Sansui 2000a Service Bulletin Clarification.

[akadrhouse]

Complete noob here so excuse my ignorance if this is obvious to others.

I had initially posted this here the "Exclusively Sansui" section, but perhaps this forum is a better fit.
I've replaced the faulty transisters in my 2000a and it got rid of the popcorn static. It still has a slight hum or buzz on my sensitive Chorus IIs so I decided to do the service bulletin pasted as a pic below.

This is my first time restoring and doing any work my vintage electronics. I wanted to make sure I'm interpreting this correctly.

My interpretation is to connect an additional wire between the negative terminals of the 1000uf50v cap and the single 2200uf80v cap by the power transformer as shown here outlined in yellow below:

This is the diagram from the service manual showing c011 and c003



Is this correct, and should I use 22 or 20 guage wire? Would this be appropriate in the pic below?


Thanks in advance for the help.

 

[akadrhouse]

Am I doing something wrong in my posting? Wrong forum, wrong etiquette?

 

[ivandezande]

Am I doing something wrong in my posting? Wrong forum, wrong etiquette?

You're good. Not sure why no one has commented.
In the diagram, the solid wire is the old grounding wire. You need to remove that path, and make the new one to the grounds on either side of the amp card.
Use whatever gauge was there initially.

 

[akadrhouse]

You're good. Not sure why no one has commented.
In the diagram, the solid wire is the old grounding wire. You need to remove that path, and make the new one to the grounds on either side of the amp card.

Thank you @ivandezande . Is the 22g wire I linked appropriate?

 

[ivandezande]

Thank you @ivandezande . Is the 22g wire I linked appropriate?

Should be.
You mention hum and buzz - don't expect these to completely go away. This mod may help, however there's gobs of parts that need replacing in this model. I've done two.
The main filters will absolutely contribute hum, and there's tons of 2SC871's that will give you the hiss.

 

[akadrhouse]

Should be.
You mention hum and buzz - don't expect these to completely go away. This mod may help, however there's gobs of parts that need replacing in this model. I've done two.
The main filters will absolutely contribute hum, and there's tons of 2SC871's that will give you the hiss.

Gotcha. I was thinking of replacing Caps in Signal Path with WIMA film caps as I read that could really improve the lower end, but I love the current sound, so have shied away from a complete refurb.

I was going to order new filter caps.

And I have no problem doing the 2SC871s. I wasn't aware they too could be a problem.
Do you know the best replacement part for those?


Also being a noobie, I'm completely lost trying to figure out which caps are actually in the signal path. This was the article in question:
https://www.qrxrestore.com/mylar-film-caps/

I have a 2000x and a 4000 that don't sound nearly as good. I'd be willing to do a complete overhaul of those.

 

[ivandezande]

Gotcha. I was thinking of replacing Caps in Signal Path with WIMA film caps as I read that could really improve the lower end, but I love the current sound, so have shied away from a complete refurb.

I was going to order new filter caps.

And I have no problem doing the 2SC871s. I wasn't aware they too could be a problem.
Do you know the best replacement part for those?


Also being a noobie, I'm completely lost trying to figure out which caps are actually in the signal path. This was the article in question:
https://www.qrxrestore.com/mylar-film-caps/

I have a 2000x and a 4000 that don't sound nearly as good. I'd be willing to do a complete overhaul of those.

2SC871 > KSC1845

Every cap technically is in the signal path, as they are all filtering it in some way or another. I don't do film caps unless the customer requests them. The electrolytic see such little voltage that no distortion is induced into the signal, and high quality electrolytics are still tons cheaper than film. I trust the engineers at Sansui to know when to use a film cap or an electrolytic, but to each their own.
Required reading: https://sound-au.com/articles/capacitors.htm

On both the 2000 and the 4000 there will probably be corrosive glue used on the amp board, right on the bias transistor. Be sure to take care of that.

 

[akadrhouse]

Should be.

The main filters will absolutely contribute hum

With regard to main filter caps. I was looking at all 80v or 100v between 2200uf and 4700uf and from reading many different places, I was unclear on how much you could go up on filter caps. These were the ones instock I was considering.
Advice?

 

[ivandezande]

With regard to main filter caps. I was looking at all 80v or 100v between 2200uf and 4700uf and from reading many different places, I was unclear on how much you could go up on filter caps. These were the ones instock I was considering.
Advice?

View attachment 1602078

Use 381LX222M080A012. 35mm diameter so they'll fit right in, very long life (3000hr @ 105C!!!), great ripple specs, and they don't break the bank.
Just my opinion.

Going up to 3300uf if you really want to won't hurt anything, just a lower F3 and a little more DC pop, and going up to 100V will make them last longer.
Remember to get new bleeder resistors for the amp blocking ones.

 

[akadrhouse]

Use 381LX222M080A012. 35mm diameter so they'll fit right in, very long life (3000hr @ 105C!!!), great ripple specs, and they don't break the bank.
Just my opinion.

Going up to 3300uf if you really want to won't hurt anything, just a lower F3 and a little more DC pop, and going up to 100V will make them last longer.
Remember to get new bleeder resistors for the amp blocking ones.

1. To clarify, I should replace bleeder resisters from the ones that are there only if I upgrade the caps to 100v and/or 3300 uf? Or I should replace them regardless. Also, this is the resister you were referring to? That bleeds off the charge after shutoff?

Thanks for the help!

 

[akadrhouse]

You're good. Not sure why no one has commented.
In the diagram, the solid wire is the old grounding wire. You need to remove that path, and make the new one to the grounds on either side of the amp card.
Use whatever gauge was there initially.

I just got home and took a closer look. My 2000a is a little weird.

• The ground goes from C004 to the right of the amp board on frame. (upper dotted line on diagram)
• Then a ground goes into amp board from that location and then back out to the frame ground on the portion of the amp board closest to the power transformer.
• I don't have a solid black line shown in diagram
• I don't have the lower dotted line

 

[ivandezande]

1. To clarify, I should replace bleeder resisters from the ones that are there only if I upgrade the caps to 100v and/or 3300 uf? Or I should replace them regardless. Also, this is the resister you were referring to? That bleeds off the charge after shutoff?

View attachment 1602138

Thanks for the help!

That's the one. New ones as it's a lot easier than reusing the old ones once you install thew new caps. Plus they're carbon comps, which aren't a very good type of resistor.

 

[ivandezande]

I just got home and took a closer look. My 2000a is a little weird.

• The ground goes from C004 to the right of the amp board on frame. (upper dotted line on diagram)
• Then a ground goes into amp board from that location and then back out to the frame ground on the portion of the amp board closest to the power transformer.
• I don't have a solid black line shown in diagram
• I don't have the lower dotted line

View attachment 1602139

Just change it to match the diagram. Doesn't matter what's there.

 

[akadrhouse]

That's the one. New ones as it's a lot easier than reusing the old ones once you install thew new caps. Plus they're carbon comps, which aren't a very good type of resistor.

So for 0.5W 330 OHM in stock for small quantities, I see the following for the bleeders. The first one is much more expensive. You suggest not using the 2 carbon options right? Are either of the last two fine then?

 

[akadrhouse]

For those interested. I was able to make all the lamps stay on when switching to phono or aux inputs by adding this jumper here between white and blue on the first ring for my Sansui 2000a. It looks like it is on the blue from this picture, but there is a 2-3mm clearance from blue or orange for the jumper.




I got the idea from @Joe Nardy here.

djez,

I don't think this is going to be of much help. I have a Model 2000, not a 2000X. The switch wiring looks completely different. Anyway, see pic below. The jumper I added is on the switch wafer furthest from the rear of the chassis. Viewed from the rear with the unit upside-down the jumper goes between a white wire at roughly 1 o'clock position and a blue wire at roughly 2 o'clock position, indicated by red arrow. Maybe this will be helpful to someone with a Model 2000 who's looking to do this modification.

View attachment 866496

Thanks,
Joe

 

[ivandezande]

So for 0.5W 330 OHM in stock for small quantities, I see the following for the bleeders. The first one is much more expensive. You suggest not using the 2 carbon options right? Are either of the last two fine then?

View attachment 1602400

Use a 1 or 2 watt metal film.

 

[thanhky1985]

Dành cho những ai quan tâm. Tôi đã có thể làm cho tất cả các đèn luôn sáng khi chuyển sang đầu vào phono hoặc aux bằng cách thêm jumper này ở đây giữa màu trắng và màu xanh lam trên vòng đầu tiên cho Sansui 2000a của tôi. Có vẻ như nó ở màu xanh lam trong hình này, nhưng có khoảng cách 2-3mm từ màu xanh lam hoặc màu cam cho jumper.

View attachment 1602445


Tôi lấy ý tưởng này từ @Joe Nardy ở đây.

When doing this there will be noise. I don't know why but it should probably be related to the FM radio.I took it off leaving just one aux light and it was silent