You can never get the Vfk within the max. 90V specs for the upper and lower triode at the same time.One cathode almost Gnd level and the other near 200V is to much.
Max.distance is 2x90V !
A solution could be separate tubes for up and down with the upper two (other channel) a heatersource of it's own,200V above Gnd.
Or another tube 😱
Mona
Max.distance is 2x90V !
A solution could be separate tubes for up and down with the upper two (other channel) a heatersource of it's own,200V above Gnd.
Or another tube 😱
Mona
Using 100V to elevate the heater like the attached schematic, I measure:
Plate lower triode
Right 137,4V
Left 135,5V
Replace the red LED by the 470R and 22µ in one channel as shown in the first schematic for testing purposes. Check voltages again afterwards.
Rundmaus
EDIT: If everything else seems ok, the LED bias scheme is the only difference to the schematic with its design voltages. Change back the bias scheme to see if the problem occurs from that.
Rundmaus
EDIT: If everything else seems ok, the LED bias scheme is the only difference to the schematic with its design voltages. Change back the bias scheme to see if the problem occurs from that.
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That is significantly closer to the design value than before. Though still different enough to make me wonder why.
You did not comment on the differences in the earlier measurements: Were the 175V a misreading?
Rundmaus
You did not comment on the differences in the earlier measurements: Were the 175V a misreading?
Rundmaus
First post 175V was a typo/mistake😱
Now heaters elevated to 100V, I guess also helps.
So have I to come back to cathode RC in place of LED?
TIA
Felipe
Now heaters elevated to 100V, I guess also helps.
So have I to come back to cathode RC in place of LED?
TIA
Felipe
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Not sure about that. I'd have to pull my Morgan Jones copy from below a large stack of physics stuff and read up on mu follower design.
Though I am able to do some fault finding by logical and general circuit design and measurement principles, I have no experience in designing mu followers.
Maybe some of the tube forum masters of old can cut in here?
Rundmaus
Lower plate both cathode RC
right channel 103.7V
left channel 102V
Thanks Rundmaus, how could I reduce to 85V?
right channel 103.7V
left channel 102V
Thanks Rundmaus, how could I reduce to 85V?
According to your link, the voltages don't seem critical and about right.
What exactly do you mean by 'noise'? And are you sure the problem is within the mu follower, not somewhere else in the (assumedly) larger circuit?
Rundmaus
What exactly do you mean by 'noise'? And are you sure the problem is within the mu follower, not somewhere else in the (assumedly) larger circuit?
Rundmaus
Like a big hum, yes I'm sure I have other line amp, tomorrow I will try with other power transformer.
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Make sure the hum is not present at the mu follower input but is there at the mu follower output. Does it really originate in this part of the circuit?
If yes, is it present on the B+ rail? How much ripple is there?
Rundmaus
If yes, is it present on the B+ rail? How much ripple is there?
Rundmaus
I'm sure hum not cames for other source because I use also as headphone amp and without nothing connected input/ouput haves the same hum. I guess little ripple because I use Salas HV shunt regulator but tomorrow I will check with the scope.
Thanks for support Andreas.
Thanks for support Andreas.
Still hum with the input shorted to ground?
The scope trace is blurred... 0.5us sounds very short. 'Hum' usually is something in the 50-100Hz range, meaning approx. 20ms to 10ms in period length.
If you have a scope available, step one would be to measure the hum you're experiencing. The frequency would surely give hints about the hum source!
The scope trace is blurred... 0.5us sounds very short. 'Hum' usually is something in the 50-100Hz range, meaning approx. 20ms to 10ms in period length.
If you have a scope available, step one would be to measure the hum you're experiencing. The frequency would surely give hints about the hum source!
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