Are your both vertical resistors same 1K6 value by the way? Because its handwritten a bit weird on the schematic.
Whoa... are you saying that the voltage dividing resistors are not a 1K6 and a 1K but two 1K6 resistors? I have a 1k6 to ground and a 1K between the base of the top BJT and the LED.
Maybe this is it? It really looks like a 1K to me...
Kofi
Maybe this is it? It really looks like a 1K to me...
Kofi
By the way, in gingertube's description of the resistors he wrote the following:
2) If you don't have a separate 5V winding to generate the -12 to -13V supply for the diffamp CCS then use what ever low voltage winding you have. The voltage isn't critical - anywhere between about -7 and -30 would be OK. You may have to adjust the 1K6 and 1K values in the current source to keep LED current at around 2 to 5 mA.
Just offering this as evidence that the intent seems to be a 1K and a 1K6...
Kofi
2) If you don't have a separate 5V winding to generate the -12 to -13V supply for the diffamp CCS then use what ever low voltage winding you have. The voltage isn't critical - anywhere between about -7 and -30 would be OK. You may have to adjust the 1K6 and 1K values in the current source to keep LED current at around 2 to 5 mA.
Just offering this as evidence that the intent seems to be a 1K and a 1K6...
Kofi
Don't know, I just spotted the narrow hand written value and wondered. I will run a simulation for you. -13V to 0V is your build's CCS contained, correct?
I'm getting about -13V at the - terminal of the cap feeding the CCS.
Also, I checked the voltage drop across the 470R in the CCS and I came up with -3.13VDC, which I believe is .006A-- WAY too little... This should mean something is wrong with the CCS, correct? Remember that the B+ is around 390VDC, which is WAY too high...
Any correlation possible?
Thanks for all the help. I know I'm close here.
Kofi
Also, I checked the voltage drop across the 470R in the CCS and I came up with -3.13VDC, which I believe is .006A-- WAY too little... This should mean something is wrong with the CCS, correct? Remember that the B+ is around 390VDC, which is WAY too high...
Any correlation possible?
Thanks for all the help. I know I'm close here.
Kofi
.006A = 6mA ! Large enough.
But, what is the voltage accros the LED ?
What is the voltage accros the 1K in the emiter of the bottom BJT ?
Also, "0V at ECC803S" means "Ground".
The current to pull from the tubes tails is 1mA. As drawn I bet the CCS will pull 1.4mA !
But, what is the voltage accros the LED ?
What is the voltage accros the 1K in the emiter of the bottom BJT ?
Also, "0V at ECC803S" means "Ground".
The current to pull from the tubes tails is 1mA. As drawn I bet the CCS will pull 1.4mA !
Not sure. Mrs. Annan made me go out to lunch with the family. That woman has seriously screwed up priorities.
Anyone else know the answer?
Anyone else know the answer?
jjustsay the reply. I think I measure about 2v across the led. I can measure the other voltage when I get home.
Maybe the led doesn't need to light to be working correctly here? Do I have a red herring and the fault is really elsewhere?
Maybe the led doesn't need to light to be working correctly here? Do I have a red herring and the fault is really elsewhere?
Everything looks in order if you have wired correctly and you have no dead BJTs. A 1.7V Vf Red LED will use 3.5mA and the CCS will be biased and will pull 1mA. I loaded a single 12AT7 tube to check it as a whole. That would pull 4.55mA via the 470R but if your LED's Vf is a bit stronger circa 2V it can easily set near 1.4mA CCS. Now tell me that your LED is IR and you can't see it alight.😀 Nah, just joking.😉
Attachments
Ok, so no IR led here. If its not lit I assume that means something is wrong still, correct?
I'll measure the voltages in a bit once I get home.
Thanks so much for the advice!
Kofi
I'll measure the voltages in a bit once I get home.
Thanks so much for the advice!
Kofi
Something can be wrong either in connections or parts. See that the 1k6 and 1k resistors show drop across each that can be showing towards 3-5mA through them for instance...find circa 1V-1.4V across the 1K opposite to the LED and so on. If you can't find those clues, inspect connections against schematic thoroughly, if nothing's still in error change LED and BJTs. A dried out joint, a wrong value for a resistor even...
OK-- so here are the voltages I'm seeing across the resistors / LED.
1K6: 2.9V
1K from supply: 2.5V
LED: 7.3V
1K between BJTs and LED: 6.6V (Right); .11V (Left)
Looks like a problem across the LEDs and an inconsistency with the 1K resistor above.
I'm still poking around, but is anyone enlightened by this?
Kofi
1K6: 2.9V
1K from supply: 2.5V
LED: 7.3V
1K between BJTs and LED: 6.6V (Right); .11V (Left)
Looks like a problem across the LEDs and an inconsistency with the 1K resistor above.
I'm still poking around, but is anyone enlightened by this?
Kofi
Last edited:
Another pesky question:
Do I have the balance pot on the ECC803S wired correctly? I have it as:
Pin 3 sees 470R resistor and leg 3 of the pot
Pin 8 sees 470R resistor and leg 1 of the pot
Leg 2 of the pot sees the two ends of the 470R resistors AND the CCS in
Is this right?
Kofi
Do I have the balance pot on the ECC803S wired correctly? I have it as:
Pin 3 sees 470R resistor and leg 3 of the pot
Pin 8 sees 470R resistor and leg 1 of the pot
Leg 2 of the pot sees the two ends of the 470R resistors AND the CCS in
Is this right?
Kofi
By the way-- both the plat and the cathode of the ECC803S are seeing about 3V, which makes sense as I suspect the CCS is not providing any appreciable current...
Kofi
Kofi
It must be forcing too much Ip. So the 1K to the right (from bottom BJT to -V) has 6.6V across? That is 6.6mA when it should do 1mA. Pulls down hard on the 220K plate resistors if so. See if the BC547s show Vbe 0.6-0.7V. Maybe they got destroyed when you had the PSU problems and need changing.
- Status
- Not open for further replies.