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Old 7th July 2011, 11:06 PM   #1
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Default Still have voltage problems with Simple SE

V11 still has 490 voltsDC while V21 remains at 455. I can't get a filament voltage reading on V11 as well.

There is 490VoltsDC on both the Output transformer primary and secondary, Red and Blue. That shouldn't be?

Both cathode ressitors have voltage but R27 gets very hot very quickly. I left the amp powered up for about 10 minutes and it didn't turn brown or burst into flame but R17 remains nice and cool. Both are 5W-560 Ohms cementos and both measure 560 Ohms on ther board.

Should I suspect C12? Why would the too high RIGHT channel B+ have the LEFT channel cathode resistor run hot?

Once again, all I did was remove the screw down board connectors and direct solder the off-board components. Honest!
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Old 8th July 2011, 02:03 PM   #2
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Took some more measurements and there's 31 Volts!!!on V11 Filament.
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Old 13th July 2011, 02:28 AM   #3
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Quote:
Originally Posted by BillEpstein View Post
V11 still has 490 voltsDC while V21 remains at 455. I can't get a filament voltage reading on V11 as well.

There is 490VoltsDC on both the Output transformer primary and secondary, Red and Blue. That shouldn't be?

Both cathode ressitors have voltage but R27 gets very hot very quickly. I left the amp powered up for about 10 minutes and it didn't turn brown or burst into flame but R17 remains nice and cool. Both are 5W-560 Ohms cementos and both measure 560 Ohms on ther board.

Should I suspect C12? Why would the too high RIGHT channel B+ have the LEFT channel cathode resistor run hot?

Once again, all I did was remove the screw down board connectors and direct solder the off-board components. Honest!
Does V11 light up? It sounds like it's not drawing any current from B+ and that is why the voltage across that OPT is the same between the red and blue wires. R17/27 will get fairly hot in operation. R17 is cool because your V11 is not passing any cathode current. What is the voltage across R27?

Please measure these DC voltages (with your meter references to ground):

1) Both sides of C11.

2) Both sides of R17.

3) Both sides of R18.

Quote:
Originally Posted by BillEpstein View Post
Took some more measurements and there's 31 Volts!!!on V11 Filament.
There is a DC offset on the heater winding, provided by the divider R3 and R4. This is normal. You need to check the AC voltage on the heater across the heater pins themselves (not relative to ground).
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Old 14th July 2011, 02:22 AM   #4
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Quote:
Originally Posted by rknize View Post
Does V11 light up?
Please measure these DC voltages (with your meter references to ground):

1) Both sides of C11.

2) Both sides of R17.

3) Both sides of R18.



There is a DC offset on the heater winding, provided by the divider R3 and R4. This is normal. You need to check the AC voltage on the heater across the heater pins themselves (not relative to ground).
V11 glows too brightly and I did measure the 31 volts at pins 7&8. The measurements you mention will have to wait until at least tomorrow.

Really appreciate the help.
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Old 14th July 2011, 02:54 AM   #5
rknize is offline rknize  United States
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Can you be a bit more specific about what is "glowing too brightly"? The filament inside the cathode is supposed to glow and the cathode itself also glows when hot. The tube plate should never glow. What is glowing too brightly?
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Old 14th July 2011, 02:18 PM   #6
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Quote:
Originally Posted by BillEpstein View Post
V11 glows too brightly and I did measure the 31 volts at pins 7&8. The measurements you mention will have to wait until at least tomorrow.

Really appreciate the help.
V11 filament glows MORE brightly than V21.

C11 reads 111vDC to the outside of the board, a low 30s mVolt reading at the inside.

R17 0-0
R18 490-490
R27 0-38vDC

6CA7 power tubes

V21 V11
1 .5mV 38vDC
2 31vDC 31vDC
3 490vDC 465vDC
4 490 465
5 91mV no reading
6 no reading no reading
7&8 31vDC 6.2vDC

No reading on 5 and 6 is mVs trending up or down

********Hold the phone......, the V11 and V21 power readings are reversed from my original post, so is which cthode resistor gets hot. It was R17 and now it's R27. I didn't keep track of which power tubes went where so it must be a bad tube. Do the plate, cathode grid readings support that?

Last edited by BillEpstein; 14th July 2011 at 02:23 PM.
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Old 15th July 2011, 01:54 AM   #7
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If the problem follows the tube, then yeah. It's a bad tube.
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