Your post #59:
OUCH!!
I should have noticed that one. In fact I did in my original test setup; too long between posts for my limited memory. My apology. If you have spare resistors, or perhaps even a spare pot of 220K (that B2 - B3 resistor) which you can adjust to slightly smaller (and measure afterwards), try to get V3 cathodes to about 100V, or while you measure, try get 110V or so across V3 anode-cathode(s). That will be a better operating point for V3.
No worry about the OPT. You are merely getting the effect of the winding resistances. You get 8V drop for B+ to anode, and 2V for B+ to screen. The G2 is tapped at about 20% of the total anode windings, thus it fits. From this the primary winding resistance comes to about 250 ohms, which is natural for that type of transformer.
OUCH!!
I should have noticed that one. In fact I did in my original test setup; too long between posts for my limited memory. My apology. If you have spare resistors, or perhaps even a spare pot of 220K (that B2 - B3 resistor) which you can adjust to slightly smaller (and measure afterwards), try to get V3 cathodes to about 100V, or while you measure, try get 110V or so across V3 anode-cathode(s). That will be a better operating point for V3.
No worry about the OPT. You are merely getting the effect of the winding resistances. You get 8V drop for B+ to anode, and 2V for B+ to screen. The G2 is tapped at about 20% of the total anode windings, thus it fits. From this the primary winding resistance comes to about 250 ohms, which is natural for that type of transformer.
OK. I have checked on the ultralinear operating condition at EICO HF-87 and it is quite simillar. The HF87 also runs 12AX7 anode voltage at about 120V.
It is tough to do DIY here due to lack of parts. For the resistor, I need to wait for Farnell to back order (1 week).
I will try to use fix resistor for adjusting the VB3+ due to high voltage.
It is tough to do DIY here due to lack of parts. For the resistor, I need to wait for Farnell to back order (1 week).
I will try to use fix resistor for adjusting the VB3+ due to high voltage.
I have swapped in the Rp3 from 220K to 180K. R12 (V3 cathode resistor ) is still 22k.
Below is the zero signal condition. (First I switch it on, then I go for a cup of coffee b4 I measure)
VB1+ 319.4V
VB2+ 301.5V
VB3+ 119.6V
V3 cathode = 79.2V
V3a anode = 238.9V, I= 1.9mA
V3b anode = 238V, I = 1.63mA
V3 Grid = 69.8V
V1 Cathode = 0.51V, I = 0.5mA
E (Filament, 6V6GT) = 6.4V AC
E (Filament V1, V3) = 6.3V DC
Picture will follow.
1. If I replace R12 to 18K, will I get V3 Anode - Cathode to 110V ?
2. How to calculate V3 cathode if I replace R12 to 18K?
3. Is the above operating condition good for listening ? No problem.
Ccschua,
To answer your question: Yes, you can listen under those conditions. But V3 will generate much 2nd harmonic distortion at the present low anode current. We do need to get that up to 2,8 - 3mA with about 120V anode-cathode voltage (I am plotting on characteristic graphs.
Again it is late and I will do new calculations in the morning, trying to change as few things as possible. We will get there yet. If you can immediately also measure the voltage over C9 and give the value of Rp1, it will help me.
Regards
To answer your question: Yes, you can listen under those conditions. But V3 will generate much 2nd harmonic distortion at the present low anode current. We do need to get that up to 2,8 - 3mA with about 120V anode-cathode voltage (I am plotting on characteristic graphs.
Again it is late and I will do new calculations in the morning, trying to change as few things as possible. We will get there yet. If you can immediately also measure the voltage over C9 and give the value of Rp1, it will help me.
Regards
Today, I throw in C8 with 1500uF 63V Nover capacitor, Riken 1K resistor at V1 gate stopper and new 47uF 50V capacitor across R2 [call this cap C2a].
I like the music now better than before.
Before I install cap C2a, the sound is very compress. After C2a, it sounds slightly more open and dynamic. ??
I like the music now better than before.
Before I install cap C2a, the sound is very compress. After C2a, it sounds slightly more open and dynamic. ??
at 15 C it is cold. Over here in equitorial we are burning hot day in day out.
The other area I look at improvement is the power supply.
The voltage at VB3+ seem to be wrong.
The ripple on V B1+ seems to be high. I wonder if this will cause harmonic distortion or it is intended.
The other area I look at improvement is the power supply.
The voltage at VB3+ seem to be wrong.
The ripple on V B1+ seems to be high. I wonder if this will cause harmonic distortion or it is intended.
An externally hosted image should be here but it was not working when we last tested it.
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