Hi all,
I have a great sounding NAP90 power amplifier. However, one channel has been shorted and a few transistors are burnt and need replacement. The one on the NAP90 are kind of obsolete, so I thought I might upgrade them in this occasion and make it better...
The ones which has burnt out are:
ZTX652
ZTX752
J13009-2 (power transistor which has been used instead of the stock ones)
Also I saw that one ZTX348C has it case broken.
Can anyone point me to any replacements that will fit, and sound at lease as good ??
Thanks a lot !
I have a great sounding NAP90 power amplifier. However, one channel has been shorted and a few transistors are burnt and need replacement. The one on the NAP90 are kind of obsolete, so I thought I might upgrade them in this occasion and make it better...
The ones which has burnt out are:
ZTX652
ZTX752
J13009-2 (power transistor which has been used instead of the stock ones)
Also I saw that one ZTX348C has it case broken.
Can anyone point me to any replacements that will fit, and sound at lease as good ??
Thanks a lot !
The ZTX652/752 are obsolete but ZTX653/753 are not - these just have higher Vceo, otherwise identical specs. Zetex became part of Diodes Inc.
The J13009-2 is probably FJP13009 (H2 grade) from Fairchild. Still in production.
The ZTX384C is long obsolete. Based on specs, the BC550C would be appropriate. From a quick look at various Naim schematics it looks like these would have been part of the input LTP - if so, both should be replaced.
You'll find all those parts on Mouser and probably Digikey too.
The J13009-2 is probably FJP13009 (H2 grade) from Fairchild. Still in production.
The ZTX384C is long obsolete. Based on specs, the BC550C would be appropriate. From a quick look at various Naim schematics it looks like these would have been part of the input LTP - if so, both should be replaced.
You'll find all those parts on Mouser and probably Digikey too.
For that list of parts to have failed, there must have been some awful accident(s). NAIM sound is a parts issue and swapping types like the input stage and VAS transistors is not a good idea if you want to keep the performance close to original.
There are always opinions about but the term "improvements" as in "make it better" can just as easily mean ruining what audiphiles prize as "sound quality". Fix it first with the right or closest available parts. If you want to try other parts options that's fine but they won't make anything better other than change the distortion to something different - perhaps OK, perhaps not but not likely better overall.
The ZTX 753/653 are the commonly preferred range as they have a 20V margin over the ZTX752/652 range. They are easily obtained at mouser etc.
ZTX 348? I don't think so. Probably you mean ZTX384C, similar to BC384C which equates to BC550C now.
J13009-2 appears to be a house code. I'm sure NAIM addicts know the basic part spec. but they won't know the particular selection/matching required for these output transistors.
BTW, the driver transistors are likely suspect too, check them out.
There are always opinions about but the term "improvements" as in "make it better" can just as easily mean ruining what audiphiles prize as "sound quality". Fix it first with the right or closest available parts. If you want to try other parts options that's fine but they won't make anything better other than change the distortion to something different - perhaps OK, perhaps not but not likely better overall.
The ZTX 753/653 are the commonly preferred range as they have a 20V margin over the ZTX752/652 range. They are easily obtained at mouser etc.
ZTX 348? I don't think so. Probably you mean ZTX384C, similar to BC384C which equates to BC550C now.
J13009-2 appears to be a house code. I'm sure NAIM addicts know the basic part spec. but they won't know the particular selection/matching required for these output transistors.
BTW, the driver transistors are likely suspect too, check them out.
Thanks all,
The NAP has been shorted out, probably by having a short between the + and - speaker outs.... One channel has been severely damaged, having a few resistors totally burnt out, as well as one ZTX652, two ZTX752 and one J13009-2, all of the same channel.
The ZTX384C (not 348, my mistake) is just physically broken so it needs replacement anyway.
From what I understand from the previous owner, he replaced the stock power transistors with four J13009-2, so they are not original. The tantalum cap has been also replaced, and I replaced the 4 electrolytic caps, with cheap brand though.
I would very much like to get the NAIM character back to it actually. I assume having the new tantalums there is a good idea (they short over time). If you say the BC550C can replace the ZTX384C then I will probably need to change it on both channels ? I have a few in hand.
ZTX753 and ZTX653 are readily available, but should I swap the same positions in the "heathy" channel as well ?
As for the J13009-2, I managed to find MJE13009 as replacement for the burnt J13009-2, should it be ok ? I have no idea what it used there before the swap, but looking here I guess they were NAIM NA005 transistors?
The NAP has been shorted out, probably by having a short between the + and - speaker outs.... One channel has been severely damaged, having a few resistors totally burnt out, as well as one ZTX652, two ZTX752 and one J13009-2, all of the same channel.
The ZTX384C (not 348, my mistake) is just physically broken so it needs replacement anyway.
From what I understand from the previous owner, he replaced the stock power transistors with four J13009-2, so they are not original. The tantalum cap has been also replaced, and I replaced the 4 electrolytic caps, with cheap brand though.
I would very much like to get the NAIM character back to it actually. I assume having the new tantalums there is a good idea (they short over time). If you say the BC550C can replace the ZTX384C then I will probably need to change it on both channels ? I have a few in hand.
ZTX753 and ZTX653 are readily available, but should I swap the same positions in the "heathy" channel as well ?
As for the J13009-2, I managed to find MJE13009 as replacement for the burnt J13009-2, should it be ok ? I have no idea what it used there before the swap, but looking here I guess they were NAIM NA005 transistors?
An externally hosted image should be here but it was not working when we last tested it.
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MJE 13009 and FJP13009 are likely very similar and they are 400V TO220 types with a high current rating too.
The part equivalent BD743 on Pitbull's schematic is also TO220 and probably closer to the house code NA005. You won't find that spec. as it is NAIM's IP. The issue is the Hfe and matching for consistency which you don't see on the schematic but I would prefer that type over the ones fitted in your amplifier. If the Hfe is not sufficient, the drivers will get too much of a work out. I would be hoping for Hfe >25 @ 2 amp collector current.
Note the required version is probably BD743C, if available, which would be a 100V part.
The link below is to a forum for total NAIM freaks and modders. The discussion seems to confirm NAIM's use of the part since they nominated the replacement. Some of the other equivalents are not so smart but it's not a technical forum and many views are quite ill-informed.
http://www.google.com.au/url?sa=t&r...loHoBg&usg=AFQjCNH6jf1Ki53S1VF6_DEnIr3IVP3Yeg
Even this is informative
http://www.ebay.com/sch/sis.html?_nkw=BD743C+Transistor+x+1+pieces+BD743+
The part equivalent BD743 on Pitbull's schematic is also TO220 and probably closer to the house code NA005. You won't find that spec. as it is NAIM's IP. The issue is the Hfe and matching for consistency which you don't see on the schematic but I would prefer that type over the ones fitted in your amplifier. If the Hfe is not sufficient, the drivers will get too much of a work out. I would be hoping for Hfe >25 @ 2 amp collector current.
Note the required version is probably BD743C, if available, which would be a 100V part.
The link below is to a forum for total NAIM freaks and modders. The discussion seems to confirm NAIM's use of the part since they nominated the replacement. Some of the other equivalents are not so smart but it's not a technical forum and many views are quite ill-informed.
http://www.google.com.au/url?sa=t&r...loHoBg&usg=AFQjCNH6jf1Ki53S1VF6_DEnIr3IVP3Yeg
Even this is informative
http://www.ebay.com/sch/sis.html?_nkw=BD743C+Transistor+x+1+pieces+BD743+
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I've actually looked at a few datasheets for interest over the weekend and I note ST Micro's BD911 (Mouser) is about right. Cheap and plentiful too! BD911 | Mouser Electronics, Inc.. I think this is a best and latest version and I like ST products - they exceed their specs in the right areas consistently. ~$1.32 for a 100V/15A part.
I guess we all are sus. about Ebay parts from unknown vendors. Those appear old enough to be genuine because shiny new parts that are over 10 years old is always suspicious to me. I can't really say but at the price, why would anyone bother to fake a small power transistor? With due respect, it's not like there are many NAP 90 or Nait 2's in need of what are pretty ordinary power transistors.
I think you'll be happy with BD911 so get some spares from the same batch in case you like to balance things up too.
No, its not in any way sensing the driver current.
Driver current will surely go up, but the sensing is still from the output emitters. The 100ohm B-E resistors are just like in normal crown amps.
Yes, agreed.
Ian,
I managed to find some BD911 locally, but they are branded "CDIL" (Continental Device India Limited)
Do you think it is good to go or should I prefer the Fairchild BD743 sold on ebay ?
I also see on their site that they have CN653 and CN753 as equivalents to ZTX653/ZTX753,
will these do any good ?
Just have some bad experience ordering parts from Hong Kong (they not always arrive :/ )
I managed to find some BD911 locally, but they are branded "CDIL" (Continental Device India Limited)
Do you think it is good to go or should I prefer the Fairchild BD743 sold on ebay ?
I also see on their site that they have CN653 and CN753 as equivalents to ZTX653/ZTX753,
will these do any good ?
Just have some bad experience ordering parts from Hong Kong (they not always arrive :/ )
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No doubt CDIL and a lot of other manufacturers make good BD911 clones. I'm sure they will also work in the application but I can't say that it will be as good as the original.
I can't locate full data sheets on CDIL's product but the specs look to be generic - i.e. not necessarily applying to that device but probably to a group of parts developed to match or better just the leading figures of the original manufacturer's spec. (sound confusing? Yes, generic product is confusing.)
I don't feel confident there without seeing the performance graphs so, if you don't mind buying from Houston, Mouser at least have a qualified product in ST's version. Mospec product looks good too, if you come across it and I forgot to mention that the lower voltage ranks BD907, BD909 are OK too but are obsolete since BD911 is one size that fits all.
I haven't had a supply problem with Ebay HK traders yet but a lot of guys who buy in small quantities and deal with unfamiliar traders seem to. Personally, I wouldn't run risks with any semi purchases since I occasionally sell and repair stuff and can't afford risks. As I suggest, stay with current manufacture, qualified parts and traders where possible.
I can't locate full data sheets on CDIL's product but the specs look to be generic - i.e. not necessarily applying to that device but probably to a group of parts developed to match or better just the leading figures of the original manufacturer's spec. (sound confusing? Yes, generic product is confusing.)
I don't feel confident there without seeing the performance graphs so, if you don't mind buying from Houston, Mouser at least have a qualified product in ST's version. Mospec product looks good too, if you come across it and I forgot to mention that the lower voltage ranks BD907, BD909 are OK too but are obsolete since BD911 is one size that fits all.
I haven't had a supply problem with Ebay HK traders yet but a lot of guys who buy in small quantities and deal with unfamiliar traders seem to. Personally, I wouldn't run risks with any semi purchases since I occasionally sell and repair stuff and can't afford risks. As I suggest, stay with current manufacture, qualified parts and traders where possible.
substitutes
I forgot to say ZTX 384C is not critical, it's likely whatever was in the parts bin since any small NPN
would likely work here as the bias controller, VBE multiplier or whatever.
Don't substitute the other Zetex ZTXxxx parts. These tend to be pushed to the limit in most NAIM amplifiers.
If you want substitutes, as drivers for the output stage, consider proper driver transistors in a larger, TO126 case.
I forgot to say ZTX 384C is not critical, it's likely whatever was in the parts bin since any small NPN
would likely work here as the bias controller, VBE multiplier or whatever.
Don't substitute the other Zetex ZTXxxx parts. These tend to be pushed to the limit in most NAIM amplifiers.
If you want substitutes, as drivers for the output stage, consider proper driver transistors in a larger, TO126 case.
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