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Tubelab SE

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If I understand you right, I can now continue the test and plug in the rest of the tubes...:confused:

Yes. Make sure that you have a reasonable sized mains fuse fitted (like 1/2-3/4 amp slow blow). If the fuse didn't pop with the 5AR4 installed you have got past the first step.

Also, be sure to have a resistive load on the speaker terminals; never power up the amp without either speakers or an 8R load connected. For initial power up and setting bias, etc, use some resistors. 10W (or greater) 8R resistors would be ideal, although 5W rated will work in a pinch as long as you don't crank up the input signal.
 
In the next test
" Put a meter from the grid of the output tubes to ground........ Set it to the most negative voltage..."

I set each one to around -130V,
The B+ is now around 1000V, is that ok?

Because I'm stupid I moved to the next test and put the 5842 tubes,
B+ was still 1000V,
no voltage was measured on the plate of the 5842, but they shine a little. What's wrong?
 
In the next test
" Put a meter from the grid of the output tubes to ground........ Set it to the most negative voltage..."

I set each one to around -130V,
The B+ is now around 1000V, is that ok?

Because I'm stupid I moved to the next test and put the 5842 tubes,
B+ was still 1000V,
no voltage was measured on the plate of the 5842, but they shine a little. What's wrong?


Pull all of the tubes except for the rectifier..........do you get the voltages in your post #75 above once again?

I'm struggling with a B+ of 1000V.....that's not really possible, and you would have popped your PS caps......are you still measuring VDC across R30?

Once you get back to the voltages in your post #75, turn the bias pots to get the most negative voltages on R33 and R34, and let us know what those voltage are, you don't need tubes installed to set the bias.
 
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I changed C4 to 2.2uF.
I removed the 5842 tubes and the measures were:
B+ 450V
B- R7 -300V
R33 to grd -120V
R34 to grd -113V
It looked OK, (the previous measurement was took at 2AM so.... :-! )

When I put the 5842 tubes B+ and B- are 450V and -300V.
From R16 and R17 to grd 0V but... the 5842 were lighten. How can it be?
 
I changed C4 to 2.2uF.
I removed the 5842 tubes and the measures were:
B+ 450V
B- R7 -300V
R33 to grd -120V
R34 to grd -113V
It looked OK, (the previous measurement was took at 2AM so.... :-! )

When I put the 5842 tubes B+ and B- are 450V and -300V.
From R16 and R17 to grd 0V but... the 5842 were lighten. How can it be?

OK, the voltages above are reasonable......and you've got the bias pots turned fully negative.

When you say that the "5842 were lighten" do you mean that the filaments were glowing? That's a good thing.

When you say R16 and R17 to ground 0V are you measuring the anode (plate) voltage of the 5842? Referring to the schematic, you want to measure at the node where the 5842 plate, coupling cap and R16/R17 meet. You could also take the measurement at pin 1 of the 5842. The target voltage for the 5842 plate to ground is around 175 volts. If it's a bit higher or lower (160-190VDC) that can be dialed in by adjusting the other trim pots (R9 and R20)

TDSL Tube data [5842]

Do you get the same readings on both channels? Do you have B+ voltage on the 10M45 CCS? If so, then double check the R values for R16 and R17.

Do you have proper load resistors on the speaker terminals?
 
Do you get the same readings on both channels? Do you have B+ voltage on the 10M45 CCS? If so, then double check the R values for R16 and R17.

Do you have proper load resistors on the speaker terminals?

In the checkout, only on the next test I'm supposed to connect a load. I think that it doesn't matter now because the output tubes aren't plugged.

R15,R16,R17 - all values are ok, measured voltage 0V. the second channel is the same.
On the 10M45 between pins A and K - 412V.
Still 5842 pin 1 to grad - 0V.:(

Between the test that I thought I measured On B+ 1000V and the test I measured 450V , I changed nothing.
Is it possible that my 1000V B+ was real and I fried the 10M45 and now it lowered to B+ 450V?
 
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In the checkout, only on the next test I'm supposed to connect a load. I think that it doesn't matter now because the output tubes aren't plugged.

R15,R16,R17 - all values are ok, measured voltage 0V. the second channel is the same.
On the 10M45 between pins A and K - 412V.
Still 5842 pin 1 to grad - 0V.:(

Between the test that I thought I measured On B+ 1000V and the test I measured 450V , I changed nothing.
Is it possible that my 1000V B+ was real and I fried the 10M45 and now it lowered to B+ 450V?

If the B+ center tap is grounded (T1-1 on the schem), there is no way to get 1000V........

Do you have the components on the top or bottom of the PCB? If they are on the bottom you need to double-check the pin-outs for the 10M45's, the mosfets and the filament regulator.
 
If the B+ center tap is grounded (T1-1 on the schem), there is no way to get 1000V........

Do you have the components on the top or bottom of the PCB? If they are on the bottom you need to double-check the pin-outs for the 10M45's, the mosfets and the filament regulator.

So if the center tap to ground came loose?
Maybe there is an intermittent connection there?
 
I pulled out the 10m45 and tried to use it as discribed in the pdf.

Vd = 25V
Rk = 100ohm
No voltage on Rk.

I thing the 10m45 is fullty or fake. :mad:
Does my conclusion right? :confused:

Does somebody now where can i buy it with reasonable shiping rates? :(
 

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Well, the 10m45 was faulty.
I got 10m90. It has the same spec, and has a 900V breakdown.

Now I have voltage on the 5842, but the max voltage measured was 166V and 155V. Only the 5AR4 and 5842 are connected.
The resistors values are OK.
Does the -306V is normal at this point?
Is it the tubes? How does it effect the Amp?

After a minute there is a little smell of burn plastic from the rectifier, what can it be?

Thanks
 

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Does the 10M90 require the same set resistor for a given current? Are you still using 332R for R16?

EDIT: I just checked the datasheets; it appears that the 10M45 flows about 8.8ma and 10M90 flows about 9.5 ma with a 332R set R........

Are you saying that with the pot adjustments maxed out you get 166V and 155V anode voltage on the 5842's?

You can certainly operate the amp with those voltages, as they are within the normal variation of 5842's according to George.

If you want to get the anode voltages a little higher, you could increase the value of R10/R21 to say 620-750 ohms or so, or fit a higher value trimpot.

The -306V is your bias voltage, correct? That's also normal for a 300B build.

When your output tubes are idling, your B+ and bias voltage will drop a bit due to loading the power transformer.

That burned plastic smell may just be "new amp smell"......;)
 
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Hi, excuse me for using this thread for a question....

I’ve just bought a choke from Ebay, 10H 250mA , to be used as choke input in the TSE.

What I don’t understand is that it has a lot of input pins, and the instructions say :

Terminal : 2 and 10
GND : 6

The question is why should I use a GND with a choke?

Is this necessary?

Many thanks
 

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It's alive :D

B+ is 310V
Voltage on R10 and R29 is 670mV.
music came out of the speakers.

but...
1) On quite and normal volume it sound ok, but when i turn the input attenuator a little for more volume a aloud hmm appear . why?

The hmm appear even with no input, but still only when the input attenuator is turned a little to the middle. (at the same point like it was with the input CD)

2)Does the voltage on R10 supposed to change? if yes then how much?
 
I would check the grounding scheme of the pot, as they can make lots of hum easily...........

Do you have a means of listening to a source at various volumes without using the attenuator? Like a preamp or other device with adjustable output?

If so, try substituting a fixed R of similar value in place of the pot/attenuator (like 50K-100K or so) and see if your hum issue goes away.

On another note.........Your B+ seems low for the current and voltage ratings for that massive power transformer.....what is the bias current on the 300B's? (measure the voltage drop across R18 and R29 with the amp idling)
 
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I would check the grounding scheme of the pot, as they can make lots of hum easily...........

Do you have a means of listening to a source at various volumes without using the attenuator? Like a preamp or other device with adjustable output?

If so, try substituting a fixed R of similar value in place of the pot/attenuator (like 50K-100K or so) and see if your hum issue goes away.

On another note.........Your B+ seems low for the current and voltage ratings for that massive power transformer.....what is the bias current on the 300B's? (measure the voltage drop across R18 and R29 with the amp idling)


Just for start, I have placed a 2.2uF that give me the 310V B+.
I'll now change it to 8.2uF to get 390V B+.
R18 and R29 have a voltage of around 670mV (I wrote R10 &R29, a mistake by my)
 
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