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innercityman

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You'll find attached the HT psu part of the G9 schematic. This corresponds to the spare psu pcb I used. I just wired the 2nd 470uf cap (C15) to the main board at the HT pad right after the jumper. And I get 246VDC at R31 and R131 which is correct I guess.
 

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rock soderstrom

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innercityman said:
You'll find attached the HT psu part of the G9 schematic. This corresponds to the spare psu pcb I used. I just wired the 2nd 470uf cap (C15) to the main board at the HT pad right after the jumper. And I get 246VDC at R31 and R131 which is correct I guess.

This is not what I see. I don't want to do your work. If you want me to help you, than draw a schematic exactly the way you have build it. Everything else is a guessing game...
 

TillM

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Why don’t you build the psu on the main board pcb ?
The Don Audio transformer has a integrated shield and is hum free.
I also used it in my builds.
I’m pretty sure, that the fault is in the wiring from the spare pcb to the main pcb.
And as RockSoderstrom said, it’s hard to guess without drawing.
 

innercityman

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This is not what I see. I don't want to do your work.

This is not what I'm asking, I just asked for some help because I'm lost and fed up with this issue I can't solve myself because of my limited electronic skills.

The spare psu pcb I used is the one that comes with the G9 PCB kit. Jacob explained that he put it on the pcb to avoid loosing space. It is an exact copy of the onboard HT and 12VDC PSU. I only used the HT part of it and let the 12VDC and 48V on the main board. As I wrote before, I had the same issue with HT psu on the main board. The only difference with the schematic is that I've replaced C14/C15 100uf 350V with 470uf 400V caps like advised.

I'll try to draw a schemo, not sure I can do that.
 

innercityman

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Why don’t you build the psu on the main board pcb ?

That's what I did first and same smoking diodes issue. I decided to build the HT psu out of the board using the spare one because I've read that it could help with hum issue. I'm sure my wiring is ok, it comes from somewhere else. Probably from the big HT caps like rock soderstrom said. And I'm also sure that if I build it back on the main board like I did first, I'll have the same smoking diode.

Anyway, as I said, I'll try to draw a schemo.
 

TillM

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hmm ... in my opinion the yellow cable from the power trafo must went to the heater, cause the heater needs at least minimum 1A. Now it works with 0,5A, cause you use the blue cable, which should go to 48v phantom.

Edit: I realize that you nearly has a problem with the preamp since a year.
 

innercityman

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I realize that you nearly has a problem with the preamp since a year.

In fact I went to another project MK47 (U47 clone which has been a success and very fun build) so I let it out for a while and came back to it few weeks ago.
 

innercityman

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Both hum and smoking diode issues solved !

The hum issue was due to non shielded audio cables, and no smoking diode anymore after replacing both 470uf 400V caps by 330uf 450V caps. So my outboard psu build and wiring was good as I thought.

Thanks to rock soderstrom for putting me on this path of investigation.
 

HyprDrivr

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Hello friends

I am building one of these and found some tropical fish that look like 220nf/250Vs.
Any reason not to use these for C2 and C10?
Any reason i should?

20210518_182109.jpg
 

zaraxisof

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Any reason i should?
They will give mojo

I happened to find some of them in bulk back then too and i use from guitar, bass tone pots and organ osc cards, to pedals, pre's and amps. I love them.😆
 

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HyprDrivr

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My G9 is finished, i will share more when i get the correct knobs.

I only have one slight problem, the +/-12v-220 volt transformer is making a lot of mechanical buzz, i assume due to saturation same as many other G9 builders.
It does not affect the signal at all, but i would rather not have noisy things in the studio.

Is there any other viable way than replacing the transformer that might solve this?
I have searched the thread and i cant find any other solutions there.
 

gyraf

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Some transformers do the buzz - depends probably on how well it's resin-dipped. And on how close to power rating you run. Try with a different/larger type?

/Jakob E.
 

zaraxisof

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Finished G9, all great. First power up without panel boards connected, just to check supplies, with bulb limiter in series with hot mains.
Dadada!
HT 246.8V with only one channel tubes on, Phantom about 46V. Trimmer adjustment for 48V (takes some minutes to get there, starts from 47.2 and gets stable at 48.12V after 15').
Will probably make new presentation thread with my build or post here.
All fine, i just have a question.

After having replaced block terminals with better ones i forgot to connect filter caps so i accidentally powered up (with bulb series limiter as always) without filter caps, just for 10-20 secs. when i realised it..

The beast works like before, all voltages being exactly like before, but just for the record, could smthng bad / damage occured there?
 

gyraf

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I don't see why that would have damaged anything permanently (other than your speakers, if you were listening to it at the time)

/Jakob E.
 

zaraxisof

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Everything runs perfect. It's a great machine, thank you Jakob. 🙂

Something last. I have many E10 incandescents laying around.
Is it so bad to use 165mA (maybe have some 100mA's too) 12V bulb instead of 50mA?
 

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gyraf

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Just try it - if it dosen't add hum, cause the 12V to shut down thermally after a while, or blind you with waay too much light - then it's OK

perhaps use a small power resistor in series with it to dampen it down a bit?

/Jakob E.
 

zaraxisof

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I see. Tried with 165mA no hum at all. Will put a 100mA just to be more safe and try to find a 50mA one.
Thanks Jakob 👍
 

HyprDrivr

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So I have finished my G9 some weeks ago. Great unit, sounds very clean and open. I have no noise whatsoever after following the antioscillation tips. I am currently running TungSol 12AT7 in it, i feel they gave some more gain and beef, and i have only crappy EHX 12AU7s. Transformers are OEP. The (way to large) heatsink is scavanged from a dead Mixcube PSU. I have ribbon cables running from the switchboards, i know people have been asking if this works and it did for me at least. I had no nice thin cables for the connectors, but standard mic cables worked out fine.

Had no issues with the build, fired up first attempt.
Only problem was a saturated reversed transformer that was solved by exhanging for another brand, Velleman was the one that was noisy for reference.
 

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