Transistor sub question 2sc458

[Markoneswift]

Hey all, I think this peticular transistor has been the subject of many 'sub with...' threads but my reason for posting is lack of alternatives in my domestic market.

I see in some places that BC550 is listed as a suitable sub but I'm wondering if any other part would be equally as good. My local store have lots of the BC / BD parts but limited options for anything else. Mouser, RS and Element 14 could all deliver to NZ but they have high postage costs and minimum order levels.

Any assistance would be great - I'm hoping to replace all the 458s in my Akai 4000D. Cheers.

 

[clinic-audio]

Hello Markoneswift

yes , I have read like you all these members replacing 2SC458 . I don't know who start this silly story saying that it is a good preventive solution to replace these "defective" or noisy transistors .

This is completely stupid to do it if yours are working well in your item .

Only one type has been affected by a discover of troubles with 2SC458LG (get noisy) and only this one ! many who don't understand electronics decided that 2SC458 all type need to be replaced . This is a real waste of time without serious reason for making this replacement . and they do copy replacement without knowing what they are doing ....

it is like those who decide to replace varistors VD1212 by 2 diodes 1N4148 in serie , same problem , and many recommend to replace ......

I am making repairs on Japanese items since over 42 years and never get any troubles with 2SC458 and VD1212

Do as you want but you will see who is right and who is wrong

Best substitute for 2SC458 is 2SC1815 TOSHIBA

 

[dlucy]

Best substitute for 2SC458 is 2SC1815 TOSHIBA

There are many vintage small signal transistors that exhibit multiple kinds of noise. The 2SC458 is but one of them.

There is a a post which directly addresses which common transistors exhibit the problems most often. The list has been built with the contributions of dozens, both full time professionals as well as hobbyists like myself. The number of years one has in a field and the type of vocation do not diminish their ability to recognize noise and it's source and eliminate those sources.

The modern KSC1815 is an acceptable replacement for the 2SC458 when used for audio amplification, but the lower noise factor of the modern KSC1845 make it a far better replacement... for audio signals.

 

[dlucy]

I see in some places that BC550 is listed as a suitable sub but I'm wondering if any other part would be equally as good. My local store have lots of the BC / BD parts but limited options for anything else. Mouser, RS and Element 14 could all deliver to NZ but they have high postage costs and minimum order levels

You can double check with the "low noise transistors" link in my signature and look at the specs for the BC559 and BC560. You'll have to compare those against the specific applications of the 2SC458 in your unit, but for most audio signal handling prior to the final amp stage, either of these should easily replace your 2AC458's and have very low noise. Just remember to match the pin out on your board to the replacement device's pin out. You may need to rotate the new device 180 degrees before installing it.

 

[audiojones]

I can tell you that I’ve seen multiple failure modes of this particular transistor in multiple gain groups time and time again over many many years. Not just background noise but squealing, pegged VU meters, low gain, excessive gain, dead channels due to shorts, opens, pretty much every failure mode a transistor can have this one has exhibited time and time again. How someone in the electronic service trade hasn’t observed this problem baffles me. Many experienced techs including @dr*audio amoung others used to have to replace these under warranty in all makes of equipment.
I have long since lost count of the Akai open reel decks I’ve had on my bench that were there strictly because of this component failing in various modes. Most of the time the 458 wasn’t even what the circuit was designed for and isn’t called out in the schematics and very often the LG group isn’t involved, Akai subbed them in because it’s what they had. They also used it for the automatic reverse trigger circuit and the muting delay time constant circuit where it has an extremely high failure rate as well.

I do agree that if you’re not having any problems at the moment you can leave them be and I don’t generally advocate blanket component replacement, however if you are having issues caused by a 2sc458 transistor or if you feel like changing them out as preventive maintenance definitely replace all of them regardless of gain group designation.

 

[Tom B]

I repaired a friends Akai 4000D. Not sure if it was a GX-4000D or plain 4000D.
The symptoms were almost no audio output on either channel. even touching the leads on the playback head only gave a very small signal and just barely registered on the VU meters. Touching the circuit board connections yielded similar poor results. I put a pre recorded tape on and used my signal tracer to troubleshoot. I assumed maybe some small signal caps were open. I checked the base of the first playback amp transistor and got audio, but almost nothing on the collector (output to the next transistor). I then sprayed circuit chiller on the transistor and signal out dropped to nothing. I then used the tip of my soldering iron to apply heat near (not touching) the side of this questionable transistor. All of a sudden, I got full audio on that channel. I then applied heat to the same transistor in the other channel and withing 2 seconds, got full audio there as well. So I had then confirmed that both of them were bad. They were 2SC458lg. I looked though the schematic and saw that there were 8 of these for the playback circuits and 6 of these for the record circuits. So not wanting to take a chance, seeing I found 2 that were open under normal load, I replaced all 14. And the unit now played and recorded great.
It appears that this type of transistor developes poor connections to the junction internally, causing noise is some applications as well as open condition in others.

 

[clinic-audio]

Tom B

100% ok with you

 

[spark1]

Hello Markoneswift

yes , I have read like you all these members replacing 2SC458 . I don't know who start this silly story saying that it is a good preventive solution to replace these "defective" or noisy transistors .

This is completely stupid to do it if yours are working well in your item .

Only one type has been affected by a discover of troubles with 2SC458LG (get noisy) and only this one ! many who don't understand electronics decided that 2SC458 all type need to be replaced . This is a real waste of time without serious reason for making this replacement . and they do copy replacement without knowing what they are doing ....

it is like those who decide to replace varistors VD1212 by 2 diodes 1N4148 in serie , same problem , and many recommend to replace ......

I am making repairs on Japanese items since over 42 years and never get any troubles with 2SC458 and VD1212

Do as you want but you will see who is right and who is wrong

Best substitute for 2SC458 is 2SC1815 TOSHIBA

You just called a number of respected members stupid. Not cool. EDIT: More precisely, you called their experience-based recommendations stupid (stupide). Still not cool.

You appear to have the opinion that there is no reason to replace components until there is an obvious failure. This is certainly a legitimate point of view, especially for someone who does repair work for a living. The professional repair techs that I know (those with storefront shops) don't generally do preventive maintenance; they prefer to repair only the immediate problem. This approach yields the highest hourly income for them.

However, it is equally legitimate for skilled hobbyists and professional restoration technicians to replace all components knows to fail with age and/or known to have a higher than normal risk of failure.

EDIT: Closing paragraph deleted.

 

[spicer]

You just called a number of respected members stupid. Not cool.

You appear to have the opinion that there is no reason to replace components until there is an obvious failure. This is certainly a legitimate point of view, especially for someone who does repair work for a living. The professional techs that I know don't generally do preventive maintenance; they prefer to repair only the immediate problem. This approach yields the highest hourly income for them.

However, it is equally legitimate for skilled hobbyists and professional restoration technicians to replace all components knows to fail with age and/or known to have a higher than normal risk of failure.

Personally, I think it is stupid to be so dogmatic on this topic.

I hear you about the stupid comment but reading the entire text gives me the impression that either English is a second language here without full consideration for word usage or is being processed through translation software which can produce all manner of ills. As an aside, I couldn't agree more about skilled techs fixing problems for highest hourly income versus skilled hobbyists and/or professional restoration technicians... that is the difference between service and restoration.

 

[Hyperion]

I advocate a 'lightest touch needed' approach to component replacement in vintage audio. Thus I incline towards not blanket replacing transistors unless I find more than one of that type faulty in a particular unit, or unless it otherwise has a particularly bad reputation. Obviously each example (or unit) is different and another unit might attract a different response from me. I do worry about amateur restorers (of which I am one), some of whom insist on replacing parts 'just because they are old' - like polystyrene or ceramic capacitors, rectifier diodes, and so on, when it just isn't necessary.

I also heard that it is just the 'LG' version of the 2SC458 which has the bad reputation, (but the news got out and people left off the LG suffix - and then it was too late - all 2SC458 were thought to be troublesome). So replacing the 'LG' suffix ones is no bad thing, and is what I would do.

 

[Markoneswift]

Seems like I have caused another debate, which was not the purpose of my original question.

To explain further, I am thinking about modernising the amp boards in the Akai using low noise transistors, replacement caps and maybe better resistors.

It's not that any component is particularly bad so this project is more for my own entertainment and experience. I hardly use the deck but I don't want to ruin it completely, hence my asking about suitable replacement components.

 

[Hyperion]

To explain further, I am thinking about modernising the amp boards in the Akai using low noise transistors, replacement caps and maybe better resistors.

It's not that any component is particularly bad so this project is more for my own entertainment and experience. I hardly use the deck but I don't want to ruin it completely, hence my asking about suitable replacement components.

Nothing wrong with that at all.

Learning about components and getting a feel for what makes a difference is a pleasing experience.

 

[clinic-audio]

Hello Hyperion

I also heard that it is just the 'LG' version of the 2SC458 which has the bad reputation, (but the news got out and people left off the LG suffix - and then it was too late - all 2SC458 were thought to be troublesome). So replacing the 'LG' suffix ones is no bad thing, and is what I would do.

that's exactly what I mean .

AK members are not stupid , replacing working components without knowing what they are doing is stupid.
Units are made by enginers with calculations and sophisticated circuits , replacing old working components by modern one will change for ever your unit .

Transistors are not valves . There is noisy transistors , yes , but replace it and only this one not all . Don't think that the same transistors as the one you have replaced , will be noisy very soon . This is a non sense .

Replacing old (good) resistors can be worse than before

Professional working on very old unit will not take the risk to replace one working cap or working specific resistor by new "modern" component because the sound of the amplifier will be gone for ever

Ask people working on original MARANTZ model 9 .There is electrolytic capacitors very very old and stay very good 60 years after .
Replace them and you will hear that the sound is no more the same .....
You did it because someone told you that you have to do it .

That's what I mean when I say "stupid" , you did it without knowing the true

I do not post here to be unpleasant but just for sharing my knowledge to other AK members

 

[redk9258]

I think I asked this question before. Is it only the outhouse shaped 2SC458's that need replaced? I have a receiver built in 1987 that has a couple of 2SC458's but they are not shaped like the outhouse. I suspect these are OK.

 

[Markoneswift]

My Akai has all outhouse-shaped 458s in it. In England we refer to that type of building as a sh!thouse, hence the often used term ' he's built like a brick sh!thouse '

 

[Hyperion]

I think I asked this question before. Is it only the outhouse shaped 2SC458's that need replaced? I have a receiver built in 1987 that has a couple of 2SC458's but they are not shaped like the outhouse. I suspect these are OK.

I think this is true, I seem to remember the outhouse / garden shed / sh!thouse packaged ones coming in for a lot of criticism.

 

[Markoneswift]

So really, if I think my 485s might be ok - as in I do not have any actual issues - would my time be better spent replacing the electolytic caps on the boards ?

 

[dlucy]

The visual guide to the two different 2SC458 transistors: http://www.audiokarma.org/forums/in...-and-replacements.731653/page-3#post-10099250

A simple write up on the two versions: http://audiokarma.org/forums/index....240-clarification-please.217432/#post-2589706

 

[Markoneswift]

The visual guide to the two different 2SC458 transistors: http://www.audiokarma.org/forums/in...-and-replacements.731653/page-3#post-10099250

A simple write up on the two versions: http://audiokarma.org/forums/index....240-clarification-please.217432/#post-2589706

Thanks - after further reading and close magnification I see I have the original and troublesome Hitachi LG variants in my boards. Great ! So, now the question - what is a suitable, domestically available alternative ? I can definitely source BC550 no problem so would that part do the trick ?

 

[petehall347]

i seem to remember BC550C as being better than BC550