I am starting a new thread with new info. See thread Possible Transformer problems. Last night I verified I had 25mV of noise at output transformers. I had been suspecting the 6.3 volt tap on the Edcor power transformer had a problem. It was reading higher than it did when I built this amp two years ago.
It now reads 7.4 volts with no load and 6.8 with tubes in. With the 5842's out the heater voltage to the pins is 8 volts, OUCH!
My discovery is the noise at the output's does not change with all the tubes removed.
I need to get the 5842 heater voltage under control and eliminate the noise or buzz/hum.
It now reads 7.4 volts with no load and 6.8 with tubes in. With the 5842's out the heater voltage to the pins is 8 volts, OUCH!
My discovery is the noise at the output's does not change with all the tubes removed.
I need to get the 5842 heater voltage under control and eliminate the noise or buzz/hum.
two separate issues?
Agree, 7.4V heater voltage is too much when loaded. Do you have access to a variac? If so, adjust variac for 6.3V heater voltage, and then measure the primary AC. It should be lose to its specification; e.g. 115 or 120V.
With the information at hand, I do not see the connection with measured output noise. It seems these are two separate issues?
Agree, 7.4V heater voltage is too much when loaded. Do you have access to a variac? If so, adjust variac for 6.3V heater voltage, and then measure the primary AC. It should be lose to its specification; e.g. 115 or 120V.
With the information at hand, I do not see the connection with measured output noise. It seems these are two separate issues?
OK so I guess what is being said I can rule out pwr transformer?
I do not have a variac.
The tech at Edcor suggested I pad down the 6.3 volt secondary to equal 6.3. If I do that would the best place be the center tap? I will need some heavy duty resistors to use. Any guess what value and wattage I should use?
I do not have a variac.
The tech at Edcor suggested I pad down the 6.3 volt secondary to equal 6.3. If I do that would the best place be the center tap? I will need some heavy duty resistors to use. Any guess what value and wattage I should use?
Hi waltroman,
Are your heaters DC or AC?
-Chris
Are your heaters DC or AC?
Your power transformer can magnetically couple to the output transformers and output the 60 Hz supply waveform. You can try rotating the transformers to where you get minimal hum, ideally this would be at 90 ° from the power transformer. There are times when you will be stuck with an odd angle too. Right now it's a bit late since you have built the chassis.
-Chris
series resistor
You need to know the total heater current and the measured heater supply voltage.
Let's say you want to drop the heater supply voltage by 1.0 volt and the heater current is 3A. The you will need a series resistor of 1/3 = 0.33 ohm (R = V/I). The power dissipated by this resistor will be 3*3*0.33 = 3 Watt (P = I^2 * R). If you don't cool the resistor take one with at least a 10W rating. Ordinary wire wound ceramic is fine.
Because the heater current is non-linear with respect to heater voltage, you may have to go to through an additional iteration to get to the optimal value.
Still you need to be aware that the heater voltage is proportional to the momentary mains voltage; so, always make reference to it.
You need to know the total heater current and the measured heater supply voltage.
Let's say you want to drop the heater supply voltage by 1.0 volt and the heater current is 3A. The you will need a series resistor of 1/3 = 0.33 ohm (R = V/I). The power dissipated by this resistor will be 3*3*0.33 = 3 Watt (P = I^2 * R). If you don't cool the resistor take one with at least a 10W rating. Ordinary wire wound ceramic is fine.
Because the heater current is non-linear with respect to heater voltage, you may have to go to through an additional iteration to get to the optimal value.
Still you need to be aware that the heater voltage is proportional to the momentary mains voltage; so, always make reference to it.
So 0.82R at 1 watt would be fine, but if you are using DC, the result might be different. You could also use a 2 watt part if you wanted, but it isn't necessary. A wirewound resistor would handle the power up surge better than any other type of resistor.
I'm just trying to make it easy for you to find parts by listing the closest available resistance value.
-Chris
I'm just trying to make it easy for you to find parts by listing the closest available resistance value.
-Chris
Thanks Win, I forgot about R3. I will increase proportionally to get the value down. Time for another Digikey order.
Now just need to address the noise/hum/buzz.
I believe the noise to be electrical. The reason for mentioning the voltage on the 6.3 volt tap was that is seemed higher than when I first checked it.
So I am left with 2 issues. the voltage I believe I can fix with a higher ohm rated resistor on C3.
I found this thread and am interested in the 2.2uF caps for the output transformer. Can someone verify the B+ tap for the output transformer. I believe they are T3-2 and T2-2
click to follow down to #5
http://www.diyaudio.com/forums/tubelab/276947-tse-buzz-psu.html
click to follow down to #5
http://www.diyaudio.com/forums/tubelab/276947-tse-buzz-psu.html
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Then you have it correct in your post #12. Don't think it makes a difference if it's T3-2/T2-2 or the other way around. The difference I have noticed is the soundstage, the way it's presented. One way it's a real centered image. The other way the image is more right left or way outside of speaker placement and my preference. sort of 3D if you will.
I am a little confused. T2 and T3 are the two output transformers. The output transformers fit between the 10 ohm resistor on one side and the plate of the 45 tube on the other. Do I understand you correctly saying installing the 2.2uF cap in either position to ground will change the soundstage dimension?
If so what would give the large soundstage?
Thank for the reply.
If so what would give the large soundstage?
Thank for the reply.
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