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

Palomar Maxi Mod

Discussion in 'CB Radio Modifications' started by Low_Boy, Apr 8, 2018.

  1. Low_Boy

    Low_Boy Well-Known Member

    Joined:
    Jan 21, 2010
    Messages:
    619
    Likes Received:
    143
    This is the second radio I have seen like this. There must not be a ceramic insulator the size of the max mod. I do not think this is getting the correct cooling. I do believe you need the insulator as a spacer in this circumstance.[​IMG]


     

  2. loosecannon

    loosecannon Sr. Member

    Joined:
    Mar 9, 2006
    Messages:
    3,051
    Likes Received:
    1,304
  3. Low_Boy

    Low_Boy Well-Known Member

    Joined:
    Jan 21, 2010
    Messages:
    619
    Likes Received:
    143
    I just can not see this getting the correct cooling with only 3/4 of the component touching the heatsink.
     
  4. Robb

    Robb Yup

    Joined:
    Dec 18, 2008
    Messages:
    10,824
    Likes Received:
    2,479
    Dunno if you are willing to go this far, but I think Bergquist might make a sil-pad for it. Max cooling and no mess with heat sink compound. No need for a mica or ceramic insulator when a sil-pad is employed. Might want to check that out as an option. Just bought 100 of them from China for the to-220 type transistor (final, driver, etc). Not the same as the transistor case you show in the pic; but I'll bet they're available from somewhere for that style of case. Just sayin . . .
     
    #4 Robb, Apr 8, 2018
    Last edited: Apr 8, 2018
  5. Low_Boy

    Low_Boy Well-Known Member

    Joined:
    Jan 21, 2010
    Messages:
    619
    Likes Received:
    143
    Robb. I believe that they are I saw them last night when looking at insulators on e bay. I think in this situation you need the ceramic insulator as a spacer the legs go through the board. I am not sure if the legs will make that sharp of a bend.
     
  6. Ranch55

    Ranch55 Well-Known Member

    Joined:
    Jan 18, 2016
    Messages:
    262
    Likes Received:
    139
    I believe that the mica insulators that are supplied with the Max Mod are sufficient.
    They are full size to the transistor.
    And I also agree that full coverage is desirable to what is pictured above.
    No, you do not need the spacing provided by the ceramic insulator, but it is not a hindrance either.. The pins are flexible and there are not any sharp bends you have to accommodate.
    I have installed the Palomar Max Mod transistor in many different brand radios. The photo above appears that it may be an AT-6666 radio .....
     
  7. Onelasttime

    Onelasttime Well-Known Member

    Joined:
    Aug 3, 2011
    Messages:
    858
    Likes Received:
    362
    I have 10 of everything Palomar sells and not a one of them came kitted out with the Mica insulator or the hardware! You can buy them separately. I just bought mine maybe 2 months ago their might have still be snow on the ground. There was no listing for them in anything less than a 10 pack from them on Amazon and none of them came with the acc. parts. Obviously, I am not the only one that has received transistors with no insulators or hardware. The Bergquist Sil-Pad is a better option anyways. A lot of high-end power supplies use thermal shrink tubing.
     
  8. Ranch55

    Ranch55 Well-Known Member

    Joined:
    Jan 18, 2016
    Messages:
    262
    Likes Received:
    139
    Yes, the last two 10 packs I purchased from Parrot Sales on Amazon came with the mica insulators and longer mounting screw hardwire.
    In fact, I have not ever received any new Palomar Max Mods that hasn't included the mica insulators and new mounting hardwire ......
     
  9. Onelasttime

    Onelasttime Well-Known Member

    Joined:
    Aug 3, 2011
    Messages:
    858
    Likes Received:
    362
    If you look on Amazon and type in Palomar Max Mod you will see they sell a hardware kit that includes just the nut, bolt and mica insulators nothing else. Now do try to keep up here because this is not a tricky abstract idea or any sort of agenda.

    If they always send out nuts, bolts and mica insulators why would they need to sell a kit that only has those items in with no transistors? I hope I have not lost you with this deep difficult idea to ponder. If they always send out such items with all of their transistors there would be no need to make these items available separately.

    In fact one of the comments Hard Drive made when he first started to use them was that he did not have the needed hardware to properly mount them and he got in touch with Erick about this. I have 10 of everything Erick sells and not a one of them came with hardware and insulators. This might surprise you but Palomar has an account on Amazon so I bought directly from Palomar on Amazon.

    I typically try to eliminate as many people as I can between me and the parts I want but I also do not like giving out my credit card number to everyone and their mom. If I can not use paypal with someone I try really hard to find another way to order with out giving that information out if I can.

    If you order small amount a small amount of Sil Pad is $0.58 cents from Digi Key for a single unit. Mica and Ceramic are even cheaper. It is a TO-247 package. $5.80 for 10 of them is not going to break the bank and not having to mess around with thermal paste makes it worth it. Sil Pads will outlive most of us on this site! LOL

    I am going to let you in on another little secret. Erick does not run out of everything at once. Do you think he is going to close up shop and not sell a thing while he is waiting for his Chinese semiconductor manufacture to spin him up him a new batch of what ever he is out of? That would be like an ice cream shop closing up early because they ran out of cones or chocolate ice-cream! LOL You would use bowls and have customers choose another flavor and keep the doors open and the money flowing! It is not unlike hotdogs versus number of hotdog buns do you toss out the odd bun or hotdog? Only if your not too bright.
     
  10. Low_Boy

    Low_Boy Well-Known Member

    Joined:
    Jan 21, 2010
    Messages:
    619
    Likes Received:
    143
    The ones i purchased came with mica insulator and mounting hardware.
     
  11. Ranch55

    Ranch55 Well-Known Member

    Joined:
    Jan 18, 2016
    Messages:
    262
    Likes Received:
    139
    Okay, you can comment, but it doesn't take away from the fact that all of the Palomar Max Mods that I have received from Palomar and from Amazon came with the mica insulators and mounting hardware included ....
    If you look at the 10 pack on Amazon right now, the description even says that the mica insulators are included .........
    So ....... okay ......
     
  12. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    1,869
    Likes Received:
    1,294
    The Palomar Max Mod transistor is the same size and shape as the 2SA1302 we have used for a while now to upgrade base-station radios. The published ratings for the Max Mod are higher than the 15 Amp rating of the 2SA1302. That's double the 7 Amp rating of the 2SB754 used by RCI for decades. And that's why we chose it, years ago. Some customers just work their radios harder than others.

    [​IMG]

    The Max Mod is probably a better choice than the 2SA1302, so long as their higher ratings are real and not just fluff.

    But the surface area it puts against the heat sink is the same for both of these. Bigger than the factory-installed transistors, but that's the biggest advantage it offers, IMHO.

    [​IMG]

    This is not the biggest package or the most heat-sink contact area you can buy in a plastic package.

    [​IMG]

    We stocked this monster to repair home stereos from the late 1980s. Can't remember the brand, just been too long.

    Not a good fit for a Galaxy mobile.

    The temperature rise in a transistor is all about the surface area it puts against the heat sink. You can burn up a 150 Watt transistor with ten Watts if the heat sink doesn't do its job. Melting temperature is the same for the 50-Watt part as it is for a 150-Watt part. It's all about temperature rise. The smaller the temperature difference between the transistor and the heat sink, the better. And more surface area is the best way to achieve that.

    The use of low-efficiency MOSFET finals and drivers makes life hard on the factory AM-modulator transistor in mobile radios, too. But making it fit takes some effort. Probably worth it if the old part is blown. Not sure I would fix something that "ain't broke" without a good reason.

    And yes, our batch of ten MaxMods came with the micas, screws, nuts and inside-tooth lockwashers.

    73
     
    #12 nomadradio, Jun 13, 2018
    Last edited: Jun 14, 2018
  13. Handy Andy

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

    Joined:
    Apr 23, 2018
    Messages:
    1,196
    Likes Received:
    845
    If it's any consolation Low-Boy, Nice Job on the install!

    (y)(y)

    The ceramic looks kinda small on the outline, so the lighting, casting a shadow of relief on the panel - clearly shows what you're talking about.

    But then too, the heat spreader insulator spacer - it should also have beveled corners to help act as a guide - that is hard to see in your photo - and not all suppliers "bevel" their spreaders either - so this is new - and if it is what I think it is, these are TO-220 types - simply by "width" of the part alone - the TO-220 ceramics like those in radios are a bit oversized to help spread heat to a larger panel - so it does look "puny" on your TO-3P package when it should have some overlap - so you are correct to ask for some others' opinions.

    TO-247 is 25mm high, by 20mm wide - or 1" by 3/4" (approx.) SAE <<--works fine for TO-3P
    TO-220 is 20mm High, by 14mm wide - or 1' x 1/2" (approx.) SAE <<---Works for Finals like the 2078

    HOWEVER IGBT - the big guns, are considerably more surface area...
    IGBT - 35mm HIGH by 22mm wide - or 1 1/2" high by 7/8" (approx.) SAE <<---better for your application

    I'm more surprised by the responses you got - I hope Palomar is reviewing these...

    :+> Andy <+:
     
  14. Onelasttime

    Onelasttime Well-Known Member

    Joined:
    Aug 3, 2011
    Messages:
    858
    Likes Received:
    362
    I prob. have for myself just a hobbyist a life time supply of NOS Toshiba, MOT, and now Palomar voltage regulators as it pertains to CB and Black box radio's. It never hurts to have options!

    The above said I think people fail to remember that in addition to installing better parts you can just not tune the radio within an inch of it's life! This will functionally improve the life span of all the parts and it will reduce the operating temperatures and loading on the parts!

    The best part about this is that it cost nothing to do either! Setting the radio to have a 4 watt carrier instead of a 10 watt carrier costs nothing. In the 1980's with exotic fuels F1 had little tiny engines like Honda's 20,000 RPM turbo charged 1.5L engine running on toluene making in excess of 1200-1500HP. Yet when you look at production vehicles a 300-400HP V8 is going to be around 5.7L and to get into 600-800HP it will be 6L+ and have a super charger etc....It will not get anywhere remotely close 20,000 RPM! Why cost versus life cycle.

    Before emissions where a thing it was common to take a high performance big block de-tune it and put a 1-2 barrel carb on it and make it a "Work Truck Engine". Often the block was the same but the crank would be cast the pistons would be lower compression and the came would have very little lift. Why did they de-tune these engines? Cost and life cycle.

    De-tuning machines and electronics is a viable cost saving measure that can greatly extend life cycle.

    It makes far more sense to lower operating temperatures and power densities inside a radio and use an external amp to get the power output you are after.
     
    Handy Andy likes this.
  15. Low_Boy

    Low_Boy Well-Known Member

    Joined:
    Jan 21, 2010
    Messages:
    619
    Likes Received:
    143
    Not my install. Something I found on the net. I would have ordered the right insulator.
     

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!