everyone's help, i'm hopefully very close to fiishing my g9 (minus a nice faceplate, though)....i was having some grounding issues, now solved!
i'm having another interesting little problem now....pretty sure it's not related to the main pcb or power supply, but maybe a wiring problem...specifically the switch pcbs....i will post pics tonight hopefully....i've tried swapping my switch panels out and have discovered that channel one is significantly louder than ch.2....along with that,the 'good' channel's line/mic/48v switch operates in reverse! the 'bad' quieter channel 2 operates just fine, except for the lower gain...channel one sounds amazing! (thank you jakob!)....but whether i put ch1 into ch2 of the main pcb or vice versa ch1 card is louder, sounds great and is backwards! i think the line input may always be on as well....
i haven't done the hf osc mod yet, so both channels top out at about notch 9 or 10 on the lorlins before the squeal, but that doesn't really bother me....i may not even do the mod just so i can use these lovely things....but....could the lack of the hf osc mod be somehow affecting the gain in ch2 and the backwards switching? or have i just soldered a switch in backwards? i've checked w/ my meter and it seems to be fine....
one caveat to this is that i have all the switches wired w/ the front tab at 6 o'clock, except for the line/mic/48 switches....but why would one work fine and the other backwards?!! ???
i think that's it for now and any advice is appreciated.....sorry to babble on....pics on their way soon...cheers, alex

hopefully these pics load...

more g9...

Been a while since I built mine. But I cut the traces and ran shielded cable to the direct inputs from the get go. Using it on a project now and the drummer is flipping out cause he can hear his ride like a clock and his hat even over my wide guitar effect. Mine was set to track from LDC's at 50% gain and 27% Output. For drum overheads. And hit about -5 in Protools wich may be a bit high but ok for me.

So you swapped the front panel boards from left to right and you saw a change? Pull both front boards and compare them maybe you did something differently between the 2?

Your pics loaded fine

Check the resistor colors and orientation of the lorin switches. Hopefully I am getting what you are saying. The left channel works fine but when you switch the front panel boards your problem follows that board. I'll do my best but am an amateur...

And Be Careful and stay away from the high voltage stuff!!

junkmaster,

Specially check that your input select switches are "programmed" right - that is, that the switch is turned completely counterclockwize before inserting the stopper pin washer.

Also double-check the sequence of cables between boards!!

Jakob E.

thanks for the insights folks...i will first try the pin-stop....i have been going through the resistors and everything seems ok....thought about just taking the harness apart and starting over completely on one or both cards....but the simplest way is usually best so i will report back after i get off work and havea chance to puzzle over it again....many thanks...alex

hi all ......did the pin-stop thing and it fixed the gain discrepency.....brilliant simpicity thanks jakob....still channel one is backwards except for the gain knob...so close yet so so far..... i might just rewire ch 1 from scratch and see if that fixes it....it sounds great otherwise....just don't want to make a faceplate w/ one channel reversed! ill report back when i have time to go throug it again...thanks again, alex

hi all....just ran through it again ....same issues...ready to re-assemble except for the mysterious line/mic/48v reversal....it's gotta be some thing simple....i desoldered the switch and tried it in different orientations and still the reversal.....checked and double-checked wiring harness continuity etc.....checked pcb w/ my loup over and over but don't see any bridging....checked resistors against other board ....should i just take it apart and rewire it again??.....so close........any thoughts appreciated....cheers, alex

hi all...i did the oscillation mod which cleared up the feedback problem....also turns out i had a faulty lorlin switch which after rigging it so it would stop where it should seems to work fine..no more reversed line/mic48v problem.....but ch1 seems to be about 30% quieter than ch2...once again i swapped the switch pcbs, tried swapping input/output molex connectors,etc....ch1 still always quieter ???...ch2 sounds amazing tho! any ideas where i could measure voltages,etc and compare the two channels? i'd like to think this is a simple wirig problem but maybe i've blown something up w/ all my messing around....any thoughts much appreciated! cheers, alex

Hi,

  I am at the point in my G9 build to cross my fingers and flip the switch. I admit I have not poured over the thread recently so if I have missed it I apologize. Is there a set of test procedures and test points to check voltages, I mean, I know the 245 and 15 and 12, but how about heater,cathode, plate and such? Also, I don't have a scope, but I do have a signal generator, are there test procedures to check high pass, noise floor etc.

  Thanks in advance,
                              Chip

O.K.      so now I have spent the last 3 1/2 hours reading the G9 META and this G9 help thread and have found some test points and readings to check when I flip the switch.
 
  HOWEVER, I have not found ( or I have not comprehended correctly) the Info on hooking up the power transformers - I find this very confusing with the corrected transformers of one being 15vac and the other 12vac. Here is a graphic that I found.

    Here is how I interpret this :

    One 15vac secondary from T1 MAINS to 15vac on PCB next to 220va, the other 15vac to back feed T2 connected to 12vac secondary, Primary on T2 to 220vac on PCB.
   
      What feeds the 12vac on PCB - ( Black Arrow )
   
        Do I combine 15vac AND 12vac together at Black Arrow as sugested by the lines indicated by the RED arrows ?


  I apologize for my Newbeeness, but my head hurts  ???


  Please .... some one take pity on me.... :-[


    Thanks in advance


                              Chip

   

Now that I've had some sleep, maybe I should give clearer Info  :-[

  T1 is 110 + 110/ 15 + 15,  and T2 is 110 + 110/ 12 + 12.  - the Black arrow indicates where the PCB is labeled 12vac.  I understand the " back feeding " or feeding T2 " the other way around " as in the G7 PSU, but then that wouldn't leave anything to feed the 12vac at Black arrow.

OR  am I supposed to combine one 15vac form T1 and the 12vac from T2 at the 12vac point on PCB ( black arrow) as the graphic indicates?