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In Reply to: RE: PING to Audio Note Kit One owners posted by beto1 on May 06, 2015 at 07:26:31
With those resistor values, the isolation bewteen the regulator(s) and the chassis is still working.
Follow Ups:
Hello Peter,
I replaced R1 (PSU Board) with a wire and put away the tubes.
I switch "on" the amp; no fuse blown.
I Did some AC measurements:
between pins 7 & 8 on 6SN7 tube= 6.8 vac
between pins 4 & 8 on 5687 tubes= 6.8 vac
between pin 2 & gnd on 5U4GB= 5.7 vac
between pin 4 & gnd on 5U4GB= 463 vac, I think is a bit "too much" high, since the secondary has a nominal voltage of 425 vac.
between pin 6 & gnd on 5U4GB= 463 vac. Same story.
Finally, I checked again the DC voltage on 300B filament= 4.94dcv both
Now I will go to the next step. One single observation, a couple of days ago, before I start this new round of tests, I have unsoldered both 300B cathode caps and resistors and they were fine.
Nonetheless, I will follow exactly your directions for analysis.
Best regards,
Beto
Hello Beto,
Your power transformers is Ok. It is normal that all tensions are higher then normal. The power transformer is now not "loaded" by anything. So no current is flowing through the transformer wires and no voltage is "lost". The 425Vac rating is only correct when the power transformer is loaded with the design current. The power transformer is capable of much more current then the Kit-1 will ever ask, and as a result the tensions will always be higher then the 425Vac. When the Kit-1 would ask about twice the current, then the tensions would be around that 425Vac.
Just for my information, because I don't think it has anything to do with your problem. I saw the photo of the inside of your amplifier. What is the capacitance value of C1 and C2.
According to the schematic they should be 47uF each. Those are the correct values. Don't increase that value. Your rectifier is much happier with the 2 pcs of 47uF in series with each other. Together they make a 23,5uF capacitor that can take 800V. After you have solved the problem, you could replace these 2 capacitor with a single 22uF paper in oil capacitor (630V or higher, for example a ASC or GE) The oil capacitor will sound better.
Before you test the function of the output tubes, it would be best to de-solder resistor R5 and R7 (on one side is enough) on the power-PCB. This will take the driver board out of the equation. (no current/tension can reach the driver board now)
Peter
Hello Peter,
I was just wondered about the rectifier voltage that is in a lot higher % than the driver tubes in respect of the nominal value, but now is clear; thanks so much for your explanation.
Regarding the big C1 and C2 caps, both are 47uF/600v Mundorf tube caps. All the components of the PSU board are new. Because of this problem, I decided to replace all the components of this board, a while ago. Also I use a board for hardwiring that I get with the kit, ten years ago, but I'd never used it, so this was the right time. I believe this option is no longer available.
The components are:
C8: 220uF/550v Jensen electrolytic
C11 and C13: 68uF/450v Nichicon KX
C12 and C13: 100uF/500v Audio Note standard electrolytics
C9: 10uF/250v Black Gate Standard
R1: 100R/5 watts Mills resistor
All other resistors: Amtrans 2 watts
C1-C2 and C8 was elected with two premises: must have a size accordingly to the reduced internal height of the kit one chassis (2004 version) and by recommendation of its performance. I have to do some modifications on the original layout since this 3 caps are too much bigger than the "snap in" original caps, so I put longer screws on the mains tx to fix a secundary plate to place C1 and C2. Then C8 could be accomodated resting on the psu board
I will take in account your recommendations on capacitors, but first I need to get out of this "short circuit" situation. Also I would like to hear first this configuration/investment for a while.
I will do the test with a wire from pin 3 (300b) to the GND screw from both sides in a moment and I will let you know inmediately.
Best regards,
Beto
OK Peter,
this are the test results, with a direct connexion from pin3 to ground on each 300B (marked with green lines on the pincture), de-solder (+) terminal of the cathode capacitors on 300B. Only rectifier and output tubes were inserted:
No problem with the fuse
Anode (Pin 1) 300B (to chassis ground), left and right: 212 VDC
Cathode (pin3) 300B (to chassis ground): no voltage
5U4GB tube went very hot, increasing temperature and color while I'm doing the voltage test.
Before I continue with the next step, what do you think?
Best regards,
Beto
Hello Beto,
I'm sorry, but I made a big mistake, because of me you connected the wrong pin to ground.
I should have said : connect the grid of the 300B (the pin with the 3K3 resistor) directly to GND.
When you do this, the tensions will probably be correct.
Please let me know.
Peter
Hello Peter,
don't worry.
I connected the grid (pin2) from each 300B to ground and here are the DC voltages:
Anode (pin 1) Right: 305 dcv
Anode (pin 1) Left: 229 dcv
Cathode (pin 3) Right: 50 dcv
Cathode (pin3) Left: 0.01 dcv
Again the rectifier went too hot, so I've made those measurements on the rush.
So, the problem is maybe on the coupling caps?
Looking forward,
Beto
Hello Beto,
Look at the tension of the left 300B cathode. It should be something like 50 to 70Volts, but not 0Volt. The current through the left 300B is going through the cathode resistor to GND.
There is a formula (V=IxR) that say that when there is a current through a resistor there should be a tension. When there is no tension, there is or no current, or no resistance.
There is current (even a lot) through the 300B (that is why the tension on the right 300B are so low). Conclusion : the resistance of the left cathode resistor is 0 Ohm (it is defective)
(however I assume that you did de-solder the cathode capacitor and the isolation between the filament regulator and chassis is still working.
Replace the left cathode resistors and do the test again.
Hello Peter,
yes, I de-dosolded the (+) terminal on both cathodes caps.
I checked again the isolation, but something changed here:
I have:
Input leg Right: 5.64 M Ohms
Input leg Left: 5.69 M Ohms
Output leg Right: 0.914 K Ohms
Output leg Left: 0.8 Ohms
So, this is below 750 ohms as you stated first. Was a bit extrange but I simply loose a bit the screw on the left side and again give me 0.914 K Ohms.
Then I run another set of measurements:
This are close to the right values:
Anode (pin 1) Right: 492 dcv
Anode (pin 1) Left: 493 dcv
Cathode (pin 3) Right: 81 dcv
Cathode (pin3) Left: 80 dcv
I am creeped about the enormous influences of that tiny washer.
This time, It seems like the rectifier runs on more fairly heat
What do you think now?
the best for you
I think you have found the problem. A connection between the regulator and the chassis.
That would explain the 0 Volt reading on the cathode of the left 300B and it would also explain the burning of the 150R resistor.Replace the isolation washer and the plastic ring that sits between the regulator and the screw. The screw is connected to the chassis, so also the screw can't touch directly any part of the regulator.
Peter
Edits: 05/10/15
Hello Peter,
This is a very good news!
if is only the isolation, will be great, almost no cost involved.
But one thing caught my attention: the first time I measured the insulation on the regulators, like you asked, was good and the second time was wrong, which tells me that the problem probably was intermittent. However, every time I tried to switch On the amp, with all tubes inserted, R1 is beginning to burn, not intermittently.
Well, surely, when replacing the regulators after the short circuit, I left them too tight, not suspecting the consequences.
Tomorrow I will buy the washers and mica to replace them. In the meantime, I will take off the GND isntalled for the test , I will connect again the cathodes capacitors and do a test, with all tubes, but without R1. If all voltages are OK, tomorrow, after replacing the washers and re-checking the voltages, I will install R1 again .... and if I have luck, will connect a source and listen to music.
Peter, I want to thank you greatly for your valuable assistance.
The best for you,
Beto.
P.S. This whole problem started with an accident when I was trying to eliminate a noise that produced exclusively with the very lower frequencies, like a motorboating. I think it was eliminated or at least reduced by putting rubber bands below the output transformers to absorb vibration. However, as it is likely that the problem is still there without being solved at the source. As hennfarm mentions in his post, it could be a problem of oscillation. You have had to deal with a problem like this before?
I have my Kit One for more than ten years and never had a problem, the noise started about two years ago.
Again, thanks so much for your help!
Edits: 05/10/15
Hello Peter,
I'm happy: I'm hearing music through my kit one.
You was right of course.
This are the new voltage measurements, with all tubes inserted, but without R1 (still is a wire):
Anode (pin 1) Right: 463 dcv
Anode (pin 1) Left: 463 dcv
Cathode (pin 3) Right: 76 dcv
Cathode (pin3) Left: 75 dcv
filaments:
between pin 4 and 3 Right: 4.88 dcv
between pin 4 and 3 Left: 4.88 dcv
The anode voltage still is higher than the nominal voltage (425dcv). I don't know if this almost 40 volts will fall when I re-install R1. What do you think?
The best for you,
Beto
The 100 ohm R1 will not change this.
What is your line voltage and which primary tap are you using on the power transformer.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hello Tre',
here we have officially 220v / 50 Hz
I checked the scheme on the user manual and is OK. I have this primaries connected:
0v (brown) linked to 120v (black)
100v (brown/yellow) to live out to mains tx
0v (white) to neutral out to mains tx
"live in" and "neutral in" are linked to the IEC terminals respectively
...but I checked the mains outlet with my multimeter and is actually 230v. I don't know if this 4.5% extra mains voltage can cause that almost 40v extra on the anode that represent a 9.5% extra.
Thank you very much for your comment,
Best regards,
Beto
Edits: 05/10/15
Try wiring it for 230 volts and see what you end up with.
Use the 115 volt taps in series.
"0" of one winding as one end......with the "115" of that winding connected to the "0" of the other winding.......and then the "115" of that winding for the other end.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Thanks for your answer Tre'
The mains tx only have a couple of 120, 110, 100 and 0v terminals. I can use the 110v (blue/yellow) to "live out to mains" and keep the 120/0v terminals in the way they are now. This would give me 230v.
Best regards,
Beto
Edits: 05/11/15
I guess I was looking at the wrong schematic. It showed 110, 115 and 120 taps.
What you said will work fine.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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: 05/11/15
"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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