• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Sansui 2000, transistors question

I'm working on a 2000A right now, actually that cap and circuit right now, with a hum problem and need to dig a bit deeper. The grounding is that multi-point chassis lug nonsense often used, not single point, and it usually leads to hum at some level. I have a very low tolerance for hum! I'll try the mod described. One request- please everybody, say hum if you mean hum, and noise if you mean the hissy stuff caused by bad 458 transistors and such. Yes, hum is one form of noise, but it just keeps things better described. Interesting thing about this unit- every single 45 year old cap so far has been good on value, dissipation factor and DC leakage. I've changed 'em all anyway, save for the tuner section. It has 2SC632 transistors, but just like the 458s, every one was noisy to one degree or another. BTW, I think there's a service bulletin to add a filter for the tone board supply, reducing hum.
 
There definitely is a SB for the 2000A and it's available for download on HFE

it just clicked in my head that that SB involves the exact capacitor you are talking about

I never checked to see if my unit has that mod done but I have not noticed any hum (although your help was invaluable getting rid of the 2sc458s, I think you were the one that told me the trick to getting the tone board out enough to work on it?)

I don't know if there was a similar bulletin re: 2000 no suffix; there may be but if there is nobody's uploaded it to HFE
 
The 2000X and 2000A are darn near identical. The 2000 is very similar, but doesn't use a handy plug-in power board, so it's harder to work on. Going from fuzzy memory, I think different production runs may be different, with some having cut and jumpered grounding or different ground wiring. Much as I love Sansui, and believe they did some cutting edge circuitry, their grounding often left something to be desired. The 881 is a prime example- I did a write-up on that one a while back.

BTW, there may be two mods. I remember one that adds an RC filter at the tone board, but also one that moves a ground wire. Sorry, I get confused between different models, but often a mod described for one can be applied to another with success.
 
All that SB did was move the ground of C004 from the amp board plug mount to the negative of C003 (Main Filter Cap) for the "A" model. If the "X" model has the same original grounding, I move it per the SB. It also has a ripple filter for btwn the power supply and the eq amp board. . I've not had to do the ripple filter yet, but all get the grounding change.

CE-013-2000A.jpg
There's a pdf copy in case the jpg is unreadable. I got it from an old Sansui site.
 

Attachments

Thanks! Don't have to search for it now. Knew only half the brain cells were gone, not the 3/4 my wife claims.
 
Conrad/Larry, Saw this pop as I'm heading off to work. Curious to hear if the plain 2000 would need similar grounding attention. Obviously laid out a bit differently.
 
Took a look last night and I hereby pronounce Sansui guilty as a repeat offender of Intergalactic Circuit Design Rule #4, no capacitor charging loop shall run common with any other circuit loop. Ideally, the cap charging loop contains the transformer, diodes and filter cap. A stub off the filter cap is used for a single point ground. It can even be a distributed ground if no heavy modulated currents flow in it. That's sort of what Sansui did, if you consider the chassis the stub, and the various chassis ground points as low current quiet grounds. C004, however, has large pulsed charging currents, so it should have been returned to the single point ground near the main filter cap. By returning it to the lugs next to the power board connector, they injected hum into the ground system. Part 1 of the SB fixes that. There are various other more subtle power and ground problems, and C004 could do a much better job if it wasn't located a quarter mile from the junction of its diodes, and the circuit it feeds. New caps are much smaller and one could reposition it, if desired. One would have to look at the individual versions of the A, X and plain units to see what needs to be fixed, as I think the factory did various cuts and different wiring while chasing hum problems.
 
Now that is priceless Conrad :)

"I hereby pronounce Sansui guilty as a repeat offender of Intergalactic Circuit Design Rule #4, no capacitor charging loop shall run common with any other circuit loop. "
Right up there with Sansui rule #3
Though shalt draw out the schematics to present galactic consternation from earthly techs 50 years hence.
-Lee
 
That reminds me, per rule #3, I think the schematic for the X isn't quite right concerning the wiring of the regulated supplies, but I'm guilty of not making good notes at the time.
 
I have another one - not sure what the rule number should be "thou shalt always include dots on schematics where points are connected" - to confuseth not 'lowly novice techs' and 'seasoned schematic' scroll readers alike.

:D
 
Last edited:
^ yeah I like that one.

Although to be fair, since I've been trying to document/plan my moves on my Scott 340B, I REALLY appreciate the parts list, board layouts, etc. in the Sansui manuals. Much easier to say, "oh, that blowed up looking thing is C43" and then start looking at what is nearby/likely to cause same in the circuit on a Sansui than on a Scott...
 
Dots on schematics were declared obsolete a long time ago, just like the little loops that show a trace jumping over another trace. IMO, when you have a copy of a copy or a low rez scan, those dots really help to clarify what's what.
 
My #1 for Sansui is " Thou shalt NOT designate more than ONE (1) part with the SAME part Number except as part of a multi section Capacitor and such renumbering shall have a SUFFIX ADDED to lessen cornfusion in furture generations.
1A is is related to #1 Thou shalt NOT use separate numbers for different sections of multi section capacitors. Thou shalt use the Cap Number with a SUFFIX to denote the section. (prevalent in the 500 and 1000A receivers.) ie: 1A, 1B, 1C, etc....
 
ConradH said:
Dots on schematics were declared obsolete a long time ago, just like the little loops that show a trace jumping over another trace. IMO, when you have a copy of a copy or a low rez scan, those dots really help to clarify what's what.
Click to expand...
What?
name an ecad software package that does not use a dot or square to signify a connection point?
 
Actually the preferred method is lines that cross are not connected. If you want them connected, they need to be slightly offset, forming Ts. Can't remember the "controlling body" or standard, but that's what I last remember.
 
Just FYI, the 2000A has some headphone hum when the volume is turned down to zero. Moving the ground wire as in part 1 of the SB gets rid of almost all of it. If you plug headphones in and out, and you get popping noises, it means your output caps are probably leaking a small amount of DC. New caps will eliminate that.
 
"The 2000A has some headphone hum when the volume is turned down to zero. Moving the ground wire as in part 1 of the SB gets rid of almost all of it. If you plug headphones in and out, and you get popping noises, it means your output caps are probably leaking a small amount of DC. New caps will eliminate that."

Sansui 2000a, 2000x not 2000?
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom