2950, 2970, 2527, DX22b etc. (ept295013z) mods

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Goldfinger
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2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

Receive:

Change C45 and C48 to 2.2uF mylar or non-polarized electrolytic
Remove C47
Change C224 to a 2.2uF, 25 volt electrolytic or Tantalum. Observe polarity
Change C221 and C222 to 2.2uF mylar or non-polarized electrolytic


Transmit:

Change C155 and C141 to 10uF, 16 volt Tantalum. Observe polarity
Change C240, C298 and C299 to 2.2uf mylar or non-polarized electrolytic

Sideband/FM Transmit:
Change C131 and C136 to 2.2uF mylar or non-polarized electrolytic


Note: For the transmit to have full width, the audio in/out wires on the echo board (one wire from J2 and one from J3) have to be disconnected and jumped together, bypassing the echo board.
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Post by HomerBB »

Goldfinger, I am not a radio tech. They seem to hate me when I take the covers off.
So could you explain exactly what is to be expected in changes from each of the modifications.

Thanks,
Homer
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Post by Goldfinger »

Most of the cap changes are extending the frequency response of the low end from 300-400 hz stock, down to 20-30 hz after the modification. Removing C47 adds more highs above 3500 hz on receive.
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Post by HomerBB »

So it is a tone change, or does it also permit better reception?
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Post by Goldfinger »

Yeah, tone/frequency response change. No changes to the selectivity or sensitivity of the receiver chain.
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Post by HomerBB »

Thanks, a lot.

It sounds like a good place to start for getting a smooth audio setup.
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Post by Goldfinger »

It does make for better reception IMHO though as the receive seems cleaner and less "crackly". Plus I use middle of the road amplified computer speakers with a sub as my speaker. It really enhances the wider audio.
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Post by HomerBB »

I might have to give it a try
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by redlght »

What effect would swapping out the stock 455ht filter to a 455f that is 6Khz?
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

You will just have crisper highs from the added high end response. On 29's, I also noticed the lower bass seems cleaner when you compare a wide radio with the stock filter to one with a 6kc. (when listening to a wide transmitter)
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Mr.Lightning »

Goldfinger, I am sure this has been asked before. Can you use NON-polarized 2.2uf in place of the polarized 2.2uf? Thanks!
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

I've never done it on a CB but I'm sure you can. Just make sure they are 25 volt or higher.
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

What's the injection stops for this board thank you, for am and ssb
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

C299 for AM, C131 for SSB
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

Is the injection cap a 2.2uf or 10 if and witch side the cap do ya inject threw .
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

Use a 10uF into the R281/R282 end of C299.
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

I used a 2.2 uf but there some feed back over the recive . I wonder if a 10 uf would stop that .
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

It's virtually impossible for the direct injection on a Galaxy/Ranger to feed back into the receive unless you aren't injecting in the right place. Are you sure the radio you are working on has the ept295013z board?
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

Galaxy saturn turbo that has the 2950 orange face board .
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

C299 farthest away from the case with a 2.2uf 50v cap
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

Pull out C298 and see if it stops.
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

You said c298
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

Yes, i wanted to see if the audio was back-feeding either through the mic amp or the talkback circuit.
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by DoubleR0788 »

Removed the cap like suggested and no more feedback over speakers .
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Re: 2950, 2970, 2527, DX22b etc. (ept295013z) mods

Post by Goldfinger »

It looks like something is funny with the talkback circuit or something. With that cap removed you won't be able to use the mic jack for modulation but if you are direct injecting, it won't matter.
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