Old MC 250 Texas Star

[Shadetree Mechanic]

S Mechanic If the 454s will work as a drop in I,ll send for new ones today. thanks Big Lou

I don't know if they will drop in, I have never even heard of any one using these. Just letting you know that they are available. It seems HG is making some of the obsolete transistors so it might be better than nothing. If you do use them, be sure to let us know how it works out.

 

[Unit 75]

I don't know if they will drop in, I have never even heard of any one using these. Just letting you know that they are available. It seems HG is making some of the obsolete transistors so it might be better than nothing. If you do use them, be sure to let us know how it works out.

Physically they will drop in but the electrical characteristics are different. You would have to change input and outputs to accommodate the higher collector to emitter and collector to base voltages on the MRF454's. The MRF455/SRF2072 will work fine.

 

[BigLou]

If you looked at my last post you can see that I,m gitting 2 454s to have when the ones in the box go. Also the CBTRICKs show the 455s AND the 454s to be just a bit dif....and are all most a drop in or it looks like that to me on the datasheet,as I said I,ll run it like it is for now. I do thank all for the help and will take all the help I can git. Thanks to all......Big Lou

 

[999]

If you looked at my last post you can see that I,m gitting 2 454s to have when the ones in the box go. Also the CBTRICKs show the 455s AND the 454s to be just a bit dif....and are all most a drop in or it looks like that to me on the datasheet,as I said I,ll run it like it is for now. I do thank all for the help and will take all the help I can git. Thanks to all......Big Lou

The MRF454 would cross to the 2SC2879. They are not a drop in replacement for the SRF2072 so to install those you will need to rework the circuit.

 

[999]

Here is an old schematic I have that might help clear some things up.

 

[nomadradio]

Cool! Must be the oldest DX667 schemo I've seen.

Not sure how it helps a guy with a two-fifty, though.

73

 

[9C1Driver]

The MRF454 would cross to the 2SC2879. They are not a drop in replacement for the SRF2072 so to install those you will need to rework the circuit.

I think that is a mis-type, an MRF454 and a 2SC2879 are not a direct replacement at all.

https://datasheet.octopart.com/2SC2879-Toshiba-datasheet-102073.pdf

https://alltransistors.com/pdfview.php?doc=mrf454re.pdf&dire=_motorola

 

[AudioShockwav]

I agree.
The 454 is not a drop in replacement for a 455,2072 or a 2879.
I think I said that about half a dozen posts ago.

73
Jeff

 

[999]

Cool! Must be the oldest DX667 schemo I've seen.

Not sure how it helps a guy with a two-fifty, though.

73

It lists different transistors and the wraps on the different transformers that go with them.
I think this more lines up with the DX600, but there is enough information to figure out how a 250 or 350 would have been setup.

 

[nomadradio]

There are four different "DX250" models listed here.

One of them should be close.

[URL]http://www.cbtricks.com/Amp/txstar/index.htm[/url]

73

 

[2315 Robert]

MRF 453 available at rf parts.