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Substitute for 2SC458?

chazix said:
I don't feel especially qualified to comment on whether it can be a sub for 2SC458, but it's an interesting part - thanks for pointing it out. It might go without saying, but watch out for the Zetex part's center-base pinout. It's interesting that the Vceo is only 40V (which is more than the 2SC458's, so no problem there with regard to substitution). But the Vcbo is 150V!
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In Recently rebuilt Setton RS-660 I used 2SC3324BL with smd adapter instead of 2SC458. But one needs to watch for Power dissipation. 2sc3324BL is smd version of 2sc2240BL. Also it's cousine 2SA1312BL good replacement for 2SA726
 
As for the ZTX1051 - never used it - but pulling up the specs.
It is listed as a Low Noise Audio part, but the actual Noise level is not listed?
Other specs would indicate it would "work" but may not be the best match to the 2SC458
This looks to be used in a higher current application with the Ic at 4A vs 100mA for the 458
 
Bill Magnan said:
As for the ZTX1051 - never used it - but pulling up the specs.
It is listed as a Low Noise Audio part, but the actual Noise level is not listed?
Other specs would indicate it would "work" but may not be the best match to the 2SC458
This looks to be used in a higher current application with the Ic at 4A vs 100mA for the 458
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There is a discussion at diyAudio and ztx1051 recommended for phono stage. one of the members measured noise levels for various transistors. zetex ( in particular 1051 and some others from ztx) measured very well. Another interesting transistor which measured very well is ztx690B
 
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ZTX851 and ZTX951 are the ones of ultra low noise that get all the mention. I have a few 851's but not installed them in anything yet, their gain is stated between 100 and 300 hFE, mine tested aprox 200 hFE.

Thought I'd add the data sheet here for the 2SC458
 

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AnalogueBen said:
ZTX851 and ZTX951 are the ones of ultra low noise that get all the mention. I have a few 851's but not installed them in anything yet, their gain is stated between 100 and 300 hFE, mine tested aprox 200 hFE.

Thought I'd add the data sheet here for the 2SC458
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True about 851's and 951 however I was talking about high gain transistors. 690 and 1051 were mentioned in numerous discussions for example this one: https://www.diyaudio.com/forums/parts/168561-transistor-voltage-noise-measurements.html.
Although with regards to 458 high gain is not that important. What i also noticed Arrow has better price for ztx than Mouser (sometimes almost half)
 
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TupolevFan said:
True about 851's and 951 however I was talking about high gain transistors. 690 and 1051 were mentioned in numerous discussions for example this one: https://www.diyaudio.com/forums/parts/168561-transistor-voltage-noise-measurements.html.
Although with regards to 458 high gain is not that important. What i also noticed Arrow has better price for ztx than Mouser (sometimes almost half)
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XTX694B/795B complimentary pairs. Center BASE though. High gain and excellent linearity. I have had none under 600hFE, and as high as 1200, but it takes a handful to get closely matched pairs.
 
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Skywatcher said:
And you would also need an adapter with the required copper surface area to meet the power dissipation requirement. But it would definitely take care of the "matching" issue. Something to look into for sure.
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I already created one ;) it is easy for me. I doubt we need 2W power dissipation. In our case we just need an adapter to mimic 2SA798 ;). I see you like this transistor I am willing to share adapters with you ;) I am serious. It will be ready in 2 weeks.
 
TupolevFan said:
I already created one ;) it is easy for me. I doubt we need 2W power dissipation. In our case we just need an adapter to mimic 2SA798 ;). I see you like this transistor I am willing to share adapters with you ;) I am serious. It will be ready in 2 weeks.
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:banana: Sounds like a plan to me. :D
 
Kicking up some questions from you smart ones who've been there done that. I'm trying to find replacements for the following out of an old CB radio. I'm hoping someone has their notes still on these and would be willing to share.
2SA733-P
2SC458-C
2SC458PG-C
2SC496-O
2SC945A-O
2SC1306
2SC1675-L
2SC1419-C
2SC1674-L
2SC1730-L
2SC1973
2SC2236-O
2SC1969-B

Thank you for the help.
 
quadmatrix82 said:
I have used 2sc1815 with success in place of 2sc458 in phono stages other areas ksc1845 or 2sc2240 is great
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Any thing different with the PG-C? It's a older manual and I've not see anything from google with that. I see the -C is 160-320 on gain or does that not matter on the new ones.

Thank you
 
TRCRdonew said:
Kicking up some questions from you smart ones who've been there done that. I'm trying to find replacements for the following out of an old CB radio. I'm hoping someone has their notes still on these and would be willing to share.
2SA733-P
2SC458-C
2SC458PG-C
2SC496-O
2SC945A-O
2SC1306
2SC1675-L
2SC1419-C
2SC1674-L
2SC1730-L
2SC1973
2SC2236-O
2SC1969-B

Thank you for the help.
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Look up the datasheets of the originals. Then you do the work of finding modern substitutes. Go to Mouser or Digi-Key and put in the parameters to see what is available.
Plus what is their role in the circuits? "an old CB radio" means almost nothing.
For example, the 2SC1419C can be usually replaced with a TIP41B or TIP42C. They are both TO-220, and both slow ft (MHz), and the TIP is heavier duty.
It takes time to look, especially for such a long list. Plus someone needs to know what they do in that "just an old CB"..
 
Thank you for the direction. That does help and I understand the vague old CB statement. Back ground is I have a Tram D80. When I turned it on it powers up but then wouldn't tx or rx but then would. I've look through it and did find a pwr wire that was not fully soldered. Cleaned it up and now when I've powered it on it seem to have corrected that however, when key'd the power out is 5w but voice is none existent unless I turn the mic gain all the way up and use a D104 handheld mic turn up all the way. It does show some modulation at that point too. I've look at the board which is seems to be the same as the Pres Wash Uniden. I have both schematics and they do seem the same. I did find that the center connection on TR 32 is cut (2sc945A-O) disconnecting the collector I believe since most parts are Japanese. I was told that this should bypass and provide max voice out all the time and why it was done. Down the line I have TR 29 (2SC458PGC and 28 (2SC945AO). If a power mic was added before I picked up the radio would it have blown them? Also reading back I've see that some of these old ones bad news and should be replaced anyway and am assuming at this point that could be one of my problems and hopefully the only one however I'm sure there is more down the line. I could be way off and it could be my IC and I'll need to replace the AN612. Thinking ahead I figured I'd as here since you all are way smarter than I in hopes someone had already looking into close replacements that way I'd have some narrowed down to look at.

Here is a snapshot of the ones I've been looking at right now from the circuit I think is the issue and my material list from the service manual.
upload_2023-1-28_8-43-3.pngupload_2023-1-28_8-44-53.png
 
Could be bad/dry/cracked solder joints. And even a resistor or three could have drifted high over time. I have a Kenwood TS-440S a friend brought over with display issues. With no display, he can't tell what works or not. Can't even set any frequencies to even test it. These are well known for having cracked solder joints on every board. Since it is complicated to access each board, doing one and reassembling won't cut it. They all need to be done while apart especially around the display area. Gonna fix a huge pot of coffee one of these days and dig into it. It may take more than a day to get them all...
With referencing the datasheets, and looking at the details, you can find many in the same gain range as the originals. Plus match closely the ft (speed) and other parameters. The 2SA733P compared with the KSA733C plus (whatever hFE group) is one place to start. Make sure the current rating is the same or higher, and the wattage rating. NOTE with the KSA733C means it has Center Collector. Without the C, it is center BASE. Only a few were like that so pay attention. The KSC945C (it's compliment) also designates Center collector.
Where are you located?
 
I'm in Tampa FL. Switching base, Yes, I have some small heat shrink I can put on it before crossing them.

So far every other part of the radio works fine. Receive is fine, meter lights up and moves and all dials adjust fine. I'm even able to use USB and LSB/PA. PA when selected has the same results as transmitting. I have to have both gains at max in order to hear voice. There is static when key'd but I have all the gain up so I'm assuming that it's not being filtered out.

hFE question. If the current one is 160-320. I've not seen one that matches perfectly. My thought is to have one that is lower and higher to encompass the span but what if that could only be full range to make that happen?

Adding just a couple shots of it. I did unhook the side board so I could see under the wire bundle. The underside shows in the red where it was cut.
upload_2023-1-28_13-38-34.pngupload_2023-1-28_13-41-33.png
 
TRCRdonew said:
I'm in Tampa FL. Switching base, Yes, I have some small heat shrink I can put on it before crossing them.

So far every other part of the radio works fine. Receive is fine, meter lights up and moves and all dials adjust fine. I'm even able to use USB and LSB/PA. PA when selected has the same results as transmitting. I have to have both gains at max in order to hear voice. There is static when key'd but I have all the gain up so I'm assuming that it's not being filtered out.

hFE question. If the current one is 160-320. I've not seen one that matches perfectly. My thought is to have one that is lower and higher to encompass the span but what if that could only be full range to make that happen?

Adding just a couple shots of it. I did unhook the side board so I could see under the wire bundle. The underside shows in the red where it was cut.
View attachment 2781344View attachment 2781349
Click to expand...
This is the Exclusively Sansui forum so I suggest starting a new thread in the Solid State forum. :thumbsup:
 
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