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Old 24th November 2009, 09:37 AM   #1
webby is offline webby  United Kingdom
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Default simplese trouble shooting

Hi All,
Well i finally started my simplese project, and having a few teething problems...
Wired it up with the following Iron.
Edcor CXSE25-8-5K OPT
Edcor xpwr059 wired 350v red to t1-red pin 1&3, brown to 5v t1-yel, red & blk t1-red-yel, 6.3v yellow to t1 green.
Hammond 193H choke wired to L1
The circuit powers up without any undue noises or smells, the tubes glow, and i get some sound. I have double checked the star earthed and the inputs, outputs and transformers have continuity.
I would describe the symptoms as if the pre amp section is working, but the output valves arenít. Very low output before the sound starts clipping.
I had a quick check of the Anode, no voltage, heaters have 34v on pin 2&7.
Pin 6 has 522v, i thought it was no connection?

I am only using valve rectification; do i need to short SW1 or jumper it in some way to pass the voltage to the Anode? I am hoping this is the issue!
Couldnít find a testing procedure or FAQ, is there such a thing available.
Any other ideas would be great?
Many Thanks
Ian
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Old 24th November 2009, 09:58 AM   #2
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Hi!
Your project is SE? What kind of Your tubes? Can You post Your schematic?
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Old 24th November 2009, 10:46 AM   #3
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The Tubelab Simple SE has lots of gain, and should provide plenty of volume.

I am concerned that you see no voltage on the anode, but 522 volts at pin 6. I believe you are correct - pin 6 should be no connection. How are you counting the pins? Looking at the board from the socket side, pin 6 should be the one right next to the silkscreened lettering "V21" or "V11". Are you certain you aligned the socket keyway properly when assembling the board?

Have you top mounted, or bottom mounted the components? Do you have the means to take and post a digital photo?

You should not need a switch at SW1. That is only required for those who choose to use the solid state rectifiers.
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Old 25th November 2009, 05:47 PM   #4
webby is offline webby  United Kingdom
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Thanks TY,
You are of course correct, I was counting the pins incorrectly.
Fresh eyes and some sleep makes all the difference..
So pin 2&7 have 34v and pin 3 has 522v.
I have used an ipod into a passive alps pot to provide test music. But would still expect it to go a lot louder before distorting. It is very quiet.
Are there any test readings that might help diagnose?
In the meantime i will dig out my camera.
Thanks for any suggestions
Ian
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Old 25th November 2009, 06:17 PM   #5
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Pins 2 & 7 are the heater connections. I think George elevated the heater supply in this design to reduce noise. That doesn't really tell us anything. You might want to check the voltage at pin 8 (cathode), pin 5 (control grid), and pin 4 (screen grid).

There are two good threads around here containing at length discussions of a problem similar to yours. If I can find the threads, I will link to them. In the first case, the builder had inadvertently swapped R15/R16 (220K/100 ohms). In the other case, the builder had drilled out the through-plated holes for the coupling caps, effectively breaking the connection.

You might also want to swap the 12AT7 tube if you have a spare, and double check your wiring around the input connector (especially if you have a volume pot).

Edit: Try reading through these threads, and see if anything appears similar to what you are observing.

Post #55 ~ #142
http://www.diyaudio.com/forums/tubes...ml#post1664764

Post #67 ~ #128
http://www.diyaudio.com/forums/tubes...ml#post1871152

Last edited by Ty_Bower; 25th November 2009 at 06:28 PM.
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Old 25th November 2009, 08:27 PM   #6
webby is offline webby  United Kingdom
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Thanks again ty,
I forgot to say that the readings i gave for the output tubes were the only ones, all the other pins read 0vdc,
pin1 = 0
pin2 = 34
pin3 = 522
pin4 = 0
pin5 = 0
pin6 = 0
pin7 = 34
pin8 = 0
reading the other threads I double checked the values ofr16,r26,r15,r25 all correct.
No input signal gave r10 & r20 =1.9 vdc each
c11=225v c21=209
But R17 &R27 = 0 I am running 560ohm so should be getting 30-40vdc, any ideas?
Thanks
Ian
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Old 25th November 2009, 08:35 PM   #7
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Quote:
Originally Posted by webby View Post
pin8 = 0


That's not right. Are you trying to use cathode feedback? If you are, did you connect the output transformer correctly? If not, did you remember to install the jumper across T2-SEC and T3-SEC?
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Old 25th November 2009, 08:57 PM   #8
webby is offline webby  United Kingdom
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Hi Ty,
Just wired as basic amp without feedback, no CFB or UL.T2-SEC and T3-SEC have jumpers and continuity checked. T3-PRI pin 03= B+ red wire, 02=nc, 01= plate blue wire, same on T2-PRI. I have just taped up the UL wire from the output transformer, does this look ok?
Thanks again
Ian
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Old 25th November 2009, 10:58 PM   #9
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Quote:
Originally Posted by webby View Post
I have used an ipod into a passive alps pot to provide test music. But would still expect it to go a lot louder before distorting. It is very quiet.
Just to check the obvious (doesn't hurt to make sure) do you have the volume on the iPod all the way up? Keep in mind the last 10mm of the volume bar on the iPod goes up in a more logarithmic pattern.
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Old 26th November 2009, 12:38 AM   #10
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Quote:
T3-PRI pin 03= B+ red wire, 02=nc, 01= plate blue wire, same on T2-PRI. I have just taped up the UL wire from the output transformer, does this look ok?
No, this won't work and will result in exactly the voltage readings you have. There is no voltage on Pin 4 which results in no cathode current which results in no voltage on pins 1 and 8. The fix is simple. The 02 pin on the PRI connectors MUST be connected to SOMETHING. Jumper it to the plate (01 pin) for triode mode, or connect the UL tap on the OPT to the 02 pin for UL mode.
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