B1 with Korg Triode

As the DIY store was absent of the “completion parts kit” I consulted NP’s list and sourced directly from Digikey. Chassis is bamboo w/plexi top, volume knob is a vintage CPU heat sink. No ringing whatsoever (have not damped the ‘tube in any way), and best of all it sounds great. Thanks to 6L6 for the well done assembly guideline. :wrench:

When I saw that volume knob this sprang to mind.
 

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Yes I have try only electrochemicals Simic II and Nichicon then only polypro ( big size )
Mixture of electrochemicals bypassed with small size ~ 2uF pp sound fantastic

I tried Wima MKS polyester bypassed w/.1uf polypro and Silmic II bypassed w/polypro. I prefer the silmics bypassed with polypro.

It is just about the only time in my life I have preferred an electrolytic for coupling but I can't argue with the sound. Others may have a different opinion based on power amp, volume pot, psu influences. I am also using a linear supply w/lm317 reg.
 
Would appreciate some troubleshooting tips. One of the triodes in the nuTube in my B1 is not glowing (and of course that channel is not working).

Other than a failed part, what do you suggest verifying?

FWIW, it's the left one from the perspective of the front panel.

Kind of ironic that it failed today given that today I started building the PSU for my F6 build.

Thanks for any help.

-- Thing
 
More information on my failed B1:

Some voltages:

The bad channel
T7 - 20.6
T5 - 9.4
The pot on that side doesn't affect voltages at the test points at all. But I verified that the pot is still working by checking voltage at the wiper.

The good channel
T8 - 9.7
T6 - 0.7

And voltages on the Nutube leads
F1 - 9.5
F3 - 0.73
A1 - 16
A2 - 8.45

It's been working without any problem since the end of October.

Wide picture was taken with power off. Closer picture taken with power on so you can see the lack of glow on the left. Please excuse the unconventional switching of red and black in the power runs.

Thanks for any help.

-- Thing
 

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Thanks for the read on my nuTube issue.

I'm wracking my brain to think of any incidents of physical shock and can't come up with anything. It failed while playing: a big loud fart out of that channel and I immediately shut everything down.

The only recent change is the power amplifier in use. Switched from ACA monoblocks to a B&K ST-140. (My unhappiness with that amp is the reason I'm building an F6 now.) When the failure occurred, I initially attributed it to the (secondhand) amp.

Is there any chance the filament was damaged some other way than physical trauma? I want to avoid making the replacement end up being a very expensive fuse.
 
Note that it might not be cathode failure - if the tube is not achieving correct bias,
you routinely see the cathode go dark. If the cathode is open, you will see no
voltage across the 475 ohm cathode resistor.

Thanks for the pointer, but alas, that measurement confirmed the other posters' diagnosis of a damaged filament. And now that I realize what I'm looking at, yeah.

Bummer. Can you buy half a nuTube? ;-)

On the bright side, an opportunity to learn about repair.