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Old 6th May 2009, 05:02 AM   #1
SA-12 is offline SA-12  Canada
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Question Triode Electronics Mark III

I would like to talk with anyone that has experience with the triode electronics mark III dynaco clone kit. I am having big problems and don't want to risk killing my tubes if I already did not do so. Please help me out some, I can give good description of my problems.
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Old 6th May 2009, 07:51 AM   #2
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What's the problem, first....
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Old 6th May 2009, 01:22 PM   #3
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Which Triode Electronics kit is it? When Ned Carlson used to work there, he sold a Mark 3 kit which had the DIYTube Poseidon board on it. Currently, the only kit I'm aware Triode is selling uses their "cascoded triode front-end". Is your problem related to the driver board, the bias supply, the power supply, general chassis wiring, or you have no idea?

DIYTube Poseidon

Triode Electronics Mark 3 (schematic)
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Old 6th May 2009, 03:46 PM   #4
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Ok thanks guys for helping, here is the list of problems.

1. The driver board is called "Triode electronics MKIII driver upgrage and uses 2 12au7 tubes. (many others possible).

2. I am confused as to what is the front and back of the amplifier, some instruction only states "pointing towards back" ect, ect. From the pics provided I find it hard to determine.

3. When I completed the build I very quickly realized I reversed the polarity on one power supply cap (the kit replaces the multisection with a powersupply board from sheldon stokes). One of the panasonic 100uf caps puked and stunk up my house for hours. I changed this and all is good, also tested capacitance and esr of remaining caps, all good.

4. I had the driver board jumpered wrong for the 12au7 tubes heaters, when I did this I was able to bias up the output tubes dead on to 1v and it held nice. I quickly realized that only one section of the 12au7 was lit so I double checked the driver heater supply and realized I had the jumper in the wrong place.

5. when I put the jumpers in the right location the amp would not even come close to .5v bias before the kt88's started flickering like crazy, distortion and light pops could be heard through the test speakers. It did pass audio very briefly before I shut it down, I hope my tubes are ok they are all new and got them with the complete kit. I quickly tried the other set of kt88 and the gz34 to rule out bad tubes, these tubes flickered too. The gz34 arked once but I bet it was because I turned the amp on to quickly after shut down. The 3 amp quick blow fuse holds durring all of this, 2 amp blows quickly.


right now I am going to build the other amp and hope for the best, going to check the driver 10 times if I have too and get those tiny 1/8 and 1/4 watt resistors supplied out and put in some 1/2 watters. I made some wiring mistakes for sure, or driver mistakes with components. The work is neat and no traces are bridged.


bottom line it seems like once the driver was working the amp turned into slag.
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Old 6th May 2009, 04:18 PM   #5
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1. Ok, it's not the DIYTube Poseidon board.

2. Honestly, I'm not sure myself which is the front and which is the back of the amplifier. If I had to guess, I'd say the power cord, switch, speaker terminals, etc. are on the back.

3. Electrolytic caps really do not tolerate reverse voltage. Glad you could sort that out. Another common mistake is to put the bias supply caps in backwards. The end result is not enough negative bias voltage, and an inability to properly bias the output tubes.

4. It's always good to double check your work. Sounds like you've got the heaters sorted out.

5. My guess is you've built an oscillator. It's easy to do if you get the transformer leads swapped on the output tube sockets, or you reverse the signal wiring between the driver board and the grid pin of the power tubes. Check the wiring carefully. It's also important to make sure the output transformer's common (zero ohm lead, probably black) is tied to ground, otherwise the feedback circuit won't work correctly.

I'm not sure how much this will help, since it shows the stock Dynaco driver board. You might want to verify you've got the solid blue and solid green leads going to the correct socket (blue/white and green/white go to the other socket).

http://i9.photobucket.com/albums/a78...tled-1copy.jpg
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Old 6th May 2009, 04:49 PM   #6
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thanks for your input, I am going to go over every wire today. I also am going to check every component on the driver board to see if anything is up with that. The kit is designed to be a complete build without adjustments other than setting bias. I used the basic tubes to go with the kit, all JJ tubes kt88, 12au7 and gz34. With these tubes no changes are claimed to be needed simply stuff the driver and do the wiring. I will keep informed with any progress and please anyone else feel free to add to this. I have contacted triode for some help, and am awaiting there responce. They know these things inside out but are closed on wednesday.
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Old 6th May 2009, 05:28 PM   #7
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If you haven't seen it already, Triode Electronics has a Word document explaining how to build the thing:
http://site.triodestore.com/Mk3instructions.doc

There is a good photo on the first page which shows the completed amplifier. Pay particular attention to step 28 & 29 (where the output transformer leads are attached to the sockets) and also step 44 & 45 (driver board is connected to the sockets).

Good luck!
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