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Old 5th February 2012, 05:10 PM   #21
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All right... these boards are up on eBay now...

Pete
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Old 8th February 2012, 08:18 PM   #22
wicked1 is offline wicked1  United States
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I got my PCB's today. Thanks!!

Now I've got to decide what I want to do w/ them... Right now my ideas are all over the map, from 300b to kt88 pentode mode, to big transmitting tubes. (I'm leaning towards something pentode mode w/ regulated everything in the power supply (I guess 'cause there's a lot of regulator talk on the forum at the moment))

Anyone else starting a project w/ these?
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Old 9th February 2012, 01:30 AM   #23
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Quote:
Anyone else starting a project w/ these?
Not right away, but eventually. My soldering iron has not been plugged in since October. I have been in West Virginia, or Sherri has been home, and we have been catching up on the life together that we have missed for the last few years. She is going back north tomorrow morning for a while, so it's time to start the lab up again.

First off we cleaned out a room in the house and converted it to storage. I will be cleaning out our rental warehouse to save the $2500 a year in rent. The room has only about 1/3 the space, so a lot of stuff will get sold, given away or trashed. I need to catch up on some Tubelab stuff, fix the stale web site and build new versions of my boards to update the parts lists, then...

There are two nearly finished guitar amps that last saw power in November, and about 8 to 10 finished PC board designs that are still in my computer, drawn up in my down time over the last year. There are a couple more guitar amps, several driver boards, two power supplies, and another amp. None have been built, so they all will go through some revisions, and some will be abandoned.

Once a driver board or two are built and working, then I will get them, along with the two I already have working, and a pair of Petes new ones together with this breadboard (I have turret boards for Octal, Compactron, and 9 pin miniature output tubes) for some serious testing. I still have a pair of 400 Watt OPT's that need something to keep them warm!

Output tubes.....everything from litttle runts, to KT88's to 45's, 300B's, and 307A's (shown with another of my driver boards) to sweep tubes...lots of sweep tubes, and UH these..... (6146a in the rectifier socket for size comparison)
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Old 9th February 2012, 01:50 AM   #24
pso is offline pso  Spain
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Will publish a list of parts and specifications of transformers ?
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Old 9th February 2012, 12:17 PM   #25
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Will publish a list of parts and specifications of transformers ?
I'm not sure who you were asking, but I am sure that there will be some amps built using these boards and they will be documented here. Unlike the red board thread the possibilities for boards like these are endless. The red board had the power supply and the output tubes on board. These boards are just the drivers, everything else goes off board, or on additional boards. The output tubes can be just about anything with reasonable drive requirements.

Pete has already done a KT88 amp, it's on his web site. I may test some KT88's but I doubt i'll do a KT88 amp since I already have one. I plan on doing the unusual stuff and at least one BIG sweep tube amp, and yes they will be documented.
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Old 9th February 2012, 12:52 PM   #26
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I will certainly document and post what I end up doing, but I am learning as I go so it will likely be a couple of months before I have any useful info up.
Pete said he's busy for a while.. Same w/ Tubelab.

George, I can't wait to get one of your universal drivers.. Or even just a schematic (Maybe I just need to look around for that.)

These driver boards definitely make for a fun project! It's great to have some of the pieces in place, like a road map. But you're still free to take it in any direction you want to go.
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Old 9th February 2012, 03:16 PM   #27
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George, I can't wait to get one of your universal drivers.. Or even just a schematic
The driver board shown in the breadboard in the first picture above was developed in this thread. The schematic is in post #460.

6L6GC AB2 Amp

The breadboard is essentially this schematic except for the power supplies. Chris and I did a collaborative effort on the driver design with me building these boards and his being PTP wired. I used bench supplies so I could experiment with a wide variety of tubes. The power supplies shown are his design and specific to 6L6 type tubes, although others will work.

The driver board shown in the second picture uses the same schematic but uses 9 pin miniature tubes. In both cases the second tube is a 6SN7 or a 6CG7/6FQ7 which is a 9 pin 6SN7. The first stage can be one of several different tubes by changing the plate load resistors. The resistor values depend on the tube type, B+ voltage and how much drive voltage you need. The values shown on Chris's schematic are for 6SN7's or 6CG7's in both places and about 400 volts of B+. As shown it puts out enough drive to crank KT88's in triode into clipping with 450 volts of B+.

I have also designed several flavors of driver boards that use the same basic schematic except that a pentode LTP is used for the second stage. The pentode can be set up for higher gain and a larger voltage swing, which I need for some of my experiments. There are several versions of PCB's that all use a similar schematic. None have been built yet. A turret board was assembled to verify the concept about a year and a half ago. It has not seen power since then.

There are two that use 3 octal tubes, a 6SN7 and two 6SJ7 or 6AG7, and another that uses a 6SN7 and two 6K6 or 6V6.

There is one that uses a 12A*7 and two 6EJ7's. Another with two tubes that each contain a triode and a pentode.

There is a PCB for the 6AU6 - 6AQ5 version all pentode amp that I built several years ago....I found the prototype while throwing stuff out. I think it could make a good little amp or a mid sized driver driver.

There are a few more that I can't remember now, mostly based on tubes that I have lots of.
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Old 9th February 2012, 11:20 PM   #28
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Hi George.

I refer to a basic parts list to start , for example C5 , C9 , R10 and R27 have no value , all other parts if they are and it seems a good point to start for KT88.
It can be assumed that all resistors are 0.5 W unless otherwise indicated?
The XPWR002 of EDCOR would work?
5K is the best impedance for KT88?

Thanks.
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Old 10th February 2012, 03:04 AM   #29
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I haven't had the time to study the parts list, but it looks like I will real soon. I am preparing for a 500 mile road trip tomorrow morning. If the hotel has fixed the internet I'll have more info tomorrow night, if not I'll be back Sunday afternoon.

I am going to the Orlando Hamfest with a stop at ESRC to stand in awe of 4MILLION vacuum tubes.

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Old 10th February 2012, 03:25 AM   #30
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George, I like that 6l6 amp! Now I've got another long thread to read. What do you do when you've built far too many amps ?

Quote:
Originally Posted by tubelab.com View Post
I have also designed several flavors of driver boards that use the same basic schematic except that a pentode LTP is used for the second stage.
About using a pentode LTP on one of your boards, that's what I was thinking about doing w/ this. Attaching your power drive circuit after Pete's PCB, to some gm70's that have been sitting in a drawer for years.. and a couple of transformers collecting rust in my basement...... But.. It's a totally crazy idea as I have no need for that power.

First up is playing w/ some smaller pentodes (same ones as your 2nd pic above). regulate the screens & bias, shunt/schade feedback.
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