[BUILD] NU FEDERAL AM-864 PCB OFFICIAL BUILD & HELP THREAD

[jefflehiress]

woww ! crazy

 

[Eliani]

Yep, you've got to love that!!

so new tubes in mine! I was able to find a couple real close to each other, now the voltages are cool!
Next up is metering, I've got a 1mA meter. But the dial wil not go upto the max value, and with extreme settings the dial is halfway the scale... not usable I would say...

What do you guys sugest?

 

[djfatum]

The VU must have 200 micro amperes (1 milli amper too much)

 

[Eliani]

The VU must have 200 micro amperes (1 milli amper too much)

Cool, that's what I thought

 

[Eliani]

This might be better in another thread, but what CNC are you using? Are you just engraving anodized aluminum? Love the look of your panel.

I’ve got a BZT PFE1000PX, and Yes anodised aluminium. And thank you!

 

[Eliani]

The VU must have 200 micro amperes (1 milli amper too much)

Could you tell me what meters you bought and where you got them? I'm having trouble finding them.

 

[jefflehiress]

Could you tell me what meters you bought and where you got them? I'm having trouble finding them.

Don audio  sells them in 200 micro amperes now...

 

[rob_gould]

Not to brag but i'm kind of proud of this build!

At least of how it looks because wiring could have been a bit cleaner, but I'm sure I'll get it next time. I'm waiting for new 6BA6/EF93 tubes to arrive, I've bought like 10 and hope to good pair out of them. I'm not totally aware of how one would match tubes, or if I even need to, but I'm guessing it wouldn't hurt as I can't seem to get C and B to the same voltage! This might explain that the input get's distorted when cranking the input?

I've yet to do the threshold/ratio range reduction mods

Really great job - you should be proud!

I've been a bit out the DIY loop for a while but seeing your project had inspired me to get back to a couple of half-finished projects of my own...

 

[Eliani]

Yeah, I tend to lose interest in certain projects after a while too, but most of the time it's lack of time or funding!

By the way, about the 200uA DC meters, Aaron from Don-Audio let me know he's doing a run for them, now available in his store, although they will not be available for another 3 to 4 weeks. So I bought another Weston 2521 meter, but instead of the 1mA I found a 200uA version. And I bought a bunch of strange 200uA meters just for future projects.

I ordered 4 more PCB's from Zayance for a single control stereo version and one with a mono switch and dual controls... looking forward to that, because I just spent over €1000 for all the parts!

 

[jefflehiress]

Hi everybody,
Here, finally I finished the unit.
not without trouble with my beginner errors when buying audio transformers without CT eg: thank you bernbrue for your information that allowed me to finish this jewelry without too much trouble.
indeed I say: "without much" because during my measurements I fall on these values, and this as well on the left unit as on the right unit:

B + = 230 V

A = 14.46V
B = 224 V
C = 227 V
D = 173 V
E = 1.09V
F = 1.09V
G = 230 V
H = Over Load on the multimeter.

When I turn on the beast, the two hands go up to +2 dB then go down slightly, tremble lightly then come to fix on -3db is in the center of the VU meter. knowing that I was mistaken for sensibility of Vu meter as seen before with Eliani.

If you have a small idea of what might possibly be there. I take.

 

[bernbrue]

Either you've got a bad output tube (12AX7) or your output transformer is not wired correctly. You should have the same voltage as on G.
Bernd

 

[jefflehiress]

Either you've got a bad output tube (12AX7) or your output transformer is not wired correctly. You should have the same voltage as on G.
Bernd

I bought a pair of 5751 RCA Jan NOS. I hope these are not the tubes: D
I will test that.

 

[bernbrue]

Post some pictures of your build. Makes troubleshooting easier.
Bernd

 

[jefflehiress]

 

[jefflehiress]

ok, so I just changed by 12AX7B China to test something else and the values are:
A = 14.30 V
B = 223 V
C = 224 V
D = 173 V
E = 315V
F = 357V
G = 230 V
H = 230 V

either, no more coherence with the previous results.
I also have the hands that are at the bottom right of the Vu meter and bouncing in rhythm ...

 

[bernbrue]

Very nice build. How have you connected the meter trimpots? Try to measure voltage on H once again. There must be some voltage.
Bernd

 

[bernbrue]

E and F are not measured correctly.
Bernd

 

[jefflehiress]

E and F are not measured correctly.
Bernd

thank you ! trimmers pots are wired on CW and C.

 

[jefflehiress]

E and F are not measured correctly.
Bernd

ok, sorry E = 315 mV 
                    F = 330 mV
you think that the bouncing needle is due to bad wiring trim pots?
When I turn the threshold to the max the needle does not bounce but is fixed a little lower.

 

[bernbrue]

Watch my video.  The meter needs to be retrimmed quite often. Did you tame the pots as suggested in the first post?

https://www.youtube.com/watch?v=0eJVCCYApOw
Very nice unit. Be proud of yourself !
Cheers
Bernd