Obsolete Transistor Equivalents

Discussion in 'General Electronics Chat' started by AudioTech, Mar 27, 2015.

  1. AudioTech

    Thread Starter New Member

    Mar 27, 2015
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    Hi,

    I'm currently repairing an amp with 2SB688A and 2SC5179 NPN / PNP complementary pair output transistors. Dodgy eBay replacements are available but I'm aware that this is not necessarily the best route to go down. Does anyone have any information on quality equivalents for these transistors specifically, or any info on selecting equivalent replacements for a range of obsolete transistors? Any publications or lists of equivalent devices would be brilliant.

    Many Thanks,
    Tom
     
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    NTE36 & NTE37 respectively, may be good substitutes... :)

    EDIT: Below is a link to the NTE36/NTE37 datasheet:
    http://www.nteinc.com/specs/10to99/pdf/nte36.pdf

    Best regards
    HP

    PS I am NOT an NTE shill!!! --- It's just easier not having to sift through counterfeits! :eek:
     
    Last edited: Mar 27, 2015
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  3. ScottWang

    Moderator

    Aug 23, 2012
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    Replacement needs to see the circuit, at least needs to know the voltage, if the voltage <45V then it can be replace by mje2955 and mje3055.
     
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  4. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Please note that I have amended my previous post (#2) with a link to the datasheet for the prospective replacements (such that you may readily evaluate their suitability):)

    Best regards
    HP
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    I just checked the linked you posted, they can be replace 2SB688A bjt in some important parameters as Vceo, Ic, Pd.
     
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  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes, you get a 'genuine' NTE part but what does that mean? All NTE does is source parts from anywhere in the world and put an NTE name on them and insert them in a nice clear plastic bag with the NTE logo printed and charge 5 to 10x the price of Digikey. If one of their vendors runs out, they just grab the next best thing to put the NTE 36 or NTE37 part number on. AFAIK, they never made a silcon part.

    They are just distributors that rename parts and confuse the market.
     
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  7. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Your point is well taken! While I've had very good experience with NTE branded ICs, AF and 'power management' semiconductors --- I advise caution with certain of 'their' RF BJTs (As, for instance, the NTE473 whose Absolute Maximum Vceo Spec. went from 18v to 40v 'overnight' thus 'elevating' their 2N6255 Sub to include the 2N3553. When asked about 'pre-respecification' devices, the Techs claim "nothing's changed but the labeling"... golly, golly!;):rolleyes:)

    Best regards
    HP
     
    Last edited: Mar 27, 2015
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    There's a publisher called ECA that does pretty comprehensive equivalents lists.

    If its a stereo amp and you use substitutes, its good practice to make an identical change to the other channel.

    There should be trade component suppliers that carry original parts, the likes of CPC in the UK.

    Look for monthly magazines specialising in TV repair etc and search the ads pages - We used to have Television magazine in the UK, unfortunately it went under, someone revived it but ironically it can only be ordered from one of the suppliers you'd be looking in it for their advert!

    Magazine distribution in the UK is run by a cartel that's robbing publishers blind - Elektor magazine withdrew newsagent circulation last October. ETI decided to call it a day a few years back - no doubt there's a few more I've never heard of.
     
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  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I can only find evidence that only Chinese manufactures ever made these two transistors. Sparsely poplulated datasheets that are half in chinese. Do you have a manufacture's name on the chips in your amplifier? If not, I would buy the parts from eBay, they are likely as good as the originals.

    Cheers.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    Don't bet on it!

    Organised crime is buying up obsolete semiconductor manufacturing equipment, if you cut samples open the chip is usually smaller than the original part - they can run off a batch of parts and stamp on pretty much any number they like on them.

    The jail time for producing counterfeit transistors is a lot less than for drug trafficing.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Interestingly, like picnicking, trafficking has a k.

    I agree that I wouldn't bet on it but likely is likely. I assumed the amplifier is not a big-name unit or valuable since it was built with obscure Chinese-made transistors. What counterfeiter is going to waste their time duplicating an obscure no-name transistor? It would be like me setting up to couterfeit crap from the local dollar store.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    Heve you ever bothered to check whether stuff you got from the $ store was counterfeit?

    In the UK we have £ stores, occasionally some of the items look suspiciously similar to more expensive stuff elsewhere - but as long as it works, who cares.

    On a slightly different theme, one of the stores last summer had plastic garden ornament frogs that make a comical noise when you cast a shadow on them - on closer inspection, they have a cadmium-sulphide light sensor which renders the whole item not RoHS compliant, AFAIK they could get fined at least £5000 for selling them.

    The summer before that they had plastic gnome (presumably farting variety) garden ornaments with the same Cd-S light sensor.
     
  13. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    That was my point. If you were going to counterfeit something, say a transistor, would you counterfeit:
    a) a very common transistor,
    b) a very high performance and expensive transistor
    c) a transistor that is already very cheaply made, sold at a low price that is so rare in the marketplace that nobody has one.

    What you are saying to the OP is, don't buy one from eBay because there are likely some very stupid couterfeiters out there trying to run business model "c". I doubt it.
    It think the OP's risk of finding a counterfeit version of this transistor is very low. Who would bother making one?
     
  14. ian field

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    They run off a batch and stamp whatever number gets ordered.
     
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  15. AudioTech

    Thread Starter New Member

    Mar 27, 2015
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    Firstly, thanks for all of your responses. Having only just joined this forum I wasn't sure if anyone would reply but I'm pleasantly surprised by all of your comments.

    The amp I'm looking at is a Hartke HA1200 120w mono bass guitar combo (about £400 new). This older model has 3x Toshiba C5197 and 3x K 2SB688A NPN / PNP (TO-3P) output transistors and a pair of matched drivers in TO-220 packages. Haven't been able to source the correct schematic as the supplier won't release it to us (helpful), so cannot say if these were the originals, but I suspect so. I've ordered a complete replacement set of NTE transistors from RS components on the advice of 'Hypatia'. Interesting point made by 'GopherT' though about them only being a distributor. I'll give them a go anyway when they arrive and report back.

    Thanks Ian re info on ECA, I'll check them out. It seems odd that I have no problem sourcing valves (tubes) that date back decades in design but always seem to encounter problems getting more recent solid state stuff. Oh well!
     
  16. ian field

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    A few years back, a well known supplier bought a large quantity of "surplus stock" CPUs and merrily set about selling them to eager customers - it didn't take them very long to discover that the packages didn't actually contain any silicon.

    These fly by night counterfeiters move quickly - any investigators search probably ended up at a deserted and derelict factory.
     
  17. takao21203

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    Apr 28, 2012
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    Japanese parts number system.

    Besides I dont get your problems. Unless you crank up the amplifier to insanity, almost any deccent power tranistor will work.
     
  18. ian field

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    Oct 27, 2012
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    There's probably any number of present day devices that exceed all specifications of the originals.

    If its stereo - identical changes should be made to both channels.
     
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