1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice

Help with HR2510 Final PA mica caps replacement and more.

Discussion in 'CB Radio Modifications' started by Xracerx13, Oct 8, 2017.

  1. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    Hi all,
    First off hello everyone. A little about me. I lurk but never post :) I am a local radio tech here in Rochester NY. I have been working on radios and amps for 35 years. My history is associate in electronics technology, work at Xerox as electronics and mechanical technician, have worked at Harris communications as a tech., and MKS instruments as a tech on all aspects from power supply up to combiners but mainly on super hi power RF amp boards used for plasma cutting and MRI machines. The HR2510 is a new radio for me and I have crammed so much in of info its ridiculous. Kudos go the my local neighbor DOC at Doc;s electronics Buffalo for pointing the way on a couple hard spots and Rogerbird for pointing out the troubled capacitor areas. I replaced all the 10v caps to 25v or better on the main board, and the usual power supply caps. Upgraded power wire from connector to board with 12g. Pre driver mod Q134 removing the network from the emitter. Modulation improvement a 1k resistor to the emitter of Q114. Added 680pf cap parallel to C127 a 330pf which is now become a 220pf, also a 220pf cap paralleled to C126 an 820pf now becoming ruffly 170pf, for more driver to final drive. Any help on these caps also appreciated. Better ground jumper for the 2166 driver. Replace antenna connector wire with a 18g Teflon wire from board to SO-239. Replaced VR112 pot with a ceramic pot of same 100 ohms. The adjusting is very touchy and I wish I could change it for another value that would act like a ten turn clarifier pot for better adjustment. Maybe then the following would happen so drastically. . This is a trouble area for me as the mA's are not steady at 80ma i set it to 75ma and the more I stay keyed down the ma bias value increases with time up to high 90's even 100 or more. . Not using the paralleled double caps on the final on foil side or a biasing diode. I will however add a .1uf 100V Mylar cap and 100 ohm 3 watt resistor for a feedback circuit on mrf455 from collector to base. L123 next to ring core reduced from 7.5T to 4.5Turns. ALL limiters AM, SSB replaced and intact. They were gone when I got this radio. The two receive diodes D111-112 with schottkys 1N5711's. Replaced various caps for HiFi receive and TX.
    I am looking for the directions found in an old post below. Only to verify pf PA cap values to my already started MRF455 mod that works great but still needs help. I have to upgrade the caps for the PA final output and I want to verify if I replace with 500v silver mica's of same pf or am I changing values here. Anyone done these PA caps and what values did you use if you did? Below is a copy of that post AND what was also suggested by JUSTme, and his suggestions rock..
    Any help is greatly appreciated. As always I want to do it right. Thanks in advance!

    Joe N2WNY alcohol@rochester.rr.com

    The old Post\\\\\\\\\\\\\\\\\\\\\\\\\\\
    here is a real good power modification for the hr-2510
    Materials:
    1 47uF to 100uF 25V capacitor. In this spot C119 I used a .47uf 160V suggested by DOCbut not sure why others are using a 100uf 35v here
    1 68 ohms resistor 1/2w DONE
    6 silver mica caps (values shows in pictures)(they are really needed)C112-117 I have no pic's Any others I should change maybe near the SSB ALC circuit
    1 SD1446 Pill (more cheap than mrf455) DONE with MRF455 double black dot
    1 small piece of wire DONE using 18 gauge Teflon wire from TP4 to incoming power wire
    Adjust am power to no more than 15 W dead carrier. Adjusted to 10W carrier when the radio is finally warmed up or else its 5W. working on that. looking at issue might be one or more of the 3 small red diodes.
    Download instructions here. Broken link
    http://rapidshare.com/files/125848670/HR2510-_____PowerMod__.zip.html

    Justme Posted a great response:
    First, this is just an ordinary improvement which can be found on the net, the only difference is you indeed replace the C's in the PA stage for larger power handling ones. no mention of value changes just higher power handling ones
    Secondly, i use thee MRF455 and get 65 watts easy, grounding the emitters is crucial, removing the - lead from where it is soldered to the PCB to the point where the emitter leads are of the new transistor will up the gain. DONE

    Secondly, you still let the DC go through the first ring-core which degrades the handling capability of said ringcore, disconnect the + through the ring-core, and bring the + directly from the + input wire through an decent rf choke and decoupling to the collector.

    Pulling 70 watts SSB and 20 watts carrier in AM and 75 modulated here.
    Then use screening to prevent the hf radiating into the rest of the radio. What type of screening? Copper tape formed around a paper cover over the ring cores only or the whole output section?

    More power is fine, but how about reception?

    Replace the first stage transistor with an decent transistor, i use thee European BFY90, you will find an replacement over there, the BFY90 is an low noise fist stage pre amp transistor with an cutoff frequency of 1300 MHz. Working on ordering this to replace Q103 but not sure if I need to also replace Q105 being thay are the same, even though it says first stage transistor.



    Then put in an xtal filter of 10.695 MHz in the MF replace the first C of 3 pF where you see 3 cans which serve as rude band-pass filter. I have a 10.695 MHz plain old crystal, the short oval case ones sold these days for cobra radio's, and its saying to put a crystal filter not a regular crystal in place of the 3pf cap found at C13. with this regular crystal suffice?
    This will prevent bleed through, sharpen the bandwidth of your MF, and improve reception.
     
    #1 Xracerx13, Oct 8, 2017
    Last edited: Oct 8, 2017

  2. bob85

    bob85 Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,899
    Likes Received:
    642
    What do you mean not using a biasing diode?

    its normal for idle current to increase with temperature because bipolar transistors conduct harder the hotter they get,

    the mv1y diodes are there to reduce bias voltage as the transistor gets hotter to keep idle current more stable & stop thermal runaway,
    idle current will be up and down like a yoyo if you don't have the tracking diode,
    its a good idea to fully warm the rig up before setting idle current even when you do have a tracking diode,

    a 2 wire 10.695 crystal is not a filter,
    a filter has 3 wires with a center ground connection like 2 crystals in series,
    i use 15kc 10.695 filters from old cordless phones because they are less critical of incorrect terminating impedance & don't make the RX too narrow,

    2510's 2830's & early lincolns have a place on the board for an extra ssb filter like the jackson uses,
    if you look at the schematic around q104 you will see hand written additions to the schematic where they left out the filter & added a few components to bypass it,
    6kc or 7kc filters work ok in that position once you remove the bypass additions,

    later versions don't have the place for the extra filter.
     
  3. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    Thanks for the reply,
    I am not using a biasing diode yet because I was told by Doc in Buffalo it wasn't needed. I new it needed it. Rogerbird did tell me to use one, btw..He suggested I try a 1n4003 and mount it so it rests against the ceramic with heat transfer compound

    As far as the crystal filter goes I couldn't edit my post to rewrite that I do in fact have an actual crystal filter that I made from CBC plans with two 10.695 crystals. Except CBC says to install at C15 and JUSTME says to install it at C13.
    Yes I have seen the 3 legged ones,

    I am not seeing the hand written stuff on any of the schematics I have for the 2510, and I believe I have a later version radio anyways..
     
  4. bob85

    bob85 Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,899
    Likes Received:
    642
    You need the diode if you want some thermal runaway protection & more stable idle current,
    a 1n4003 will work ok, you can file a flat on the diode to get better thermal contact but its not critical to it working,

    either place will work for the filter, not sure if one is better than the other, both may effect the operation of the noise blanker,

    i have not seen a later 2510, the later version we got in the uk were Lincolns with the revised mainboard & crystal filter on the FM board,
    its 20 years or more since i was putting filters in them.
     
  5. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    Good morning,
    I know its better to have the diode up against the transistor body so this is a dumb question. Why cant I just re-use the original and mount it to the heatsink direct to original place where the 477 used to be? In this spot it would not be directly behind the transistor.

    Picture below is not my radio, its something I found on the net for diode placement purpose. In this pic it shows the diode with the negative cathode coming down to the left. But wouldn't it be better if the positive anode is attached to the other emitter down on the board rather than the heatsink one. Also the board layout pic I have shows the diode complete opposite of which I believe is the wrong way and an error on the PCB layout. My MV1YH's are sealed in black epoxy so I cant see the diode but there is a white dot on the left, I take it for the positive side.
    Could you confirm this for me, please?.

    455protectiondiodeLarge.JPG hr2510_pb111ab_main_pcb.gif
     
    #5 Xracerx13, Oct 10, 2017
    Last edited: Oct 10, 2017
  6. bob85

    bob85 Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,899
    Likes Received:
    642
    i can't see which way the diode in the pic is connected,

    the cathode goes to ground, anode connects to the bias supply so that it shunts the bias supply to ground & only allows about .6v on the base of the transistor,
    if the diode is the wrong direction it won't do anything,

    you can measure the mv1y with a multimeter on diode test & compare it to a diode that has a clearly marked cathode to confirm which way round it goes,

    the diode or mv1y can be mounted on the heatsink as close as possible to the transistor or mounted on the transistor cap as shown in the pic,
    mounting it further away from the transistor slows response time due to thermal lag,
    for best tracking you want the diode as close as possible to the source of heat,

    if it was me doing the 455 final mod i would etch a small board like the factory 455 mod to minimise inductance but wires will probably work ok if you keep them short.
     
  7. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    besides a 1n4003 that i don't have in stock, what else can i use?
    i have 1n4004 and 1N4001 and 1n4148 and 1n914.
    I measured the mv1y and apparently the side with the white dot is the negative.
     
  8. bob85

    bob85 Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,899
    Likes Received:
    642
    you can use most silicon diodes or the base emitter junction of a suitable bipolar transistor, not germanium or schottky diodes,
    any of the 4000 series should work.
     
  9. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    Just in case this post is read meticulously I want to correct what i wrote accidentally C126 and C127 are now ruffly around 1000pf.

    I will try my local parts place for a 1n4003 since i need other stuff :D, if its a no go I will use the 1n4004. thanks Bob85.
     
  10. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    Got the bias diode in just now. I used a 1n4004 and I was quite surprised that the Bias setting jumped down from 75ma to 35ma just from the addition of the diode.
    Its hooked up correctly. Is this normal?
    I'm waiting for the radio to warm up before I reset it to 75ma again.
     
  11. bob85

    bob85 Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,899
    Likes Received:
    642
    Yes that's normal, idle current should be easier to set & more stable.
     
  12. Xracerx13

    Xracerx13 Member

    Joined:
    Jul 24, 2015
    Messages:
    17
    Likes Received:
    3
    The final bias is most certainly easier to set & more stable. I also installed my home made 10.695mhz crystal filter built using a CBC International schematic and that works great. I stuck it in C15.. the place CBC calls for rather than C13 as someone else mentioned.
    Looks pretty busy, don't it.

    IMG_20171012_154511.jpg IMG_20171012_155114.jpg
     
  13. bob85

    bob85 Supporting Member

    Joined:
    Mar 30, 2005
    Messages:
    2,899
    Likes Received:
    642
    looks like you have been busy with the iron.
     
  14. Onelasttime

    Onelasttime Well-Known Member

    Joined:
    Aug 3, 2011
    Messages:
    858
    Likes Received:
    363
    My President Lincoln I bought new in 1998. No problems at all. When I recapped I used the exact same values in most location just higher voltage and higher grade caps. I did not add any silver mica caps. My radio came with MRF455 from the oem and their are not any silver mica caps inside. I did replace a lot of ceramic caps in recieve with film caps or bipolar electrolytics to change receive audio does nothing for sensitivity. In the transmit area I lowered the values of some caps to allow more highs to pass and replaced some ceramics with higher value film caps to allow some more bass deeper into the audio not in the first stage becasue it would block too many highs and Highs are what you need on am and SSB to really talk long distances with out wasting power. More bass sounds good for local rag chewing but kills propagation and pile up breaking! When their was space I did go with a tad more capacitance but space is limited in that chassis both diameter on pad and height. Be more concerned with low ESR good ripple performance and higher temp. rating than the 85 C. Also be aware that replacing ceramics with electrolytics will not last as long as ceramics. The bipolar and any of the film caps are great for audio because they keep the audio from getting muddy or harsh. When we use electrolytics to pass audio through we normally are looking for some dampening at specific freq's to help out an audio circuit or opamp that is not ideal. In this application we want to take some harness out and we want to dampen the white noise some. Doing that knocks the noise down a bit fromt he audio and it makes the voices sound warmer. We are counting on the signal we want to hear being far louder than the noise. Just know that it will make it harder to hear really weak signals it is not changing the receivers selectivity or sensitivity but it is changing the audio output that makes it to your speaker.

    On the RF carrier do not go that high 15 watts carrier is a bit high with out having an rf control on the front of the radio. I would recommend 10w carrier at the most. Heat is an issue.While they used a huge mass of alumnium in that heat sink the sinks are thick and fat. So it will absorb heat from the finaly nicely it will not radiate it or transfor it to the air as well as a thinner it would having a lot of thinner fins of the same total mass. Surface area counts when trying to dump that heat into the air. keep in mind that this radio uses low level modulation on audio and with out doing some work instead of 4:1 you should look for 3:1 with regard to swing to carrier ratio. FM 2 for deviation is super safe some guys go as high as 3 on FM deviation but 2-2.5 is great. I am not sure if lifting the leg of the amc limiter and installing resistor address this because I have not done that mod in terms of getting 4:1 instead of 3:1.

    I think the first stage in the audio is 2x .22uF and some people replace those two caps with 1uF which is waaaaay too much .44uF is a better compromise since it does nto kill SSB performance. That amount of added bass and blocked high's will kill SSB performance. Further in the tx audio I installed a 1uF film cap but some people put a 2uF in place of that ceramic disk cap and that is just too much unless all you want is AM local rag chewing.

    I left the germanium diodes in the receive because I have never had any issues with receive sensitivity but I did replace the NBL with schocktys and I think it helped in that area. I will not lay a cap on it's side with long leads on a mobile even with hot glue that is just bad practice to have long leads inside a radio for mobile application. Even if stray rf is not an issue.

    Do not put a 10 turn on this radio for RIT that is really silly. If you need more than you can get out of the clarifer which is doubtful just move the carrot under the digit you want to adjust and adjust it that way. Also if you just have your heart set on it a veractor diode aka super slide diode will give you a bit more. Their is no space for a 10 turn on this radio on the face and it would just be silly since you have direct access to the VFO! Even if their is space on a radio for a 10 turn you really need a real freq. counter to use it well and trying to use a 10 turn in a mobile is hilarious unless parked.

    A recap, electret mic, and eq do wonder's for these radio's! Likewise a recap, really good mic and SP1a The ones that go crazy with mod's often are a step backwards overall. Just because you can do a mod does not mean it is the best way to go. When you make internal mod's they are not easily undone and you have to live with them 24/7 better am performance at the cost of FM and SSB performance is a stupid trade off in my book since you are turning an all mode radio into an almost AM only radio by default! Often it is better to do a bit less to these radio's and add an eq to get what you want. This way your not compromising FM and SSB performance!

    Your milage may vary! LOL....Cheers.
     
  15. CrazyFin

    CrazyFin New Member

    Joined:
    Nov 20, 2017
    Messages:
    8
    Likes Received:
    0
    Been lurking around here for a while now as well and felt that I just had to post and say that this thread is really great with good examples.

    I do not currently have the HR2510 (had a couple in the past) but I certainly will be able to use some of the ideas in this thread on my other radios I am trying to repair/fix (=mostly remove bad mods and re-tune/re-align). Will be posting some questions soon with scope and spectrum pics.

    Anyway, I have tried to re-read the thread a couple of times trying to figure out some of the cool wire mods and the small circuit board I see in the right picture in post 12 by @Xracerx13.

    May I ask what:

    1. The yellow/green wire with the ferrite is for and what connection points is it between when looking at the schematic?

    2. The red wire going through ferrite? Is it for some external power supply? I do see the short red and black wire of thicker gauge going from the power supply socket on the chassi down to the board.

    3. What mod/add-on is the small circuit board with the grey electrolytic and white wire?

    and finally (I think... :unsure:)
    5. What is NBL abbreviation for? (Being a Finnish living Sweden... :confused:)
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!