rci 2970n2

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479tx
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rci 2970n2

Post by 479tx »

I found the post where Goldfinger told someone which caps to parallel with larger value non-SMT (modder beware of course) for the 2995 DX. I'd like to try something similar to open up the lower end of the TX of a rci 2970n2 (I'm using a Drake R8B as a separate receiver which already does 6k beautifully)

From the specs on the 2995dx (can't imagine the 2970n2 would be too terribly different, although I hear its a different board) is 400hz-5000hz on AM TX. 5khz for a high end isn't bad for stock. If you could just get the low end down to 75-100 or so...
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Post by 479tx »

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Post by Goldfinger »

Is the 2970n2 surface mount or discrete components like the 2950DX? I've never worked on one before.
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479tx
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Post by 479tx »

2970n2 = SMT.

I also have a 2950-dx (also SMT) that I'd feel less bad about "tacking" some 1uf caps across in the right spots to get the TX frequency down below 400hz a bit.

If anyone has the right locations :)
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Post by Dago 971 »

Any update on this? I just acquired a 2970 myself and I would like to widen out both the receive and transmit.
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Post by Goldfinger »

Sorry 479tx, I musta let this thread slip my mind back in September. If it's the same as a 2995:

Receive:

C87: change to a 1-2.2uF mylar or non-polar electrolytic
C47: make smaller for more highs.
C48: 1-2.2uF
C193: 1-2.2uF


Transmit:

C163: Change to a 10uF Tantalum (observe polarity)
C199 and C262: change to 2.2uF mylar
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Post by 479tx »

To those that are curious,

You can (if you are careful, and have a steady hand) solder light weight poly or tant caps across the existing caps you're supposed to change (shorten the leads, and bend them like a U shape) with good results!

I didn't feel comfortable removing the existing SMT components but this works just as good.
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Post by Goldfinger »

Yes, leaving the old smaller value caps doesn't hurt a bit in parallel with the larger replacements.
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Post by 426 »

On the 2970N2 the di point would it be C199 or 262
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Post by Goldfinger »

262
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Post by 426 »

Thanks
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Re: rci 2970n2

Post by RangerTechDX »

Are ceramic smt cap ok in place of the mylars?
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Re: rci 2970n2

Post by Goldfinger »

Yes, for the hifi conversion, the uF value is whats important not the style of cap. SMT would be better as it will solder in more securely than grafting in a discrete component.
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Re: rci 2970n2

Post by RangerTechDX »

Hello GoldFinger! I was curious if you studied making any changes in the modulator section?
Thanks in advance!
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Re: rci 2970n2

Post by Goldfinger »

Yes, in 2014 when I posted this mod I didn't know about the cap change on the modulator circuit yet.

Change C260 to a 330uF, 16V (or greater)
If this cap isn't changed, there will be roll-off below 100hz.
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