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Sansui Transistor Suffix Letters?

MarkMeyer

MarkMeyer

Active Member
I did some searching, but couldn't come up with what some of the extra suffix letters mean on some of the Sansui transistors.

For example; I'm wanting to replace the TR603 transistor on the AU-717 protection board, and it's specified to be a "2SC945 (Q,P)".

So I do a search at Mouser using "2SC945" and come up with 3 hits, but no reference to the (Q,P) part, and more interesting, the 3 that come up that match the basic number are of different specs.

I'm not really sure what to do here, and I'm still curious what the "(Q,P)" means at the end of that transistor designation.
I note that there are other letter combinations behind other resistors called out in other locations as well but I'll be darned if I can find anything that explains what they mean.

Anybody?
 
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I'm not a real transistor expert, but I can tell you that for most transistors I've researched, those letters refer to different gain ranges (hFE) available for a given transistor. If you can find the datasheet for the transistor, it will usually describe what these are. For example, on the following datasheet for a 2SA992 http://www.ortodoxism.ro/datasheets/nec/2SA992.pdf, you'll see that P means 200-400 hFE, F is 300-600 hFE and so on. The transistor will usually say which range it is on the case itself, so if you can find the datasheet you should be able to get a figure you can work with. In this case, Fairchild makes a replacement KSA992 that uses the same system, so I got lucky.

It would seem ideal to match these ranges on the replacements as people have said straying too far makes an amp unstable, but this is only on the grapevine, not firsthand knowledge. I hope others will chime in to correct any of my mistakes. Good luck.

Collin
 
I did some checking a while ago on these suffixes - and came up with the same result as noveltone. (I am also not a transistor expert).

I haven't had to replace any transistors in my AU-717 yet (touch wood) - except I am suspicious of my TR603 being possibly a bit worn out. Providing the replacement has enough current and voltage rating, hfe in this position won't be much of an issue as it is being used in a switching role where this is less critical.

Regarding replacements and observing hfe values (except in the case above) - noveltone is straight down the line again - so its a case of "what he said" ...others may have more on this.

John
 
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Ah, not always it could be anything that is changed in the values of the transistors not just the gain.
 
Noveltone, good try, but I'm not sure it's that easily answered because there are so many more letter suffixes given in just the AU-717 manual alone. However, you have certainly come up with the closest I've seen to explain those mysterious letters.
Perhaps only the ones that pertain to a particular transistor are shown in the specs for a given transistor, but it would sure be nice to find a "master list" of all the values that are defined by those suffixes.

Other various suffix letter combinations given for different transistors in the AU-717 manual include:
(G,H)
(F,G)
(E,U)
(F,G,H)
(B,V)
(Q,P)
(D,E)
plus my favorite, (M,L,K)... (got MLK?)

... and probably others if you browse through the AU-717 manual.

The link you gave doesn't even begin to cover all the other suffix designations shown in the manual, so I'm starting to wonder if it might be a "Sansui thing" to denote some kind of code used only within the Sansui company.
That would sure make things interesting trying to find replacements.
 
Then if it is a gain value as you suggest, EW, how critical is it to match the replacement transistor to that exact gain shown in the manual?
Does one have some leeway like we do with capacitors, or do we need to "nail it" in order to keep things stable?
 
'Close enough' usually does just fine. It's pretty ususual to be able to know or specify what gain grouping you get before you order a part. What's more, 90% or better of the transistors in a Sansui AU-717 (and other 70's gear) were discontinued years ago. So the trick here is getting familiar with transistor specs and finding modern transistors that will work as good as (or better) than the originals.
 
MarkMeyer said:
Then if it is a gain value as you suggest, EW, how critical is it to match the replacement transistor to that exact gain shown in the manual?
Does one have some leeway like we do with capacitors, or do we need to "nail it" in order to keep things stable?
Click to expand...

The BJT suffix is the HFE grade/grouping. JFETs use them as well for IDSS classification. The part suffix is printed on the package and usually appended with the date code.

Here are more examples:

NEC 2SC945
Toshiba 2SK389 low noise dual JFET
Sanken 2SA1216 LAPT 200W PNP BJT and its complement 2SC2922

Does it matter to get the correct grade? Depending on the application.

When purchasing power amplifier output complementary devices made by Sanken, the HFE grade must be the same for both NPN and PNP device. Some counterfeit Sanken power transistors are missing the HFE grade designation that is printed on the package.

For small signal stages, this depends on how the stage biasing was configured , amplifier S-stability comes to mind.

Muting circuitry with simple biasing can become too sensitive if the grade used is higher than the one specified on the schematic.

You can't compare transistor grading with electrolytic capacitor brand difference. Totally different subject.

BTW, not all transistor manufacturers grade their products.
 
Joe, I see that your link to the NEC 2SC945 does in fact show both the Q and P designations for it's hfe2 rating, so if I have this right in my head, those letters actually ARE important when considering replacements for a transistor.

Plus, only those relevant hfe2 specs designated by the particular suffix letters will be shown on a particular data sheet, so if the specified letters are shown in a spec sheet, then that part meets those specs. It a part's suffix letters aren't shown, then it doesn't.

In the case of the 2SC945, it appears that the NEC part you linked is exactly the part that will properly replace the original transistor Sansui used for that purpose.

Thanks all!
 
Here's the lowdown about why manufacturers specify gain groupings... Most transistors made are sorted into gain groups, reflected by the letter at the end of the part number. Furthermore, there may even be groupings considered 'reject groups'...no letter at all, or a letter designating a group not even shown on the data sheet (quick example that is fresh in my mind is the 2SA979. The data sheet shows gain groups of 'F' [250-500], 'G' [400-800], and 'H' [600-1200], but there are also 'E' group devices out there with gains lower than the 'F' group, and 'no-letter' devices with gains lower still. These last two groups are considered 'reject quality'. Not totally useless, but substandard and will not be marked with the manufacturers logo).

The point is this...the amplifier manufacturer KNOWS there are tons of groupings for gain, and has to specify what they consider to be the minimum in order for the device to meet the original specifications. Not that it won't work if you installed a device with lower gain, but it may not be able to meet the original specifications if you do so.

In your specific case with a 2SC945, this is a 'throwaway' part...the generic Japanese equivalent of the ubiquitous 2N3904. ("Hey Fukashi! I need a buffer transistor here! What do I use?" "Awww...just toss in another C945".) There's nothing special about the C945...it's not high-voltage, nor particularly low-noise (although not bad here), or high-current or high gain. Even the 'P' ranking has a range of 200 to 400, which is nothing special.

My point here is that the manufacturer is perhaps more telling you what not to use (cheap, low-gain devices, such as an 'R' group C945) , than specifying what you must use. In most cases, it is easy to find a replacement that will work just fine...in the case of the C945, there are dozens and dozens of devices that would make a fine substitute.
 
So EW, am I correct that what you're explaining is that when there are suffix letters, those letters denote the minimum gain (hfe) required for that part, but that higher gains are fine if available?

Specific to the 2SC945 example, and to the NEC link given earlier, that spec sheet shows 4 gain levels from 90 to 600, but the letters given in the Sansui manual specify Q and P which (in that spec sheet) cover from 135 to 400 (the middle range of that part in that spec sheet).
SO, would I be correct to choose a comparable transistor with a minimum gain of 135, but could use anything higher for that spec?

And then where are we when a number is thrown into the mix such as another transistor for the AU-717 given as a "2SA750(3)(E,U)"?

Still learning here, and appreciating the time given to us hobbiests by people like yourself who are more skilled.
 
On an 'ideal' transistor, base current approaches 0, which means 'ß' approaches '∞'. Higher gain is nearly always a desirable thing. If specs called for a 2SC945 (Q, P), and you found a 'K', I cannot imagine that being a bad thing.

As far as substituting other transistors, gain (or 'ß', pronounced 'beta', after the Greek letter) is one of only 5 or 6 parameters that need to be taken into consideration, and is likely the least important.

As far as the '3' you quote in the 2SA750(3)(E,U), not a clue buddy.
 
BalancedXLR said:
Yeah Mark the (3) in the 2SA750(3)(E,U) had me scratching my head. I dug out my 717 manual and did not see the (3) anywhere just 2SA750(E,U) throughout. Its used on a number of boards so can you point out what board# you saw that on or in the parts list?
Click to expand...

The one I picked out for example is on page 8 of the AU-517/717 manual that shows the two driver boards (F2721 & '22).
Look at the 3rd and 4th lines from the top on the right for the TR03 and TR04 components.

... And EW, I certainly did notice the myriad specifications each transistor has, and the reason I'm attempting to find an "exact" crossover replacement is exactly for that reason; because while it's easy to match up what appears to be the most obvious ones such as Vcbo, Vceo, Vebo, Ic, Ib and Gain, it's all the other specs that I'm not sure about that might come back and bite me if I miss matching up an important one.

The last time I had to scratch my head this much, I had more hair. :sigh:
 
Methinks the man is worrying too much about things he need not worry about. If replacing transistors was as difficult as you are trying to make it, nothing would ever get repaired.

These aren't tubes. Transistors all work pretty much the same way.
 
EchoWars said:
Methinks the man is worrying too much about things he need not worry about. If replacing transistors was as difficult as you are trying to make it, nothing would ever get repaired.

These aren't tubes. Transistors all work pretty much the same way.
Click to expand...


I hear 'dat. Unfortunately, I'm the kind of person who has always sweated the small stuff. We are a tortured breed. :tears:

All my entire life, asking "what?" or "how?" has never been enough for me. I always want to know the "why?".
While that penchant for detail has served me well over the years, it does sometimes lead to picking fleas off a rats behind, at least, until I finally do understand the "why?".

Thanks, EW. You are one of the people who continue to push me in the right direction.
 
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