Input grid to ground, measured from before the grid stopper (ie incl. the grid stopper) is 8M one side and 12M the other.
But SY, what is this diode you are talking about? I don;t have any diode anywhere near the phase splitter?!?
Fran
But SY, what is this diode you are talking about? I don;t have any diode anywhere near the phase splitter?!?
Fran
OK, if that's the input grid to ground, you haven't got grid leak resistors connected. This would definitely explain the low plate voltage.
And there's a diode that goes from phase splitter grid to cathode, just to protect it at turn-on. It should be set up with cathode (banded end) to phase splitter cathode.
And there's a diode that goes from phase splitter grid to cathode, just to protect it at turn-on. It should be set up with cathode (banded end) to phase splitter cathode.
OK, where do the grid leak R go? Damn, I've missed something somewhere haven't I?
Will an ordinary 1N4007 diode be OK - and just to ensure against stupidity, that would go from pin 7 to 8 with the band to pin 8?
**************
The 630-hlmp-6000 (mouser P/N) measured at 1.6V with the 9V battery/1KR trick.
But be warned - they are tiny. If it wasn't for the leads they would be smt size. Not made for thick fingers!
Fran
Will an ordinary 1N4007 diode be OK - and just to ensure against stupidity, that would go from pin 7 to 8 with the band to pin 8?
**************
The 630-hlmp-6000 (mouser P/N) measured at 1.6V with the 9V battery/1KR trick.
But be warned - they are tiny. If it wasn't for the leads they would be smt size. Not made for thick fingers!
Fran
No, no dice I'm afraid.
I added in the grid leak R - grid to GND now measures 95-110K. I also added the diode as per the instructions.
But the voltage is still low. And I found something else - I was thinking about connecting the star ground point to earth and said I'd check to see was there any V across it. Turns out there was about 30V (DC) between the circuit ground and mains earth.
So I joined these together with a jumper. However voltages haven't changed all that much:
Channel 1:
pin 1 39.8V
pin 2 -43mV
pin 3 0.98V
pin 6 varies, but approx 1.5V
pin 7 39.8V
pin 8 39.6V
Channel 2:
pin 1 24.5V
pin 2 400mV
pin 3 316mV
pin 6 10V
pin 7 24.5V
pin 8 24.25V
Definitely I have made a right good balls up somewhere along the way. I just can't see where. B+ is steady at 350V.
What the hell have I done wrong!?!
Fran
on the plus, side, and just to give me a break from looking at the wiring, I made up the 2 LED arrays and fitted them in. They are small - much smaller than I thought they would be. I didn't fit the EL84 yet so I don't know if there are other problems there too.
I added in the grid leak R - grid to GND now measures 95-110K. I also added the diode as per the instructions.
But the voltage is still low. And I found something else - I was thinking about connecting the star ground point to earth and said I'd check to see was there any V across it. Turns out there was about 30V (DC) between the circuit ground and mains earth.
So I joined these together with a jumper. However voltages haven't changed all that much:
Channel 1:
pin 1 39.8V
pin 2 -43mV
pin 3 0.98V
pin 6 varies, but approx 1.5V
pin 7 39.8V
pin 8 39.6V
Channel 2:
pin 1 24.5V
pin 2 400mV
pin 3 316mV
pin 6 10V
pin 7 24.5V
pin 8 24.25V
Definitely I have made a right good balls up somewhere along the way. I just can't see where. B+ is steady at 350V.
What the hell have I done wrong!?!
Fran
on the plus, side, and just to give me a break from looking at the wiring, I made up the 2 LED arrays and fitted them in. They are small - much smaller than I thought they would be. I didn't fit the EL84 yet so I don't know if there are other problems there too.
Those numbers mean you've made a systematic mistake. I'll bet you've got some wiring switched between the input tube and the phase splitter.
133k to pin 1.
Grid stopper (I think it was 1k) to pin 2, with the grid leak and input at the other end of it.
1k to ground and 6k8 from transformer connect at pin 3.
Pin 1 and pin 7 are connected together via a grid stopper resistor, 1k. 47k to B+ at pin 6, 47k to ground at pin 8.
Right?
(Equivalently, you could make 6,7,8 the input and 1,2,3 the phase splitter).
133k to pin 1.
Grid stopper (I think it was 1k) to pin 2, with the grid leak and input at the other end of it.
1k to ground and 6k8 from transformer connect at pin 3.
Pin 1 and pin 7 are connected together via a grid stopper resistor, 1k. 47k to B+ at pin 6, 47k to ground at pin 8.
Right?
(Equivalently, you could make 6,7,8 the input and 1,2,3 the phase splitter).
OK,
All correct except I have a straight link from pin 1 to 7 - no grid stopper in there.
The grid stopper was spec'd at 1.5K I think.
Would the missing grid stopper from pin 1 to pin 7 do it?
Fran
All correct except I have a straight link from pin 1 to 7 - no grid stopper in there.
The grid stopper was spec'd at 1.5K I think.
Would the missing grid stopper from pin 1 to pin 7 do it?
Fran
No, it would be more likely to be the cause of HF oscillation.
OK, resistances to ground from pin 1, 2, 7,and 8? Resistance to the B+ rail from pin 1 and 6?
OK, resistances to ground from pin 1, 2, 7,and 8? Resistance to the B+ rail from pin 1 and 6?
OK,
amp powered off:
pin1 - GND: open circuit
pin2 - GND: 445K
pin7 - GND: open
pin 8 - GND: 70k
pin 1- B+: 400K
pin 6 - B+: reading fluctuates, but around 700K
amp powered on:
pin1 - GND: can't get a reading, meter reads 0R, flicks to kOhm range then back to 0
pin2 - GND: open
pin7 - GND: as per pin1
pin 8 - GND:as per pin 1
pin 1- B+: 0R
pin 6 - B+: 0R
Fran
amp powered off:
pin1 - GND: open circuit
pin2 - GND: 445K
pin7 - GND: open
pin 8 - GND: 70k
pin 1- B+: 400K
pin 6 - B+: reading fluctuates, but around 700K
amp powered on:
pin1 - GND: can't get a reading, meter reads 0R, flicks to kOhm range then back to 0
pin2 - GND: open
pin7 - GND: as per pin1
pin 8 - GND:as per pin 1
pin 1- B+: 0R
pin 6 - B+: 0R
Fran
Ouch! Don't try taking resistance readings with the power on!
OK, you clearly have some wiring errors. From pin 3 to ground should be about 950R, pin 8 to ground should be about 47k. Pin 1 to B+ should be 133k, pin 6 to B+ should be 47k. Likewise, from the far end of pin 8's 47k to ground, there should be a short. From the far end of the 133k to B+ should be a short.
If you've got a nearby person who can trace your work and compare it to the schematic, now's the time to get a fresh set of eyes in there.
OK, you clearly have some wiring errors. From pin 3 to ground should be about 950R, pin 8 to ground should be about 47k. Pin 1 to B+ should be 133k, pin 6 to B+ should be 47k. Likewise, from the far end of pin 8's 47k to ground, there should be a short. From the far end of the 133k to B+ should be a short.
If you've got a nearby person who can trace your work and compare it to the schematic, now's the time to get a fresh set of eyes in there.
Thanks yet again SY, and apologies for my klutz...
I am going to rewire this completely in a few hours when I get home from work. I will check as many things as possible along the way. One thing I did notice (and I will have to go back and check it again) is that if I try to measure the resistance of the 135K (ie the 2 x 270K) with the 10K||330pF I don't get 135K. So when I rewire it I think I will leave out the 10K||330pF to simplify matters. They can be added back in later.
I have emailed a friend who lives about 2 hours away and if I can't get this sorted in the next few attempts, I will seek other eyes.
*****************
Can I go ahead to test the EL84 power section - would I want to disconnect the feed through the coupling caps first? If there are also problems there, then I definitely need help and need to be less ambitious.
Fran
I am going to rewire this completely in a few hours when I get home from work. I will check as many things as possible along the way. One thing I did notice (and I will have to go back and check it again) is that if I try to measure the resistance of the 135K (ie the 2 x 270K) with the 10K||330pF I don't get 135K. So when I rewire it I think I will leave out the 10K||330pF to simplify matters. They can be added back in later.
I have emailed a friend who lives about 2 hours away and if I can't get this sorted in the next few attempts, I will seek other eyes.
*****************
Can I go ahead to test the EL84 power section - would I want to disconnect the feed through the coupling caps first? If there are also problems there, then I definitely need help and need to be less ambitious.
Fran
Sorry for the confusion,
yes the 10k is in series with the 330pf, but then all that is in parallel with the 135K. In this order:
B+>>10K>>330pF>>to socket pin
The 135K is wired between the B+ and 10K/330pF and socket pin.
If that makes any sense!
Fran
yes the 10k is in series with the 330pf, but then all that is in parallel with the 135K. In this order:
B+>>10K>>330pF>>to socket pin
The 135K is wired between the B+ and 10K/330pF and socket pin.
If that makes any sense!
Fran
That's how it's supposed to be, yes. But you've indicated 400k between the plate and the B+ supply instead of 133k...
Yes, fresh set of eyes needed! 😀
Yes, fresh set of eyes needed! 😀
Hello,
Are those measurements with the tube in the socket?
Are you sure you got the pins of the tube alright? (on duncanamp pages you can see that pin config. and that shows the tube from the underside).
If you take the tube out of the socket you should read what SY has indicated otherwize you clearly have a wrong value/defect component on that pin.
/Axel
Are those measurements with the tube in the socket?
Are you sure you got the pins of the tube alright? (on duncanamp pages you can see that pin config. and that shows the tube from the underside).
If you take the tube out of the socket you should read what SY has indicated otherwize you clearly have a wrong value/defect component on that pin.
/Axel
Hi John,
Yes, you might well be able to help, I've emailed stephen as well. When are you free??!!!! I will be home in an hour or so and I might give you a ring then. Would you email me your number?
**************
feppe:
I do believe I have the pins correct. Looking into the chassis pin 1 is just to the left of the gap and pin 2 is next one going clockwise.
This is with the tube in the socket.
Arrghh, don't tell me I should be measuring al this with the valve out!
Fran
Yes, you might well be able to help, I've emailed stephen as well. When are you free??!!!! I will be home in an hour or so and I might give you a ring then. Would you email me your number?
**************
feppe:
I do believe I have the pins correct. Looking into the chassis pin 1 is just to the left of the gap and pin 2 is next one going clockwise.
This is with the tube in the socket.
Arrghh, don't tell me I should be measuring al this with the valve out!
Fran
For the resistance readings, it won't matter whether the tube is in or not, so don't worry too much.
OK, hold on:
Would
Pin 1 - GND - 90.7V
Pin 8 - GND - 89.1
Pin 6 - GND - 340V
on both channels look more correct? Thats with the valves out.
Fran
Would
Pin 1 - GND - 90.7V
Pin 8 - GND - 89.1
Pin 6 - GND - 340V
on both channels look more correct? Thats with the valves out.
Fran