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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sun 12, 2017 2:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: aston, pa, usa
I've still got 6GY6 and 6888 tubes if anyone needs them.

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"All glory is fleeting" - George Patton
KB3QNN 73


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Thu 16, 2017 9:25 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
Posts: 53
I'm going to give this transmitter a try. Not satisfied with the Lil7 transmitter. Did I hear of a kit available somewhere or just have to get all the parts separately? Either way, looks like a fun project to work on. At least I have a good handful of the parts on hand.

Jeff


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Fri 17, 2017 4:27 am 
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Bill Hamre did have a kit with parts, but after 10 years or so most of the interest in building was history... He did mention just prior to your post he has 6888 tubes...


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Fri 17, 2017 5:43 pm 
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Thank you Tom for clarifying. Just wanted to see if their was a kit before scouring around for all needed parts. Luckily I do have a handful of parts. I guess the challenge for me is locating a good matching coil or learning how to coil my own. But for now, I'll start with the power supply.

Jeff


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sat 18, 2017 2:24 am 
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Jeff

I have a remainder of one of Bill's kits, plus a few coils on hand...

Lemme know what you need and I'll send the parts I have...

I dunno if UHF converters are still cheap on ebay, that's generally where I'd source my "project boxes"... They'll almost always have chassis, sockets & transformer needed... The Granco & Mallory are usually the best ones to use, no doubt are others...


Tom


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sat 18, 2017 4:51 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
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Thank you Tom.

If you have most of the kit left, let me know how much you want for it. I either have or it is not hard to get all the capacitors and resistors, same with the diodes. Sockets, tubes and coils would be a great help. I've got plenty of jacks and have several 1 meg hertz crystals and I think I have a transformer that would work, it's a 120v in 125/12v out rated 15mA and 300mA. Do you think that would work? If wiring the tube filaments in series should divide the 12 volts to 6volts each? Or using a resistor of the appropriate value? Or is the Amperes ratings too small?

Let me know what you will part with and how much you want for them.

Jeff


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sat 18, 2017 4:53 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
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Also I just posted the radio this will transmit too. As for a project box, I don't know exactly what I am going to do other than the whole enclosure will be in a wooden cabinet, hand made.


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sat 18, 2017 5:32 pm 
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Your transformer has to low of current rating... Probably ought to have a 30-40ma rating on HV winding and a 6888 has a 800ma heater and 6C4 is 150ma, you'd want at least a 1A rating for that... For a some headroom 1.5A would be better... To series tube heaters the current must match, a 150ma tube in series with 800 would receive almost all the voltage...

BTW I assume you are building the 6C4 - 6888 version??


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sat 18, 2017 5:57 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
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Yes, that is the one I am going to build. I had intended to mention that. I was afraid that rating would be too low for the transformer. Just spending a little time looking around, that value of transformer is tougher to find.


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sat 18, 2017 6:48 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2188
Location: aston, pa, usa
Jeff,

PM me with a mailing address and I'll send you a 6888.

Bill

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KB3QNN 73


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sun 19, 2017 12:29 am 
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Do you have tubes such as 6AV6 or 6AT6??

With different basing connections either can be used in place of 6C4... And give a increase gain...


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sun 19, 2017 1:41 am 
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No, but i saw that the place where i get my capacitors and resistors has one for six and a half bucks, thats not too bad. Antique electronic supply.


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sun 19, 2017 4:02 pm 
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j8000 wrote:
No, but i saw that the place where i get my capacitors and resistors has one for six and a half bucks, thats not too bad. Antique electronic supply.

Hang on, I can come up with the audio amp tube, no charge...

Got a box of some used ones, have to test to be sure it's good...


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Nov Sun 19, 2017 4:33 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
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Ok, sounds good. I found a much less expensive transformer at old radio parts. It's more of a hassle to order their, but the prices and selection are superior. So it'll take a few days to get my order through. Also want some crystal radio items from him as well.

Jeff


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Dec Tue 24, 2019 7:10 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
Posts: 53
Finally got the transmitter to work. After frying the power transformer I got discouraged and put the project on hold until a few days ago. Used some transformers from an old radio a lady gave me that was in sorry shape.

Anyway, the transmitter works okay, I used the schematics on the top of the page here. It needs a lot of cleaning up. I had to use full power to get a standard MP3 player to work, but I was sharing the station with a strong radio broadcast that comes in good in the dark hours. I will test again in the day.

I had to substitute a few parts, so I expect better results when I clean this up and set the frequency to something quieter. It's a shame though, I bought ten of the 1Mhts frequency, so if anyone wants 6 or 8 of them I'll send them to you.

Jeff


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Dec Tue 24, 2019 7:24 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
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I think I'll start cleaning up the power supply. The biggest issue I have is I'm using two transformers, which doesn't bother me too much as I'm not worried about excess space, but the heater voltage is less than 3 volts. While I did able to get the transmitter working, I don't really want to run it much on low voltage.

Q1- So, where now a days do you folks buy your transformers at?


Also, I would like to have a tube powered power supply, so for question two:


Q2- What is a good tube powered supply scematic that isn't too complicated that works well for transmitters?


Thank-you,

Jeff


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Dec Tue 24, 2019 8:02 pm 
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Joined: Nov Wed 08, 2017 3:28 pm
Posts: 53
Actually I'll prob. just order a transformer from Mousers. I see they have a few 6.3's that fairly reasonable.


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 Post subject: Re: Three different 6888 & 6GY6 xmitt versions...
PostPosted: Dec Wed 25, 2019 6:08 am 
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Joined: Nov Wed 08, 2017 3:28 pm
Posts: 53
Tried it again earlier when the station was much quieter and it transmits great on two radios. The pot im using is shot, it's either shorted or opened. I,ve even got a microphone to work, but it is going to need a pre amp as the signal is very faint.

So while i wait power supply parts, i will switch out the pot with an old radios part and start work on the pre amp.

Merry christmas,
Jeff


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