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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sat 30, 2017 11:14 pm 
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Blustar1 wrote:
I think that it's well overdue to open up an old thread. Given that the Electronic Goldmine G12951 (Epec YS57H-110FA equivalent) transformers just don't seem to be available anymore for the 12AV6-12CS6 AM transmitter kit, why can't one just substitute in a simple 12VAC 2A power transformer to begin with? Basically, all one then really needs is a full wave bridge connected to the line, and that should deliver something like 170VAC RMS for the B+. Of course, we would also need a 5VDC power source for the can oscillator, but I would imagine something can be conjured up (with a little ingenuity) by tapping the 12VAC secondary along perhaps with the inclusion of a simple 5VDC regulator. This is just something from the top of my head, but it's just a thought. Any other suggestions?



Some good thoughts there. How about two 120-12volt transformers. Power the first with 120, connect 12volt - to 12volt on second transformer. Take, and condition 120volts from second transformer. Use the 12volt windings for the filaments, and a 7805 for the crystal.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 12:01 am 
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john8750 wrote:
Blustar1 wrote:
I think that it's well overdue to open up an old thread. Given that the Electronic Goldmine G12951 (Epec YS57H-110FA equivalent) transformers just don't seem to be available anymore for the 12AV6-12CS6 AM transmitter kit, why can't one just substitute in a simple 12VAC 2A power transformer to begin with? Basically, all one then really needs is a full wave bridge connected to the line, and that should deliver something like 170VAC RMS for the B+. Of course, we would also need a 5VDC power source for the can oscillator, but I would imagine something can be conjured up (with a little ingenuity) by tapping the 12VAC secondary along perhaps with the inclusion of a simple 5VDC regulator. This is just something from the top of my head, but it's just a thought. Any other suggestions?



Some good thoughts there. How about two 120-12volt transformers. Power the first with 120, connect 12volt - to 12volt on second transformer. Take, and condition 120volts from second transformer. Use the 12volt windings for the filaments, and a 7805 for the crystal.

That's the transformer hookup we used on the 6LE8 transmitter, works just fine... I don't see a need to modify circuit to osc, ground end of B+ winding should work just fine...

BUT rather than jump through all these hoops, a conventional xfomer with 6 &120v secondaries could be used... Swap tubes to 6CS6 & 6AV6 instead of using 12v flavors... Of course it's now bearing a strong resemblance to the 6C4/6GY6 transmitter... Now days I'd use a 6GK5, 6HA5 etc as audio amp... For uber cheapie tubes a 2GK5 & 5HZ6 or 5GX6 could be used in series...

As far as operating from line without transformer isolation, you're on your own...

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 5:49 pm 
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35Z5 wrote: "That's the transformer hookup we used on the 6LE8 transmitter, works just fine... I don't see a need to modify circuit to osc, ground end of B+ winding should work just fine...

BUT rather than jump through all these hoops, a conventional xfomer with 6 &120v secondaries could be used... Swap tubes to 6CS6 & 6AV6 instead of using 12v flavors... Of course it's now bearing a strong resemblance to the 6C4/6GY6 transmitter... Now days I'd use a 6GK5, 6HA5 etc as audio amp... For uber cheapie tubes a 2GK5 & 5HZ6 or 5GX6 could be used in series...

As far as operating from line without transformer isolation, you're on your own..."


35Z5: Yes, definitely using transformer isolation is desirable, but the goal here was simply to get a discussion going, and not to present an actual circuit. Now, the fact that it would bear a strong resemblance to the 6C4/6GY6 transmitter was why the use of the 12V transformer(s) was originally suggested. What we were actually searching for was simply an alternate power supply for the 12AV6-12CS6 transmitter.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 6:59 pm 
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Tubes, 12AV6, 12CS6, were used when we bought transformers with specific voltages at a decent price. Nice to use transformers with isolation and a 6.3 volt filament winding but they weren't available, in quantity, at a reasonable price.

AES, www.tubesandmore.com has one for $42...

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 7:39 pm 
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AES has this 4A with dual primaries for $18. Too lite?

https://www.tubesandmore.com/products/t ... ry-126v-4a


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 7:48 pm 
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Oh, it's definitely not too light, but rather more than enough.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 8:00 pm 
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https://www.suburban-electronics.com/di ... RANSFORMER

Perhaps something like this. It's retailing for $12.95. Hopefully, there are cheaper ones around than this.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 8:06 pm 
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https://www.jameco.com/z/P-8657-R-Power ... 21400.html

This one looks more promising. It's retailing for $11.95, and even cheaper in quantity.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 8:47 pm 
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Blustar1 wrote:
Oh, it's definitely not too light, but rather more than enough.


You use the other 120V primary as a secondary. Full isolation. No need for 12V back to backs.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Dec Sun 31, 2017 9:52 pm 
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I didn't think of using it in that way, but that is definitely an advantage.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jan Mon 01, 2018 3:18 am 
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How about the LP-427? Light duty, rated at 1 amp, also has the dual primary and a 6-0-6 output. I have found them for around $5 online including eBay. Happen to have one here and verified the second input has 120 vac on it when the other input is powered. I would assume that since it is spec'ed at 1 amp with either 220 v or the two primaries paralleled that running a single input would make it a .5 amp.

Here is one of the listings; http://www.mpja.com/12V-1A-Center-Tapped-6-0-6-Transformer/productinfo/27838+TR/

Have not tried it but since I dug it out it, maybe I could make an isolation transformer for an AA5. I may try that. Even if the output was slightly lower would be OK. I will see if there is a heat issue. Anyway the price for it was good.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jan Mon 01, 2018 7:01 am 
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black85vette wrote:
How about the LP-427? Light duty, rated at 1 amp, also has the dual primary and a 6-0-6 output. I have found them for around $5 online including eBay. Happen to have one here and verified the second input has 120 vac on it when the other input is powered. I would assume that since it is spec'ed at 1 amp with either 220 v or the two primaries paralleled that running a single input would make it a .5 amp.

Here is one of the listings; http://www.mpja.com/12V-1A-Center-Tapped-6-0-6-Transformer/productinfo/27838+TR/

Have not tried it but since I dug it out it, maybe I could make an isolation transformer for an AA5. I may try that. Even if the output was slightly lower would be OK. I will see if there is a heat issue. Anyway the price for it was good.



Better yet Rick. Just gets better and better. The transmitter is well worth the build.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jan Mon 01, 2018 6:23 pm 
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The LP-427 transformer with the 1.0A output may handle it. The 12AV6 & 12CS6 tube heaters combined will draw 0.3A. Keep in mind though that a later 12AV6-12CS6 revision included the MP3 player along with the LM7805 5V regulator. Then one also has to take into account the can crystal oscillator as well. At the moment, I'm not totally sure at all what the MP3 player, the LM7805 regulator and the can crystal oscillator will actually draw, but here is what I came up so far (Please do recheck this):

MP3: ?????????
LM7805: 5 mA (Quiescent current)
1.0 Mhz can crystal oscillator: 7mA


12AV6 & 12CS6 heaters: 0.3A combined


Last edited by Blustar1 on Jan Mon 01, 2018 7:04 pm, edited 1 time in total.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jan Mon 01, 2018 6:51 pm 
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I doubt the second primary would handle even a AA5, but easily meet the needs B+ of a 12AV6/12CS6 xmitter, plus MP3 player etc would power from the low volt secondary...

Would simplify the xmitt, voltage doubler not required..

Orig Tx designed for the available xformer

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jan Mon 01, 2018 7:19 pm 
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35Z5 wrote:
I doubt the second primary would handle even a AA5,


You are correct. I hooked up a radio to the transformer and fed it from my variac / iso test set. Watched the voltage on my meter and it only gets to about 50 volts output. :-(

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Feb Wed 21, 2018 11:40 pm 
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I'm going to revive this yet again. After reading until I am cross eyed, I am finally going to post and ask a few questions. I have been getting bits and pieces here and there. Basically I like Norms design and want to follow his 6888 build. I don't want to hijack this thread, so I will ask a few questions and start my own thread. I have a BTL UHF unit on the way for a box, and I have a sleeve of NOS Phillips 6888 tubes on hand. Yes, I want it to glow. I have the schematic with the 6C4 and 6888, which intrigues me.

Whats the advice on using the original BT power trans? If its too weak, then will that LP-427 transformer power it with the unused 120v primary winding for the B+? Most of the reading I have found have the freq set at around 1000kz or so, but I dont recall anything on the lower spectrum. Will a tuning cap from an old AA5 work? What is the frequency range on this design? Then of course, the coils. Sounds like Mouser?

Hope this is not too many questions...

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Feb Fri 23, 2018 4:16 am 
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Ok, the BTL showed up today and I can tell by looking the transformer on it is way too small. You think the current rating on that LP-427 would handle the 6888 and 6C4? I think the filaments are ok.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Feb Fri 23, 2018 4:17 pm 
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Ever since Norm and Tom came up with with the 12AV6/12CS6 design for those 100 tranny's for kits it became our best seller over night. When it ended we went into withdrawal! This new discussion about iron and an alternative power supply is great.

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