Recently I took home an abandoned NAD 7240pe receiver. It was literally left in the trunk of a car sent for recycling. I could not resist temptation so took it home. When plugged in the lights / display worked and the tuner functions worked as in scanning, locking onto stations and lighting the stereo indicator light.
Checking DC offset produced about 13mv per side so a pair of speakers was connected. There was no sound at all but connecting it's pre- outs to a power amp was fine so the preamplifier works but not the power amp.
According to the online service manual, 2 different "rail voltages" should be present at 2 pairs of filter caps and the correct voltages were confirmed. I took that to mean the transformer was OK.
I next wished to test for bias voltage and that service manual identified which resistors to measure across and also to remove a "solder jumper".
I have no idea what that solder jumper is.
However, as I examined the board looking for it, I discovered that two output transistors were disconnected as in unsoldered from the board.
There are a total of 10 transistors - 4 different part numbers as per the manual on the heat sink. It seemed seemed logical then to check all of them. I did so using a DMM (all I have) with them still in place.
Two are questionable but the other 8 seemed to be damaged so I'm going to conclude that is so with all of them.
I am tempted to try finding replacement outputs for all of them but am wondering what may have caused all 10 to fail in the first place.
Provided I can determine what new transistors would work, is that going to be a waste of time?
Checking DC offset produced about 13mv per side so a pair of speakers was connected. There was no sound at all but connecting it's pre- outs to a power amp was fine so the preamplifier works but not the power amp.
According to the online service manual, 2 different "rail voltages" should be present at 2 pairs of filter caps and the correct voltages were confirmed. I took that to mean the transformer was OK.
I next wished to test for bias voltage and that service manual identified which resistors to measure across and also to remove a "solder jumper".
I have no idea what that solder jumper is.
However, as I examined the board looking for it, I discovered that two output transistors were disconnected as in unsoldered from the board.
There are a total of 10 transistors - 4 different part numbers as per the manual on the heat sink. It seemed seemed logical then to check all of them. I did so using a DMM (all I have) with them still in place.
Two are questionable but the other 8 seemed to be damaged so I'm going to conclude that is so with all of them.
I am tempted to try finding replacement outputs for all of them but am wondering what may have caused all 10 to fail in the first place.
Provided I can determine what new transistors would work, is that going to be a waste of time?
Causes of failure:
1/ Short on output of amp, fried speaker or shorted output lead.
2/ Fault in bias circuit causing output transistors to short out rails.
3/ Failure in cooling system duff fan or case outlets covered.
And many more......
1/ Short on output of amp, fried speaker or shorted output lead.
2/ Fault in bias circuit causing output transistors to short out rails.
3/ Failure in cooling system duff fan or case outlets covered.
And many more......
Thanks! I only imagined an internal fault. User error or abuse never occurred to me. I will check the bias as planned and if not horrendous, replace the output transistors.
When you have fixed the original fault and replaced the output transistors for the correct type! remove the solder bridges and set up the bias. See page 5 of the service manual.
I don't know how to determine the original fault. Other than a DMM I have no test equipment nor have I ever used any. Short of wholesale component replacement, all I can do is what's possible with the meter.
I located and disconnected what I believe are the solder shorts on R471 & R472 as per page 5 of the manual. Seeing both ends of the resistor connected for normal operation seems odd. The few instances I measured bias current before was pretty straight forward and required no such step.
Bias was low - 1.5mv on the side with the "un-molested" output transistors and 0mv on the other with the disconnected ones. I have not yet attempted any adjustment to increase it.
I checked to see what voltages were present at the points where the output transistors connect and I was reading rail voltages (~70 volts & ~24 volts) on some, 0 volts on others and slightly over 1 volt on yet others. I hope the service manual will shed some light on what E-C-B voltages should be there when the power is on.
There were some post I've read about this receiver which say that the outputs are prone to failure. Perhaps that is all it is and replacing them (if I can determine suitable substitutes) will solve the problem.
I located and disconnected what I believe are the solder shorts on R471 & R472 as per page 5 of the manual. Seeing both ends of the resistor connected for normal operation seems odd. The few instances I measured bias current before was pretty straight forward and required no such step.
Bias was low - 1.5mv on the side with the "un-molested" output transistors and 0mv on the other with the disconnected ones. I have not yet attempted any adjustment to increase it.
I checked to see what voltages were present at the points where the output transistors connect and I was reading rail voltages (~70 volts & ~24 volts) on some, 0 volts on others and slightly over 1 volt on yet others. I hope the service manual will shed some light on what E-C-B voltages should be there when the power is on.
There were some post I've read about this receiver which say that the outputs are prone to failure. Perhaps that is all it is and replacing them (if I can determine suitable substitutes) will solve the problem.
This PE "Power Envelope" model is not a simple amplifier. It has a second set of output transistors (2SD1062/B826) supplied by +/-71V rails, in series with the usual output transistors (2SD1067/B817) on low voltage supply rails of +/-43V. That's something like the Class G principle, which switches the rails on demand to permit higher peak power bursts with better efficiency than would a much higher power amplifier . Either way, both schemes provide some extra power before the onset of clipping power for the audio transients that some folk are twitchy about.
The lower rail transistors should work fine without the benefit of the PE boost transistors but don't forget those PE boost transistors and their drivers have to checked as working too, without shorting the higher voltage supply, before you try to test the basic amplifier section. This may not be an easy repair 😱
The lower rail transistors should work fine without the benefit of the PE boost transistors but don't forget those PE boost transistors and their drivers have to checked as working too, without shorting the higher voltage supply, before you try to test the basic amplifier section. This may not be an easy repair 😱
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The biggest source of failure in NAD amps in my experience is dry joints. Particularly around the power supply section. Open circuit connection to the transformer centre tap causes spectacular failures.
Well, I am not optimistic about this. Especially since I recently had a less than fulfilling experience with an integrated amplifier. I really don't want to become as preoccupied and frustrated as that made me.
I have continued searching online for any examples of similar NAD 7240pe transistor issues and there were some. I found one that described output transistor failure and replacement but if I comprehended correctly, the cause was the transistors themselves in that writer's case. However it went on to describe a sort of domino effect or cascade failure whereby other than output transistors, it was stated other devices and some resistors could be damaged depending on if the failure was by the outputs becoming open or shorted.
Being restricted by possessing only a DMM, I am inclined to remove all the outputs and check them out of circuit. I am not expecting them to be good but perhaps I can learn something somewhere that will explain if the readings I get mean open or a short. That may determine if I need to look closely at the driver pairs - if I can identify which those are.
This may be odd, or not, but all the fuses are intact of which I believe number 6.
I have continued searching online for any examples of similar NAD 7240pe transistor issues and there were some. I found one that described output transistor failure and replacement but if I comprehended correctly, the cause was the transistors themselves in that writer's case. However it went on to describe a sort of domino effect or cascade failure whereby other than output transistors, it was stated other devices and some resistors could be damaged depending on if the failure was by the outputs becoming open or shorted.
Being restricted by possessing only a DMM, I am inclined to remove all the outputs and check them out of circuit. I am not expecting them to be good but perhaps I can learn something somewhere that will explain if the readings I get mean open or a short. That may determine if I need to look closely at the driver pairs - if I can identify which those are.
This may be odd, or not, but all the fuses are intact of which I believe number 6.
While there might be output transistors blown simply replacing them doesn't always fix the root cause.
I would remove all the semiconductors and test them for Hfe as well as diode tests.
While they are out check all resistors.
Check capacitors for shorts and replace any electrolytics if the amp is old.
I had a faulty amp where all the transistors checked ok but on Hfe test one of the transistors had a gain of one !
I would remove all the semiconductors and test them for Hfe as well as diode tests.
While they are out check all resistors.
Check capacitors for shorts and replace any electrolytics if the amp is old.
I had a faulty amp where all the transistors checked ok but on Hfe test one of the transistors had a gain of one !
The domino effect certainly happens when catastrophic failure of the output transistors occurs fast and a spike of high loading causes the voltage amplifier stage to fail, burning out the low current transistors, perhaps the input stage too and then everything between them and the output transistors. I've only seen a number of large PA amps fail so completely but plenty of average domestic amplifiers where only the VAS transistors followed the output stage. Modern designs usually have a current limiting shunt transistor fitted to the VAS transistor base, to prevent that type of failure. Not on this one, though.
Unfortunately, this is what DC coupling in an amplifier means. Not only is the audio directly coupled between stages but so is any DC potential that may change dramatically in a fault condition.
I'ts not clear that there is extensive damage yet but if only a power transistor or two failed, its not unusual that the transistors protected the fuse instead of the other way around. Wire fuses are cheap but not fast enough to protect power transistors that are operating close to limits.
Whilst you can't check a transistor fully in-circuit, you can check that the most common failure, a C-E short, hasn't occurred if your meter reads down to low resistance, say less than 0.1Ω, consistently. A continuity buzzer is not good enough for tests, since it will probably trigger at 30-70Ω which is pointless here.
Nearly all failures can be put down to user abuse.
It is very rare for solid state to fail due to old age.
It is very rare for solid state to fail due to excessive mains/battery voltage.
And be concerned about that domino effect.
It will probably fail again if you don't complete "ALL" the repairs.
Last night I pulled all the output transistors and checked them today as time allowed. My testing is limited to the diode setting of my DMM and nothing further as it does not do Hfe.
Those transistors on one end of the heat sink checked OK but 3 of 5 on the other side were bad - Q424, Q426 & Q430. Although the other 2 were "good" the readings were just a little higher than acceptable which I understand is .45 volts. Where voltage is supposed to be, I obtained just slightly under .5.
So this might not be a total catastrophic failure, just severe. It surprised me that all output transistors on the one side were fine. I say that because neither channel produced any sound.
I'm not familiar with the term VAS transistors. If those are likely affected (or the cause of failure) I don't know which ones they are.
The suggestion of replacing all semi conductors and electrolytic capacitors is a daunting one. Not necessary the capacitors, I've done some of that, but there are many transistors on the amplifier side of this receiver. I'm not home so don't have the exact number in front of me but I believe the total is around 60 comprised of 10 or 12 different part numbers.
Given time, it is possible for me to remove and test each transistor according to the limit of my DMM. Finding replacements on the other hand - who knows?
It's just a matter of determining, with my limited abilities and resources, if I can entertain the notion of a successful outcome. As mentioned previously, such was not the case with an integrated amplifier I tried to extensively "recondition".
Those transistors on one end of the heat sink checked OK but 3 of 5 on the other side were bad - Q424, Q426 & Q430. Although the other 2 were "good" the readings were just a little higher than acceptable which I understand is .45 volts. Where voltage is supposed to be, I obtained just slightly under .5.
So this might not be a total catastrophic failure, just severe. It surprised me that all output transistors on the one side were fine. I say that because neither channel produced any sound.
I'm not familiar with the term VAS transistors. If those are likely affected (or the cause of failure) I don't know which ones they are.
The suggestion of replacing all semi conductors and electrolytic capacitors is a daunting one. Not necessary the capacitors, I've done some of that, but there are many transistors on the amplifier side of this receiver. I'm not home so don't have the exact number in front of me but I believe the total is around 60 comprised of 10 or 12 different part numbers.
Given time, it is possible for me to remove and test each transistor according to the limit of my DMM. Finding replacements on the other hand - who knows?
It's just a matter of determining, with my limited abilities and resources, if I can entertain the notion of a successful outcome. As mentioned previously, such was not the case with an integrated amplifier I tried to extensively "recondition".
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With the bad power transistors removed, it's simple to check the basic health of other transistors in-circuit if it powers up safely (don't forget the light bulb limiter). Measure Vbe on all transistors. It should be a little under 0.7V or one diode voltage drop for any simple type of BJT. Of course, C-E shorts should also be checked by measuring for any Vce as before. At this point, you only need to remove those that measure bad. However, this does not mean that transistors measuring good can't have less common faults like low gain or be noisy etc. The schematic also shows relevant circuit voltages for checking operation too, noting that removing transistors will alter some voltages in that area of the circuit. There are still plenty of things to check 🙂
NAD 7240PE - Manual - Stereo Receiver - HiFi Engine
Vbe means Voltage across (or between) the base and emitter of a bipolar junction transistor (BJT)
VAS means Voltage Amplifier Stage and in this design the Voltage Amplifier transistors are Q413/415 and Q414/416 respectively in the L and R channels.
NAD 7240PE - Manual - Stereo Receiver - HiFi Engine
Vbe means Voltage across (or between) the base and emitter of a bipolar junction transistor (BJT)
VAS means Voltage Amplifier Stage and in this design the Voltage Amplifier transistors are Q413/415 and Q414/416 respectively in the L and R channels.
Thanks Ian, that helps a lot. I took your advice re the dim bulb tester and panicked during the second or so it got bright right at amplifier turn on but it went out quickly. It's a 100W bulb so in this case, I guess no-glow at idle is OK.
The less than ,7 volts was acceptable for Q414 & Q416 as one was .5 and other .6. Not so with Q413 & Q415. Those reading were unstable and fluctuated quite a bit. Since I would change all 4, I did not see a point in checking C to E shorts. Plus, those transistors are mounted snugly to the board so cannot access the Collector leg from the component side. Trying to find a particular solder point on the foil side of a board this crowded is not something to look forward to.
As it happens, I have on hand a good supply of 2SA970-GR transistors for Q413 & Q414 and a local supplier has some stock of 2SC2240-GR (at least I hope they're GR) for Q415 & Q416. I hope to get those tomorrow.
You may remember some months ago, advising me on a Toshiba SC335 power amp. That one amp turned into three hence I have about two dozen 2SA970-GR's leftover as I was trying to match pairs, crude though my method was. Complexity wise, those Toshiba amps appear like a cake walk compared to this NAD receiver
If it allows, I shall spend time tomorrow examining the schematic to learn where on the board I'm to measure those voltages for the output transistors.
As for the outputs transistors, I did an earlier cursory search on Mouser's website using their "transistor finder" filters. Now knowing replacement is necessary, I'll do a more diligent search and/or look to Digikey and Newark Element 14.
The less than ,7 volts was acceptable for Q414 & Q416 as one was .5 and other .6. Not so with Q413 & Q415. Those reading were unstable and fluctuated quite a bit. Since I would change all 4, I did not see a point in checking C to E shorts. Plus, those transistors are mounted snugly to the board so cannot access the Collector leg from the component side. Trying to find a particular solder point on the foil side of a board this crowded is not something to look forward to.
As it happens, I have on hand a good supply of 2SA970-GR transistors for Q413 & Q414 and a local supplier has some stock of 2SC2240-GR (at least I hope they're GR) for Q415 & Q416. I hope to get those tomorrow.
You may remember some months ago, advising me on a Toshiba SC335 power amp. That one amp turned into three hence I have about two dozen 2SA970-GR's leftover as I was trying to match pairs, crude though my method was. Complexity wise, those Toshiba amps appear like a cake walk compared to this NAD receiver
If it allows, I shall spend time tomorrow examining the schematic to learn where on the board I'm to measure those voltages for the output transistors.
As for the outputs transistors, I did an earlier cursory search on Mouser's website using their "transistor finder" filters. Now knowing replacement is necessary, I'll do a more diligent search and/or look to Digikey and Newark Element 14.
Re output transistors: The inner pairs are very commonly copied Sanyo 2SD1047/B817 which are long obsolete but even branded copies are not all good, as far as I know. KEC product (branded K) is a reliable substitute which can be bought through distributors, Ebay, Alibaba etc. There are several other brands and fakes too but don't mix the individual types - fit complementary pairs both of the one brand and if there is an Hfe group marking like O, R, Y then keep that the same for each pair too. You don't need the worry of too many mismatches in the one output stage if it means struggling to set bias or needing to further troubleshoot.
The outer complementary pairs are a smaller Sanyo TO220 package and are switching types, only rated for 50V Vceo which seems crazy but they are only exposed to the difference between the 71 and 43V rails or approx. 30V, depending on the sag of those rails under load. It seems dicey to me but that's NAD! 2SD1062 is fairly common but the complement 2SB826? On-semi listed them when they bought Sanyo semi. division but never produced them, it seems. http://www.onsemi.com/pub_link/Collateral/2SB826-D.PDF
The outer complementary pairs are a smaller Sanyo TO220 package and are switching types, only rated for 50V Vceo which seems crazy but they are only exposed to the difference between the 71 and 43V rails or approx. 30V, depending on the sag of those rails under load. It seems dicey to me but that's NAD! 2SD1062 is fairly common but the complement 2SB826? On-semi listed them when they bought Sanyo semi. division but never produced them, it seems. http://www.onsemi.com/pub_link/Collateral/2SB826-D.PDF
Thanks again! Yesterday morning while idle in the field, I spent considerable time on the alltransistors.com site to look up specs and the Mouser site to find replacements. My iPhone is old/slow so I drained it's battery and found that my charging cord had gotten broken.
It seems Mouser has in stock 2SD1047-E and 2SB817-E but you don't recommend using those?
Mouser don't have 2SD669A-C or 2SB649A-C.
Their "transistor finder" came up with KSC2690AYS for the former and KSA1220AYS for the latter.
I was planning on ordering from them as I've done so before but what you said about "branded copies" concerns me. My experience sourcing parts is limited and I've bought locally when possible but when it's not, I've generally used Mouser. Since they are held in somewhat high regard (at least in North America) I thought ordering there was a safe bet.
As mentioned, i have on hand a supply of 2SA970-GR for Q413/414. I thought I'd need to get 2SC2240-GR's for Q415/416 but lo and behold - I have 4.
After I figured out a ground point, I checked voltages at the collector points for the output transistors and hope you don't object to my listing them:
Q424 +67.3v Q425 -40.6v
Q428 +67.3v Q429 -40.6v
Q418 +63.7v Q417 reads in millivolts and varies up and down
Q430 -67.2v Q427 +41v
Q426 -67.2v Q428 +41v
With regards to Q417, could diode D419 be the problem?
It seems Mouser has in stock 2SD1047-E and 2SB817-E but you don't recommend using those?
Mouser don't have 2SD669A-C or 2SB649A-C.
Their "transistor finder" came up with KSC2690AYS for the former and KSA1220AYS for the latter.
I was planning on ordering from them as I've done so before but what you said about "branded copies" concerns me. My experience sourcing parts is limited and I've bought locally when possible but when it's not, I've generally used Mouser. Since they are held in somewhat high regard (at least in North America) I thought ordering there was a safe bet.
As mentioned, i have on hand a supply of 2SA970-GR for Q413/414. I thought I'd need to get 2SC2240-GR's for Q415/416 but lo and behold - I have 4.
After I figured out a ground point, I checked voltages at the collector points for the output transistors and hope you don't object to my listing them:
Q424 +67.3v Q425 -40.6v
Q428 +67.3v Q429 -40.6v
Q418 +63.7v Q417 reads in millivolts and varies up and down
Q430 -67.2v Q427 +41v
Q426 -67.2v Q428 +41v
With regards to Q417, could diode D419 be the problem?
The 2SD1047/B817 transistors offered by Mouser are from 2 different manufacturers, though the specs are broadly similar on paper. What concerns me is the low Ft and small stock of B817 that doesn't move (is it real?) and the fact that there is no Hfe grading, so what will be the Hfe of the parts you receive? It's rare that I'd opt for Ebay product even when it is genuinely branded and has a manufacturer's datasheet but superficially at least, it should meet their marked part spec.
Just for interest, this offer featuring a newer laser marking is intriguing, considering KEC also manufacture in China: 5pairs NEW Genuine 2SB817 2SD1047 B817 D1047 10pcs | eBay
Note there are generic parts datasheets circulated by Chinese sellers, often headed "Savant IC" or similar but and they have no apparent connection to specific manufacturers or sources. Even though most parts are now produced in China, the manufacturer's datasheet is the only guarantee of the quality on offer, assuming their reputation is good. Anyone honest enough to brand and support their product with accurate data should be reputable, in my book.
I'd like comment from others with repair experience using these types here, as I think it may be better instead, to substitute standard (and cheap, excellent) OnSemi parts like NJW3281/1302 here than mess with mismatched or poor copies of the originals. I hesitate to recommend that though, with this somewhat complex design and possible increased risk of instability
You can buy 2SD669A/B649A copies cheap and everywhere on Ebay - I have bought a few lots for experimenting but they proved good as spares, though I test Hfe according to needs. Given the low unit price, this is no big deal and most parts prove acceptable. I would not substitute KSC2690/A1220 , even though they seem to be copies of excellent Sanyo parts. They just don't seem to perform like them as drivers and not like the 669/649 type at all. You could take the fact that they are seldom specified in designs contributed here, as agreement. Unfortunately, a TO126 package is reverse pinout to more common TO220 package drivers, which limits the number of available substitutes and these are becoming fewer.
Drop-in replacements for 2SC2240/A970 are Fairchild KSC1845/A992 - much cheaper than NOS and most copies, yet still in production. They're widely used here for low noise, medium voltage applications.
Re: D419/Q417. I assume your output transistors are removed as they would have been after testing and sorting into good/suspect. The driver transistors would all be suspect if outputs had failed and the voltage at the base of Q417 for example, could have been pulled to the -43V rail and overloaded the diode. They commonly fail shorted which isn't hard to check but neither is an open circuit. If the VAS transistors Q413/415 have failed, then that same current path, via Q417, is likely the culprit. D419/417 are high voltage, low current 1SS81 types with only about 200mA current rating - around that of common signal diodes.
Just for interest, this offer featuring a newer laser marking is intriguing, considering KEC also manufacture in China: 5pairs NEW Genuine 2SB817 2SD1047 B817 D1047 10pcs | eBay
Note there are generic parts datasheets circulated by Chinese sellers, often headed "Savant IC" or similar but and they have no apparent connection to specific manufacturers or sources. Even though most parts are now produced in China, the manufacturer's datasheet is the only guarantee of the quality on offer, assuming their reputation is good. Anyone honest enough to brand and support their product with accurate data should be reputable, in my book.
I'd like comment from others with repair experience using these types here, as I think it may be better instead, to substitute standard (and cheap, excellent) OnSemi parts like NJW3281/1302 here than mess with mismatched or poor copies of the originals. I hesitate to recommend that though, with this somewhat complex design and possible increased risk of instability
You can buy 2SD669A/B649A copies cheap and everywhere on Ebay - I have bought a few lots for experimenting but they proved good as spares, though I test Hfe according to needs. Given the low unit price, this is no big deal and most parts prove acceptable. I would not substitute KSC2690/A1220 , even though they seem to be copies of excellent Sanyo parts. They just don't seem to perform like them as drivers and not like the 669/649 type at all. You could take the fact that they are seldom specified in designs contributed here, as agreement. Unfortunately, a TO126 package is reverse pinout to more common TO220 package drivers, which limits the number of available substitutes and these are becoming fewer.
Drop-in replacements for 2SC2240/A970 are Fairchild KSC1845/A992 - much cheaper than NOS and most copies, yet still in production. They're widely used here for low noise, medium voltage applications.
Re: D419/Q417. I assume your output transistors are removed as they would have been after testing and sorting into good/suspect. The driver transistors would all be suspect if outputs had failed and the voltage at the base of Q417 for example, could have been pulled to the -43V rail and overloaded the diode. They commonly fail shorted which isn't hard to check but neither is an open circuit. If the VAS transistors Q413/415 have failed, then that same current path, via Q417, is likely the culprit. D419/417 are high voltage, low current 1SS81 types with only about 200mA current rating - around that of common signal diodes.
Yet again, thanks! I just ordered the 5 pairs of 2SB817 / 2SD147 through the link you provided. Also ordered 5 pairs of 2SB649A / 2SD669A from a Hong Kong vendor (70 sold) with nearly 25,000 transactions & 99.4% positive feedback.
Regarding 2SC2240 / 2SA970, if I'm not to use those I have, will Fairchild replacements with the letter suffix FTA be suitable?
In the meantime, I shall disengage diodes D417/419 and check them. I have not investigated yet but if they're common as you imply, then I should be able to get those locally.
Regarding 2SC2240 / 2SA970, if I'm not to use those I have, will Fairchild replacements with the letter suffix FTA be suitable?
In the meantime, I shall disengage diodes D417/419 and check them. I have not investigated yet but if they're common as you imply, then I should be able to get those locally.
Additional in lieu of EDIT:
I re-read your post. Was I mistaken to think that e-bay link to replacements for 2SD2047 / B817 was an endorsement? Although I did place an order, those On Semi numbers (G suffix) are available from Mouser. If advised to do so, I'll re-order and consider the extra cost a learning experience - read, re-read and re-read again.
I re-read your post. Was I mistaken to think that e-bay link to replacements for 2SD2047 / B817 was an endorsement? Although I did place an order, those On Semi numbers (G suffix) are available from Mouser. If advised to do so, I'll re-order and consider the extra cost a learning experience - read, re-read and re-read again.
Sorry I wasn't clear but I was only endorsing the Ebay product I had bought and used, which was the very common copies of Hitachi 2SD669A/B849A and the earlier, print marked KEC KSD1047/B817
Fairchild KSC1845/A992 are now the only 120V low noise signal transistors we have so they feature on most larger projects here. I buy 100 at a time and use them like many here do and I've no gripes either. I just hope the supply hangs in long enough to build a large stash for times when the only new small parts are SMDs.
The FTA suffix refers to preforming of the leads, such that it drops into 2.54 mm pitch holes used on most through-hole boards. It makes little difference as you'll be hand-fitting parts to probably different spacings.
To complicate matters, Fairchild also just became part of On-Semi and the on-line datasheets have an identity problem but the On-Semi PDF illustrations showing ammo pack taping here on Fairchild's site explain: https://www.fairchildsemi.com/products/discretes/bipolar-transistors/small-signal-bjts/KSC1845.html
I don't expect you'll go too far wrong with the KEC power transistors but I would like to hear what others with more experience think in regard to On Semi's NJW parts there.
Fairchild KSC1845/A992 are now the only 120V low noise signal transistors we have so they feature on most larger projects here. I buy 100 at a time and use them like many here do and I've no gripes either. I just hope the supply hangs in long enough to build a large stash for times when the only new small parts are SMDs.
The FTA suffix refers to preforming of the leads, such that it drops into 2.54 mm pitch holes used on most through-hole boards. It makes little difference as you'll be hand-fitting parts to probably different spacings.
To complicate matters, Fairchild also just became part of On-Semi and the on-line datasheets have an identity problem but the On-Semi PDF illustrations showing ammo pack taping here on Fairchild's site explain: https://www.fairchildsemi.com/products/discretes/bipolar-transistors/small-signal-bjts/KSC1845.html
I don't expect you'll go too far wrong with the KEC power transistors but I would like to hear what others with more experience think in regard to On Semi's NJW parts there.
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