The official G9 help thread

[steppenwolf]

When the hum is gone when you turn down the vol knob, the problem should be before that stage. You might have a problem somewhere around the first gain stage. What's your B+ voltage AFTER the regulator? If you use 10uF 250V filter caps on the board, you might want to check them. I noticed that the voltage rises up to around 280V before the tubes gets heated properly, so the regulator can't regulate(it needs a few mA to do that), as a cold tube has nearly infinite resitance...
It should go down to 250V pretty fast, though. I included a stand-by switch because of that.
Maybe the regulator shuttet down, there was no heater voltage, but you B+ was still up high. In that case, the regulator couldn't clamp down the B+ to 250V and the cap got higher voltage for too long?
What rating do they have in your circuit?

 

[JimiH]

On the board I have 10uF 250V capacitors. If the HT regulator has crapped itself would I be expecting the hum to be there regardless of the output volume? I guess I had better check anyway...

 

[JimiH]

For those of you who care, and i hope that there are some of you out there, my problem was grounding. For some strange reason my G9 decided it wanted the ground connection redone after I did the oscillation fix. So anyway, it has nice new high voltage rated filter caps on the board, a nice new 78S12 and it is grounded properly. I can't get over how low the noise coming from this thing is. I'm not sure I can even hear it through the noise from everything else! I wish I had means to measure it. Anyway, my G9 is going down well with everyone and sounds great and we all lived happily ever after.

 

[gyraf]

:thumb:

 

[maxheadroom]

Jimi, nice to hear that good news :grin:

pics would be nice too :thumb:

 

[maxheadroom]

i have some questions about the G9. for the power supply, i wired the
two toroids (230V/1x15 and 12V/230V) without the PCB and the second
toroid began to hum. i replaced the second toroid with another two (30VA and 50VA) and the hum is not away.
while reading the PSU schematic the question why is 15VAC is in use came out.
for the 12VDC heater voltage i think its enough the supply the regulator with 12VAC. for this, the power loss is lower.

Is that a idea?

the next question is about the external mounted caps C14/C15.
i got two from RS with a M8 srew to mount it on the backsidebanel of the
housing. after measuring the connections and the mounting screw i found
out the the screw is connected with the negative pole of the cap.
so, when i mount the two caps on the chassis, i connect the GND/0V with the chassis. is this ok for the further grounding connections?

 

[steppenwolf]

Hi!

I used two toroids, too and the second one hummed, too.
I measured and the second one took 600mA of current with no load!
I solved the problem with a resistor between the secondary of the first and the secondary of the second one...

Greets,
Stefan

 

[fucanay]

Ok Stupid question time.

Has anyone used D Shaft Lorlin switches on the G9? I'm having a hard time finding the right ones in PCB mount and .25 inch. 6mm is no problem, but knobs are a pain in the ass to find in 6mm locally.

But I'm concerned about knobs not lining up right with the D Shaft.

Now if someone had some not to expensive knobs that are 6mm and fit with Purushas G9 case, I'd be fine with the 6mm ones.

Ok, too much coffee and I'm rambling.

Thanks

Matt

 

[JimiH]

My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.

 

[fucanay]

[quote author="JimiH"]My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.[/quote]

Yeah, The orientation is important when you have printing on the front panel though, right? Otherwise the knobs won't point to the right place. That's kind of what I was fearing. I guess I'm going to pick knobs and pots at the same time and get all 6mm stuff. Bah.

Matt

 

[maxheadroom]

so, yesteday and today i completed my G9 with the 230V / 2x12V and
12V / 230V toroids.
the hum on the toroids was away.
with all the tubes i measured:

HT: 240VDC
Heater: 11,98VDC
Phantom: 48,1VDC

the power dissipation on the 7812 is lower, so my (big) heatsink is still warm, not hot.

 

[JimiH]

[quote author="fucanay"][quote author="JimiH"]My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.[/quote]

Yeah, The orientation is important when you have printing on the front panel though, right? Otherwise the knobs won't point to the right place. That's kind of what I was fearing. I guess I'm going to pick knobs and pots at the same time and get all 6mm stuff. Bah.

Matt[/quote]

Yeah that's what I was getting at. I thought it would matter, but if you just rotate the knobs and they have a little screw in the side (I guess I should have mentioned that) it just means it tightens on the round bit, not the flat bit of the shaft. It still works rather well. If it means anything I am using a purusha case and the flats on my rotary switches didn't line up, but my knobs are still pointing to the right places thanks to the screws.

 

[fucanay]

[quote author="JimiH"][quote author="fucanay"][quote author="JimiH"]My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.[/quote]

Yeah, The orientation is important when you have printing on the front panel though, right? Otherwise the knobs won't point to the right place. That's kind of what I was fearing. I guess I'm going to pick knobs and pots at the same time and get all 6mm stuff. Bah.

Matt[/quote]

Yeah that's what I was getting at. I thought it would matter, but if you just rotate the knobs and they have a little screw in the side (I guess I should have mentioned that) it just means it tightens on the round bit, not the flat bit of the shaft. It still works rather well. If it means anything I am using a purusha case and the flats on my rotary switches didn't line up, but my knobs are still pointing to the right places thanks to the screws.[/quote]

Thanks man. I went ahead and ordered the 6MM ones because I found some knobs that I really like that come in either size. Knobs are too expensive though, bah.

Matt

 

[fucanay]

Ok, another question, that shows my newbieness.

I still need to order the C14/C15 Caps. Does this cap do both at one time?

http://www.tubedepot.com/cp-jj-100x2-500v.html

I don't understand the whole 100 x 100 thing and I couldn't find anything about them anywhere.

Cheers

Matt

 

[Stagefright13]

I used 2 JJ 50/50 caps from Triode. Work fine. But I don't think something that big is necessary. I like the guitar amp look... You need 2 100 caps with an appropriate voltage rating. And the big caps need clamps to mount them. So don't forget the mounts if you go that way. Each cap is a dual 50 so 100 when chained.

Caps needed 2: 5050clampmount
Clamps needed 2: clamp-1-38

At http://store.triodestore.com/

Hope I helped somewhat. You can get smaller cheaper caps but I don't know wich others will definitely work besides these. I'm just an amateur experimenter!

 

[fucanay]

Well, I have two smaller ones of the correct rating, but they look nowhere near as cool as the big one and I like the idea of the clamp mount for structural integrity. But if I need two of the big ones, I'll just make due with what I have. No need to spend $20 or so for things that I won't see after I close the case, I guess.

 

[maxheadroom]

what SNR @ 200 Ohm (EIN) is for a G9 normal?
i want to measure my G9, but at the moment i can't do it at home with my soundcard, because its a bad one and i will measure false.
is there a option with a good fluke?

 

[maxheadroom]

has anybody measured the crosstalk from CH1 to CH2?

 

[kazper]

For the C1/C15 caps I used a pair or Radial caps and secured them to a 2x2 PCB from Radioshack.

 

[flintan]

Do the heater and the phantom PSU's need to be isolated from each other or can i use a single secondary 15V transformer?

I'm asking only because i have a bunch of 1x15V transformers lying around..


[quote author="steppenwolf"]Hi!

I used two toroids, too and the second one hummed, too.
I measured and the second one took 600mA of current with no load!
I solved the problem with a resistor between the secondary of the first and the secondary of the second one...

Greets,
Stefan[/quote]

Why is this? Could it be if the transformer has different DCR/voltages between the two parallelled windings? I've been trying to understand this and found some interesting reading here: http://sound.westhost.com/xfmr2.htm#8.series-parallel

If this is the case, wouldn't it be better then to use a single 12V winding for the second transformer?