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.
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.
Hmmm...I am not an expert, I hope one will chime in. I suggest trying the resistor instead of the ccs. This won't work as well in the final circuit, but might help you determine where the problem lies. Also, if at all possible, completely disconnect the output stage, even the mosfets, so you can see if it is causing a problem.
Pain in the...
Pain in the...
Thanks, it's not clear exactly what size is required and how to wire it in. Do I need to wire in between B+ and plate?
I'm using the online calculators, the previous one I used was a little too simplified. It appears that 45K is required to for the 450V @ 10ma.
Anyway from here: Voltage Divider Calculator
27.5K/17.5k = 45k
Is this correct?
I'm using the online calculators, the previous one I used was a little too simplified. It appears that 45K is required to for the 450V @ 10ma.
Anyway from here: Voltage Divider Calculator
27.5K/17.5k = 45k
Is this correct?
You don't need a voltage divider, just a resistive load. The ccs is a more ideal load, many les complicated amps use simple resistive loads. So all you need is a single resistor between B+ and the plate. The value of this resistor is determined by the B+, the desired plate voltage, and cathode bias, which then determines the current in the tube. Since the current is not constant, the load line on the tube curves is sloped rather than a more ideal horizontal as with a ccs. With a pure resistor load, the tube will operate in a less linear fashion and not achieve the full MU of the tube, which in this case may be inadequate, although may be fine and certainly will for testing.
I ran a simulation on tubecad, and I thought less than 45 K was needed, but my B+ was lower.
It is 6am here and the baby has a fever, so I can only try again a little later.
But if you put in a 45k and set the bias low, you may just get too low a plate voltage. Play with the bias a bit and measure it all. That may be adequate to determine if the problem is the ccs or something downstream.
Be sure the resistor you use is rated enough to handle the voltage drop at the current of the tube. That could require a 3 or even 5 watt resistor.
I have took my of these ccs, I could mail some out, but don't know how that is to S.A. From Denver...
I ran a simulation on tubecad, and I thought less than 45 K was needed, but my B+ was lower.
It is 6am here and the baby has a fever, so I can only try again a little later.
But if you put in a 45k and set the bias low, you may just get too low a plate voltage. Play with the bias a bit and measure it all. That may be adequate to determine if the problem is the ccs or something downstream.
Be sure the resistor you use is rated enough to handle the voltage drop at the current of the tube. That could require a 3 or even 5 watt resistor.
I have took my of these ccs, I could mail some out, but don't know how that is to S.A. From Denver...
Thank you again, good luck with the baby.
I have around 450v B+, I'll pick up some big 45K resistors tomorrow and see what happens... Is there a way to test a CCS off board?
Thanks for the offer, let me see if I can confirm where the problem lies and I can purchase the CCS's off you if you have some spare.
I have around 450v B+, I'll pick up some big 45K resistors tomorrow and see what happens... Is there a way to test a CCS off board?
Thanks for the offer, let me see if I can confirm where the problem lies and I can purchase the CCS's off you if you have some spare.
I'll try and run a simulation again later and let you know some more accurate values to pick up. If I can get the right number, you could try it in the entire circuit to drive the output and see if you can hear music! It wouldn't be optimal in this circuit, but it would be encouraging to be able to hear it.
When I had the problem with my build, by not grounding the 5842 grid leak, I thought is was the ccs so I bought a bunch. I will use some in other circuits, but...they are definitely not $30 each. I paid more like $4, maybe less. And I have too many.
I would measure some voltages on mine, but i didn't use the pcb, rather made a semi- point to point and modular build. Then I jumpered it all together to test and now have the modules apart to build back into the chassis that my wood working skills are slow (and poor) at building and my daughters fevers have stymied me working on. She comes first after all. But side time is good to see if I can help you troubleshoot.
I am curious on your measures on the MOSFET. They seem a bit odd, but solid state devices defy me. That is why I suggested also trying the driver stage completely separate from the MOSFET and output stage.
Oh, since I didn't build on the pcb, I also have two unused pcb's around, since I believe in paying george for his intellectual property, but if somehow you found a fault in a board, or kill it unsoldering things,I could send one of those too.
When I had the problem with my build, by not grounding the 5842 grid leak, I thought is was the ccs so I bought a bunch. I will use some in other circuits, but...they are definitely not $30 each. I paid more like $4, maybe less. And I have too many.
I would measure some voltages on mine, but i didn't use the pcb, rather made a semi- point to point and modular build. Then I jumpered it all together to test and now have the modules apart to build back into the chassis that my wood working skills are slow (and poor) at building and my daughters fevers have stymied me working on. She comes first after all. But side time is good to see if I can help you troubleshoot.
I am curious on your measures on the MOSFET. They seem a bit odd, but solid state devices defy me. That is why I suggested also trying the driver stage completely separate from the MOSFET and output stage.
Oh, since I didn't build on the pcb, I also have two unused pcb's around, since I believe in paying george for his intellectual property, but if somehow you found a fault in a board, or kill it unsoldering things,I could send one of those too.
I have spare mosfets that I can try out as well but I would like to keep them in case of a rebuild, I've disconnected the coupling caps before and I couldn't get it to work then either, but a few things have changed since then so I'll give it another shot, I quite fancy the idea of a resistor to bypass the CSS just to see if anything else is wrong and to pinpoint the problem.
It looks like I might have to rebuild this if I want it working, a bit of a pain in the *** but maybe less hassle than to restart something else completely from scratch considering the investment in the power transformer, tubes, OPT's and caps, the lounge can look like a warzone for a few more weeks I suppose...
It looks like I might have to rebuild this if I want it working, a bit of a pain in the *** but maybe less hassle than to restart something else completely from scratch considering the investment in the power transformer, tubes, OPT's and caps, the lounge can look like a warzone for a few more weeks I suppose...
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