The official G9 help thread

Ok, I got one:
recently I developed a very nasty and loud rumbling/oscillating LF noise
on channel 2 only (channel one is fine). Its the closest to the PS.
I swapped tubes briefly to see if that was the issue but to no avail.
Over the last few days it has gotten louder/worse.
When turning the Gain and output trim down, the noise dies down then....gone.
I have no doubt some part has decided to die but I thought I'd
toss this out for any idears before I dive in for troubleshooting.

Cheers!

..maybe the 10u polyester cathode-decoupling for the first gain stage gone wrong?

Jakob E.

gyraf said:

..maybe the 10u polyester cathode-decoupling for the first gain stage gone wrong?

Jakob E.

Click to expand...

I will check that first.
Thanks Uncle Wonka*/Gyraf!!

* - reference = Willie Wonka and the Chocolate Recording Studio

EDIT: confirmed hum on the scope at position.
Replaced the crappy mylars with nice Solens.
DEAD quiet...there was a TINY hum on the working channel that is now gone as well.
THANK YOU jakob!!

Hi,

Just about to start building a g9.  I've got a couple of nice 35VA 230:17.5+17.5v transformers, shielded with mu cans, lying around.  Would it be within the tolerance to use these for the build, maybe with larger heatsinks?  Or should I order the recommended ones from the BOM?  Just trying to save a few pennies, and use up some of my spare parts...

Thanks,

Josh

Hi, i am continuing to build the G9 i have all the materials exept toroids..

I think i am having 2 problems, i am in a 220v place.

1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it

Any ideas why this may be happening?

Sorry if it was discussed early, i didnt had much luck using search this time.

But i will appreciate all help, i guess i will change the componentes for the high voltage regulator, with new ones(i hope i dont get this problem again, maybe its a resistor which i messed up with the value). If you need some photo to see this problem i will upload one tomorrow.

Thanks in advance!

Did you double check all the solder points for the diodes?
Other thought is, how are you heat sinking your rectifier?

I'm not the brightest bulb in the knife drawer, but maybe its somewhere in that area.
The other thought is, it sounds like your 2 problems might actually be one...

Hi,
    I've got a strange one for ya.  I have two G9s now and have noticed something on the third one and checked the other two and have found something strange.
  I intermittently have a signal drop out to a very faint signal on the right channel only on both units, if I tap the faceplate the sound crackles and comes back, if I continue to tap the front panel it crackles some more goes in and out as if there were a loose connection.
  I have extensively checked for loose connections, poor solder joints ect. but have found none. Could it be the Lorlin switches ?

  any thoughts on this ?  ... anyone ?

Thanks,
            Chip

stitch-o said:

Did you double check all the solder points for the diodes?
Other thought is, how are you heat sinking your rectifier?

I'm not the brightest bulb in the knife drawer, but maybe its somewhere in that area.
The other thought is, it sounds like your 2 problems might actually be one...

Click to expand...

I will double check, every diode is in its right position.

Its maybe a transformer issue?

If the R34 is glowing orange, and nearly in fire, i guess it had more than 10 watts there has to be some problems making a bridge or something with that Resistor, all of the other ones were ok, but i couldnt measure the voltage in the exit of the TL783

I am going to bring my camera to post a photo of that section, transformers wires, and tracks.

Graph said:

1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it

Click to expand...

Seems, IC1 isn't regulating.
Check, if the current setting resistors R35 and R36 are 470R and 47R, giving a total of 517R as they are wired in series.
If you mistakenly fitted both as 47R (total series resistance 94R), the regulator would be set for theoretical 1331V output and R34 has to dissipate 17.7W. You won't get more out of your regulator than you put in, so unregulated raw DC voltage sets the upper limit. With your 275V raw DC, R34 only has to stand 3.65W with the wrong fitted current setting resistor. With correct values, output voltage is set for 243V and R34 has to stand 0.58W, so a 1W part should be sufficient.
Just an idea ....
good luck

Harpo said:

Graph said:

1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it

Click to expand...

Seems, IC1 isn't regulating.
Check, if the current setting resistors R35 and R36 are 470R and 47R, giving a total of 517R as they are wired in series.
If you mistakenly fitted both as 47R (total series resistance 94R), the regulator would be set for theoretical 1331V output and R34 has to dissipate 17.7W. You won't get more out of your regulator than you put in, so unregulated raw DC voltage sets the upper limit. With your 275V raw DC, R34 only has to stand 3.65W with the wrong fitted current setting resistor. With correct values, output voltage is set for 243V and R34 has to stand 0.58W, so a 1W part should be sufficient.
Just an idea ....
good luck

Click to expand...

I will check the resistors when i got home

Really, much thanks, if thats the problem i will fix it quick.

Harpo said:

Graph said:

1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it

Click to expand...

Seems, IC1 isn't regulating.
Check, if the current setting resistors R35 and R36 are 470R and 47R, giving a total of 517R as they are wired in series.
If you mistakenly fitted both as 47R (total series resistance 94R), the regulator would be set for theoretical 1331V output and R34 has to dissipate 17.7W. You won't get more out of your regulator than you put in, so unregulated raw DC voltage sets the upper limit. With your 275V raw DC, R34 only has to stand 3.65W with the wrong fitted current setting resistor. With correct values, output voltage is set for 243V and R34 has to stand 0.58W, so a 1W part should be sufficient.
Just an idea ....
good luck

Click to expand...

Well, i just arrived to my house. I cut the resistors out, and measured them, they were 47 and 470 ohm. They were not the problem. I will continue cutting the resistors. R37 was fine too and R33 was a bit black, it measured 380ohms. The thing that was left of R34 measured 680ohms.. did this value came really down a lot or the resistence was bad in first place?(i was sured i measured them before soldering it), maybe that was the problem, its a shame that the track was damaged so i will put a small cable tomorrow.

R34 was a 2 watts resistor.

If that wasnt the problem.. the regulator was really cool, it didnt got any hot at all.. its on he correct side. The zener diodes, i guess they were the right value, at least that was the value they were labeled. 1n4007 were alright too, and capacitors are in the correct side, i made a small pcb with the - and 2 separte +, they are 100uf 350v.

Any idea how should i start debugging this if this wasnt the problem? i have removed the resistors for now, tomorrow will buy new ones and try again. If the problems keeps happening. Any ideas? i guess here are no solder bridges and i have not found one between 240v and ground.

Anyways.. sorry for my english, i am from latin america.

Graph said:

the regulator was really cool, it didnt got any hot at all.. its on he correct side.

Click to expand...

Your regulator is dead. Leave the rest alone and solder a new one in. Then double check all connections. and I mean all traces.

The regulator should get at least warm, but normally you'd even want a small heatsink on it.

The regulator should get at least warm, but normally you'd even want a small heatsink on it.

Click to expand...

Yes, definitely. If your TL783 is dead, you may want to recheck integrity and orientation of your protection-scheme around it - the 1N4007 and the three 39V Zeners.

Jakob E.

gyraf said:

The regulator should get at least warm, but normally you'd even want a small heatsink on it.

Click to expand...

Yes, definitely. If your TL783 is dead, you may want to recheck integrity and orientation of your protection-scheme around it - the 1N4007 and the three 39V Zeners.

Jakob E.

Click to expand...

Ok!! Thanks Kingston and Gyraf, i will buy new ones on monday.

Anyways, the diodes were in the correct position, i checked them lots of times. Maybe they sold me the wrong ones(Zener)..

So, i blew up the tl783 and 2 resistors? Anyway, it has a small heat sink, isolated. But anyways, neither the first time i used it was hot, neither warm. i will change all those parts, i think it will be easier, but if its happening again, either i am really stupid or there is a problem before, with the transformers or something else or maybe the tl783c were broken before buying them.. or i applied too much heat

Thanks!

Hi,

I have a query regarding the transfomers. I have just completed my G9 and fired it up last night for the first time. I had no smoke and the tubes were glowing so I was pretty happy. This is my very first electronics project so was really pleased with myself. Anyway after about 5 minutes I noticed a smell and upon checking 1 of the transformers was really hot!!. I turned it straight off and thought I would ask for advice as I didn't wan't to damage anything.

The transformers have been wired as per frank ng's diagram and I have checked and double checked that it is correct. How hot should the transfromers get exactly. The other one was warm only but this one was pretty hot. The one in question is transformer 2 which is connected to the mains 230v.

Could this just be down to a faulty transformer or should I be looking elsewhere? Is there an easy way to troubleshoot this.

Regards

Ian

G9 issues

These things have probably come up before but I've just noticed them so thought I'd better share...

1. HUM
If you use one of the cases from Paruska, the thick paint / coating on the case is a good insulator and will stop it connecting electrically to itself, giving you poor screening. This can cause lots of HUM. I noticed with mine that when I put the lid on, the hum got worse because of the induction in the lid! Drilling off the paint around the screws and adding lots of crimped washers fixed this nicely.

2. polarity / 'phase'
Using some boards bought ages ago from Swedish Chef - could be an old version - the absolute polarity gets inverted wrt the front panel labelling. Three places this could be wrong - input labelling or output labelling on the PCB, or the front panel. Injecting a signal (sawtooth) into the instrument input gave correct phase, so I think it may be the labelling of +/- at the mic input on the PCB. Flipping the wires at the input XLR gives an easy fix, but do check polarity of your finished build.

z50

Thanks z50! Great stuff. Going to fire up mine some day soon with P case

Secondary connections to 15v

Right I still carn't work this out. I have seen lots of posts regarding the wiring for 115v models but is there one for 230? I wired it up as ngfrank detail but T2 gets very hot. I'm sure this is not right. I have attached a drawing for the connection to 15v (this is the bit I think I may have got wrong.) Can somebody tell me if this is ok or if not how this connection should be made with the three secondaries I have left.

Regards
Ian

Sorry problem with pic. Please find it here..

Not knowing your specific transformer(s), your coloured wires don't make much sense because every transformer manufacturer uses his own colour scheme.
Your 3 secondaries might/would be 2 secondaries and 1 primary winding or the other way round.