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SANSUI QUARANTINE ACTIVITY

maxhifi

maxhifi

Addicted Member
I'm sure I'm not the only one trapped at home, so here's an activity for any Sansui fans in the same boat as me (ok more like in your own boat, with nobody around and nothing to do)

I was thinking it could be fun to take a piece of Sansui gear out of storage, which I haven't used in a long time, and try and re-acquaint myself with it. In this case, it is my SP-3005 speakers which I built new cabinets for several years ago. I had to play a very heavy and unpleasant version of Tetris to get them out from the back of the furnace room, but now they're set up in my listening room, and I'm enjoying having them back in action!

I wonder what treasures other people have collecting dust, which could be re-animated to pass the time over the next weeks or months
 
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I got my B-2102 on the bench, changed the 2 core mains cable for a 3 core, and connected the earth to chassis ground. Then I went through the setup procedure, and for the first time I get reasonable results for the 'Hot to Ground' DC offset adjustment. (owners of this and many other Sansui's with a similar design will understand why this is significant).
So, worth a banana :banana:
 
Hyperion said:
I got my B-2102 on the bench, changed the 2 core mains cable for a 3 core, and connected the earth to chassis ground. Then I went through the setup procedure, and for the first time I get reasonable results for the 'Hot to Ground' DC offset adjustment. (owners of this and many other Sansui's with a similar design will understand why this is significant).
So, worth a banana :banana:
Click to expand...

How does grounding the chassis help with this?
 
The power supply depends on the establishment of a virtual ground for the split rail supplies, if the earth ground is added it seems to help with balancing the split rails which in turn stabilises the 'Hot to Ground' measurement. ;)
 
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Hyperion said:
The power supply depends on the establishment of a virtual ground to supply the split rails, if the earth ground is added it seems to help with balancing the split rails which in turn stabilises the 'Hot to Ground' measurement. ;)
Click to expand...

This sounds far fetched, but obviously works in practice! Would be interesting to find out why/how, when there's no actual electrical connection between the primary and secondary of the power transformer, and thus no reference to earth ground within the amplifier.
 
I've cranked out the AU-X1 and set it up again in a new room with my KEF 104.2's. Im going to setup my TT connected to that next, using the amazing MC preamplifier stage that member Wyn Palmer designed. It sounds fresh as.

I've also got a new-to-me Au-777D coming to me from Japan. Once I get that I can see if it works - and it will get the full restore treatment anyway. It can sit alongside my AU-999 and look purdy.
 
I haven't found time to tackle any long-overdue Sansui restoration work, but being home and working out of the 'cave' has been brilliant so far! It is making me fall deeply in love with my system all over again. Apart from down-time during video conferencing calls, I've been listening as much as possible.

My wife is also working from home, and our two kids are being 'home-schooled' via a web-based curriculum during this crisis, so having some separation between each other during the day is important. I think I'd drive them nuts otherwise!


sansuicorona.jpg
 
Placed an order for a full refresh of my latest import....777d. Got really lucky on this auction as the amp looks brand new inside and out. Looks like the previous owner waxed and polished the faceplate/knobs too. I’m used to working on dusty, sticky, cruddy old things so this one will be a real treat. Just hope Mouser isn’t shut down.....usually I get a shipping notice within 24 hours but haven’t gotten one yet
 
pete_mac said:
I haven't found time to tackle any long-overdue Sansui restoration work, but being home and working out of the 'cave' has been brilliant so far! It is making me fall deeply in love with my system all over again. Apart from down-time during video conferencing calls, I've been listening as much as possible.
View attachment 1807630
Click to expand...

That's more or less how I am spending my days too. Have to go pause the music each time I get a Skype or Teams invite!
 
Hyperion said:
The power supply depends on the establishment of a virtual ground for the split rail supplies, if the earth ground is added it seems to help with balancing the split rails which in turn stabilises the 'Hot to Ground' measurement. ;)
Click to expand...

Does the accuracy of the 6.8k resistors which split the rails come into play? It looks like they did away with using a centre tapped winding on the power transformer, in order to enable the 4/8 ohm switch to function properly and not be too complex.
 
maxhifi said:
Does the accuracy of the 6.8k resistors which split the rails come into play? It looks like they did away with using a centre tapped winding on the power transformer, in order to enable the 4/8 ohm switch to function properly and not be too complex.
Click to expand...
Yes it does, changing the values (lower) has been tried by AK member phonomac (on his AU-D11 II) with some success, but the lower they are in value the hotter they get, I am pretty sure he came to the conclusion that it isn't the complete answer, as there are trade-off's (he's much cleverer than me at analysing this ;)). I haven't tried changing/reducing the values, and I have no plans to at present.

I have discovered a new candidate to try the earth modification on - my AU-D11 II, I fitted a 3 core mains cable ages ago but didn't connect the earth core to chassis ground - I'll try it 'before' and 'after' for verification.
 
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Hyperion said:
Yes it does, changing the values (lower) has been tried by AK member phonomac (on his AU-D11 II) with some success, but the lower they are in value the hotter they get, I am pretty sure he came to the conclusion that it isn't the complete answer, as there are trade-off's (he's much cleverer than me at analysing this ;)). I haven't tried changing/reducing the values, and I have no plans to at present.

I have discovered a new candidate to try the earth modification on - my AU-D11 II, I fitted a 3 core mains cable ages ago but didn't connect the earth core to chassis ground - I'll try it 'before' and 'after' for verification.
Click to expand...

Interesting. If I was to propose a modification to stabilize things further, it would be to put a 470 - 1000uF capacitor across each 6.8k resistor. This would most probably make the virtual ground point more stable and less prone to drift. Of course there is also a strong argument for leaving well enough alone, but us quarantined people like solving problems:)
 
maxhifi said:
If I was to propose a modification to stabilize things further, it would be to put a 470 - 1000uF capacitor across each 6.8k resistor. This would most probably make the virtual ground point more stable and less prone to drift.
Click to expand...
Begs the question 'why didn't Sansui do this'?
 
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