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2sc458, 2sc2240 Clarification please

Hello Fred. I am about to rebuild a bunch of Akai R2R's and am looking for the 2SC2240 with no avail. There are substitutes at NTE.com But they warn you that it may not be the perfect substitute. My intention is to rebuild these units and improve the quality to better than spec (if possible). What wouldd you recommend as a replacement for the 2sc2240? Alas are their any brands of caps you prefer and would recommend?
I must say I am kind of shocked that these parts age even without use (2cs458) as I have a new GX635 that has barely seen the light of day and has been stored indoors...it sounds like ass lol...
Any help would be greatly appreciated.



Fred Longworth said:
The original 2SC458 was made by Hitachi, and installed in a funny-looking rectangular package with a little "roof" on the top that slopes down from front to back. These were based BCE reading left to right. At the time of manufacture, these were considered an excellent choice for a low-noise, small-signal transistor -- and were used widely. Unfortunately, they began to leak and generate noise and operating-point errors.

A few years ago, "new generation" 2SC458's began appearing. These were in a more modern package -- like the 2SC2240, which read ECB from left to right. I consider many of these "new 2SC458's" to be counterfeits, i.e. other transistors relabeled.

* * * * *

Back in the late 1970's, when 2SC458's began to fail, I used the 2SC1775 as a replacement. I chose it because in the spec manual it was called out as a low-noice small-signal device with a bandwidth not dissimilar to the 2SC458, and because the 2SC1775 was used in many machines I encountered -- and the device never seemed to fail.

By the early 1990's, the 2SC2240 had proved itself as a wonderful small-signal, low-noise transistor, again with an acceptable bandwidth, so I began using it as a replacement for the 2SC458.

* * * * *

A brief look at the specs reveals that the 2SC945 is an older-generation small-signal transistor not intended for super low-noise applications. It works fine as a basic, small-signal transistor, and is fine for many applications. I would never stick it in a low-noise circuit.

In transistor selection, like many other aspects of electronics, the devil is in the details.

* * * * *

As of this writing, I have probably replaced about 10,000 2SC458's with better-performing devices.

Fred
Click to expand...
 
quadtech said:
Caveat emptor - I was unlucky to get a bunch of fake 2SC2240
exactly like the ones described here.

http://www.audiokarma.org/forums/showthread.php?t=285234

I'd rather go with a reliable option like the Mouser one posted by Steve.
Click to expand...

I won't buy any active or passive devices off of ebay.BD Enterprise is the real deal -pricey-with min orders of $15( If you need Sankens its the place to go). Mouser is more conveniant,less expensive-no min order amounts and have just about whatever you need.
 
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quadtech said:
Caveat emptor - I was unlucky to get a bunch of fake 2SC2240
exactly like the ones described here.

http://www.audiokarma.org/forums/showthread.php?t=285234

I'd rather go with a reliable option like the Mouser one posted by Steve.
Click to expand...

I guess I got lucky, the ones i got worked perfectly. Living in Canada I have to take my chances on the parts that cost the least shipping. Shipping from the big shops like mouser can get expensive, 2 dollars in transistors and 15 to get them here doesn't make good financial sense.
 
I went to a local Electronic store in order to change my 2sc458 trans... They told me that the 2240 are not longer available and that a good replacement is the japanese 2sc1313... What do you think? Is that a good replacement? What about noise performances?
 
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The 458s in my 2000x were bad; IMO the original 458 is evil. Data sheets are only marginally useful in choosing a good substitute as the noise numbers may not reflect the operating conditions in your actual application. I tested a variety of parts in a copy of my 2000x circuit and ended up using 2N5088. There are actually a lot of good subs, but you have to choose wisely based on operating voltage and current. There's a write-up on my site with curve tracer photos of what a good and bad 458 looks like. I don't worry much about pinout, just determine what it was and insert the new device accordingly. BTW, the sound improvement with new devices was amazing.
 
How do you know you are not buying counterfeits (i.e. renumbered transistors)? As some people mentioned before, I think it is best to play it safe and stick to what it is widely available and not obsolete.

I needed replacements for the 458's on my 1030 and could chose between 2sc2240's available from John Doe online or the KSC1845 from mouser. I went with the last option. They should be arriving soon, I will let you know how they perform.

I will also use them as replacement for several 2SC1328's on my 2216.
 
Fred Longworth said:
The original 2SC458 was made by Hitachi, and installed in a funny-looking rectangular package with a little "roof" on the top that slopes down from front to back. These were based BCE reading left to right. At the time of manufacture, these were considered an excellent choice for a low-noise, small-signal transistor -- and were used widely. Unfortunately, they began to leak and generate noise and operating-point errors.

A few years ago, "new generation" 2SC458's began appearing. These were in a more modern package -- like the 2SC2240, which read ECB from left to right. I consider many of these "new 2SC458's" to be counterfeits, i.e. other transistors relabeled.

* * * * *

Back in the late 1970's, when 2SC458's began to fail, I used the 2SC1775 as a replacement. I chose it because in the spec manual it was called out as a low-noice small-signal device with a bandwidth not dissimilar to the 2SC458, and because the 2SC1775 was used in many machines I encountered -- and the device never seemed to fail.

By the early 1990's, the 2SC2240 had proved itself as a wonderful small-signal, low-noise transistor, again with an acceptable bandwidth, so I began using it as a replacement for the 2SC458.

* * * * *

A brief look at the specs reveals that the 2SC945 is an older-generation small-signal transistor not intended for super low-noise applications. It works fine as a basic, small-signal transistor, and is fine for many applications. I would never stick it in a low-noise circuit.

In transistor selection, like many other aspects of electronics, the devil is in the details.

* * * * *

As of this writing, I have probably replaced about 10,000 2SC458's with better-performing devices.

Fred
Click to expand...

Not to ressurect old threads, but this point deserves writing down. The author is 100% correct. The old weird pentroof 2SC458s are BCE when reading the label.

My mouser order just came in and I just swapped them out for new KSC1845s. 1000% better. I did a measure before hand, the 458s had an Hfe of 92-100, the new ones are 200 and I ordered 'regular' suffix. the 43 year old magnavox world radio is currently burning in.
 
varox84 said:
How do you know you are not buying counterfeits (i.e. renumbered transistors)? As some people mentioned before, I think it is best to play it safe and stick to what it is widely available and not obsolete.

I needed replacements for the 458's on my 1030 and could chose between 2sc2240's available from John Doe online or the KSC1845 from mouser. I went with the last option. They should be arriving soon, I will let you know how they perform.

I will also use them as replacement for several 2SC1328's on my 2216.
Click to expand...

I just replaced the 458's in my 1030 with the KSC1845's and the perform very very admirably.
 
Nice to hear that! I will spend my evening replacing the 2SA722's and 2SC1328's on a 2216 with KSA992 and KSC1845... I will also replace 458's on a 1030 with KSC1845. Will let you know my impressions.

Cheers!
 
Hello I'm new to the forum and just bought a marantz 2220 that has a noisey right channel. I am getting a list of parts together for a recap and transistors. My question is, will the KSC1845 replace all 2sc458's on each board? If read that these should be replaced when found but the service manual shows a different suffix for some of them. Thanks

Sent from my SCH-I815 using Tapatalk
 
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