How to perform the 2sc2999 and Schottky diode swap

[Carl]

do you happen to know the factory part number for the am detector? im thinking the 2sc2999 cannot be swapped in but im shure low noise diodes could be installed in the d1, d2 positions for a little better performance

 

[unit725pa]

am detector on cobra 29 and cobra 25 is 2sc1674L on cobra 29 tr7 and on a cobra 25 tr1 i hope this helps

thank you

 

[Carl]

great, the 2sc 1674 is the one you want to remove so this mod will work for you just fine. d1, d2 can be replaced with the diodes but i do not know the noside blanker diode numbers. should make a big difference as is though

 

[unit725pa]

great do to hear

 

[Carl]

get the parts here

 

[NorthStar]

all the 2sc2999's will do is increase the noise.

 

[Carl]

i posted it on the other site as well. worked great on my radios, with the exception of my 2950. it did reduce noise on this radio a good deal. perhaps its becuse it is used as a base.

 

[beantown]

Justin that "but" will get ya in trouble every tim

Justin,
The parts that are listed are of a "higher gain" "lower noise floor" components, are they not? The spec are definateley better than the stock stuff, if I am reading this correctly. I'll take the lower noise floor any day! As long as that noise is not actual signals, bring it on. My darn 2517DX is in dire need of just this sort of Mod. Darn floor noise sucks and can't see the recieve being any better. It's unreal what this thing "hears". Now if I could up that by 6db, I might finally make that elusive Australian contact I have being hunting for two years. I understand the front end issues, there is no way to help or re-adjust something?

I know your a very busy man right now and hearing a more theoretical approach (laymen stuff for me please ) on why this won't help would be greatly appreciated! Come to think of it, if I could just put the recieve section of my TR296FDX (can you say Grant XL) in my 2517 i'd be one happy camper. That's a whole new thread in it's self!!

Thanks,
Beantown

 

[Robalo]

nice ! bump

 

[Robb]

I bought my first receive kit from eBay last year, and put it in a Ranger TR-696FD-1 that I got from Sparky's CB Shack. Not noisy at all! Quite the opposite is true. The stock transistor is the noisy culprit. That is why it is best to change it out. It is the first IF amp and if it gets noise here; it will be there down the chain. I liked this mod so much, I bought 60 of the Sanyo 2SC2999'e's. If one looks it up - it has the lowest noise specs than all of these transistors available. I had to pay a bit more for them (a bit hard to find too); but it was worth it. I put them in my 29, 148, and a few other radios of mine. I've also done this mod for a few friends of mine, and they just thought it was neat - you can really tell the difference. I only had to re-tune the 29; because it needed one anyway.

The Shottky diodes can be bought by the pound. About 3 cents apiece out here in Silicon Valley CA. One doesn't necessarily have to put the diodes in all positions. Two of the diodes are used for the noise blanketer circuit, and the other two for the receive circuit. If you can only get a few of these diodes, just put them in the receive section. This will give the radio the extra sensitivity that you seek. The transistor will amp it up real clean. That's my experience - anyway...

 

[Robb]

These five parts in the receive kit (one 2SC2999 and four 1N6263 Shottky barrier diodes) can be found on eBay for about $5 including shipping. It will work as promised; but the advantage is find the Sanyo 2SC2999'e' version. Many of those sellers don't use that brand. A common 2999 can be had for $.50 each; but the Sanyo part is about $2.50 each - IF you can find them. The often will not sell just one part online - so good luck! Is it worth it - to use the Sanyo instead of other brands? My attitude is that if you expect a radio like the Grant XL to have a better receive than it does - then why not spend the extra two bucks? It's not as though the diodes are going to cost a lot - so why not. It is a very clean amp/transistor...

The Shottky diode should cost no more than a quarter each. But can be bought for a much cheaper price if you are close to an electronics parts house. And I don't mean Radio Shack either! A dime apiece is a fair price. If all you can get is a Radio Shack part and price - it will do. Really, you only need a few - it won't break the bank. In fact - for the small amount of money spent on this simple project, I think you may find yourself doing more of them. As I did...

The circuit board on most radios will show which way the banding/orientation of each diode you replace. I did two at a time; then I'd check my work. Check as you go and for a neat job; it might take 30 minutes to an hour for the whole thing. It was a satisfying experience that helped me understand at least another circuit in the radio. If for no other reason - I needed to get more exposure and experience working with and understanding radios and their components. But the benefit to the radio was realized when I took it for a test spin on my base antenna and then in my mobile. I think the mobile experience REALLY cinched the notion for me - that this mod is a solid one. The evidence was there while using it on a base antenna too. I think that a mobile radio benefits the most...

One post said that the change in the diodes in the receive section of the radio won't overload it. Yes and no. The whole point in changing these receive diodes is to allow more current in; so conceivably if a signal is strong enough and close enough it will splatter a tad. Or worse if it is just too close and too powerful. That is the best time to use the RF sensitivity knob on your radio. In truth - it gives that knob a true purpose! I've never had any problem with my radio in that regard - but I can see it happen in a worst case scenario. In any case, it provides a usable and enjoyable trade-off. I have seen a mod for the Ranger TR-696FD-1 to replace a resistor in the IF amp circuit that make make it more sensitive still. But that is the mod that WILL damage your radio's receive if you don't play your cards right. So the Shottky treatment is safe and practical - but not necessarily bad for the radio...

Will one need to re-adjust the S-meter on the radio after the mod?
ANS: Not necessary - but I did. It will push it up a bit in reference to the new receive characteristics by an S-unit or so.
Would I need to re-adjust the receive section in the radio after the mod?
ANS: Absolutely not - but it wouldn't hurt either.
Bottom line: you will like what you hear.,.

 

[MisterFatty]

A common 2999 can be had for $.50 each; but the Sanyo part is about $2.50 each - IF you can find them.

How many you want? .34 cents each, .22 if ya buy em 50 at a time....

 

[Robb]

How many you want? .34 cents each, .22 if ya buy em 50 at a time....

Sure would want to know where you bought the Sanyo 2999'e' for that price..
Or are you referring to the lesser quality 2999 for that price?

 

[BOOTY MONSTER]

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is this a good place to do business with ?

 

[15minigrass]

How bout one for a President Grant Export????