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Red wire mod / Volting? opinions.

Discussion in 'General CB Services Discussion' started by Low_Boy, Jun 17, 2018.

  1. Low_Boy

    Low_Boy Sr. Member

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    So I have been thinking about this for a few days. I read doing the red wire mod will bypass the regulators and the radio will run cooler.



    My thoughts on this. The final and driver will be getting more voltage and the radio will possibly put out more power. So a 2SC1969 is good for over 12V and when you run the radio in sideband you end up with full supply voltage on the driver and final. So the final is capable to run at full voltage, we will say 13.8V. So is this a FCC thing of getting a radio to put out less power? If it is acceptable for a radio to run full power on SSB why not on AM.
    I would love to hear what others have to say about this.
     

  2. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    It will not run cooler and the regulated voltages go to more places than just the finals
     
    rabbiporkchop likes this.
  3. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Low Boy, before you do that...

    Install an Ammeter in the power line going to your radio.

    Put a power (wattmeter) on your antenna or resistive load...

    Then use SSB and observe the meters.

    Do the same for AM. - FM too for that matter.

    This is so you can understand that Carrier may be one factor, A power at a frequency.

    Adding Audio to modulate the carrier to generate an envelope of power around the carrier is another.

    I've gotta keep this simple so other can take the ball but you'll see that AM power in envelope can take up to 4 times more power than SSB - which is why SSB radios are the more preferred radios versus AM only types.

    If you try to run AM power full carrier - you could not generate enough audio power or overcome the carrier - then you need FM mode to do that. And its' class of operation C, D and E or above - and that requires another type of power, called deviation - where the frequency shifts around the carriers' "center" and the receiving radio tunes into this signal but keeps it's tuning "centered" and the FM signal is decoded, demodulated - from the straight-line center of the receiver BEAT FREQUENCY (its own IF) resonating and heterodyning with the incoming signal and the incoming signal generates the "shift" you head as audio or music or the intelligence embedded in that signal.

    So the DRIVER in your radio will be doing all the work, but the Finals can be run on full rail voltage - hence the Red Wire On Bottom (RWOB) mod. But you aren't affecting "carrier" that's done way up the TX chain towards the Pre-driver and mixer - the Driver and Final do all the audio work...onto the carrier.

    You can lose some audio punch with this setup - and if you use an HR2510 - you already know of the audio limitations on the AM envelope because the HR2510 (and any Jackson from that era) is "low-level" modulated - it doesn't have the audio envelope impressed upon the plates, or across the collectors of the Finals and Driver like a typical CB or SSB / CB radio has. It's done at the beginning of the chain, back at the mixer, the 7320 - it has a "preamp" that they use as an audio amp to mix into the two other signals - else it's cutoff (FM mode or CW). So it has to be done on the low-level side to obtain envelope, the 2510 doesn't have a pass transistor setup.

    Then if you wish, you can do the RWOB mod and use the Driver only and the finals will do all the power out work. But you will only be using the driver - so NPC mods and stuff aside, Driver only RWOB mods can't use NPC - they won't compete well against fully modulated radios in similar setups.

    Yours may last longer, as long as you don't go crazy and over modulated the driver, that can fail because of excessive audio and will bear the load from all your audio - its' (The Driver) your pinch-point for audio and you may not like the results unless you take steps otherwise to impose two-stage audio - injecting it further up the chain.

    When you look at how the pass transistor switching works, you'll see that in SSB modes, they (the Driver and Finals) get full power but no audio yet the pass transistors seem to stay cool and you see power racing off the rails to the antenna as you talk into the microphone.

    Why - Pass transistors are being used as a simple On-Off switch for SSB and FM - the AN612 and the Mixer (the 7310 - note difference in numbering) are doing all the work,.

    IN AM mode the pass transistors are now the "mixer" and take DC power and Audio signal making it into a Bias plus Audio - it's a linear operation. And the level of power that is there is not used as a simple switch on or off. It's a varying load swing - 12 Volts is one voltage, but you have voltages between 12 and 0 (or carrier at 4.5VDC) that exist at any given moment in time as you talk - these pass transistors have to take the supply rail - drop it down to that - as both voltage and current vectors - so this process of making DC rise and fall with audio - being linear - is pretty dynamic and generates a lot of heat as power from DC is changed modified - is rerouted and shifted it has to be dissipated as heat - is also what kills those pass-transistors - so operating as a full on mode helps the Driver and Final do their job for SSB mode.

    :+> Andy <+:
     
    #3 Handy Andy, Jun 17, 2018
    Last edited: Jun 17, 2018
  4. jon666

    jon666 Sr. Member

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    any of them mods are trashy. like the super wacky pack.
    then you fry your audio ic. trust me been fixing radio for 25 years or so. its like putting the firecracker looking thing in over modulation. but its your radio, do with it as you please
     
  5. M0GVZ

    M0GVZ Sr. Member

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    IT IS ABSOLUTE AND UTTER BULLSHIT, ALL OF IT. Mods like that are done by braindead halfwits who think they have the knowledge of Steve Wozniak but in reality have absolutely zero understanding of electronics - "All the gear, no idea."

    The regulators are there for a reason, to regulate the voltage and current so the circuit doesn't get overdriven and you end up killing things. A device WILL NOT run cooler if its using more power.

    Whilst you MAY get a power increase it'll be so pointless as to not be worth bothering and whilst doing it you'll be seriously reducing the lifespan of the components. On a properly calibrated S meter doubling the power gets you half a S point. That's it. So if its 12W you'd need to go to 24W to see just half a S point increase. It won't increase that much.

    If you want more power buy a linear amplifier.
     
    rabbiporkchop, unit_399 and Tallman like this.
  6. sp5it

    sp5it Master of puppets

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    RWOB - running final(s) bypassing TR51 - linear modulator is very good thing idea.
    TR-51 is not stressed especially in high power, dual mosfet radios.
    Of course you have to turn down AM power pot afterwards.
    Mike
     
    Shadetree Mechanic likes this.
  7. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    The reason SSB is preferable over AM is because SSB is all information with no wasted RF power. If you are transmitting 25 watts of SSB it is 100% modulation. No wasted carrier or wasted side band.
    AM signal is Carrier, Upper Side Band, and Lower Side Band.
    SSB is just the Upper Side Band or the Lower Side Band with no wasted RF power.

    Also the mantra: "If it ain't broke don't fix it" comes to mind. I have worked in manufacturing almost all of my career and I will guarantee you if a company can knock Five cents off of the cost of a unit by leaving parts out they will do it. So if you bypass a regulator excess voltage will kill your radio sooner or later.

    And as M0GV said "Get an amp." all of these little piddly mods will do nothing noticeable on the other end of your communications.
     
    #7 Tallman, Jun 17, 2018
    Last edited: Jun 17, 2018
  8. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Low-Boy, work with us here.

    We're not against upgrades, but there are limits to anything you can do.

    I myself run a jumper on older PC-122's but they are not excessively overmodded - again I did up those pages to help those to get some understanding of all the stuff out there. R151 discussions, Asymmetrical discussion - Diode Bias mods - even Pre-Driver mods - simple stuff. But they - if done right - won't make a radio go haywire or damage it - but they are not to be toyed with - they are there, designed for, preservation of the radio for a lot longer time.

    When I did up those pages - I never imagined others would use these techniques on the playing field as a means to generate more power - they were there to reduce interference and extend the life of a radio - not to make it a shoot out candidate.

    In light of what others are saying, I'm looking at it from a standpoint of preservation. I am well aware of how others feel, but I'm not here to make everyone happy- I simply can't. I'm here to tell you straight up - that if you do this - why are you using Twin finals? You have done a lot of work to the radio - I'm stepping in here to caution you about going too far with this. I've repaired a lot of radios in my lifetime - and I developed a passion for using them like their intended purpose - but not as an experimenters whim or fancy. I do what I do to protect their investment - if it means that it may harm others or damage the radio - I hand it back to them with a kindly no-thank-you and we go on our merry ways.

    IF you do the RWOB - you may run into a problem with the Driver - being able to operate the Twin Finals properly without issues. I'm concerned that the Driver if it's a Bi-polar- my not work well in some radio chassis. I've had some issues around SS3900's and Jacksons but have had great luck in the 949 and 959's - one type has an insulated chassis (that EPT360011Z and the Unidens') while the Negative Ground Only radios like the 9x9 series from Galaxy take well to them. It's sometimes a crapshoot unless you really understand that too much of a good thing - usually is.

    IF you've doneup the Driver as an MOSFET mod and like the results - everything else pretty much falls into place. You have my blessings. You have plenty of templates to borrow from - in helping you get the twins and the driver to work in unison.

    IF you still use a Bi-polar for the Driver, there may be a problem - that's from the Drivers' output network to go into the Final as well as the ability for the AM Regulator to damage the driver from heavy modulation and swing mods like the NPC - let alone the power you will need to go into the Finals will have to be bi-amped like a bridge.

    It's those jumpers and caps they use, and the trimmer levels for each final - to equalize the load sharing and make sure both are "sync'd" to each other so the phase relationship for their output is correct. You may need to "tweak" more to obtain the symmetry (equal drive). You had posted a question or two about it - so I only hope you got the twins working well and now you just have the problem of keeping the heat down on the AM Regulator.

    Again, if you use the RWOB, done right, you have my blessings, but remember that BOTH finals have a considerable amount of current that can go thru them at any moment in time - so you may need to run a wire from the power supply (the internal one of the radio) to each Final - both the same length and gauge to arrive at their respective feeds at the same time. You can do that above the radios' component side - like they do on the Grant and Cobra 148 / 2000's /142's - they "jumper" because they were aware of trace thickness and copper as a conductor has limits.

    Switched of Unswitched? You have an HR2510 - so you already know of the Final and Driver power supply problems. They are not switched - they go straight to the power input - supply rails - by the Power Filter section. You may need that so you don't blow the switch contacts like a fuse in this radio...

    There is also the problem with power dissipation. This may sound like a broken record and perhaps it is, but you can only get so much cooling from the heat that can get transferred off the parts, onto the back panel, and any heat sink for mass - heat mitigation and thermal transfer. You may save the pass transistor - but damage the Twin Finals from overheating even when you still use Bias diode Zeners - the sheer amount of heat they generate can do a number on all parts involved - including the traces.

    So if you do the RWOB - that is - IF IT IS the only way you're going to extend the life of what you got - THEN REMEMBER THIS IS IMPORTANT at least the pass transistor in the regulator is going to stay cooler - but you only have the driver doing all that work. so don't do a lot of mods - like NPC or Clip Limiters - read- study the R151 discussion first - because a 2166 is nearly UNOBTAINUM right now and you'd be forced to go to totally MOSFET in Driver and Final pairings - so decide what you are trying to do, save the radio - or create a beast.

    IF you are saving a radio from extinction - do it properly. (Is twin finals really necessary?)

    IF all you want to do is have more power - get an amp. (See Above)

    :+> Andy <+:
     
    #8 Handy Andy, Jun 17, 2018
    Last edited: Jun 18, 2018
  9. Low_Boy

    Low_Boy Sr. Member

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    Wow a lot of info here. I was not thinking of doing the mod but have been wondering exactly what was happening when this mod was done. Pardon spelling and errors trying to do this on my phone and keypad small for my fingers.
    Thanks all
     
  10. Onelasttime

    Onelasttime Sr. Member

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    It is a worthless mod.

    If you want to run the radio cooler put bigger regulators in.
    Make sure your running bjt's over Mosfets in rf production.
    Turn the power output down.
    Make sure you are close to 100% modulation.
    Get an EQ with compression or install a compressor. Learn when to use them and when not too.
    Tweak the audio via minor cap value changes make sure the EQ can do it's job even when hooked into the mic socket.

    Last but not least get a linear amplifier class AB or switchable.

    A 2x transistor amp like a MRF455,454,2SC2879 etc.....will do more for you and be cheaper in the short run and long run than all of the published mods for a radio!

    Just switching from MOSFETs to bjt's and turning the power output down even without upgrading the regulators will run cooler by a large margin. Why do you think we do not have 1.5L turbo engines spinning at 20,000RPM making 1200-1500HP like we saw in the 1980's in Formula 1. You could do it but the durability and cost would be out of sight and in a daily driver 1200+++HP would almost never make anything better in daily driving. So instead we have 1.5L engines that might be able to spin to 6500rpm and they make 136HP-150HP and will run for 500,000 miles.

    Stop digging for gold in the manure pile and talk on the radio more. Do the smart thing and just get an amp that matches the power output of your radio and antenna system. Cheers!
     
  11. 357

    357 Walkin' the dog

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    be nice to know what radio this is
     
  12. Low_Boy

    Low_Boy Sr. Member

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    It is no particular radio. Just something I was thinking about. Just a thought.
     
  13. Onelasttime

    Onelasttime Sr. Member

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    It never stops amazing me that no one ever thinks about turning the power down to make a radio run cooler! LOL
     
    rabbiporkchop likes this.
  14. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    I would but I get laughed at for even mentioning 4.5V.

    But SP5IT did mention ...
    The idea here is less touch of any aspect for the customer - so they don't do anything that blows it up.

    In light of "Volting the Final" you may gain a watt or two of power out - but that is in AM mode though. In SSB the Pass Transistors are full on anyways - so no real change has to be made except as SP5IT and I concur with him, turning down the AM Power pot is the better option. Less heat generated all around.

    Also AMC automatically responds to this (lower carrier AM Power setting) by increasing Mod percentage before the Limiter kicks in - hence the R151 discussion.

    :+> Andy <+:
     
    #14 Handy Andy, Jun 19, 2018
    Last edited: Jun 19, 2018
  15. 543_Dallas

    543_Dallas Sr. Member

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    I did this with a few cobra 148s because it was what the cool kids were doing. Running the final at higher voltage increased the headroom for the positive peaks but the negative peaks were squared off before they hit baseline.

    It was a trash mod so I stopped doing it. It did make the AM regulator run cooler but the final ran hotter. I had a box full of little surplus heatsink that I started mounting the AM regulators to. With the grant xl the regulator was already mounted to the back of the chassis. Adding that little piece of heatsink to the chassis was enough to keep the regulator from overheating under normal.....long winded operation.
     

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