Sansui 2000A noise in headphones - not in speakers

In the Sansui AU-X1 the headphone circuit is linked to the power switch.
So there are actually two switches behind that power button rather than just one.
The power switch piggy backs on headphone switch.
Same plunger that engages the headphone circuit also pushes the power switch into the on position.

Does the 2000A have the same kind of double switch?

If so, try cleaning out the part that activates the headphone circuit.
 
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I have no idea, I will have to look at it.

I rotated it out and am using a little 80s Luxman receiver now so I'll have a look next time I have free time.
 
Ronito6 said:
In the Sansui AU-X1 the headphone circuit is linked to the power switch.
So there are actually two switches behind that power button rather than just one.
The power switch piggy backs on headphone switch.
Same plunger that engages the headphone circuit also pushes the power switch into the on position.

Does the 2000A have the same kind of double switch?

If so, try cleaning out the part that activates the headphone circuit.
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In this era of Sansui amps there is no dedicated/separate headphone circuit. The headphone output is taken from the main amps output via resistors to knock the signal down a bit.
 
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N8Nagel said:
that's a pretty unit, smurfer77... well it seems like I will have to do this sooner rather than later. Sansui was left on overnight (easy to do if you are spinning CDs or watching TV, as the only light on on the faceplate is the orange "AUX" light and it is not visible when standing up due to the height of my rack...) Came down this morning to turn on radio and when I bent over I can now hear the hiss from the speakers where I could not before. So obviously whatever's causing it is getting worse.

I have not yet had a chance to get my scope 100% operational do you think it's a safe bet to just go ahead and order the transistors discussed in this thread?

Also, I have heard tell of people matching transistors, I'm assuming that this is desirable when used in the same function but in stereo pairs, is that a concern for what I'm doing? I do not have the ability to test transistors, I really am just starting to collect test equipment as for years a Fluke meter was all I had or really needed.

thanks!
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While it's always possible there is an issue with something else, it's very likely that replacing the transistors on your main amp board will fix the issue. And even if not, it future proofing the amp and possibly getting you lower noise anyway I would go ahead and order the parts. If your Fluke has a diode/continuity feature (my very old Fluke does) this might help you with double checking pinouts on the old transistors. When you replace, just do a pair at a time and check the amp is still working after each pair before moving forwards. if you get stuck with the pin orientation, give a yell. (if the schematic and PCB match you should be okay, but still, you could check the pin orientation as you pull them out to be safe...)

There is no need to worry about matching these particular transistors. While it never hurts and I often do it, there is no real reason to worry about it in this part of the circuit. For example, you could match open loop gain, but these guys are in negative feedback loops and the gain is dictated by the circuit, not the transistors (providing the maximum gain of the transistors is sufficiently large compared to the in-circuit gain, which it is)
 
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Well I stopped by the only electronics store that I'm aware of in my whole general area because I happened to be driving right by it... I gave them the 2N5088 number and they only had one equivalent in stock, and it was NTE brand... same thing with the original part number... I guess that's why I was asking if Fairchild was OK as I've heard disparaging remarks about the quality of NTE products lately. Guess I will have to put a Mouser order together later today. Still gotta get the scope working too...
 
N8Nagel said:
Well I stopped by the only electronics store that I'm aware of in my whole general area because I happened to be driving right by it... I gave them the 2N5088 number and they only had one equivalent in stock, and it was NTE brand... same thing with the original part number... I guess that's why I was asking if Fairchild was OK as I've heard disparaging remarks about the quality of NTE products lately. Guess I will have to put a Mouser order together later today. Still gotta get the scope working too...
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Yeah, jump on mouser or digikey. I support my local electronics shop for other stuff, but they just don't have the transistors I need.
 
Definitely get good stuff from Mouser or Digikey, not NTE and certainly nothing from eBay. I haven't specifically tested the other part numbers in this thread, but suspect they should work just fine. The 5088 is a low noise device and one I compared on the curve tracer to the original 458 parts, plus did a noise test on, but there's nothing that fussy about these circuits. My guess is you'll be shocked at how good the unit is with new transistors. As said above, the only thing to check and recheck is the pinout. Happy New Year!
 
OK so I popped the top on this guy today to identify where I had to go to replace these even though I don't have them yet... looks like there are two 2SC458LGs on F-1180 (Driver Amp Brock) [SIC] I'm probably going to Hell because I thought that typo was very amusing... anyway there are 6 more on F-1122 (Tone Control Block) and one on F-1190 (Multiplex Block)

Now here's the thing... it looks like the whole goshdarned thing needs to come apart to get to F-1122. Should I just replace the two on F-1180 first and see what happens or do you think it's worth it to replace them all? I'm also assuming that if I replaced the one on F-1190 I would need to realign afterwards, and I don't have the equipment to do so, so that one's a sleeping dog... yes?

I also see that there are other 2S* transistors throughout this unit, is it *only* the 458s that are likely to be causing noise?

Thanks so much for the help guys, I really do appreciate you bearing with me on this. It's such a pretty little unit but it falls on its face next to the Luxman that I'm using in its place.
 
petehall347 said:
i know i am jumping in late here and not read everything . but did you try the headphones in another amp ?
its generally sounds good on phones and crap through speakers if there is a problem .
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Yes I did, I tried both pairs of headphones on a Marantz 1070 and that one is dead silent. I also tried at least one pair on every amp currently operational and everything else sounds quiet. It's definitely an issue with the Sansui, and I posted earlier that yesterday morning I came downstairs to find that it'd been inadvertantly left on overnight and either something changed or there was just a much lower level of background noise and I could now hear the hiss out of the speakers as well. Swapped for a Luxman R-5030 that I had laying around and everything is all better.

I know the Luxman is a technically better unit, but the Sansui is just pretty (and let's be honest, I'm just not a fan of the rectangular button 80s aesthetic) and I am really trying to either fix everything or get rid of gear that doesn't work correctly.
 
i read through now .i actually deleted my post but you caught it in action .. yes i agree on noisy transistors . just change them for modern low noise ones .
 
No worries man, I appreciate anyone jumping in with good suggestions. I'm a mechanical guy but am trying to learn what I can about electronics and how to fix this stuff.
 
N8Nagel said:
OK so I popped the top on this guy today to identify where I had to go to replace these even though I don't have them yet... looks like there are two 2SC458LGs on F-1180 (Driver Amp Brock) [SIC] I'm probably going to Hell because I thought that typo was very amusing... anyway there are 6 more on F-1122 (Tone Control Block) and one on F-1190 (Multiplex Block)

Now here's the thing... it looks like the whole goshdarned thing needs to come apart to get to F-1122. Should I just replace the two on F-1180 first and see what happens or do you think it's worth it to replace them all? I'm also assuming that if I replaced the one on F-1190 I would need to realign afterwards, and I don't have the equipment to do so, so that one's a sleeping dog... yes?

I also see that there are other 2S* transistors throughout this unit, is it *only* the 458s that are likely to be causing noise?

Thanks so much for the help guys, I really do appreciate you bearing with me on this. It's such a pretty little unit but it falls on its face next to the Luxman that I'm using in its place.
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The tone control block comes before the pre-out/main-in and if reversing those really didn't shift the noise to the other channel then you know the problem is after the tone control section. It's up to you whether you feel you want to put modern low noise transistors in the tone control block now (I would personally, but I don't mind that kind of labour) but if the noise/problem is as described, you should focus the trouble shooting on the sections down stream.

Here is what I would do in your situation. The transistors are cheap, maybe buy a handful, but just start with the 2 in the main amp and find your problem first, before going on with further rebuilding. Refer to my post #18 - there are a couple of other transistors on the main amp boards that can be replaced with the same transistor, so grabbing extras could be handy in case the problem isn't in those first 2 that you change...

Whatever you do, leave all sections related to the tuner (i.e. multiplex block, etc), alone... messing with those can require tuner alignment, which is non-trivial without specialist equipment.
 
Good advice above. I wouldn't mess with the tuner at all unless it has some sort of problem, then it will need alignment after service anyway.
 
well, I haven't given up on this thing but USPS apparently has... my mouser order is lost in the ether :(

Guess I will just have to suck it up and reorder
 
Hi guys, I finally have a few 2N5088s in my hand. Don't know what happened to my first order, but I have them now. Per Fairchild's datasheet those are C-B-E looking at the transistor from the wire end, with the flat down.

Looking at the board diagrams in the manual it appears that the original 2SC458 were B-C-E looking at them the same way. Correct?

I'm pretty sure i'm right I am just pretty much a complete n00b when it comes to electronics repair and don't want to turn this unit into a paperweight. I'm assuming the right thing to do is to slide some small heat shrink over one of the legs and cross them when soldering in...
 
N8Nagel said:
Hi guys, I finally have a few 2N5088s in my hand. Don't know what happened to my first order, but I have them now. Per Fairchild's datasheet those are C-B-E looking at the transistor from the wire end, with the flat down.

Looking at the board diagrams in the manual it appears that the original 2SC458 were B-C-E looking at them the same way. Correct?

I'm pretty sure i'm right I am just pretty much a complete n00b when it comes to electronics repair and don't want to turn this unit into a paperweight. I'm assuming the right thing to do is to slide some small heat shrink over one of the legs and cross them when soldering in...
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Not a bad thing to be careful about pin orientation, especially since some of the sansui PCBs are marked incorrectly. Do yourself a favour and take a pic of the original components installed so you that after removal will know which way they were oriented (again, don't trust the PCB markings, if any, on sansui boards).

Yes, if you lay them flat and look from leg end, the pin-outs you mentioned are I think correct (from left-to-right). I do notice that i recommended ksc1815 for 2SC458 substitution. The 2N5088 is only 50mA max collector current rated compared to 100mA for the 2SC458, and the emitter-base voltage is also lower spec than original. You will probably be okay though...but generally you would get something overspec if the desired part is not available.

Yes, just 'sleeve' on of the legs and carefully bend the legs to get the correct legs in the correct through holes. I prefer using sleeving harvested from small diamter wire like thin hook-up wire; never had much success with finding heat shrink tubing in sufficiently small diameter for this job.

Cheers
David
 
Hmm... where do you find specs on the old parts? I bought the 2n5088s on the recommendation of another poster above (ConradH I think?) who said they had the lowest noise of the options for replacement. This is outside my field of expertise so I'm kind of following a recipe here rather than doing real troubleshooting. The only indications I have of what the orientation of the old parts is is the silkscreening on the board and the info in the SM, the package of the old transistors doesn't look like the new ones and not being an electronics guy without a datasheet I wouldn't know what I was looking at.

I'd have popped the 2n5088s in already (at least on the driver board; the tone control board looks like a right PITA to get out although I'm willing to be surprised) except I was moving stuff around and I haven't a clue where my soldering station is :( Do you think I should consider ordering the KSC1815 and not use the 2n5088s?
 
N8Nagel said:
Do you think I should consider ordering the KSC1815 and not use the 2n5088s?
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No, stick with the 2N5088's they are better for this than the KSC1815's. :thumbsup:

Apart from the missing soldering iron :( what is the problem?... is it identifying exactly how to orientate the replacement transistors?
 
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Hyperion said:
No, stick with the 2N5088's they are better for this than the KSC1815's. :thumbsup:

Apart from the missing soldering iron :( what is the problem?... is it identifying exactly how to orientate the replacement transistors?
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No real problem, just the comment about not trusting the silkscreening makes me nervous, because that's about all I have to go on. The new ones are TO-92, the old ones have three leads apparently in a different orientation (assuming the screening and SM are to be trusted) but package is different (they're kind of small 2001 monolith looking) no way to verify w/o datasheet though and my eyes are not good enough to identify mfgr. markings on old transistors even if datasheets are still available

I'm guessing since others have changed these successfully though that the SM must be correct otherwise there'd be a lot of blowed up 2000x's out there and not too many singing...

just gotta find my stuff and get at it I guess
 
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