MRF 455 mod board

[rfoverlord]

Does anyone know of anywhere that is selling the mrf 455 & board for the 2510 and or lincoln since 477 & 497 are scarce? I would like to find one to have a as spare, as i have a spare 477 but i would like all the spare parts i can think of for these radios.

 

[rfoverlord]

No one has done the change over? I know i can mount one on the heat sink, i just thought it would be easier to have it on a board.

 

[DIRTYWHITEBOY]

I must have got lucky,my lincoln came with the 455 final.

 

[AudioShockwav]

Three RF Output Modifications for the HR2510 & Lincoln
MOD 1
When using a power mic with the HR2510, with the ALC cranked up, you will
Overdrive the Final. Two Solutions exist, Keep the ALC turned down, or
replace the final (MRF477) with a MRF497. This will cure the overdrive problem.
To pull a few more watts from the HR2510, you may replace the pre driver ,
Q134 (2SC2086) with an ECG or NTE 340. The 340 pin outs are opposite the
2SC2086 (the 2SC2086 is BCE and the 340 is ECB). Set the bias with VR112 to
70 - 80 Ma in USB on 28.000 MHz with a 1kHz tone and the ALC set to peak.
MOD 1a
This is an improvement on MOD1. This suggests you change the MRF477 with
the MRF497, making the necessary Bias adjustments. (as in MOD 1). Then instead
of changing Q134(2SC2086), you modify the circuit to provide more Gain.
See "The Better High Power Mod" page for more info.
!!!!!ATTENTION!!!!!
The following mods [Mod 2 & Mod 3] WERE missing some 'Key' information.
With the help of a few of you out there we have solved the problem.
Thanks, Rogerbird
MOD 2
This will cure the overdrive problem and allow you to pull a a few more watts also.
The MRF477 may be replaced with a MRF455, But since it is not a TO-220
case a mounting problem exists. A piece of aluminum, 1" wide by 2" long by 1/16 "
thick may be used to mount the MRF455, Then your new heatsink may be mounted
to the chassis heatsink underneath the circuit board. Small pieces of hook up wire
must be used to connect the circuit board leads to the leads of the MRF455.
The SECRET to make this work is to STRAP the Emitter of the MRF455 to one of the mounting screws.
With the help of several people, we have found that Uniden is using this
method to cure the problem I had before.
I have found in some radio's you may need to add or change
some of the coupling capacitors to get nominal output,
But, overall this mod is cheaper than the MRF497 mod and more robust!
I have even been able to mount the MRF455 directly to the rearpanel.
Just mark and drill 2 holes to mount it.
Also for a Bias Diode you can use a 1N4001 diode, Just make sure it
is in contact with the ceramic of the final to detect its heat.
This final set-up will last forever.
MOD 3
To double the output power you must make a new circuit board, 1" by 2",
that will accommodate two final assemblies (using two MRF455).
Remove Q132, C124, C125, D164, R157, VR112, L126 and R180.
Order Duplicate parts from Uniden Parts Department.
9900 Westpoint Drive, P.O. Box 5043, Indianapolis, IN 46250 Tel.#317-842-1036.
The Uniden part numbers are:
Q132 - BDBZ0529001
C124, C125 - BCCG815615Z
D164 - BDFY0058001
R157 - BRFT611004Z
VR112 - BRTY0182101
L126 - BLDY0221001
R180 - BRFT614704Z
The new circuit board assembly (both new finals) must be attached to the radios large
finned heatsink. Use hookup wires to attach the input, output and ground leads of your new
board to the junction of C126 and R180, R158 and L135. Study the schematic carefully,
duplicate both final assemblies as per schematic. Double check everything. If you don't have
a service and repair manual, Order one through Uniden Parts.

The HR2510 uses low level modulation so it will never be as loud as a radio using high level
modulation (on AM only), but by turning up the AMC, and the previous mod they become
AM performers also.
The above information was created by Thomas..and edited by Rogerbird

This was pulled off of rogerbirds Page.
I still do not know were to get the board unless it can be had from Uniden.
Hope it helps a little.

73
Jeff

 

[Switch Kit]

The things we do for a little more never siezes to amaze me.

 

[rfoverlord]

Thanks guys for the replies, i have all of rogerbirds mods on one of my computers. I wasn't doing it for a power increase, it was for spare parts if needed, i all ready have the 497 in it, which is funny because i still run the factory power setting out of it, just runs cooler. I haven't run it mobile in over 2 years just power them ( i have 2) up for a weekend to keep them "fresh". I just thought it would be nice to have a spare around but it's not that important to me.

 

[spider451]

sir i can make what u ask for out of copper clad and with a dremel tool pretty easy as i was doing it for years in galaxy radios based on the board u are asking about.

 

[Wire Weasel]

RF Parts in California should have the final. If they don't have your RF part....then it may not exist.

 

[rfoverlord]

wow! I can't believe anyone would read this old post. My origninal 2510 with the chip switch, and the detector diode mod has a 497 in it. not that i really need another since i no longer run a 2510, but i know that it works and i have a spare. kinda like my boomer 250 sittin on a shelf next to a TS 350hdv and 500hdv with active biasing(peekaboo). I'd rather let them sit then have some punk run around the neighborhood splattering.
But thanks for the reply, I already have an account with RF parts since i get most of my parts from them.

 

[mechanic]

There is a fellow that can get MFR477s, $38 plus shipping AND in limited supply... I too worry about my 2510s, all three and a HTX-100.

mechanic

 

[rfoverlord]

thanks for the info about someone still having a surplus. I might have to pull out one of them since the XYL got her license. Just set it up as a dedicated tech radio.