Preparing for G99X restoration [advice needed]

delboyko

New Member
I have a G99X that's been waiting on the table for a few months now.
Poor fella got a bruise or two during shipping and did not play very happy from the first minute. After a little persuasion, he started singing happily.
Then I tried to dial in the offset and bias but I slipped and touched the wrong pins and that's when I learned the smell of defeat. There are no words to explain how shitty I felt at that particular moment and for the rest of the day.

I had big plans for my G99X. I read so much about D11 II and since they share so much I wanted for him to grow up one day and be like the older brother. In the meantime, I got AU-717 playing in the background.

Long story short, I'm making a list of parts to be replaced. Here are my doubts and thought:

1. Sansui replaced PS caps with orange film caps. There is a lot of these on almost every board. Should I replace them and with what. I could go with C0G(easy) or PS(hard). What would be your call?

2. Is there any need to increase the capacitance of power supply caps?

3. Some of the D11 II owners did a resistor upgrade to all metal film and I'm not sure that I'm ready to go this far. What PCB would benefit the most from switch to metal film...Control, Amp, Driver ...?

Here's a top view of mine G99X. Underneath it is D11 II (recaped) just for reference to see where did Sansui save some money.
20180322-170937-2.jpg


Here's a D11 II(restored) from rayner06. Hope he doesn't mind borrowing his photo.
G2NWvn5.jpg
 
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1. Sansui replaced PS caps with orange film caps. There is a lot of these on almost every board. Should I replace them and with what. I could go with C0G(easy) or PS(hard). What would be your call?
? 'PS' = Polystyrene ? - these are the best you can use - and I don't think Sansui would have replaced Polystyrenes with those orange films - which may be Polystyrene anyway. You could replace the ceramics on the PCB's (v.small & brown) with C0G/NP0 ceramic if you like, (except those near the main rectifiers), I have left all the orange capacitors alone, only found in the Phono EQ on my AU-D11 II.
2. Is there any need to increase the capacitance of power supply caps?
I didn't feel I needed to, space is limited, so I went with Nichicon Gold Tune, same value.
3. Some of the D11 II owners did a resistor upgrade to all metal film and I'm not sure that I'm ready to go this far. What PCB would benefit the most from switch to metal film...Control, Amp, Driver ...?
If you use it, the Phono EQ would benefit most - but leave behind the quality resistors that are already there, glossy bodied :naughty: pale green/grey ones IIRC. Other than that, the 'Control Amp' would benefit most. Note that if you change out the carbon composition resistors, (dark brown bodies), you might alter the sonic signature slightly - which is why they were put there in the first place.

Update
I just checked on the 'Orange films' - they are Polypropylene - second only to Polystyrene as a desirable dielectric for audio purposes.
 
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? 'PS' = Polystyrene ? - these are the best you can use - and I don't think Sansui replaced Polystyrenes with those orange films. You could replace ceramics on the PCB's (v.small & brown) with C0G/NP0 ceramic if you like, (except those near the main rectifiers), I have left the orange capacitors alone. (on my AU-D11 II).

Yes, polystyrene. They're quite hard to get and I would have to turn to eBay...and most of the money spent will be on shipping. I'm really sad that Sansui cut the production costs on them.
Not sure if you're implying somebody else replaced it or you didn't notice the change. Take a closer look, I edited the first picture.

Control board is where G99X differs most from D11 II but I think it's mostly in PCB layout because schematically they look quite similar to me. I might order MF for control and EQ board and try it out after the recap.
 
Well, you said this:-
"1. Sansui replaced PS caps with orange film caps"

I initially didn't pick up that you were referring to the pictures :)
 
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I would recommend against PS, they are extremely heat sensitive and one microsecond
too long with your 100w iron on that solder joint and it melts.

I see orange films, and the occasional Nichicon Muse ESs, are you certain it has not been
recapped? check the parts list for specs, I suspect the owner of the pictures you used
did actually recap. check with him or search his threads. no sense upgrading your unit
using his pictures.

post pictures from your own unit. @Hyperion - his advice is good. use PP until it
doesn't fit.
 
I would recommend against PS, they are extremely heat sensitive and one microsecond
too long with your 100w iron on that solder joint and it melts.

I got a nice soldering station, a steady hand and a nice working table although am somewhat concerned about this. I soldered one PS cap so far and it's working fine in my AU-717 but let's call it beginners luck. :D
I got 4pcs of 5pf and 8pcs of 3pf PS caps. Only ceramic caps go this low. (not counting MICA)
Other values are: 470,560,680,1500pf.

I see orange films, and the occasional Nichicon Muse ESs, are you certain it has not been
recapped? check the parts list for specs, I suspect the owner of the pictures you used
did actually recap. check with him or search his threads. no sense upgrading your unit
using his pictures.

I must've done something wrong since a lot of confusion here. Upper pic is mine G99X and lower is random D11 II which happens to be recapped as well.
Pics are posted to see the differences which I want to compensate with this restoration project.
 
I got 4pcs of 5pf and 8pcs of 3pf PS caps. Only ceramic caps go this low. (not counting MICA)
Other values are: 470,560,680,1500pf.
You are really overcomplicating this for yourself, ;) as it seems like you are getting ready to change most if not all the capacitors in your unit. You only really need to concern yourself with Electrolytic capacitors, Trimmers, (Zener diodes ? - optional), and maybe some resistors. Polystyrene capacitors are difficult for 'soldering novices' as Bob says, because they are so easily damaged by overheating during soldering. Film capacitors don't 'wear out' like electrolytic capacitors - but can become faulty on reasonably rare occasions. The small ceramic capacitors I mentioned could be changed - but don't absolutely need to be, the unit might sound nicer with the low value ones (less than 100pF) replaced with C0G/NPO ceramics.

Try to limit yourself a bit otherwise the result can be a non-working unit which nobody can help you with because you have 'touched' so many components that it is not possible to fault find online any more. Please forgive my words of caution if I have not assessed your level of knowledge and expertise correctly.
 
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Try to limit yourself a bit otherwise the result can be a non-working unit which nobody can help you with because you have 'touched' so many components that it is not possible to fault find online any more. Please forgive my words of caution if I have not assessed your level of knowledge and expertise correctly.

I'm just following the usual procedure seen here on AK when trying to get out the best from the amp.
I want to keep this simple but Sansui is the one to blame for using this orange film caps. :angel:
Also, I find restoring very entertaining.
 
OK, that's fine - I for one will help you all I can with whatever you want to do, just so you know what you are getting yourself into. :)
 
So, I've made a BOM list on Digikey for every board with the components I intend to change.

The list consist of:

1) All electrolytic caps except the main filter caps(saving those for later). I used Nichicon FG where ever I could.
2) Replacing orange film caps with polypropylene (C0G where unable to do PP because of capacitance).
3) Replacing small ceramic caps with PP where Sansui used polystyrene on D11 II. (driver, control and main amp)
4) Replace all trimmers with Bourns 25 turns units.

I've decided not to change orange caps on Protection boards. My guess is they have no impact on the sound?
Also, I'll skip the EQ board since I don't use Phono.

I was comparing the schematics of a G99X and D11 II while making the list. Speaking as a novice, differences are really minor.
All components of EQ, Control, Tone, Power supplies and Protection can be found in the same arrangement on both schematics. A few film bypasses are missing on G99X, and of course trimmers from the EQ and Control. But Sansui makes up for those trimmers in power meters. :biggrin:
Driver board has the most evident difference in the initial stage and I've highlighted it in the pictures below if anybody cares. I'll post pictures of actual PCB after recaping.

Driver board "D11 II" vs "G99X"
driver-D11-II.png
driver-g99x.png


Before ordering I have two questions:

1) Are there any resistors that should be replaced?
2) Does Digikey have any good speaker post that could fit in this bracket?
20180322-182120.jpg
 
Driver board has the most evident difference in the initial stage and I've highlighted it in the pictures below if anybody cares. I'll post pictures of actual PCB after recaping.

Driver board "D11 II" vs "G99X"
driver-D11-II.png
driver-g99x.png

And those simple components that you have highlighted are the key to performance of the AU-D11 II. That is the cascode configuration which maximizes the linearity of the amp.
 
And those simple components that you have highlighted are the key to performance of the AU-D11 II. That is the cascode configuration which maximizes the linearity of the amp.

Why would they abandon it than? Could this be a cost saving measure?
 
Almost certainly cost saving - not just the components but assembly time/labour as well.

You have to remember that the AU-D11 II, although introduced in 1983 was probably designed in 1982 when the founder/owner was either still in control or had just resigned (due to financial wrong-doing by the finance director). After his departure the Bank of Tokyo, as major share-holder, put an accountant in to run the business. The rest, as they say, is history.
 
What I wanted to say is, if they wanted to save, why cut there if it's like you say vital to outstanding performance.
That is a no no even for someone as basic as an accountant.
 
Why would they abandon it than? Could this be a cost saving measure?
Yes, possibly, and they most likely looked at the design and felt there was no real performance advantage to having it there.
Sansui have always done this, for example if you look at the design of the G22000 and then compare that to the G9700 which was is its successor to some degree, they did away with the fancy dual FET phono pre, eq and flat amp, the 9700 has a very simple signal path in the pre using 2SA992/2SC1845, and its very simple, yet the specs show slightly better performance in terms of SNR and THD than the G22000....
I like the 9700 design, its really simple, they did away with what they didn't need and was clearly "engineer luxury" design aspects.
To be honest, after selling my G9000 the other day and having put the G7700 in its place in the Lab, I have to say, the G7700 holds up amazingly well against the G9000, the tuner to be honest, may sound a little better...

So what I am saying is I believe the pressure would have came from the bean counters to eliminate anything unnecessary which has little effect on performance....
 
So what I am saying is I believe the pressure would have came from the bean counters to eliminate anything unnecessary which has little effect on performance....

But that's the issue right there - deciding what is 'little effect on performance' and 'unnecessary'
 
But that's the issue right there - deciding what is 'little effect on performance' and 'unnecessary'
The Bean counters want to save money, they ask the designers/engineers how they will achieve it.. Something like that I imagine, but its only speculation on my part...
 
The conversation generally goes something like this:

B.C What could we take out from this design to save money?
Eng. Well I suppose we could take the cascode out, I'd need to do some tests to check on the effect
B.C Never mind the tests, they would cost money too, just delete the parts.

Been there, done that, got the scars, t-shirt and fridge-magnet :crazy:
 
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