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In Reply to: RE: PING to Audio Note Kit One owners =) Update! posted by Tre' on May 11, 2015 at 07:07:28
Hello Tre'
mine is the 2004 version, with a Hammond H300990 mains tx.
I have contacted the local energy provider and they will visit my house in an hour to check the voltages. I have checked again the outlet voltage and remains at 230v, but I want to be sure if this can vary over the days or will stay steady. Depending on this, I will change the tabs to 230 or I will build or buy a voltage regulator.
I don't know if in theory, if I match the outlet voltage with the actual 220v configuration (or if I change the configuration to reach 230v, if this is the new mains voltage in my neighbourhood) I can reduce 9.5% the H.T. on the 300B anodes.
Kind regards,
Beto
Edits: 05/11/15Follow Ups:
"I don't know if in theory, if I match the outlet voltage with the actual 220v configuration (or if I change the configuration to reach 230v, if this is the new mains voltage in my neighbourhood) I can reduce 9.5% the H.T. on the 300B anodes. "
Probably not, but it will get you "close enough".
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I have the response from the technicians from the local energy company: my house is very close to the street transformer. This tx provide 230 volts to ensure they can provide within 7% to the most faraway house in the neighborhood due to the lost in the transmission line. So I got the full 230 volts and this, according to they, would be steady in the time.
So, I will change the mains tx configuration to reduce in an small % the H.T to preserve tubes life (the maximum for a 300B , as far as I know is 450v.)
kind regards,
Beto
"(the maximum for a 300B , as far as I know is 450v.)"
Yes, that is true but understand that is the max rating for the voltage across the tube.
The voltage across the tube is the plate voltage minus the cathode voltage.
In your case that is 463 - 75 = 388
So you have only 388 volts across your tube.
Your cathode resistor is 900 ohms with 75 volts across it so the current is 83.33ma. current = voltage divided by resistance.
That means the output tube's plate is dissipating .08333 x 388 = 32.33 watts. That is within the rated 40 watts.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
OK Tre', you are right. I'm just refering to the 300B data sheet that states that the maximun plate voltage must be 450v.
Anyway it's seems to be a good thing to decrease the plate voltage to reach a value closer to the design, increasing to 230v the mains tx operation voltage.
Thanks for your input!
Beto
Hello Peter, Tre',
I changed the power tx wiring to match the actual 230v and I'm glad to share the new values:
with all tubes inserted, but without R1 still is a wire (nominal value):
(425v) Anode - pin 1 Right: 433 dcv, was 463 dcv on the previous test
(425v) Anode - pin 1 Left: 433 dcv, was 463 dcv
(70v) Cathode - pin 3 Right: 70.5 dcv, was 76 dcv
(70v) Cathode - pin3 Left: 69 dcv, was 75 dcv
(75v) pin 4 Right: 75 dcv, not measured on the previous test.
(75v) pin 4 Left: 74 dcv, not measured on the previous test.
filaments:
(5v) between pin 4 and 3 Right: 4.88 dcv, was the same
(5v) between pin 4 and 3 Left: 4.88 dcv, was the same
I like to say thank you so much for your tremendous help. Peter, you knew very quickly what the problem was. Only respect and gratitude.
You believe that is absolutely necessary to re-install R1? has any effect on the sound, besides preventing hum?.
Best regardsBeto
Edits: 05/11/15 05/11/15 05/11/15
Hello Beto,
Good to read that your amplifier is working again.
I'm sorry that I did not answer you earlier, but I have been away the last week. (to the High End show in Munich, Germany). Nice to see that Tre helped you with your last questions.
Best regards, Peter
Hello Peter,
thanks so much for your words and I hope you had a very nice time on München, a very nice city, by the way.
Yes, you pointed exactly where the problem was! and Tre helped me to realize that I did not have the correct mains voltage, so now my amp is running at a very precise standard.
After doing almost a week of tests with different kind of music at different volume, with different preamp tubes, the noise in the output transformers still is there when I play very low frequencies at high volume...so I am returning to chapter 1, before I accidentally have caused the short circuit, while I was routing the wires on the filament board to eliminate a little hum, when I have installed a pair of rubber stripes down the output transformers to eliminate the vibration noise....then happens the well known history: the short circuit had damaged the regulators so I have replaced it but left them too tight, so one isolation washer was a bit damaged provoking a contact from the regulator to the chassis. Mine is not the regular filament pcb board, it is the hardwire version, so one have to be very careful to leave the regulators in perfect coincident length to the perforations on the heat sink in order to not stress the isolator washer...
One thing caught my attention; when this noise happens, there is a variation on the filament glow, the more the music is high volume/low fq, the more intense is the glow. I was noted this when the problem appears some years ago and now I can confirm as part of the analysis. Varies exactly in the same "rhythm" than the music intensity. The noise is like there something inside the tx that is hitting the tx shrouds. tiny hits on a rhythmic basis, directly related with the "over saturation" on the music.
Since a long time, I am doing a lot of research on the web and the more difficult task was to get the appropriate name to this phenomenon to search the appropriate posible solution. Buzzing, motorboating, oscillation, to name a few, but still I don't find the exact match and how to cure it. I believe that the rubber straps I put under the txs help in a small degree, by the way.
Since I don't know if the variation on the intensity of the filament glowing is normal when the music tends to sound full and complex at high volume, I can't discard that maybe the problem is some kind of gas leaking inside the output tubes or a mechanical problem inside them that is transported to the output transformers, etc.
One explaination I received earlier was "this is that there is some airgaps on lamination and the electromagentic flux generated by the current flow, activate this with vibrations"...but I'm sure that this was not there the 7 years before, so in some point this begins to happen.
At least I can hear music and sounds a little better than before and this noise is only happens with very low frequencies. Those frequencies are not present on orchestral, acoustic instruments music, traditional jazz, rock, blues, folk, etc, but there are some electroacoustic music, noise music, experimental music, etc that can have a huge degree if very low fq.
Any clue will be gratefully received.
The best for you,
Alberto
.
Have Fun and Enjoy the Music
"Still Working the Problem"
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