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   Home » Melquiades Amplifier » Melquiades For Dummies™ - step by step. (29 posts, 2 pages)
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  »  New  Building Melquiades: Chronicle of full-range..  VR2 issue leading to jump in current on 6C33 tube...  Melquiades Amplifier  Forum     44  411973  06-09-2006
  »  New  “Melquiades” amplifier: a year later...  Considerations about Melquiades’ layout....  Melquiades Amplifier  Forum     33  318680  10-05-2006
  »  New  Full range Melquiades implementation..  Solved...  Melquiades Amplifier  Forum     81  522900  02-23-2011
  »  New  Building Melquiades: questions and answers...  PeaceMAT XS™...  Melquiades Amplifier  Forum     96  530135  10-09-2007
08-12-2008 Post does not mapped to Knowledge Tree
decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #: 21
Post ID: 8014
Reply to: 8013
Fitting
Very many thanks. I do not want to make him change too many things given that he has generously agreed to keep the price fixed. May I ask what sockets you used - I could then obtain the same ones? Do not worry if you cannot remember. Regards, d
08-12-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 22
Post ID: 8016
Reply to: 8014
The tubes sockets for Milq

I do not remember which one I used. I remember that I was deciding if to mount them on chassis vs. to have a small board with tube sockets under the chassis and bring the tubes through the chassis. The board mounting is better as it decuples the tube from the chassis vibrations.  However, in the original Melquiades I decided to go for chassis-mount as it is ease with point to point wiring. In Melquiades DSET I deseed do not change it as the 3-6 channels unit has no chokes-transformer on amp side and therefore no vibration. However, when I converted 3-channel Melquiades into 6 channel DSET I replaced the sockets from whatever I had to Connex sockets. I found the hold the tube much better, much more flexible in mounting and have zillion if other advantages. I drill up the size of the holes in Super Melquiades to accommodate the new sockets.


http://www.partsconnexion.com/catalog/tubesockets.html

The Canadian sell them very expensive, but you can find then from Taiwan on eBay for under $10. Unfortunately I was not able to found better sockets for 7-pin gas tubes…

Anyhow, determine what sockets you will be using and how you will be mounting them and THEN place the order for the chassis. Drilling yourself is fine but not for tubes sockets as it will be too visible. It is very easy for John (or whoever) to change the dimension of the holes.

The Cat

PS: God, I am so happy that I am going to do over this crap all over again!!!!


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-12-2008 Post does not mapped to Knowledge Tree
decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #: 23
Post ID: 8017
Reply to: 8016
Eastern promise
Thanks, Romy. I suppose I also ought to check the size of the metre, unless you happen to recall the source of the one you used...

Incidentally, it is possible to go all teflon & gold (including the 7-pin miniatures) from here:

http://www2.117.ne.jp/~y-s/parts-socket-e.html

Their mounting plates look good too.

Prices are, of course, preposterous.

Regards, d
08-13-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 24
Post ID: 8019
Reply to: 8017
Try it before you buy it.

There was a conversation about the Melquiades meters in past:

http://www.romythecat.com/GetPost.aspx?PostID=3694

However, I have a concern about what you do. You are trying to come up with chassis or an idea of better parts for Milq but you have no parts yet to build the amp. If you do have the part then why don’t you prototype the Milq in order to verify for yourself the amp actually worth to built as a final, sassiness enclosed amplifier? It I might be zillion reasons why you might find that Milq is not good enough for you (The Romy turned out to be a full of shit would be one of them) Anyhow, if I were you I would defiantly built a quick and dirty “on table” assembly of a functional amp to liar what the amp does. If you have all part then it will take for you a day. If you have not a lot of experience to build amps then it would be a wonderful play-ground for you to experiment with amp building…

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-14-2008 Post does not mapped to Knowledge Tree
decoud
United Kingdom
Posts 247
Joined on 03-01-2008

Post #: 25
Post ID: 8025
Reply to: 8019
Risk
Yes, this is an experiment, but it may as well look good for all that.
07-29-2019 Post does not mapped to Knowledge Tree
Terry Maddocks
United Kingdom
Posts 5
Joined on 04-04-2017

Post #: 26
Post ID: 25534
Reply to: 8025
Getting on board... Finally
I'm a little late to the party here, but better than never I suppose!  I'm getting there with parts acquisition, I have valves and output transformers, chokes on order. Next will be power transformers, and finally.. everything else.. Decoud did you ever get your Melquiades finished? 


"Music is enough for a lifetime, but a lifetime is not enough for music" Sergei Rachmaninoff
06-20-2023 Post does not mapped to Knowledge Tree
anthony
Posts 335
Joined on 08-18-2014

Post #: 27
Post ID: 27127
Reply to: 8019
6c33c heater wiring
A small word of advice regarding wiring the 6c33c heaters.

My DSET's have now have several thousand hours of use and I love them to death.  I've not heard any amplifier able to do what they do.  The first amp has over 10,000 hours now and has never failed.  The second amp has fewer hours (still 10,000 hours or so) and has failed twice and I now know the very simple cause and offer it as advice to those still contemplating building this amplifier or any amplifier using 6c33c tubes.

The first failure I attributed to a tube that failed in a way to short circuit the 6c33c heaters which caused the transformer to short circuit, push crazy amps into the wiring, melt some insulation, release a little bit of the magic smoke and because I was out of the room when it started eventually damaging the heater transformer.  This was an incorrect diagnosis.  I replaced the wiring and transformer considering it a freak event and happily listened to that amplifier for about another 6,000 hours.

A couple of days ago the same thing happened six hours into the days playlist.  Mmmm...a freak should not happen twice...there is obviously a design or implementation issue.  After much thinking I got out the FLIR thermal camera and poked it around inside the DSET that has never failed and the underside to the 6c33c socket, including the adjacent section of wiring was running at about 100 degrees celcius, which is very warm, certainly warmer than I expected.  The heaters have been wired with an 18AWG solid core with ultra thin mPPE insulation.  I chose ultra-thin so that the two conductors would be very close together when twisted thus aiding AC field cancellations.  The datasheet rates this insulation at 105 degrees celcius which is roughly the temperature underneath the 6c33c sockets.  Bingo!

What has been happening, in my estimation at least, is that at some point the insulation eventually runs warm enough to begin to weaken or melt and when that melt reaches the twisted section of wiring a short circuit is created and the whole thing runs away from there.  Considering the sheer amount of time these amplifiers have been turned on, I may be fortunate that it has only happened twice now, but the solution is very simple:  the amplifier filaments to all 6c33c tubes is to be re-wired using wire with teflon insulation which has double the temperature rating (200C) of the original wire I used.  Builders should be careful to route all wiring so that is is not close to the 6c33c tubes and also consider a fuse on the secondaries of any heater transformers just in case.
06-21-2023 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 28
Post ID: 27129
Reply to: 27127
If it good for my hand it good for my amp.
Anthony,
  
I feel that 18AWG is a bit too weak for the filaments. I usually use 12. I do not know if you allow to have any ventilation around the 6C33C, I did. In my full range amp, I had holes around the 6C33 panel.
 
http://www.goodsoundclub.com/Site_Images/MakeMelq9.jpg

The 6-Ch version with 3x6c33 has the same holes a cooling fan

http://www.goodsoundclub.com/Site_Images/SuperMilqInside.jpg

Yes, certainly the Teflon insulation will help but generally you should have some kind of outlet for hot air outside of the chassis. I typically follow the rule that the temperature on a sealed tube amp inside after a few hours of operation should be comfortable for my hand.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
06-21-2023 Post does not mapped to Knowledge Tree
anthony
Posts 335
Joined on 08-18-2014

Post #: 29
Post ID: 27130
Reply to: 27129
Amp still open
Romy,
My DSET amps are still open (no top plate) so are fully ventilated, but I have left vents in the top plate around all of the valves and installed two computer fans (running very low speed) that push air from the bottom and out the vents on the top plate.  Teflon coated 14AWG wire is inbound to make the repairs next week.

My FLIR thermal camera shows that the bottom of the tube socket is a little hotter than 100C which translates to plenty of heat in the first couple of inches of wire but quite cool after that.  The only other warm things in the amp are the final resistors in the B+, but nowhere near as warm as the base of the 6c33c tube sockets.

Rgds,

Anthony 
Page 2 of 2 (29 items) Select Pages:  « 1 2
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  Building Melquiades: Chronicle of full-range..  VR2 issue leading to jump in current on 6C33 tube...  Melquiades Amplifier  Forum     44  411973  06-09-2006
  »  New  “Melquiades” amplifier: a year later...  Considerations about Melquiades’ layout....  Melquiades Amplifier  Forum     33  318680  10-05-2006
  »  New  Full range Melquiades implementation..  Solved...  Melquiades Amplifier  Forum     81  522900  02-23-2011
  »  New  Building Melquiades: questions and answers...  PeaceMAT XS™...  Melquiades Amplifier  Forum     96  530135  10-09-2007
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