Cold means switched off amp, everything at roomtemperature. Again? Are you serious? How often do you thinck i would want to repeat my self? Please reraed what has been written, and read more carefully, please! There is a limit to my patience!
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I got the cold part. There were a lot of measurements you wanted. Some I had, some you didn't need after all. Not trying to be difficult. Sorry to **** you off - wasn't my intention! Physically a challenge to get the amps open and didn't want to miss something in your posts.
3 chokes and 1 OPT primary resistance measurements is not a lot. I need those measurement results to get as close as possible to reality. Till now, my caluculations where based on datasheet values but the real values may differ by tolerances of manufacturing this parts.You can measure them when the amp has been switched off, tubes and everything has cooled down to roomtemperature. Measure also with reversed probes just to make sure. Should there be a difference in the results you must desolder one side of the winding and measure again.
Not a lot I agree. I just wanted to make sure I provided ALL the measurements you wanted. Not trying to be lazy - just complete! Sorry if it came across otherwise!
6H chokes (C-14X Triad) - 151Ω and 149Ω
150H choke (156CHammond) - 3.4KΩ
OT (Monolith) -279Ω
All checked with probes reversed. Fluke 179 meter.
Thanks!
150H choke (156CHammond) - 3.4KΩ
OT (Monolith) -279Ω
All checked with probes reversed. Fluke 179 meter.
Thanks!
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"All checked with probes reversed." Normally the method is to check with probes shorted to confirm approx zero ohm reading.
Trobbins, goes without saying to null out probe resistance when measurin low resistances, but the lowest expected was around 150 ohm, so a little proberesistance would not change the results when measuring those components. But in circuit measurements can get f...d up by all kind of things, so i thougth, as WntrMute is unexpirienced, reversed probe checking would add propability to get accurate results.
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I was reading in another thread about the total mA draw. https://www.diyaudio.com/community/threads/where-do-all-those-mas-go-on-reckoning-the-total-load-seen-by-the-pt.
This statement was made.
This statement was made.
Would this be a way a simpleton like me could get the total draw for my amp?
That would be applicable for your 2nd choke, as it is operating in a CLC filter, so the AC voltage is relatively low and shouldn't concern a meter. Safety is the main concern imho.
That seemed easy. I checked the voltage across the second choke which has a measured resistance of 150Ω.
At 60mA on the meter I measured 10.1V =>67.3 mA
At 50mA on the meter I measured 8.4V => 56 mA
At 40mA on the meter I measured 6.9V => 46 mA
The measured voltages hunt around a bit I'm assuming due to the "unsettled" power supply.
At 60mA on the meter I measured 10.1V =>67.3 mA
At 50mA on the meter I measured 8.4V => 56 mA
At 40mA on the meter I measured 6.9V => 46 mA
The measured voltages hunt around a bit I'm assuming due to the "unsettled" power supply.
WntrMute, with the new values, I calculated:
current trough R, 330+47k, = 406/377 = 1.08mA
current through EF86, (Ik) = 3.33/2.21 = 1.51mA
current through150H choke = 15.6/3.40 = 4.59mA
above current summed are 7.18mA + 60mA meter current = 67.18mA total
As you can see, now, that we have the measured resistances of choke 3400 and OPT 279 ohm (instead of datasheet valuesi 3700 and 338ohm)
there is practically no difference between calculated and what you have now measured 😉
Current through OPT, 14V/279 = 50.18mA
From 50.18 we deduct the current trough the 470k feedback resistor, 392V-112V=280V, 280/470k=0.6mA
3c24 anode current Ia = 50.18-0.6= 49.58mA,
3C24 anode dissipation, Pa = Ua x Ia = 392V x 49.58mA = 19.44W
Metered 3c24 cathode current is 60mA.
From the cathode current we deduct the anode current to get grid current.
3c24 grid current Ig = 60 - 49.58 = 10.42mA
3C24 grid dissipation Pg = 15.6 x 10.42 = 162.55mW (gridcurrent is the reason for the difference between 67.3 and 56, 46mA when you lower from 60mA to 50 or 40mA cathode current (metercurrent).
6S4A cathode and anode current is the same because it is, contrary to 3C24, negatively biased so no gridcurrent.
This current, Ik = Ia, flows partly through the choke 4.59mA, and partly trough the 3C24 grid 10.42mA, together 15.01mA.
To get the real cathode to anode voltage we deduct the voltage loss from the 220 ohm anode resistor and the 15.6V lost in the cathode cicuit.
6S4A anode to cathode voltage Uak = 406-3.3-15.6 = 387.1V
6S4A anode dissipation Pa = 387.1 x 15.01 = 5.81W
As you can see now, the real values of the choke and OPT resistances has a huge impact on the calculations.
With the real values, the 6S4A dissipation fell from a dangerous level of over 9W to a healthy 5.8W.
The 3C24 dissipitation rose from meager 16W to almost 20W.
Now, if 60mA on the meter is the current you gonna use we can safely say that B+ 406V at 67.3mA is all you need from your PS.
To those 406V we now have to add the voltage loss of chokes, rectifiers and the power transformer.
My guestimate for the dc-voltage losses is roughly 20-25V for the chokes, I would thinck something like 20V for the 866A , and 8-10V for the transformer, all together 48-55V.
So, we need a total of 454 -461Vdc, wich calls for a transformer no load voltage of 504-512V.
Your transformer has a estimated no load voltage of 473V, so we are 31-39Vac, 28-35Vdc short.
This seems a lot, could you tell me what B+ voltage you really get with 60mA on the meter?
(amp must be running a couple of hours to heat up proper before measurement)
B.t.w, I came up with an second option to get you where you want to be, but first i need the real B+ with 60mA on the meter.
current trough R, 330+47k, = 406/377 = 1.08mA
current through EF86, (Ik) = 3.33/2.21 = 1.51mA
current through150H choke = 15.6/3.40 = 4.59mA
above current summed are 7.18mA + 60mA meter current = 67.18mA total
As you can see, now, that we have the measured resistances of choke 3400 and OPT 279 ohm (instead of datasheet valuesi 3700 and 338ohm)
there is practically no difference between calculated and what you have now measured 😉
Current through OPT, 14V/279 = 50.18mA
From 50.18 we deduct the current trough the 470k feedback resistor, 392V-112V=280V, 280/470k=0.6mA
3c24 anode current Ia = 50.18-0.6= 49.58mA,
3C24 anode dissipation, Pa = Ua x Ia = 392V x 49.58mA = 19.44W
Metered 3c24 cathode current is 60mA.
From the cathode current we deduct the anode current to get grid current.
3c24 grid current Ig = 60 - 49.58 = 10.42mA
3C24 grid dissipation Pg = 15.6 x 10.42 = 162.55mW (gridcurrent is the reason for the difference between 67.3 and 56, 46mA when you lower from 60mA to 50 or 40mA cathode current (metercurrent).
6S4A cathode and anode current is the same because it is, contrary to 3C24, negatively biased so no gridcurrent.
This current, Ik = Ia, flows partly through the choke 4.59mA, and partly trough the 3C24 grid 10.42mA, together 15.01mA.
To get the real cathode to anode voltage we deduct the voltage loss from the 220 ohm anode resistor and the 15.6V lost in the cathode cicuit.
6S4A anode to cathode voltage Uak = 406-3.3-15.6 = 387.1V
6S4A anode dissipation Pa = 387.1 x 15.01 = 5.81W
As you can see now, the real values of the choke and OPT resistances has a huge impact on the calculations.
With the real values, the 6S4A dissipation fell from a dangerous level of over 9W to a healthy 5.8W.
The 3C24 dissipitation rose from meager 16W to almost 20W.
Now, if 60mA on the meter is the current you gonna use we can safely say that B+ 406V at 67.3mA is all you need from your PS.
To those 406V we now have to add the voltage loss of chokes, rectifiers and the power transformer.
My guestimate for the dc-voltage losses is roughly 20-25V for the chokes, I would thinck something like 20V for the 866A , and 8-10V for the transformer, all together 48-55V.
So, we need a total of 454 -461Vdc, wich calls for a transformer no load voltage of 504-512V.
Your transformer has a estimated no load voltage of 473V, so we are 31-39Vac, 28-35Vdc short.
This seems a lot, could you tell me what B+ voltage you really get with 60mA on the meter?
(amp must be running a couple of hours to heat up proper before measurement)
B.t.w, I came up with an second option to get you where you want to be, but first i need the real B+ with 60mA on the meter.
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Measuring also the no load voltage of your transformer would take out much guessing about the voltage 866A and transformer losses.
Would you be able to SAFELY measure the no load AC voltage betwee ground and one of the 866A anode caps ?
(both 866A MUST be removed from the amp when you do that)
But please be carefull, would be best to take both 866A out, clip some isolated crocodile clamps on one of the anodecaps (isolate the caps properly so they cannot fall down and short or something) and one to ground and touch nothing but the on/off switch.
And remember, it is at least 470V AC !!!
Would you be able to SAFELY measure the no load AC voltage betwee ground and one of the 866A anode caps ?
(both 866A MUST be removed from the amp when you do that)
But please be carefull, would be best to take both 866A out, clip some isolated crocodile clamps on one of the anodecaps (isolate the caps properly so they cannot fall down and short or something) and one to ground and touch nothing but the on/off switch.
And remember, it is at least 470V AC !!!
Unloaded the PT produces 944V end to end and 472 each side.
@60mA, the B+ is 387VDC.
Thanks for your work!
@60mA, the B+ is 387VDC.
Thanks for your work!
Ok, voltage drop is because of the positiv temperatur coefficient of copper.
With 384V we need a quadrupler, or a 6VA 30V 200mA transformer with 10% regulation and a 1A, low voltage biridge rectifier, both solutins have ups and donws, i will tell you later about, if you are interrested.
With 384V we need a quadrupler, or a 6VA 30V 200mA transformer with 10% regulation and a 1A, low voltage biridge rectifier, both solutins have ups and donws, i will tell you later about, if you are interrested.