Today I've almost everything on hand to complete the project . It's just missing one thing: time. This is difficult, especially now that I have to be careful in the assembly ( do not want to spoil the chassis ) . However , I'm using the prototype almost every day and is operating very well. I think I will finish this project only in December . I also bought an oscilloscope with a good quality (digital), and I hope I will complete the assembly with the necessary measurements . This time I will need your help to use the oscilloscope and do the rights measurements.
The capacitors of the photos below are just for testing. In the prototype I used four 950uf / 400v . Now I'm going to test with these 8500uf / 350v . I think I'll end with something like 3200uf / 350v to 400v .
I know that the tube diode was the first diode ever invented (in fact it was the first tube ever invented). For many years it worked quite dependably and it was the only choice for rectifying current for high voltage power supplies. Nowdays, after solid state technology was developed in the 1950′s, it was found that solid state diodes could do the job of tube diodes, and better. So, I will use fast diodes, family MUR (MUR 4100) and I need to choose the right capacitors. Although we have a lot of information on this forum, I have not found conclusive answers about the ideal limit for use in tube amps . Some texts reinforce the idea of increasing hummm when you have a high capacitance . I'll get the answer in practice. After testing , I will have the answer . About the other components I have no doubt and they are already defined . Here are some pictures of the new components :
The capacitors of the photos below are just for testing. In the prototype I used four 950uf / 400v . Now I'm going to test with these 8500uf / 350v . I think I'll end with something like 3200uf / 350v to 400v .
I know that the tube diode was the first diode ever invented (in fact it was the first tube ever invented). For many years it worked quite dependably and it was the only choice for rectifying current for high voltage power supplies. Nowdays, after solid state technology was developed in the 1950′s, it was found that solid state diodes could do the job of tube diodes, and better. So, I will use fast diodes, family MUR (MUR 4100) and I need to choose the right capacitors. Although we have a lot of information on this forum, I have not found conclusive answers about the ideal limit for use in tube amps . Some texts reinforce the idea of increasing hummm when you have a high capacitance . I'll get the answer in practice. After testing , I will have the answer . About the other components I have no doubt and they are already defined . Here are some pictures of the new components :
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Thanks !
Well, the longest operation was to R&D the design and settle the prototype of the circuit to have the required performances, outside of the TVA-1 chassis. Before that, I seriously tested and measured the transformers (mainly the output ones) to check their condition and performances : let me say that the M&A TVA-1 output transformers are really top quality...
I have built/converted 2 M&A TVA-1, and it took me circa one month part time for the assembly (design excepted) AFAIR for the 2 amps. But I have the adequate tooling (GreenLee, column bench drill, etc...) for the mechanical part of the job. You need correct tooling and take your time and patience, otherwise you may not do an enough "neat" job...
And yes indeed, if it is not working, let´s start to work ... Time is the problem! So take time, don't be in a hurry... I have a 300B SE pair of mono amps to realize, the prototype is still OK ten years after, everything is ready, complete, in carton... One day I will find time and extra-motivation !
A+!
A+!
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Hello evrybody. My name is Alex and I live in south France Montpellier. Thank you all for the quality of this forum.
I inherited this week a Michaelson & Austin TVA-1 which hardly needs to be fixed. I plugged it in last evening and all the fuses shut down in a spaceship sound of perdition.
It's a deeply mooving situation for me because my oncle is in a hospital, he wasn't a rich man but its life was based on love of Mozart and Schubert music. I sure will repair the TVA-1 and appreciate it. I will back later with questions. Thx
Alex
As you know, this amp is reputed to be capricious and fragile. I have just been given this one with the warning that one of the transformers needs to be changed, but we don’t know which one. To be precise it was in its cardboard box in a garage for twenty-two years without encountering a single electron. That means several components and in particular a transformer needs to be changed.
Does anyone here have the technical reference for the transformers? An address where they make them at a reasonable price?
Any advice?
Tips?
Comments?
Thanks for all.
Does anyone here have the technical reference for the transformers? An address where they make them at a reasonable price?
Any advice?
Tips?
Comments?
Thanks for all.
Hi
First of all you need to give some more information. Were speakers connected? Did the amp play before the fuses blew? Did sound come from the speakers or from the amp itself?
How long was the amp turned on before fuses blowing? Etc.
As far as I remember, there is a fuse in series with each loudspeaker and one one the primary side of the mains transformer.
If a transformer is broken, let us hope it is the mains transformer.
Try to give an exact description of what happened, and I am sure someone here will be able to help.
By the way I think this should have it's own thread.
Regards, Torben
First of all you need to give some more information. Were speakers connected? Did the amp play before the fuses blew? Did sound come from the speakers or from the amp itself?
How long was the amp turned on before fuses blowing? Etc.
As far as I remember, there is a fuse in series with each loudspeaker and one one the primary side of the mains transformer.
If a transformer is broken, let us hope it is the mains transformer.
Try to give an exact description of what happened, and I am sure someone here will be able to help.
By the way I think this should have it's own thread.
Regards, Torben
Well, hello Torben and thanks for your comment
“Were speakers connected?” No! it wasn’t! Now I know that’s not the way to do it
“Did the amp play before the fuses blew?” No it did not.The fuses that blew were the ones in the appartement.
“Did sound come from the speakers or from the amp itself?” From the amp itself. And an orange flame flickered under the structure.
“How long was the amp turned on before fuses blowing?” Half a second. Actually, I wanted to wake the component up slowly with the method “switch on one second, wait ten minutes, one second switch on etc.”
This amp did not work any longer, that why it was in the garage.
What can I do now? I am going to open it. Change all the accessible components that look bad (toasted J ), take the transformers apart and test them, Jeeeze it’s a tricky spiritual mission to have delicate ears.
To speak about something else than wreckage, destruction, sound and fury signifying nothing, I would also like to tell you about the preamp I’m planning to use. It is a Dayton Wright SPS MK3. Does anyone here see what it is?
“Were speakers connected?” No! it wasn’t! Now I know that’s not the way to do it
“Did the amp play before the fuses blew?” No it did not.The fuses that blew were the ones in the appartement.
“Did sound come from the speakers or from the amp itself?” From the amp itself. And an orange flame flickered under the structure.
“How long was the amp turned on before fuses blowing?” Half a second. Actually, I wanted to wake the component up slowly with the method “switch on one second, wait ten minutes, one second switch on etc.”
This amp did not work any longer, that why it was in the garage.
What can I do now? I am going to open it. Change all the accessible components that look bad (toasted J ), take the transformers apart and test them, Jeeeze it’s a tricky spiritual mission to have delicate ears.
To speak about something else than wreckage, destruction, sound and fury signifying nothing, I would also like to tell you about the preamp I’m planning to use. It is a Dayton Wright SPS MK3. Does anyone here see what it is?
Hi again
I hope someone more qualified than me steps in to help soon. But while we are waiting:
Could you take a better photo of the power transformer (from underneath) and also the power switch. Check if the mains fuse in the amplifier is blown.
Also take a picture of the power supply board. To me it seems like there are fewer diodes than usually in a TVA1.
Torben
I hope someone more qualified than me steps in to help soon. But while we are waiting:
Could you take a better photo of the power transformer (from underneath) and also the power switch. Check if the mains fuse in the amplifier is blown.
Also take a picture of the power supply board. To me it seems like there are fewer diodes than usually in a TVA1.
Torben
Maybe you can get better attention to your problem if you open another thread. People that was here in the past, may not return. But feel free if you want stay here.
This unit has a big OT transformer to put 75 watts at output. If you turned on the unit without connect speakers, maybe the OT has failed.
To start you need to disconnect everything from OT and power transformer. De-solder every point. Then start measure the resistance between windings. Start from power transformer. If it is not open, then next step will be measuring voltages.
After you get the resistance between windings from power transformer, we can do the same to the OTs.
Don't try to turn the amp on before those measurements.
Post your measures here.
This unit has a big OT transformer to put 75 watts at output. If you turned on the unit without connect speakers, maybe the OT has failed.
To start you need to disconnect everything from OT and power transformer. De-solder every point. Then start measure the resistance between windings. Start from power transformer. If it is not open, then next step will be measuring voltages.
After you get the resistance between windings from power transformer, we can do the same to the OTs.
Don't try to turn the amp on before those measurements.
Post your measures here.
Hi
You tell us that the fuses in the appartment blew. That should not have happened, as there is a mains fuse in the amplifier. This fuse is situated AFTER the power switch and that is why I asked you about a photo of the power switch. If there is a short in the power switch the mains fuse in the amplifier will not help so that COULD be why the fuses in the appartment blew. So if you are very lucky (probably not) the problem could be the power switch.
Well, somebody told you there is a faulty transformer. If that is the case, it will almost certainly be the power transformer.
Torben
You tell us that the fuses in the appartment blew. That should not have happened, as there is a mains fuse in the amplifier. This fuse is situated AFTER the power switch and that is why I asked you about a photo of the power switch. If there is a short in the power switch the mains fuse in the amplifier will not help so that COULD be why the fuses in the appartment blew. So if you are very lucky (probably not) the problem could be the power switch.
Well, somebody told you there is a faulty transformer. If that is the case, it will almost certainly be the power transformer.
Torben
Hi again
What I wrote in the previous message about a mains fuse is probably wrong. In some schematics of the TVA1 there is a mains fuse on the primary side of the power transformer but in other schematics it is not there.
My brother owns a TVA1. It has a fuse in the power supply after the power supply capacitors.
Torben
What I wrote in the previous message about a mains fuse is probably wrong. In some schematics of the TVA1 there is a mains fuse on the primary side of the power transformer but in other schematics it is not there.
My brother owns a TVA1. It has a fuse in the power supply after the power supply capacitors.
Torben
Hi Hermann, thank you.
Here is a picture of the front panel:
Left to the right :
Speakers output left
Fuse 3 amps
Fuse 3 amps
Speakers output right
input
Switch main/on
Fuse 5 amps
TVA-1 logo
I opened another thread called "Up sh*t creek with a TVA-1 Michaelson & Austin". I do not know if it has been validated by the moderator yet.
For personal logistic reasons (I do not have enough space to do that), it's going to take me some time to open the amp and begin to change things wield the welder. But I will keep you posted.
Here is a picture of the front panel:
An externally hosted image should be here but it was not working when we last tested it.
Left to the right :
Speakers output left
Fuse 3 amps
Fuse 3 amps
Speakers output right
input
Switch main/on
Fuse 5 amps
TVA-1 logo
I opened another thread called "Up sh*t creek with a TVA-1 Michaelson & Austin". I do not know if it has been validated by the moderator yet.
For personal logistic reasons (I do not have enough space to do that), it's going to take me some time to open the amp and begin to change things wield the welder. But I will keep you posted.
There is a simple way to test your amp, considering that you are facing problems to remove the soldering.
Remove all tubes and replace the blowing fuses. Turn on your amp using a bulb test. Start with a 15-watt bulb. If it lights brightly, the power transformer is shorted.
Passing the dim-bulb test doesn't mean your amplifier works. But if not passing, you will need to desolder some components.
Some usefull links:
Powering Up Your Radio Safely With a Dim-bulb Tester
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html
Remove all tubes and replace the blowing fuses. Turn on your amp using a bulb test. Start with a 15-watt bulb. If it lights brightly, the power transformer is shorted.
Passing the dim-bulb test doesn't mean your amplifier works. But if not passing, you will need to desolder some components.
Some usefull links:
Powering Up Your Radio Safely With a Dim-bulb Tester
http://www.diyaudio.com/forums/power-supplies/167579-light-bulb-tester.html
Thank you very mutch apnneto, I will do this as soon as I have a place to do it.
And firs of all, I would have to test the transformers...
I am looking for a good seller of tube KT88 and ECC 83 and ECC 81...
For thoses of you who are interested by this, I also use a preamp/headphone amp DOGE 6210. Very good little amp, who need to be tweaked of course, but clear and deep.
http://www.tubophile.com/images/BE Doge 6210 VIIs.jpg
And firs of all, I would have to test the transformers...
I am looking for a good seller of tube KT88 and ECC 83 and ECC 81...
For thoses of you who are interested by this, I also use a preamp/headphone amp DOGE 6210. Very good little amp, who need to be tweaked of course, but clear and deep.
http://www.tubophile.com/images/BE Doge 6210 VIIs.jpg
Try tubedopt.com. I usually buy tubes there. They are fast for shipping and solving any problems that you might have.
After turn on the power amplifier with light bulb connected, we can try to find the problem with it. I think it will be easy find the problem, but maybe not so easy to fix it.
After turn on the power amplifier with light bulb connected, we can try to find the problem with it. I think it will be easy find the problem, but maybe not so easy to fix it.
Hello apnneto, I am glad that what I did in 2009 has been of help to you.
I am not very often on this website, and I have not re-opened my TVA-1 since 2009... it works perfectly and I just listen to the music.
I have red several recent posts in this forum which define the TVA-1 as prone to current run-off and burning the output tubes. Based on my experience I would like to highlight that, in my opinion, the "flammability" of TVA-1, i.e. the tendency to burn the outlet tubes, is due to the insufficient voltage rating of the coupling capacitors (0.47 microfarad). Once I put good Wima 1000V rated ones the amp bias and currents have become stable as rock. Hope this can be of help.
Cheers to the Forum members!
I am not very often on this website, and I have not re-opened my TVA-1 since 2009... it works perfectly and I just listen to the music.
I have red several recent posts in this forum which define the TVA-1 as prone to current run-off and burning the output tubes. Based on my experience I would like to highlight that, in my opinion, the "flammability" of TVA-1, i.e. the tendency to burn the outlet tubes, is due to the insufficient voltage rating of the coupling capacitors (0.47 microfarad). Once I put good Wima 1000V rated ones the amp bias and currents have become stable as rock. Hope this can be of help.
Cheers to the Forum members!
Hi Gorlando,
Thanks for your initial post. It guided me in building my clone.
I have used the amplifier virtually every weekend and have not had any problems. I agree with you about the high voltages. I used two transformers for testing: the first one with 190-0-190 and the second with 210-0-210. I believe that the best option is the first with the lowest voltage. As you, I used 1000v for coupling capacitor.
Anyway, it's really a hifi amp. I did some mods in the FB loop due to OT(i don't have the original ones), but i did not have time to update the schematics.
Thank you again for your excellent post on revamping of your amp.
Thanks for your initial post. It guided me in building my clone.
I have used the amplifier virtually every weekend and have not had any problems. I agree with you about the high voltages. I used two transformers for testing: the first one with 190-0-190 and the second with 210-0-210. I believe that the best option is the first with the lowest voltage. As you, I used 1000v for coupling capacitor.
Anyway, it's really a hifi amp. I did some mods in the FB loop due to OT(i don't have the original ones), but i did not have time to update the schematics.
Thank you again for your excellent post on revamping of your amp.
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