Help with HR2510 Final PA mica caps replacement and more.

[Xracerx13]

CrazyFin,

The yellow/green wire with the ferrite is for a better higher current power source for the final and attaches at board right where power comes in to board and goes to TP4.

The small guage red wire going through ferrite is for the dual external 30mm cooling fans. The fans have a mini on/off switch tucked into the heatsink fin so I can choose to have them on or off rather than on all the time when I turn on the radio.

The small circuit board with the grey electrolytic and white wire are original parts and is not a mod.

NBL is short for noise blanker usually abbreviated with just NB.

The circuit board with the blue heat shrink is a CBC international channel guard filter and reduces the band pass for less cross channel interference.

Hope that helps

 

[CrazyFin]

The yellow/green wire with the ferrite is for a better higher current power source for the final and attaches at board right where power comes in to board and goes to TP4.

Aaaah! Interesting solution! I guess this should work´for other CB:s as well that has a similar final stage as the HR2510 (which are quite many)

The small gauge red wire going through ferrite is for the dual external 30 mm cooling fans. The fans have a mini on/off switch tucked into the heat sink fin so I can choose to have them on or off rather than on all the time when I turn on the radio.

I feel embarrased now. Should have guessed that right away since I have a similar solution one of the CRT Hercule Turbo:s staring at me from the "to-do-shelves"... Good solution to reduce interference from the fans with the ferrites.

NBL is short for noise blanker usually abbreviated with just NB.

He he, yepp I was guessing at Noise Blanker but since they normally are abbreviated with NB and not NBL I thought it was a special type of diode that in this case was replaced with schottky diodes

The circuit board with the blue heat shrink is a CBC international channel guard filter and reduces the band pass for less cross channel interference.

Yepp, indeed. I have read most of the CBC International books and been reading through a LOT of the excellent info files at cbtricks.com. I´ve been thinking of testing on of those as well.

Thanks for all the good info in this thread. Now it's time for me to start working on one of the CRT Hercule Turbo:s again. Will post my issues/questions in new threads.

 

[Xracerx13]

Here's a little something for whoever is feeling up to doing it.
I have this done in my HR2510 and it works great.

The HR2510 repeater offset mod. Spoken of, but never any documentation available to do the mod.

It is a 100khz offset TX frequency crystal switch for FM mode only repeater use on 10 meters using the roger beep button to enable it.
After the mod the roger beep button will only work as an On Off for the circuit in FM mode, and will not do anything in any other mode. If you change modes to say SSB or AM the circuit will turn off if roger beep button is still depressed. The roger beep tone becomes permanently disabled after this circuit addition.
All that is needed is some extra various components listed below, and placed as seen in my crude picture.
The orientation in the photo is looking at the radio from rear to front. I'll correct it some day to make it easier on the eyes.

Parts and tools needed:
1. one 10.7975mhz crystal
2. two 12v 8 pin 2 NO - 2 NC DPDT relays
3. two 3.9k 1/2w resistors
4. two 1N4148 diodes
5. one .02uf 100v ceramic disc capacitor
6. one .01uf 2kv ceramic disc capacitor
7. Some good insulated wire
8. An exacto knife

 

[giulio1cr136]

Hello everyone, I write from Italy, I really like the forum and I found the post useful. I would like more information on how to mount mrf455 on president lincoln. I arrived to get only 35watt p.e.p. in ssb with the mod a q134. I am sure that i have to change all the capacitors from c112 to c 116 to recalibrate the output inductance, someone can help me. Thank you

 

[Xracerx13]

Ciao Giulio,
SIlver Mica Caps for Power Amp Output coils area to so-239.

C112 100pf 500V
C113 33pf 500V
C114 180pf 500V
C115 180pf 500V
C116 150pf 500V
C117 390pf 500V
Recalibrate L123 it has 8 turns(7.5 Actually)... take OFF 4 turns. Near the new Mylar PA caps in picture



To mount MRF455 against heatsink you have to first remove the heatsink from frame, then drill 2 small holes on heatsink on solder side of board, and then tap them so you can screw in some good metric bolts.
then use teflon wire to make connections.


To boost the power for the MRF455 to work the best....
add 680pf mylar capacitor to C127 in parralel to boost input to driver
also a 220pf cap paralleled to C126 to boost input to final
and add extra ground to diver transistor


hope this helps you Giulio.
Ciao

 

[giulio1cr136]

Hello
thanks for the suggestions, I have already done half the work in recent days. I will add new capacitors to mica. I have compared the values and I have seen that they are the same as the originals of the lincoln scheme. I looked carefully at your photos, I noticed that you have eliminated bias trimmer and you have enlarged the cable section of the two toroidal windings. Why was the bias trimmer removed? how was it replaced? the work you've done has made the power greater or are just tricks?
thanks, see you soon
1CR136
Giulio

 

[Xracerx13]

Sorry Giulio,
the picture with the bias trimmer missing is not my radio. I did not have a picture of my radio with the new MICA caps and the coil shortened so I used a picture I found online to give you an idea...... the other two picture are of my radio
Yes the caps are the same value but they handle 500v now and they are not ceramic. Everything I have done and just showed you DOES increase the power.

You do not need to remove the bias trimmer, and you do not have to re-wrap the toroids but you can re-wrap them if you want to. I did not

 

[giulio1cr136]

Hi,
These are the first photos of my work. They are waiting for the capacitors at MICA purchased on the web. When I shortened the L123 coil to 4 turns the radio gave less power, I added a capacitor. From 330p in parallel and now from 50 watts peak in ssb. I tested the radio by injecting a 1khz signal but after a few seconds the peak power is lowered, I think it is first necessary to replace all the capacitors and then check the power.
Ciao

 

[VICTOR L ALVARADO]

Hi,
These are the first photos of my work. They are waiting for the capacitors at MICA purchased on the web. When I shortened the L123 coil to 4 turns the radio gave less power, I added a capacitor. From 330p in parallel and now from 50 watts peak in ssb. I tested the radio by injecting a 1khz signal but after a few seconds the peak power is lowered, I think it is first necessary to replace all the capacitors and then check the power.
Ciao

Ciao Giulio,
SIlver Mica Caps for Power Amp Output coils area to so-239.

C112 100pf 500V
C113 33pf 500V
C114 180pf 500V
C115 180pf 500V
C116 150pf 500V
C117 390pf 500V
Recalibrate L123 it has 8 turns(7.5 Actually)... take OFF 4 turns. Near the new Mylar PA caps in picture
View attachment 24914


To mount MRF455 against heatsink you have to first remove the heatsink from frame, then drill 2 small holes on heatsink on solder side of board, and then tap them so you can screw in some good metric bolts.
then use teflon wire to make connections.
View attachment 24911

To boost the power for the MRF455 to work the best....
add 680pf mylar capacitor to C127 in parralel to boost input to driver
also a 220pf cap paralleled to C126 to boost input to final
and add extra ground to diver transistor
View attachment 24913

hope this helps you Giulio.
Ciao

Hi ..every one ...can I use a mfr 454 ...in this mod ... or not ..thanks

 

[Xracerx13]

Hi ..every one ...can I use a mfr 454 ...in this mod ... or not ..thanks

Sorry it took over a year to respond but if anyone is reading this in the future......
YES you can use a MRF454 or SRF3749 or 2sc2290 or SD1446.

 

[Xracerx13]

I wanted to share that I recently replaced the RF first stage pre amp transistor Q101, from a 2SC1674L to a BFY90 and I am amazed at the difference and increase in receive response. I bought the BFY90 five years ago when I started this post and project but I never installed it, and I wanna kick myself now for waiting so long.

BFY90 is a 4 leg EBC style transistor so legs 2 and 3 need to be swapped to make it ECB (1,3,2). Cut off leg 4 (case) its not needed.

 

[Handy Andy]

To help others follow along...

 

[AudioShockwav]

This has good info.

73
Jeff

 

[Xracerx13]

Thanks man.

 

[Xracerx13]

Here's a pic of Q101 a BFY90, between the 2 cans, installed and its orientation.
As a follow up to post #20 & #22 a better look at my final PA caps and the red coil L123 which was shortened.
Also in the pic the toroid's are now re-wrapped from 24g to a larger 22g. Scratches are from glue removal.