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Newby needs lots of help with heathkit dx-60




 
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Author Topic: Newby needs lots of help with heathkit dx-60  (Read 413 times)
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kk4rsv
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« on: July 04, 2020, 11:08:59 AM »

Hey Everybody.  Happy 4th of July Independence Day!! 
I have  a heathkit DX-60 I have been using some on AM, just mostly getting use to it. I really like AM its got a very nostalgic feel and I love tubes.  I have read a lot of the tech post regarding the DX-60 and have got the bug to build and external modulator for it. I have found several schematics and articles for one of the modulators. One uses 6DQ6gt's and I really like it as I have  a lot of DQ6 tubes. And another uses 807's which I do not have. My background. I have built and repaired many amplifiers from 4cx250 tetrodes to 3cx3000 triodes. So I have enough basic knowledge and experience except on the area of modulation transformers. Both of the Modulator units I have found use Mod transformers that I cannot find anywhere.
The 807 Mod unit I found on here in an article and it uses UTC s-2 and a Stancor A3892 30 watt transformer. The 6DQ6GT uses a  Interstage transformer 1:3 primary-to-secondary ratio Thordarson 20A22 and a Modulation transformer, 4000-4000 ohms UTCS-19. I cannot find anything like these. So where do you folks find your transformers?
  Do you know any substitutions for these?
Can you run Mod transformers back to back to get your correct impedance? Such as a 4k ohm CT primary with a 12 ohm secondary, 2 of these transformers with the secondarys tied together to have 4k ohm to 12 ohm to 12 ohm to 4k ohm? if that makes sense to you.
this is an article with the 6DQ6GT's I am sure some of you have seen it before. Like I said I am a Newby so I will probably ask lots of dumb questions. All input is appreciated.
https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1955/12/page26/index.html


Thanks & 73
KK4RSV
Darrell

* 807 modulator.pdf (1134.18 KB - downloaded 13 times.)
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« Reply #1 on: July 05, 2020, 08:53:26 AM »

Other considerations:

1. The DX-60's Power Supply was designed for Screen Modulation, not plate modulation, and does not have the capability to support plate modulation

2. Unless you added some extra finals, you would only need a 15-20 Watt modulator. Extra finals mean a seriously upgraded power supply

Why not keep the Dixy screen modulated and add some modifications to increase modulation percentage and to control output power.

I would recommend locating a schematic for a plate modulated transmitter that outputs at least 200 Watts carrier and build it from scratch.


Phil - AC0OB

* DX-60 Schematics and Modifications General.pdf (3712.47 KB - downloaded 19 times.)
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kk4rsv
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« Reply #2 on: July 05, 2020, 11:07:06 AM »

Sounds like a good suggestion Phil but right now I am just starting to dabble in AM and I am not sure yet I want to get that deep into it.
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KD1SH
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« Reply #3 on: July 05, 2020, 06:21:55 PM »

If I might inject my five cents worth here, I wholeheartedly recommend the mod described here:
http://amfone.net/Amforum/index.php?topic=26603.0
It's simple, requires only a small handful of inexpensive parts, and will make your DX-60 sound so good that nobody will believe you're running a "Dixie Sixty".
The only caveat is that you're going to need a source of line-level audio to make the most out of this mod, like Steve says.  You can use microphone level input, using the existing mic amp stage, but the results will be far better using line-level.
I'm using a DBX 286S mic amp with mine, and the audio reports have been great.
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kk4rsv
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« Reply #4 on: July 05, 2020, 06:45:57 PM »

KD1SH are you referring to the first mod in the first entry of the page you listed the link to?
KK4RSV
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KD1SH
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« Reply #5 on: July 05, 2020, 06:57:23 PM »

That's the one.  Easy, cheap, eliminates the controlled carrier, and sounds really nice.  Expect to get 10 to 15 watts carrier.  Low power, but enough to drive an amp.

KD1SH are you referring to the first mod in the first entry of the page you listed the link to?
KK4RSV

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kk4rsv
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« Reply #6 on: July 05, 2020, 07:01:04 PM »

That's the one.  Easy, cheap, eliminates the controlled carrier, and sounds really nice.  Expect to get 10 to 15 watts carrier.  Low power, but enough to drive an amp.

KD1SH are you referring to the first mod in the first entry of the page you listed the link to?
KK4RSV


KD1SH Ok I am going to give that a  try. I will hold off building a modulator until later. Thank you Sir.
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