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How to perform the 2sc2999 and Schottky diode swap
- Thread starter Carl
- Start date
how did you use this in the place of a 2sc2999? it has 4 legs and a totally different design compared to a 2999. the original part is a 3 leg trans.
Well; two of the legs -IIRC- are the same. But you are right. After all, the GasFet is a FET. Not a bipolar transistor like the 2999. They are not direct replacements. A FET requirements would need to be met first, and then it would work. Some circuit changes would become necessary, IIRC.
Don't think that impedance is the issue, because the FET's have a very wide range.
But the voltage requirements would be different.
When I used to work on cars, not having a dyno, the 'rule of thumb' I used was a "seat of the pants" feel as to whether or not the performance mod was successful. Turns out that for a small to midsize car, even something as small as 5 rwhp COULD be 'felt' in the drivers seat. Likewise, performance on the street, strip, or at the gas station ultimately became the deciding factor as to whether or not the mod was successful.
To me, radio is a lot like that; I've had success with the 2SC2999's, and I've had nothing with them in the way of a "by-the-ears" comparison.
Turns out that IF the radio already had a 2SC2876, then the 2SC2999 was (basically) useless for me. However, IF the radio had a 1674, then MOST times the 2SC2999 made a 'by-the-ear' discernible difference (to me.)
The rigs the 2SC2999's seemed to make the MOST difference in were:
HR-2600's, 2510's and Lincolns
TR-296's and Cobra 148-GTL's
Cobra 29's
and MOST Galaxy/Ranger radios.
The 3 specific late model radios that they did NOT make any difference to MY ears were:
DX-94HP
DX-98VHP
and
RCI-3900HP
Also, of note, the NTE107 (which is a substitute for BOTH the 1674 AND the 2999) seems to work ONLY on the DX chassis radios (i.e: 949's and 959's); when tried in Cobras, Unidens, Rangers, RCI's, Presidents, etc., the NTE107 does not appear to make any difference.
Another interesting thing about the 2SC2999's vs. the NTE107 equivalents was that no matter how much I turned up the gain in the receiver (where adjustable) via slugs and/or pots on an NTE107 I could never bring it into oscillation, whereas, if I took the 107 out and installed a 2999 in its place, sometimes I could get it to self-oscillate (generate noise.) To me, this would indicate that an NTE107 is probably MORE like a 1674 than a 2999 as far as gain and/or noise thresholds. Therefore, I am now LESS inclined to use the NTE107 as a sub for a 2999. However, WHY they seem to work in DX-949/959's but not so much for other radios is anybody's guess; I suspect it has more to do with the REST of the receiver circuitry in these particular makes/models then it has to do with the actual particular devices themselves. Really dunno.
As for the barrier diodes, I've often used 1N5711's with success in the AM product detectors, but MIXED success in the Noise Blanker sections (even AFTER alignment.) I wonder if the 1N5711 diodes switch fast enough or too fast when compared to germaniums?
Truth be told, I'm just a "hobbyist" who's pretty good with a soldering iron and NOT an RF Engineer, so I am certainly out of my depth in this discussion; I am merely attempting to share my observations in pursuit of the Radio "Art".
To me, radio is a lot like that; I've had success with the 2SC2999's, and I've had nothing with them in the way of a "by-the-ears" comparison.
Turns out that IF the radio already had a 2SC2876, then the 2SC2999 was (basically) useless for me. However, IF the radio had a 1674, then MOST times the 2SC2999 made a 'by-the-ear' discernible difference (to me.)
The rigs the 2SC2999's seemed to make the MOST difference in were:
HR-2600's, 2510's and Lincolns
TR-296's and Cobra 148-GTL's
Cobra 29's
and MOST Galaxy/Ranger radios.
The 3 specific late model radios that they did NOT make any difference to MY ears were:
DX-94HP
DX-98VHP
and
RCI-3900HP
Also, of note, the NTE107 (which is a substitute for BOTH the 1674 AND the 2999) seems to work ONLY on the DX chassis radios (i.e: 949's and 959's); when tried in Cobras, Unidens, Rangers, RCI's, Presidents, etc., the NTE107 does not appear to make any difference.
Another interesting thing about the 2SC2999's vs. the NTE107 equivalents was that no matter how much I turned up the gain in the receiver (where adjustable) via slugs and/or pots on an NTE107 I could never bring it into oscillation, whereas, if I took the 107 out and installed a 2999 in its place, sometimes I could get it to self-oscillate (generate noise.) To me, this would indicate that an NTE107 is probably MORE like a 1674 than a 2999 as far as gain and/or noise thresholds. Therefore, I am now LESS inclined to use the NTE107 as a sub for a 2999. However, WHY they seem to work in DX-949/959's but not so much for other radios is anybody's guess; I suspect it has more to do with the REST of the receiver circuitry in these particular makes/models then it has to do with the actual particular devices themselves. Really dunno.
As for the barrier diodes, I've often used 1N5711's with success in the AM product detectors, but MIXED success in the Noise Blanker sections (even AFTER alignment.) I wonder if the 1N5711 diodes switch fast enough or too fast when compared to germaniums?
Truth be told, I'm just a "hobbyist" who's pretty good with a soldering iron and NOT an RF Engineer, so I am certainly out of my depth in this discussion; I am merely attempting to share my observations in pursuit of the Radio "Art".
Thanks
I found the 959 radio here
http://www.cbtricks.com/radios/galaxy/dx959/graphics/dx959_sch.pdf
As LC says this one is very similar to my mk2 148GTL-DX but I spotted they have included a very basic upgrade to try and offset the noise seen in my hissy 148 video.
If you look at the top of the schematic near the centre you will see R26 and D7.
D7 gets biased from the AGC line via R26 and acts like a crude variable attenuator and this reduces the gain of Q9 by damping the tuned circuit of L2.
This mod will therefore share some of the AGC action with the mixer at Q8.
This will help preserve the S/N ratio better so these EPT radios won't be as hissy as the mk2 148GTL-DX on FM and AM.
I suppose I could try fitting the diode attenuator/switch to a 148 and test it but there's a risk the AGC will go unstable or introduce distortion at certain signal levels on big AM signals. The D7 mod is quite crude but it's probably quite effective. I'd still expect some hiss though and I would have thought they would have modded the 455kHz stage a little more elaborately to give a better AGC action on AM and FM.
I would like to try this AGC improvement on my 959. Can you provide instructions for the non-technical person?
Man, I learned a lot reading this thread, especially that guys will fight about anything LOLOLOL, my transistor is bigger than your transistor. I have been through this thread several times looking for the location and parts to replace in a Stryker 955 to do this mod. I appreciate the help.
I have more than a few of the origonal sanyo transistors left, but have my doubts as to the real effectiveness of them. Even doing an HFE test on them and using the highest gain ones I could find, I never really seen a noticeable improvement. I wouldn't bother doing this mod on any of the "newer" chasis designs being made today as the first Rx amp already has a higher gain than their older through hole counterparts (1674) had, And what this modification was origionaly ment for.
Good luck
Oh, and I think there was a thread on here somewhere where this modification was tested in great detail and still was no real evidence that the mod worked.
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I have more than a few of the origonal sanyo transistors left, but have my doubts as to the real effectiveness of them. Even doing an HFE test on them and using the highest gain ones I could find, I never really seen a noticeable improvement. I wouldn't bother doing this mod on any of the "newer" chasis designs being made today as the first Rx amp already has a higher gain than their older through hole counterparts (1674) had, And what this modification was origionaly ment for.
Good luck
Oh, and I think there was a thread on here somewhere where this modification was tested in great detail and still was no real evidence that the mod worked.
Thanks for the reply, I am on an email back and forth with one of the Stryker Techs, still waiting on definite and now it seems that there may be a tiny amount of improvement with just the 6263's Then again if its not discernible whats the point?
This is true. I gave up on all this years ago. Good luck to you if you decide to persure it.
Does anyone Know how to contact GOHZU ?
I know this thread has been dead a while.
He seemed to up to snuff on recieve alignments.
I would like to know if Sinad is the best for aligning the cb for recieve.
As far as s/n ratio.
I know Sinad is used for FM but have been told not for AM mode.
Also until it gets above 30 mhz its not necessary.
Like most of the experts , they are not gonna waste the time to explain.
As 543 mentioned on another thread. They do well when they preach
but Not so well when asked too many questions.
Thanks
I know this thread has been dead a while.
He seemed to up to snuff on recieve alignments.
I would like to know if Sinad is the best for aligning the cb for recieve.
As far as s/n ratio.
I know Sinad is used for FM but have been told not for AM mode.
Also until it gets above 30 mhz its not necessary.
Like most of the experts , they are not gonna waste the time to explain.
As 543 mentioned on another thread. They do well when they preach
but Not so well when asked too many questions.
Thanks
The sinad measurement is kind of useless. What if you increase the output of the speaker simply by just changing a small component? Did the receive just magically become better?
I think using the minimum detectable signal might perhaps be more useful.
I've seen a lot of guys using these schottky diodes and 2sc2999 with decent results for weak signals but then they don't alter the AGC circuit to prevent front end overload.