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Old 11th July 2013, 12:51 AM   #81
evanc is offline evanc  United States
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Sounds like it to me. Being able to watch the B+ and bias for both outputs would be good. A variac is cheap used and is real nice.
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Old 11th July 2013, 01:16 PM   #82
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Quote:
Originally Posted by ranhaber View Post

If I understand you right, I can now continue the test and plug in the rest of the tubes...
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.
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Old 11th July 2013, 11:06 PM   #83
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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?
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Old 11th July 2013, 11:26 PM   #84
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Quote:
Originally Posted by ranhaber View Post
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.

Last edited by boywonder; 11th July 2013 at 11:28 PM.
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Old 12th July 2013, 07:52 AM   #85
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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?
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Old 12th July 2013, 01:14 PM   #86
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Quote:
Originally Posted by ranhaber View Post
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?
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Old 12th July 2013, 05:46 PM   #87
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Quote:
Originally Posted by boywonder View Post

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?

Last edited by ranhaber; 12th July 2013 at 06:10 PM.
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Old 12th July 2013, 09:06 PM   #88
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Quote:
Originally Posted by ranhaber View Post
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.
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Old 13th July 2013, 03:02 PM   #89
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Quote:
Originally Posted by boywonder View Post
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?
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Old 14th July 2013, 10:53 AM   #90
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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.
Does my conclusion right?

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