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

Caps, cap, capacitor, direct inject, bass, lows, hi fi, hifi, hi-fi, high fidelity, mod, mods, modification, upgrade, widen, wide audio, Goldfinger, Cobra, Galaxy, Ranger
User avatar
Goldfinger
Site Maintenance
Posts: 2936
Joined: Sat Jun 30, 2007 12:27 am
Location: Beaver State

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

Postby Goldfinger » Sun Nov 11, 2012 1:46 pm

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 and C298 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.
wwpdx
wwpdx.com
User avatar
HomerBB
WWPDX MEMBER
Posts: 652
Joined: Sat Jan 10, 2009 9:52 am
Location: NW Arkansas

Postby HomerBB » Sun Nov 11, 2012 6:00 pm

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
ImageImage
User avatar
Goldfinger
Site Maintenance
Posts: 2936
Joined: Sat Jun 30, 2007 12:27 am
Location: Beaver State

Postby Goldfinger » Mon Nov 12, 2012 2:04 pm

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.
wwpdx
wwpdx.com
User avatar
HomerBB
WWPDX MEMBER
Posts: 652
Joined: Sat Jan 10, 2009 9:52 am
Location: NW Arkansas

Postby HomerBB » Mon Nov 12, 2012 5:20 pm

So it is a tone change, or does it also permit better reception?
ImageImage
User avatar
Goldfinger
Site Maintenance
Posts: 2936
Joined: Sat Jun 30, 2007 12:27 am
Location: Beaver State

Postby Goldfinger » Mon Nov 12, 2012 6:19 pm

Yeah, tone/frequency response change. No changes to the selectivity or sensitivity of the receiver chain.
wwpdx
wwpdx.com
User avatar
HomerBB
WWPDX MEMBER
Posts: 652
Joined: Sat Jan 10, 2009 9:52 am
Location: NW Arkansas

Postby HomerBB » Mon Nov 12, 2012 6:52 pm

Thanks, a lot.

It sounds like a good place to start for getting a smooth audio setup.
ImageImage
User avatar
Goldfinger
Site Maintenance
Posts: 2936
Joined: Sat Jun 30, 2007 12:27 am
Location: Beaver State

Postby Goldfinger » Tue Nov 13, 2012 11:20 am

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.
wwpdx
wwpdx.com
User avatar
HomerBB
WWPDX MEMBER
Posts: 652
Joined: Sat Jan 10, 2009 9:52 am
Location: NW Arkansas

Postby HomerBB » Tue Nov 13, 2012 12:03 pm

I might have to give it a try
ImageImage
User avatar
redlght
WWPDX MEMBER
Posts: 189
Joined: Sat Jan 30, 2016 12:44 am

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

Postby redlght » Mon Feb 29, 2016 1:41 pm

What effect would swapping out the stock 455ht filter to a 455f that is 6Khz?
User avatar
Goldfinger
Site Maintenance
Posts: 2936
Joined: Sat Jun 30, 2007 12:27 am
Location: Beaver State

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

Postby Goldfinger » Mon Feb 29, 2016 3:16 pm

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)
wwpdx
wwpdx.com

Return to “rx and tx mods”

Who is online

Users browsing this forum: No registered users and 1 guest