Sansui 2000 Receiver queries

[Dalmacio]

Greetings! It's been awhile since my last post here in Audiokarma and my first post in the Sansui section, the obvious reason is I got myself this Sansui 2000 receiver for free. I have been lusting for a Sansui amp ever since I got myself bitten by this vintage bug and I already have three Kenwood-TRIO and 1 Yamaha amp. But I've always wanted a Sansui as this was the amp that first started me, at a very young age, to appreciate hi-fi music the way it's supposed to be listened to.

The amp as usual was dirty from long storage but initial cleaning inside and out gave it a sort of improved appearance.

Now comes the inevitable question, after having fired it up, and was able to check the DC, I am in a quandary as to where the pots for DC adjustment are located. Is the diagram for this amp the same as the one for the 2000A series?

I have not read many posts regarding this particular amp as that of the 2000A and I'm wondering if they are basically the same.

I'll be hoping for some inputs from you guys and all will be greatly appreciated. Thank you in advance.

 

[Ishmael]

Dal I join you in your curiousity, as I have a 2000A and wonder what differences there are between the 2000, 2000A and 2000X. I have noticed that it seems the 2000X has quite a following and there is mention of issues with circuit board and transistors with these models. If you look in the web there is a very nice article concerning the replacement of a 2000X's transistors and the subsequent improvement in sound. My 2000A is experiencing similar noise issues to those addressed in the 2000X transistor replacement article, when no music is playing we can hear audible noise coming through the speakers. This amplifier seems to be a perfect match to the speakers we have it partnered with, so we will be having our local shop explore a full restoration of capacitors and transistors. I believe if you search on HiFi Engine you will find information on the 2000 series and maybe a service manua, it's free to join, which you need to do to get access to owner/service manuals.

 

[quartermoonp]

Dal,

The Model 2000 is different from the 2000(with letters) and it is pretty rare in comparison to the "a" and "x" models. I'm currently working on my model 2k as it has some issues so you might look for that thread. As I fix it I'll also update folks on what I'm using for replacements, etc. There are several members on here that have the 2k so you're in luck. You can get the service manual at http://www.hifiengine.com/library/sansui/2000.shtml
You'll just have to register an account to download it.

 

[Ishmael]

Quarter what are the differences between the 2000, A, X models? Are there AK threads that have previously discussed this? You might want to check out http://conradhoffman.com/Sansui2000x_mods.htm online as he describes and details with excellent photography his replacement of transistors in a Sansui 2000x to remove noise generated by them. Have you posted your thread on your model 2K? If so what is its title?

 

[quartermoonp]

I believe the main difference is that the A and X models are set up where you can isolate the preamp from the actual amp. The layouts/pcb boards, etc are different as well.

There are also service updates for the A and X models that should be done (think the A model was a grounding issue). If can't find these at Hi Fi Engine, perhaps another member has them or you can buy them online.

One thing upfront, if you're going to do replacement/recap you'll want to go off the values of the actual components on the PCB boards. Sansui was never good at documentation for changes at component level.

 

[Ishmael]

Thanks quarter on the component values, I'll have to check the back of my 2000A to see if it has a pre-out. I will check on Hi Fi Engine for source materials.

 

[Dalmacio]

Notwithstanding the un-adjusted DC offset....

This amp is now playing b-e-a-u-t-i-f-u-l-l-y, albeit with intermittent scratchy noises and pops on the right channel remedied by turning the knob Speaker Selector. I have cleaned the pots and the noise comes out infrequently now, probably needs more 'exercise' for these 45+ year old knob/pots.

And as stated above, this amp hasn't lost its sweet sound as I have listened to this when I was still a wee lad during the seventies (my cousin gave the amp). Its warmness and detail in the music is what sets it apart from my other amps which are by any means not also-rans: a Kenwood 8100, 7300 and a Yamaha CA 800 II.

I was able to browse the service manual for this amp but there is no instruction for the adjustment of the DC offset, only for the bias. There are four trim pots for the left and right driver boards, I believe the bigger ones are for the bias, anyway I hope some other members can chime and share their knowledge and this will be truly appreciated.

Ishmael and quartermoonp......thanks a lot guys for the valuable input....Instant good karma's gonna get you!

 

[larryderouin]

The 2K has separate AMp board, the 2K A and X both have a mirrored single board. The pots are marked on the boards as noted in the manuals. The A & X models are almost identical except for the board numbers (and a few parts). Externally identical, but internally just a little different. Wattage is 5w different between the A & X. 2K is IIRC about 30WPC.

The 2K and the 2K A&X models are single rail, Cap coupled. There is no DC OFFSET. Only BIAS! There is a Output balance that you use a scope and an oscilllator to adjust the sinewave. This would roughly equate to offset. If you don't have a scope just adjust the bias.



The 2sc458 transistors in all 3 get noisy. They present with what I call "RICE KRISPIES". Replacing them with KSC1845's will alleviate the problem.

The later "A"'s used some boards from the "X". There was some overlap. Sansui never made a manual update for this. So if you have an "A" or "X" get both manuals just in case.

Service bulletins for the 2000A are here...... http://www.obsincst.com/servlet/Categories?category=Sansui+Manuals

SERVICE BULLETIN FOR 2000A, IMPROVEMENT OF THE AM METER INDICATION, CE-024 7 CE-014

SERVICE BULLETIN FOR 2000A, MODIFICATION OF NOISE (INPUT SHORTED), CE-023

SERVICE BULLETIN FOR 2000A, MODIFICATION OF THE POWER CIRCUIT, CE-013


Unless you have problems with the AM meter, don't worry about the 1st one. The last one is in the Manual on HIFIENGINE for the 2000A. It was done for the "X".

I'd also incorporate the 2nd if/when you recap the unit.

DeOxit is not always a one time relief. I have to redo my Sansui 1000A about every 6 months for the 1st 3 years but now it's fine. So multiple cleanings are indicated. If it goes in-out, up-down, roundy-round, clean it! Just Spraying it with DeOxit won't cut it. Spray inside the slot where the leads enter the pot or a hole to the inside. Exercise 5 times and let it sit for an hour. Do them all at this time. After an hour, hit it again and exercise the living hell out of each switch, and pot. The DeOxit softens the environmental sulfates on the contact, and the friction cuts thru to the clean surface.

And when you get really adventurous, dissassemble each one and clean completely!

I'll let you guys buy the last two service bulletins. I paid for and put up the 2K manuals on Hifiengine.

 

[Ishmael]

Larry thanks for the great info. Rice Krispies, yep, with nothing playing through the receiver, even with volume turned down my wife can hear the crackle sound. Given the service bulletin for our 2000A I am first going to have both the gounding issues fixed per the service bulletin recommendation. It has an odd habit, which I hope the grounding fixes, which is when the tuner is selected if you plug into the phone inputs the sound just stops, same if you are playing CDs through AUX, did they intend this, or, could this be grounding? Once you unplug from all but the AUX input the tuner and CD inputs works just fine. Once we have the grounding fixed per the service bulletin, I will then look at replacing the transistors and caps. We really love this receiver as it really has a synergy with our early 60s Wharfedale speakers (together they nail acoustic, jazz, the human voice). I will look up the service bulletins too.

 

[larryderouin]

First off NEVER PLUG IN A SOURCE OR UNPLUG A SOURCE from the receiver without turning it off 1st. Sounds like someone could have gotten inside before and crosswired something. The grounding service bulletin won't fix this. Check for loose wiring, dry solder joints on all the boards, and broken switches internally.

The Noise service bulletin may or may not corect this or the rice krispies, but the 2sc458's are a known problem 40+ years later.

On the 2000A the transistors on the EQ board (small one off the side mounted vertically) are replaced with mpsh10's. IIRC they are 2sc871's or something like that. I don't have the manual in front of me right now.

UNPLUG the JUMPERS on the back, and turn on the unit. This separates the amplifier board from the preamp, and tone control boards. Listen for the Rice Krispies. If you still get them, then the 2sc458's in the amp are flaky. If not then it' the tone control board. In any case while you are in there replace all of them (about 10).

 

[Ishmael]

Larry again thanks for all the advice. Here's what happened that created no sound, as I have just re-created it again. Over time I have acquired two sets of the old vintage plastic topped male RCA plugs that you could put into un-used female RCA inputs on the back of your receiver, to keep out radio waves I believe. Our Sonty STR-6800SD is going into the shop for some repair/restoration so I moved our Sansui 2000A into our bedroom system, and while doing so used the two pairs of plugs on the top two inputs Tape REC and Tape Mon to block unwanted radio waves(record/monitor). When I turned the Sansui 2000A on and turned up the volume there was no sound at all, although all lights worked and signal strength was pulling in a good AM reception. Turning it off I removed the RCA plugs, turned it on and got sound. Tonight I tried things again, trying each set of RCA input plugs and getting no loss of radio signal until I put the plugs in the top Tape REC RCA inputs at which point no sound. Is this a case where the presence of RCA plugs in the RCA Tape REC cuts out the playing of music via radio or AUX for CDs even though the plugs are mearly caps without wires? Because this is repeatable, and depends on the presence or absence of the plug into the Tape REC RCA plug I don't think I am dealing with a faulty connect, but likely something simple that I am just missing about the operation of this receiver?

 

[elliott66]

The Tape REC jacks will present whatever signal you have selected. The RCA 'caps' are actually shorting caps, so when you plug them into the REC jacks it shorts whatever signal you have selected to ground. No sound.

I was given a 2000 when I was a teenager, did some mods to it (replacing the output coupling caps and bypassing them, replacing transistors on the power amp boards and replacing the main volume pot which I now regret..). It's still in the family, I gave it to my dad. Loved it, it sounded fantastic and had a great FM tuner.

 

[skippy124]

Those caps are shorting plugs and are meant to be used on unused phono rca inputs only.

If you put them on the tape rec rca's then you effectively short out the aux input, and the output from the tuner section is also shorted out.

Cheers

John

 

[Dalmacio]

larryderouin, I greatly appreciate your priceless info about these wonderful Sansui amps, and from what I have gleaned so far from this forum and from other various audio sites, these pre-1973 Sansui amps have a distinct sound compared to their subsequent models.

And yes, elliot66, the Model 2000 truly sounds fantastic!

 

[Ishmael]

Great site for learning, thanks for explaining the old vintage plugs which I now know as shorting caps, and why they did what they did and to keep them in the unused RCA phono inputs. What did they do when installed in the unused RCA phon inputs? What was there purpose? I do plan to follow Larry's suggestions. First have all the grounding issues as discussed in the Sansui service bulletin addressed and then take the plunge and have the transistors and caps replaced, check all solder connections, etc.. We love the sound of this receiver, even with the current noise in the signal path, with that noise removed and everything freshened up it will be great to hear. Again great site and thanks for help, information and background about this receiver.

 

[Dalmacio]

A side note:

Just checked the serial number of my Sansui Model 2000 and guess what -- it will be 45 years old tomorrow.....Date of Manufacture..........February 1969........wow.

 

[larryderouin]

Ishmael; Turn on the 2000A with nothing connected except for the speakers and antenna. Switch it to phono. Hear the hiss/hum with the volume all the way up? Now turn off the unit and install the RCA Shorting plugs in to the phono jacks, and repeat the test. Notice the difference? Use the shorting plugs in the Phono/Aux positions ONLY when you don't have a source to connect to them. It helps with keeping spurious noise out of the circuits when in FM/AM or TAPE Monitor.

NEVER SHORT the TAPE MON or REC JACKS. Like skippy said it'll short out the signal path and can cause problems.

 

[larryderouin]

A side note:

Just checked the serial number of my Sansui Model 2000 and guess what -- it will be 45 years old tomorrow.....Date of Manufacture..........February 1969........wow.

Practically ANCIENT, ain't it! Mine is Oct. 68. I was 13 at the time and thought anyone over 30 didn't know shite. Now anyone under 25 is a child! And my 1000A is a Feb 1966. Almost 11 at the time. But I've got a FISHER that is actually older than I am. 1951 Fisher Coronet (Warwick cabinet). My dad was 19 at the time and I was a future gleam in his eye.

 

[Ishmael]

Larry, worked like a charm. Without the plug installed when I turned Phono 2 up all the way, lots of noise. Then after installing the plug, turned it up and dead silence. When I switched to Phono 1 without the plug installed and turned it all the way up, same noise. Now I'll be looking for a second pair of the vintage shorting plugs for Phono 1 as we listen to the tuner or our CD player through AUX (no slight to vinyl, its just after buying the etire catalog on vinyl, 8-track, cassette, and now CD, we're staying with CD, though considering HD computer storage, but that technology seems still too up in the air).

 

[Ishmael]

Checked my 2000A August 1970, 43 years young and still making really fine music, and its wood case survived too, a few character gouges and a corner ding, but with the right speakers and the right music this is still as good as it gets. Just going to get better after we do a full restoration.