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Tram D201 Mods How to Undo them.

Discussion in 'CB Radio Modifications' started by LLFordman, Nov 3, 2009.

  1. LLFordman

    LLFordman Member

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    I have been searching the web to no avail trying to find out what the power, VFO transmit and audio mods are for a Tram D201 but I have found very little info.
    Anyone have this info? I have two D201's currently, one works pretty much as advertised but the other one puts out a carrier of almost 15 watts with a 6L6 which I am sure isn't right. This one also has an internal squeal when the mic gain is above 12 o'clock but yet the squeal isn't transmitted audibly and the squeal noise is still there even without a head on the D104. Makes no sense.
    Anyone know about the 6146 mod?


     
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    Last edited: Nov 3, 2009
  2. packrat

    packrat Active Member

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    The most common power mod, and the easieat to undo, is to jump the power resisters to bypass them. There are two resisters on the bottom side near the 6l6 tubr socket. Look for two identical resisters, and see if they have been jumpered. If so, remove the jumpers and you should be good to go.

    PR
     
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  3. LLFordman

    LLFordman Member

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    Thanks much for the reply and the info. Had both radios on the bench side by side tonight. Radio "A" has a jumper on the 1.5k resistor and radio "B" has a jumper on the 2.7k resistor. That explains why "A" puts out 6 watts and "B" puts out 10 watts instead of the 3.8-4.2 watts the book states when neither is jumpered. I think the 6 watt output should be fine. Maybe more swing with the jumper removed though. We'll see.

    When I bought radio "B" it already transmitted on the VFO and radio "A" did not. I discovered tonight that radio "B" has a jumper and a wire removed on the crystal/manual switch. Is this part of the VFO mod to transmit? Radio "A" does not have this mod done to the switch, yet it still transmits on the VFO after I made a trace cut and jumper under the main board that I copied from radio "B"

    Sorry if that's difficult to follow. I wish I could find someone with drawings of these various mods.

    Any thoughts on the squeal radio "B" is making? It changes when varying both the mic gain and the transmit tone control. That makes me think its in the first amp stage but I haven't seen anything abnormal with the o-scope yet.

    Thanks again for any help you can provide.
     
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  4. MisterFatty

    MisterFatty Poppin Fresh!

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    You have to consider the age of the radios, your going to have Resistors that have changed value, failing capacitors, dirty/loose pins on tubes, lifted failing traces on the PCBs. All of the above is common issues. One or more are most likely causing your radios issues.

    Checking components in the audio section would probably be a good start.

    Here is some info regarding the various mods.

    the 6146 mod is not difficult, I would however suggest an outboard amp over any internal changes.
     

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  5. MisterFatty

    MisterFatty Poppin Fresh!

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  6. King Mudduck

    King Mudduck FEAR THE DUCK!

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    Have you checked Grumpy's radio forum? If it's still around there are more than a few guys on that site who know a great deal about the old tram radios. If you still cant get the radio worked out to your liking then contact electronic service center ( they have a web site ) in Elkin NC and ask them to put you in contact with Ray. He is one of,if not the best tech when it comes to the old tube radios on the east coat.
     
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  7. LLFordman

    LLFordman Member

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    Excellent info! Thanks guys. I am going to go in further with the generator and comm analyzer (borrowing from work) tonight to try and see what the levels are starting at the first amp stage and working my way in. If it comes down to testing every component individually then so be it.

    At this point both radios work quite well, save for the squeal on radio B. I am just a picky SOB and want it to work properly or as best as it can given the age.
    I most likely won't mess with the 6146 swap but will study the info just for my own knowledge.

    I have browsed Grumpy's forum in the past but didn't find too much on the Tram D201's. I will look again.

    I'll be sure to post my findings. More to follow.

    Thanks again.

    BTW, when the "squeal" is occurring, if you try to modulate through the squeal your voice sounds like it has a rumble in it. I am thinking AC getting in somewhere it shouldn't be but haven't seen any on the O-scope yet.
     
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    Last edited: Nov 4, 2009
  8. Radio Tech

    Radio Tech Radio Operator

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    Check the BA board reall close. A lot of problems start there. Those caps get a lot of heat on them. Many folks change the resistor to cement type 5 watt. These should be carbon film or metal Ox. resistors. Wire rounds do not work well in this circuit and could possibly contribute to squeals and hows in the RX. The pins coming up from the board also come loose with vibration since there is nothing holding the board up but the pins.

    At the base of the audio tube towards the back is a 2 watt resistor. Can not remember the value. But it goes bad quite often in these older rigs. I have seen this changed out in many units to the wrong value.

    Also check the 10uf X 4 X 450 cap real good on each leg.
     
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  9. LLFordman

    LLFordman Member

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    A bit of progress tonight. After grounding the ALC/Compression circuit per the alignment instructions, the "squeal" is completely gone and everyone says the radio sounds very nice. I tested most of the components in the ALC circuit and haven't found anything faulty. Voltages are where they should be. At least I am in the right neighborhood now. I also removed the jumper for extra power and re-neutralized the driver and final so it is back to 4.2w out with a forward swing to 10-12w. Also noticed the noise blanker is inop as well.

    More work.
     
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  10. MisterFatty

    MisterFatty Poppin Fresh!

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    NB was not one of the radios high points...
     
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  11. Eastside

    Eastside Well-Known Member

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    Are these mods also the same for the Titan 2?
     
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: tram, tram d201

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