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Tubelab SE 300b Build Thread

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#241
That's good to know. I'll look into changing R6.
You blew a current regulator. U2, or U3 depending on channel. I did the same thing. It also blew the mosfet. I think the tube was still good even after glowing.
This is all great information. So hopefully after I lower B-, I should be finally done. Thanks a million.
 
#242
I haven't read though in detail. The -150 on the schematic is as the amp was originally designed for 45s. I had two builds for 300Bs with 400V B+ and B- was around -300V - no problems, and normal. In a third for EML 320Bs I ran 525V B+, though I used 10M90s and 900V MOSFETS in that one.

For the CCSs I've seen some large variances so I always measure the device and tune the current set resistor.
 
#243
Has anyone actually talked to George and gotten an answer on this topic?
I would really like to know if I am done or note.
When by AC is at about 123 volts, my B+ is at about 375 volts, and my B- is at about -290 volts. These are approximate numbers as my AC drifts around a little.😱
 
#244
Guarnera said:
You blew a current regulator.
Click to expand...

No, it blew the mosfet that does the impedance matching for the output tube (either Q1 or Q2 but I went ahead and replaced both). Mine is the FDP5N50NZ-ND that came from Digikey. The CCS's were fine. Music was playing fine and then I heard a low pop... music was gone... then back playing... then gone... then playing... then gone for good. That's before I lowered the voltage and that's the first time I noticed the 5842 plate glowing. Weirdest thing I've ever seen.
 
Last edited:
#245
Guarnera said:
Has anyone actually talked to George and gotten an answer on this topic?
I would really like to know if I am done or note.
When by AC is at about 123 volts, my B+ is at about 375 volts, and my B- is at about -290 volts. These are approximate numbers as my AC drifts around a little.😱
Click to expand...

The -150 being for 45s is from George. He's answered the question several times - buried in many threads here.
 
#246
JP said:
"Show me on the doll where the aliens touched you." - SY
Click to expand...

Love the signature. Every time I read it, I die.

Guarnera:
SE AmpCad.jpg
SE Amp CAD says that in order to bias the 300B to 75mA @ 384V, you need -76V of B-. So -150V seems like plenty for the MOSFET to draw from. Raising the B+ requires slightly more B-. Lowering the plate idle current also requires more B-.

The only problem with raising R6 to 40K is that the second cap in the filter takes longer to charge but I don't know if there are any transients that the cap is required to fill since this is Class A. Maybe someone can answer?
 
#247
JP said:
The -150 being for 45s is from George. He's answered the question several times - buried in many threads here.
Click to expand...

Well, I can't read through every post, But I do believe this. I read through the
webpage again. And George says that you can us 45's, 2A3's, or 300B's with out changing any parts.
So I guess I'm done. I have been running her 10 hours a day, trying to get 300 hrs. on my Psvane treasure II 300B's, with no problems. I have a 2.25" square fan inside the power supply unit aiming at the 5 volt regulator heat sink. I have run her for two hours without the fan on without the regulator shutting down. But when I run her for 10 hours straight I turn the fan on. You cant hear it when music is playing. But when its finally set up in the den, I probably won't use the fan much.
So now I'm waiting on my Quantum, CD transport to be completed. It should be done really soon. I'm supposed to be getting S/N 004. One, two, and 3 were prototypes, so I should be getting the first completed unit. Can't wait.
I want to thank everyone here for all the help on this project.:cheers:
 
#250
Guarnera said:
Well, I can't read through every post, But I do believe this. I read through the
webpage again. And George says that you can us 45's, 2A3's, or 300B's with out changing any parts.
So I guess I'm done. I have been running her 10 hours a day, trying to get 300 hrs. on my Psvane treasure II 300B's, with no problems. I have a 2.25" square fan inside the power supply unit aiming at the 5 volt regulator heat sink. I have run her for two hours without the fan on without the regulator shutting down. But when I run her for 10 hours straight I turn the fan on. You cant hear it when music is playing. But when its finally set up in the den, I probably won't use the fan much.
So now I'm waiting on my Quantum, CD transport to be completed. It should be done really soon. I'm supposed to be getting S/N 004. One, two, and 3 were prototypes, so I should be getting the first completed unit. Can't wait.
I want to thank everyone here for all the help on this project.:cheers:
Click to expand...



I am totally wrong about the Quantum CD transport. I don't know where I got that about 001 to 003 being prototypes. I must of imagined that. 003 went to the Netherlanders I believe? And got great reviews.Mine should be 004. Sorry for the confusion.:scratch:
 
#251
Hi Jdrouin,

I'm in the research of the perfect case and have to tell you that yours is the greatest and most elegant I have seen. This is why I'd like to ask you some questions about the building so that I can do something similar, if you don't mind.

Firs question would be, how did you do the case??? Did you buy just an aluminium sheet and then drilled and "folded"?? Drilling is no problem since I have appropriate hardware, actually giving the "case-form" is my concern..

Black drilled top case is also aluminium? Same process just painted in black?

Regarding to the painting did you use any specific heat resistant spray paint or just a normal one, those used for graffiti?

Thanks a lot for your time!


jdrouin said:
Well, too late now!

Vents drilled by jeffdrouin, on Flickr

Panel cut by jeffdrouin, on Flickr
Click to expand...
 
#252
Hi capitanalga,

I used a Bud Industries aluminum chassis, size 17" x 10" x 3" and matching bottom plate from Amazon.

There are other manufacturers like Hammond that make similar products.

Rubber feet from Angela.

I printed out the drill guides from the Tubelab website to get the holes aligned, and then made up my own drill pattern for the venting.

The removable top panel and openings for the power transformer and IEC inlet I drew with a T-square and ruler, and then cut by hand with a rotary tool and Dremel #426 cutoff disc.

The paint is Rustoleum matte French cream for all surfaces, including aluminum. No high temp paint needed. This paint sticks well to the aluminum, though next time I might try spraying it with aluminum primer first.

Also, the case is large and thin enough to be a little wobbly, so I reinforced it with some aluminum flat bar and a couple of angle brackets. It was an easy improvement with cheap hardware parts.

Here's an inside pic of how it looks.

Wired PCB by jeffdrouin, on Flickr

The angle brackets are bolted with the output transformer mounting bolts. The assembly puts enough tension across the top of the chassis that you don't have to drill into the sides to add more. It would be even more stable if I did that, but I made a compromise for the appearance because I wanted smooth side surfaces without a lot of bolts.

Also, I would leave the interior unpainted as it will lead to better chassis grounding. I'm currently making a phono preamp and will be using the same paint, but with unpainted insides.

Good luck!

Jeff
 
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#253
Thanks a lot!! Box is on the way!!

I'll share seme pics once finished!

Thanks again


jdrouin said:
Hi capitanalga,

I used a Bud Industries aluminum chassis, size 17" x 10" x 3" and matching bottom plate from Amazon.

There are other manufacturers like Hammond that make similar products.

Rubber feet from Angela.

I printed out the drill guides from the Tubelab website to get the holes aligned, and then made up my own drill pattern for the venting.

The removable top panel and openings for the power transformer and IEC inlet I drew with a T-square and ruler, and then cut by hand with a rotary tool and Dremel #426 cutoff disc.

The paint is Rustoleum matte French cream for all surfaces, including aluminum. No high temp paint needed. This paint sticks well to the aluminum, though next time I might try spraying it with aluminum primer first.

Also, the case is large and thin enough to be a little wobbly, so I reinforced it with some aluminum flat bar and a couple of angle brackets. It was an easy improvement with cheap hardware parts.

The angle brackets are bolted with the output transformer mounting bolts. The assembly puts enough tension across the top of the chassis that you don't have to drill into the sides to add more. It would be even more stable if I did that, but I made a compromise for the appearance because I wanted smooth side surfaces without a lot of bolts.

Also, I would leave the interior unpainted as it will lead to better chassis grounding. I'm currently making a phono preamp and will be using the same paint, but with unpainted insides.

Good luck!

Jeff
Click to expand...
 
#254
No problem. Btw, for the brace, I got a strip of 1" wide, 1/8" thick aluminum flat bar from the hardware store (ca. $6 USD) and cut it to size with the rotary tool and cutoff disk. I then drilled the holes to attach it to the angle brackets with bolts.
 
#256
PCB is here, parts ordered to populate PCB. I have an enclosure design drawing copied somewhat from a fella on this board. Two piece for easy access. I need to try and figure out which ps and choke I need. Would like to go with the Electra Prints.
 
#257
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