Galaxy DX 2527 (EPT295013Z) Direct Injection Help

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Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Tue Jul 18, 2017 7:54 pm

Hello all! i'm new here so please bare with me if i sound dumb or anything silly like that. I have a galaxy dx 2527 that i want to direct inject (bypassing ALL preamps). I had it "simi" direct injected i think at one point. I say semi because line level inputs were driving it and it honestly didnt sound very good. i currently have a Cobra 142 that is direct injected and it takes about 25-35 watts of audio wattage to drive the modulator. any help with this project would be greatly appreciated. thank you.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 31 » Tue Jul 18, 2017 8:44 pm

.
Last edited by 31 on Thu Jul 20, 2017 11:58 am, edited 2 times in total.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Wed Jul 19, 2017 8:13 am

Thanks! Let me make sure I have this correct, I need to injection at C299? Witch side? + or -?
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 31 » Wed Jul 19, 2017 9:28 am

C299 is a non polarized capacitor, lift the star side and tie your line level audio there.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Wed Jul 19, 2017 9:33 am

The cap you inject through needs to be higher in value than the original.. Most people use between 2.2uF and 10uF. I'd use a 4.7uF-50V, non-polarized electrolytic.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Wed Jul 19, 2017 10:13 am

does it need to be non-polarized? only reason i ask is because i have a cap already that is 10 and 50 but it is polarized
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Wed Jul 19, 2017 10:14 am

Correction. i have a 4.7uf 50v, not 10uf. it is polarized
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Wed Jul 19, 2017 6:47 pm

also, i read somewhere that the audio lines need to be removed from the echo board in this radio and jumped together. is that true?
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 31 » Thu Jul 20, 2017 6:43 am

Nope, when you direct inject, you bypass the echo board and the mic preamp.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Thu Jul 20, 2017 7:43 am

Is it possible to use an electrolytic polarized capacitor? What polarity goes where?
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Thu Jul 20, 2017 8:34 am

I have used polarized before and I connected the + to the resistor junction and the negative to the line-in jack, as there is some positive DC potential there.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Thu Jul 20, 2017 8:38 am

Cool. Thanks Goldfinger. I've heard a lot about you on the band. It's a pleasure on my end to speak with you. Thank you all for the help.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 31 » Thu Jul 20, 2017 11:56 am

Hmmmm?
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 31 » Thu Jul 20, 2017 11:57 am

Guess I need to step to the side from now on. My work here is done. Aloha
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Thu Jul 20, 2017 12:05 pm

Thank you very much 31 for all of your info. Thanks to you, I now have the correct injection spot. Thank you very much!!!!
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Thu Jul 20, 2017 6:57 pm

ok. so i got it all ran and ive ran into the same problem i had last time i tried this. the levels are super sensitive. seems like it barely takes much to "clip". i cant have much eq or any other effect. this is strange because the other radios i have direct injected handle it all fine. is this normal for this radio? when i turn it down to not clip, its not modulating very much and its very quiet. any thoughts?
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Thu Jul 20, 2017 7:31 pm

I apologize 31, I wasn't thinking about it in terms of stepping on toes, it wasn't my intention. I deleted any redundant posts and edited one (of mine) to keep the flow.
Once again, I am sorry.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Thu Jul 20, 2017 7:51 pm

That radio have a swing diode installed on the modulator? (in series with R281)
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Thu Jul 20, 2017 8:06 pm

yes it does
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Thu Jul 20, 2017 8:16 pm

Yeah, that mod doesn't work well with direct inject.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Thu Jul 20, 2017 8:30 pm

oh ok. so i should take that mod out. the only thing im worried about is dead key and modulation power. i want to keep that 1:4 ratio as close as i can. or should i worry about that? pardon me, im still learning about some of this stuff.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Thu Jul 20, 2017 8:48 pm

Yes, put R281 back to normal.
If you need a swing mod that doesn't interfere with the direct injection, do this:

Galaxyswingdiode1.jpg
Galaxyswingdiode1.jpg (46.17 KiB) Viewed 1497 times


In your case though it will be the junction of C301, D99, R286
As you make the resistor lower in value, you will get more swing, even at lower dead keys. Some radio's you can go as low as 100 ohm.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Fri Jul 21, 2017 7:59 am

Thank you goldfinger. Ok. Please bare with me. I think I am understanding your diagram for the original swing mod. The only thing I am worried about is removing the current swing mod. I'm not sure exactly what all has to be removed/replaced. Again, I apologize for all of these questions.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Fri Jul 21, 2017 8:20 am

If it has the R281 mod, there will be a diode in series with it. Either remove the diode and solder the free end back down or if the leads are screwed up,just replace R281 with a fresh 4.7K.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 677KY » Fri Jul 21, 2017 8:51 am

Ok. Thank you. When I get off work I'll do it and let you know. Thanks again goldfinger. I'm pretty sure I understand the original swing mod.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Fri Jul 21, 2017 10:26 am

It's not necessarily the "original" swing mod, I only called it that because it was the first one I saw in a Galaxy radio when the Pluto was king(in the 80's). In other words it's the first swing mod I ever encountered for these chassis. It does work better than any of the other methods though and it's the only one that works with direct injection. The other swing mods are affected by the high time constant of the large injection cap.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 391redneckradio » Thu May 31, 2018 7:53 am

I have my Galaxy 2527 direct injected at c240. Is this ok? I have heard c298, c240 never heard of doing it at c299. Just wonder which place is better. Thanks
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby Goldfinger » Sat Jun 02, 2018 1:18 pm

I looked for awhile at the schematic and never found C240. C299 is the correct place to inject.
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 391redneckradio » Wed Jun 06, 2018 9:54 am

Its there. Thats where Stickman said to put it before he passed away. It works good at c240 but it dont work on SSB. Will it on SSB at c299?not trying to be a pain, im very in to this studio audio and i try to learn all I can. Thanks in advance for your help! God bless!
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Re: Galaxy DX 2527 (EPT295013Z) Direct Injection Help

Postby 391redneckradio » Wed Jun 06, 2018 9:57 am

Look below the audio transformer about 2 to 3", toward the front of the radio and its there. Mylar cap. C240.

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