I just got a old Texas Star MC250 on e-bay it,s not putting out the watts it can put out. I git 110 with 2 watts in on AM, on SSB it swings to 130 watts. I no it can do more but I don't want to push it to hard. I can git 2 HG2879,pills for a good price. What I need to no is will the HG2879 pills just drop in it has the 2290 pills in it now. Thanks Big Lou.
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Old MC 250 Texas Star
- Thread starter BigLou
- Start date
No.
If you want to convert it from a 250, with two 2SC2290 into a DX350 with two 2SC2879, the parts changes to do it are shown on the schematic.
Posted here: [URL]http://www.cbtricks.com/Amp/txstar/dx250_dx350/index.htm[/url]
It shows the component values and transformer turn counts for the 250 and the 350.
The circuit values need to match the transistor type that's being used.
73
NOMADRADIO Is right on point . The first box I cooked was a TS DX350 I made the mistake of "dropping in" pills that were listed as an "upgrade kit" I never even pulled up a schematic I was more worried about flowing pretty solder on the tabs
then checking twice and soldering once It keyed , it threw a carrier , it smoked a $200 kit bc I didn't bother to look at the transformer size , resistance at choke points or capacitance on the hot legs as you can tell by my terminology Im not a pro tech or tuner just a mud-duck with lots of toys and the will to learn lol This forum has taught me tons !! I have been "reading the mail " for years but all my recent problems or projects have gone great because of some of the cool smart decent people on here ! I finally said F it and posted and I learn something new every time I scroll around !
Let us know what you do with your kicker and how it goes !
73's 4-2-ZERO Brian from New Jersey
The MC250 shouldn't have Toshiba transistors in it if it's original and the schematic above would be wrong for it. If it does have Toshiba transistors in it, there is a very strong change that the capacitor values are off all over the place in that box, not to mention the number of turns of wire in the transformers.
Even if the original transistors are still in it, the capacitors would most ;likely be bad from age and heat anyway.
Either way, the box should most likely be looked at by someone that knows what they're doing.
EDIT: I just re-read what you posted and it has 2290's in it now and those are replacement transistors in that box. Unless it has been reworked completely to make them function properly, it will need to be.
Even if the original transistors are still in it, the capacitors would most ;likely be bad from age and heat anyway.
Either way, the box should most likely be looked at by someone that knows what they're doing.
EDIT: I just re-read what you posted and it has 2290's in it now and those are replacement transistors in that box. Unless it has been reworked completely to make them function properly, it will need to be.
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SRF 2072 are RF Parts in house numbers from many years ago, and that sounds right for a amp that old.
2879' s will not drop in.
I would take it to someone that has experience working on RF amps for repair.
Just curious, what watt meter are you getting your readings from?
73
Jeff
2879' s will not drop in.
I would take it to someone that has experience working on RF amps for repair.
Just curious, what watt meter are you getting your readings from?
73
Jeff
The amp might be working just fine. On AM you said a 2 watt dead key input, what does the radio swing as far as peak watts? And what is the PEP wattage when you tested on SSB?
cbtricks.com says the equivalent replacement final is a Motorola MRF455. The datashet says the MRF455 is a 60 watt device at 30 MHz. Depending on your peak wattage drive 130 watts seems correct for that amplifier.
http://www.cbtricks.com/Amp/txstar/datasheets/index.htm
If you do decide to get new finals for that amplifier the MRF455's are 50 bucks each. Probably more then you paid for the amp.
https://www.rfparts.com/mrf455a-mot.html
Shadetree Mechanic
Delaware Base Station 808
I really would run it as is.
The input and out put you are posting seems fine for that transistor with the meter you are using.
Just because it says model 250 don't mean that it will 250 watts and I think that is a Avg reading meter you have.
As long as it is working I would not mess with changing anything.
FYI
The MRF 454 is a little different than the 455.
More output and slightly different tuning to optimize for best output.
73
Jeff
The input and out put you are posting seems fine for that transistor with the meter you are using.
Just because it says model 250 don't mean that it will 250 watts and I think that is a Avg reading meter you have.
As long as it is working I would not mess with changing anything.
FYI
The MRF 454 is a little different than the 455.
More output and slightly different tuning to optimize for best output.
73
Jeff
S Mechanic If the 454s will work as a drop in I,ll send for new ones today. thanks Big Lou
If you looked at the link I posted the MRF 455 IS the direct replacement for an SRF 2072. Not sure if a 454 final will work or not. Good luck.