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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Fri 01, 2015 6:34 pm 
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Location: Clayton, Ind.
Two-deck build question, from kit from Bill, who is a wonder:

I'm using two perf boards to build a two-level transmitter. Goal is to have the four tubes visible through the old speaker openings of the old Detrola cabinet.

The top deck so far has the transformer and the power supply section, which will use two 6AL5s per Jeff's design.

The lower deck will have the 6av6 and 6cs6 tubes, the variable resistor, the AA5 variable cap, and two switches with wood knobs (one just a rotary on/off switch and one the gain control).

The rear panel will be from an old "pressboard" clipboard with vent holes, etc. It will have the antenna jack, the audio jacks, power cord with strain relief, fuse, a hole to reach the variable resistor, and later will have the mp3 player.

Some questions:

1. Leads from audio jacks, and probably from antenna jack, will be about 3 to 4 inches long, with a little slack for when the back is opened. I was planning to use small coax - is that overkill? Rest of RF component leads around the 6av6 and 6cs6 will be as short as possible.

2. Any other leads I should use coax for? The leads to the gain control will be rather long, 5 to 6 inches.

3. Some builds I see here put the osc right next to the power supply; others near the RF section. So, in my case, top deck or bottom deck? Any coax?

4. The ground bus will run from a terminal strip on the top deck either as (A) one U-shaped length: to the "left" along the bottom of the top deck, then down to the bottom of the bottom deck, then to the "right" to pick up the remaining grounds including all the way to the gain control pot, so about 6 plus 3 plus 9 inches; or (B) one 6-inch run from the terminal strip under the top deck, and a second down 3 inches from the terminal strip, then about 6 inches under the bottom deck. Benefits or disadvantages of either (A) or (B)?

5. I am picking up (I hope) the couple of tube sockets I need at the IHRS meet tomorrow in Kokomo. I have one "wafer" socket for 7-pin that I like because it is so low-profile and the bottom deck will sit only 3/4 inch above the bottom of the case. Any drawbacks to those if they serve the 6cs6 and 6av6?

That is all, thanks for any insights.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Fri 01, 2015 11:50 pm 
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TDane wrote:
Some questions:

1. Leads from audio jacks, and probably from antenna jack, will be about 3 to 4 inches long, with a little slack for when the back is opened. I was planning to use small coax - is that overkill? Rest of RF component leads around the 6av6 and 6cs6 will be as short as possible.

Maybe but isn't going to cause any harm... A 100 pf across the gain control usually shunts any RF present on the audio...

2. Any other leads I should use coax for? The leads to the gain control will be rather long, 5 to 6 inches.

I've used shielded cable on a couple builds when gain was like 6-8" from input, may be overkill but had no problem so I don't know

3. Some builds I see here put the osc right next to the power supply; others near the RF section. So, in my case, top deck or bottom deck? Any coax?

If it's not difficult to mount it at the RF output that's best, but I've never had a problem either way...

4. The ground bus will run from a terminal strip on the top deck either as (A) one U-shaped length: to the "left" along the bottom of the top deck, then down to the bottom of the bottom deck, then to the "right" to pick up the remaining grounds including all the way to the gain control pot, so about 6 plus 3 plus 9 inches; or (B) one 6-inch run from the terminal strip under the top deck, and a second down 3 inches from the terminal strip, then about 6 inches under the bottom deck. Benefits or disadvantages of either (A) or (B)?

As long as it's of sufficient size I think either configuration is OK, I'll generally use solid #14 stripped from a piece of junk Romex cable...

5. I am picking up (I hope) the couple of tube sockets I need at the IHRS meet tomorrow in Kokomo. I have one "wafer" socket for 7-pin that I like because it is so low-profile and the bottom deck will sit only 3/4 inch above the bottom of the case. Any drawbacks to those if they serve the 6cs6 and 6av6?

I know of no reason the wafers won't work, used them on one I built...

That is all, thanks for any insights.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Sat 02, 2015 1:55 am 
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Location: Clayton, Ind.
Thanks, Tom, x 5. Feels like I am on the right track.

At the last two hamfests I went to, I bought a 12cs6, a 6cs6 and I think 2 of the 3cs6s - but can I find the 6 now? I could have sworn I put it with the others, and the various -av6s, but it's not there. Maybe a cat ate it. Hope I can find one tomorrow.

Tom

AHA! I found two at IHRS. I was wading through a box of about 250 TV tubes when a nice guy came up, "what are you looking for?" A 6CS6 for an in-home AM transmitter. "Oh, it's going to have a light-colored plate like that one," and pointed right at a 6CS6. Wow! Saved me a lot of time. But no sockets though, the vendors that usually are there that have assorted stuff (miniatures aren't in the radios in the IHRS wheelhouse) like that weren't there. But it was a great day.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Mon 04, 2015 4:26 am 
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That guy no doubt knew what he had... :lol:

Still the 75 or so 12CS6 and the hand full of 6CS6 I've had all had grey plates... RCA did mfgr several types with "silver" plates, one being 6BY6 that can be used in place of 6CS6...


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Fri 15, 2015 6:33 pm 
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Location: aston, pa, usa
Sad day in ARF homebrew history. The last of Norm Leal's 12AV6/12CS6 parts kits one hundred donated power tranny's is shipped! We may now need a new curtain burning design for our power supply. Just like the original AA5 design, ironless! Back to our roots. Can somebody post the "as built" schematic by 35Z5 that I'm using with the kits so that we can gather ideas.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Fri 15, 2015 11:53 pm 
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A 24v power transformer with a B+ tripper would no doubt work, gives approx 107v if I remember correctly...

Still -- may be just as well to concentrate on the LM386, it's far easier to build plus gives similar performance, range etc...


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Fri 15, 2015 11:59 pm 
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Location: aston, pa, usa
BTW the 386 parts kits were by far our most popular of the parts kits in about the last year. Also, no negative feedback about them that I have heard. However, if you just have to have an AM broadcaster that is vacuum tube you can do the 6888 with the PCB by Jon Stanley.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Sat 16, 2015 12:02 am 
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Location: aston, pa, usa
viewtopic.php?f=12&t=260727
--------------------------------------------------------------------
above is clickable 6888/PCB link

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Sat 16, 2015 12:04 am 
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Location: aston, pa, usa
viewtopic.php?f=12&t=193042&start=700
---------------------------------------------------------------------------------
above is clickable 386 link

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Sat 16, 2015 1:29 pm 
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Location: Weimar, Texas
bill hamre wrote:
BTW the 386 parts kits were by far our most popular of the parts kits in about the last year. Also, no negative feedback about them that I have heard. However, if you just have to have an AM broadcaster that is vacuum tube you can do the 6888 with the PCB by Jon Stanley.


John's PCB is very nice. It's laid out well. It's compact. Whoever manufactured the board did a first class job. There's one optional mica trimmer (C5) that has been a bear to find but since it's optional I'm not too worried about it.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: May Wed 20, 2015 5:06 pm 
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If anybody thinks I owe them any part just PM me.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Sat 18, 2015 12:33 am 
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http://www.goldmine-elec.com/pdf/243_pgs78-87.pdf

This could just be an old listing, but it does show Electronic Goldmine selling the G12951 transformer for $2.98 each. Scroll down near the page bottom to where the transformers are shown.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Sat 18, 2015 12:49 am 
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Blustar1 ,

that looks to be a old ad


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Sat 18, 2015 12:59 am 
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Yeah, it could be.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Sat 18, 2015 2:42 am 
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I have been getting zapped when I touch my input connector, but the transmitter still seems to work okay and isn't causing any apparent damage to anything I am using for input. Any idea what gives?


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Sat 18, 2015 4:03 pm 
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http://www.ebay.com/itm/YS57H-110FA-EPE ... _151wt_847

Harbor City Electronics is selling 3 of these EPEC transformers on eBay which might work. They're listed at $19.93 each, but one can make an offer.


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Thu 23, 2015 1:26 am 
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The schematic doesn't show for me. None of my browsers show anything but the little ? icon. Do you have a link to the image, perhaps?

EDIT: The site that used to have all of your links, and the pic, is no longer there. Just send me to a web hosting site.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Thu 23, 2015 3:58 am 
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Schematic on first page is up, still working on other broken links...


Tom


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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Thu 23, 2015 6:41 pm 
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I submitted a bid of $5.00 each a few minutes ago to Harbor City Electronics for the three Epec YS57H-110FA xformers, but the seller counteroffered with $12.00 each for the three xformers. Anyone who's interested can submit an offer for $12.00 each.


Last edited by Blustar1 on Jul Sat 25, 2015 5:28 am, edited 1 time in total.

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 Post subject: Re: 12AV6-12CS6 Transmitter(Revised Schematic)
PostPosted: Jul Fri 24, 2015 2:11 am 
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I was sort of curious today as to how far I could pick up the signal from the 12AV6-12CS6 transmitter using my '71 Passport pocket transistor radio. After inserting a CD into a Califone 2395AV-02 AM/FM /CD/dual cassette player, I then proceeded to plug the player into the audio jack of the xmitter. Well, I could plainly hear the music from the CD beginning from the upstairs at the north end of my house (where the xmitter was located), all the way downstairs to the south end, across my entire yard, and then across the neighbor's driveway which all spanned a total of 118 feet. That's not bad at all for a low power xmitter.


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