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Old 14th March 2013, 08:58 PM   #31
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You will need to rewire your circuit.....But, why not to use the other half of the 'AT7 as a SRPP?
There is no need to rewire or redesign the circuit, it works great the way it is designed. Both halves of the 12AT7 are already used.

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It's a proven design with others running without fan aid. I'm doing something wrong.....This is how i assemble them:
That looks wrong.

It is not clear if you are putting the CCS chips on the top of the board or the bottom of the board. Either way your picture does not match either drawing in the assembly manual. If you can't find the assembly error, please post a picture of the CCS chip mounted on the board, and we will figure it out.
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Old 16th March 2013, 09:44 AM   #32
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Originally Posted by rknize View Post
OK, so you are no longer trying to use a FET here? Good.



Zero volts across all four resistors? That would mean that the CCS and/or tube are not passing any current at all. So let's review:

You originally had DN2540s here, but were experiencing part failures so you switched back to the 10M45S. You have a 330ohm resistor in there now, right? I assume the resistors still measure the correct resistance.
Yes, checked all of them


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Originally Posted by rknize View Post
Looking at your other voltage measurements and assuming the resistors and PCB are good, it seems that the 10M45S is an open circuit right now. You have B+ on R14/24 and a few volts on R13/23.

So the question is, what is taking out your FETs/CCSs? Perhaps you have a shorted input tube? I assume that the heat sinks/hardware are not touching your chassis anywhere, right? The tab on the CCS is connected to the "anode" of the CCS, so it will have B+ on it.

What are you using for an input tube? Do you have a spare to try?
No, the sinks don't touch anything, they are inverted assembled.

I have a few 12AT7 and tried some with the same results.... I checked the condutivity in the board and everything seems right :S

I must be doing something really stupid and assume it as right

I'm posting some photos, please take a look too


Thank you Russ
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Old 16th March 2013, 09:57 AM   #33
RuiR is offline RuiR  Portugal
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Originally Posted by tubelab.com View Post
...

That looks wrong.

It is not clear if you are putting the CCS chips on the top of the board or the bottom of the board. Either way your picture does not match either drawing in the assembly manual. If you can't find the assembly error, please post a picture of the CCS chip mounted on the board, and we will figure it out.
Thank you George

I looked and looked several times and can't find anything wrong

As i said before, within this solder/unsolder i damaged the tracks... to make sure a perfect conductivity i replaced them with wire as you can see. It wasn't rocket science but one never know and i might screwed up

Click the image to open in full size.

Click the image to open in full size.

The tracks conections between the mosfet and R13/23 and R19/29 are in the other side of the board.
The track between C21 and R23 and R29 was replaced with a wire. At R23, a wire pass through the board to the other side to establish connection with the driver tube. Checked conductivity within these points.

Click the image to open in full size.

Click the image to open in full size.

Replace tracks with wire, conductivity checked.


Click the image to open in full size.

10M45 bended. I assembled them on the lower side of the board.

Can you spot anything wrong?

Yepp, my board is a mess and the suposed cleaning liquid didn't help too


Thank's
Rui
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Old 16th March 2013, 09:15 PM   #34
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The installation looks correct to me, based on this picture:

Click the image to open in full size.

Your coupling caps look a bit melted.
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Old 18th March 2013, 09:00 AM   #35
RuiR is offline RuiR  Portugal
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Originally Posted by rknize View Post
The installation looks correct to me, based on this picture:

Click the image to open in full size.

Your coupling caps look a bit melted.

Touched them with the iron and ruined their finish

Yep it seems to me all fine too
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Old 20th March 2013, 02:52 PM   #36
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Hi

Still scratching my head....

Measured the voltage in the 12AT7, without imput signal and speakers attached

Pin 1 - ~29 VDC
Pin 2 - 0 VDC
Pin 3 - VDC
Pin 4 - (-0.8) VDC
Pin 5 - ~29.5 VDC
Pin 6 - = Pin5
Pin 7 - 0 VDC
Pin8 = (-0,5)VDC
Pin 9 - (-0.8) VDC

Click the image to open in full size.

Can this help?

Thank's
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Old 20th March 2013, 04:00 PM   #37
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Hmmm...something is wrong with those measurements. The plates (pins 1 and 6) match the DC offset on one of the heater pins (pin 5). Are you sure those measurements are correct?

Perhaps it's because the heater has AC and not DC on it and it's confusing your meter. Or, you may have a short between one of your plates and the heaters. The heater supply is floated to around 20-30VDC (depending on B+) by the divider comprised of R4 and R3. So you should see this DC offset on all of the heater pins (4, 5, and 9). If you measure across the heater (pins 4-9 or 5-9) with your meter set to AC, you should see the 6.3VAC heater supply.

A short between the plates and the heater might explain the short live of your CCS's. I could be the tube, but I would inspect you soldering around the socket on both sides of the PCB very carefully.
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Old 20th March 2013, 06:10 PM   #38
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Originally Posted by rknize View Post
Hmmm...something is wrong with those measurements. The plates (pins 1 and 6) match the DC offset on one of the heater pins (pin 5). Are you sure those measurements are correct?
You are right, they are inverted... they are correct now:

Pin 9 - ~29 VDC
Pin 8 - 0 VDC
Pin 7 - (-0.5)VDC
Pin 6 - (-0.8) VDC
Pin 5 - ~29.5 VDC
Pin 4 - = Pin5
Pin 3 - 0 VDC
Pin 2 = (-0,5)VDC
Pin 1 - (-0.8) VDC

Quote:
Originally Posted by rknize View Post
Perhaps it's because the heater has AC and not DC on it and it's confusing your meter. Or, you may have a short between one of your plates and the heaters. The heater supply is floated to around 20-30VDC (depending on B+) by the divider comprised of R4 and R3. So you should see this DC offset on all of the heater pins (4, 5, and 9). If you measure across the heater (pins 4-9 or 5-9) with your meter set to AC, you should see the 6.3VAC heater supply.
Measured across them and got ~6.1VAC

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Originally Posted by rknize View Post
A short between the plates and the heater might explain the short live of your CCS's. I could be the tube, but I would inspect you soldering around the socket on both sides of the PCB very carefully.
Nothing wrong here then?


Thank you
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Old 20th March 2013, 07:35 PM   #39
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Looks fine. There is nothing on the plates, which is expected given that we know that your CCS's are likely not working. Have you already tried replacing them? Maybe we should try replacing the CCS with a resistor to make sure everything else is in order before blowing up any more silicone.
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Old 20th March 2013, 07:41 PM   #40
RuiR is offline RuiR  Portugal
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Originally Posted by rknize View Post
Looks fine. There is nothing on the plates, which is expected given that we know that your CCS's are likely not working. Have you already tried replacing them? Maybe we should try replacing the CCS with a resistor to make sure everything else is in order before blowing up any more silicone.
Yes, already had with the same result :S

I'm open to all suggestions, I need help although I have a few spare resistors and i can buy some in the hardware store.


One more thing... i just take some readings at R13 and initially the voltage rise until ~40VDC and then lowers to ~0VDC. I only have one multimeter but the time interval matches the one B+ takes to rise until 450/480 VDC.... this brings something?

Last edited by RuiR; 20th March 2013 at 07:44 PM.
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