Build coming together nicely - Page 5

jrobson · 21st January 2012, 01:08 PM

New tubes, still same problem, plates are in the minus, once B+ comes up goes to 0v then stays there... I think I'll find a solid state that is suitable for the Sachiko's rather.

jrenkin · 21st January 2012, 01:20 PM

Did you wire in the volume pot and the 5482 grid leak resistors? I found the amp wouldn't work at all without the 5842 grid leak installed and properly grounded. It oscillated such that nothing else worked.

jrobson · 21st January 2012, 02:13 PM

Hi
Thanks, I wired the pot, no difference.
Which ones are the grid leak resistors?

jrenkin · 21st January 2012, 02:42 PM

R8 and R19, 121k to ground. Also, don't forget the grid stopper for the 5842, it is not in the schematic, but is in the parts list. 4.7k on the 5842 grid.

jrobson · 21st January 2012, 02:47 PM

Yes R8 and R19 are in, but not the grid stopper, if it wasn't part of the manual it isn't in, but I'll have to check my stash quick to see if it's there, I bought everything on the parts list I'm sure.

jrobson · 21st January 2012, 02:56 PM

Found the 4.7k's, I followed the manual so 1k's in now, I'll replace them quick.

Thanks!

jrobson · 21st January 2012, 03:02 PM

Sorry my mistake, already 4.7k... I think I had extra because of a minimum order requirement for those

jrenkin · 21st January 2012, 03:08 PM

Nuts, so that's not it.

jrobson · 21st January 2012, 03:15 PM

Yeah, you had me excited there for a moment, ha ha ha...

jrenkin · 21st January 2012, 03:35 PM

I retread this thread. You have zero volts on both 5842 plates and the pins of the ccs that aren't directly connected to B+. if you are referencing to a correct ground there must be a short somewhere to that ground. It is probable not the tubes or ccs because it would have to be a fault with both, and even ten I would think you would see at least some voltage, not zero. So there has to be a short.
If you have enough spare parts, rewire the driver circuit point to point and jumper it in and try again. Isolate the stage by not connecting the coupling cap. You should be able to at least establish the voltages in isolation, although they may be high since there is little load on the circuit.

Also, you can try a test without the ccs, you would use a resistor instead, large enough to drop from operating B+ to the goal 175v at roughly 10ma. Just to see.

Good luck! Don't give up. This is a well proven circuit and it will work.

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21st January 2012, 01:08 PM	#41
jrobson diyAudio Member Join Date: Aug 2011	New tubes, still same problem, plates are in the minus, once B+ comes up goes to 0v then stays there... I think I'll find a solid state that is suitable for the Sachiko's rather.

21st January 2012, 01:20 PM	#42
jrenkin diyAudio Member Join Date: Nov 2007 Location: Denver, Colorado	Did you wire in the volume pot and the 5482 grid leak resistors? I found the amp wouldn't work at all without the 5842 grid leak installed and properly grounded. It oscillated such that nothing else worked.

21st January 2012, 02:13 PM	#43
jrobson diyAudio Member Join Date: Aug 2011	Hi Thanks, I wired the pot, no difference. Which ones are the grid leak resistors?

21st January 2012, 02:42 PM	#44
jrenkin diyAudio Member Join Date: Nov 2007 Location: Denver, Colorado	R8 and R19, 121k to ground. Also, don't forget the grid stopper for the 5842, it is not in the schematic, but is in the parts list. 4.7k on the 5842 grid.

21st January 2012, 02:47 PM	#45
jrobson diyAudio Member Join Date: Aug 2011	Yes R8 and R19 are in, but not the grid stopper, if it wasn't part of the manual it isn't in, but I'll have to check my stash quick to see if it's there, I bought everything on the parts list I'm sure.

21st January 2012, 02:56 PM	#46
jrobson diyAudio Member Join Date: Aug 2011	Found the 4.7k's, I followed the manual so 1k's in now, I'll replace them quick. Thanks!

21st January 2012, 03:02 PM	#47
jrobson diyAudio Member Join Date: Aug 2011	Sorry my mistake, already 4.7k... I think I had extra because of a minimum order requirement for those

21st January 2012, 03:08 PM	#48
jrenkin diyAudio Member Join Date: Nov 2007 Location: Denver, Colorado	Nuts, so that's not it.

21st January 2012, 03:15 PM	#49
jrobson diyAudio Member Join Date: Aug 2011	Yeah, you had me excited there for a moment, ha ha ha...

21st January 2012, 03:35 PM	#50
jrenkin diyAudio Member Join Date: Nov 2007 Location: Denver, Colorado	I retread this thread. You have zero volts on both 5842 plates and the pins of the ccs that aren't directly connected to B+. if you are referencing to a correct ground there must be a short somewhere to that ground. It is probable not the tubes or ccs because it would have to be a fault with both, and even ten I would think you would see at least some voltage, not zero. So there has to be a short. If you have enough spare parts, rewire the driver circuit point to point and jumper it in and try again. Isolate the stage by not connecting the coupling cap. You should be able to at least establish the voltages in isolation, although they may be high since there is little load on the circuit. Also, you can try a test without the ccs, you would use a resistor instead, large enough to drop from operating B+ to the goal 175v at roughly 10ma. Just to see. Good luck! Don't give up. This is a well proven circuit and it will work.