Kale
Super Member
No, I am sill working on it. Lot of work must be done....
Bargain AU-X1, Did I get a Good Deal
- Thread starter fuelie
- Start date
No, I am sill working on it. Lot of work must be done....
Kale
Super Member
This AUX1, what I am restoring, had "hard life", and it had hours and hours working time before I got it for restoration, so because of that glue becomes dark, but if you will work on yours AUX1, I suggest you to clean glue on yours AUX1 because it is dangerous too, even if it looks like better...
Nicowico
Active Member
you are rewarded with a very nice sound
fuelie
New Member
My $259 AU-X1 has very little sign of the Cap Glue as compared to my current and previous Integrated units that I have worked on. It appears that during production they applied just enough Cap Glue to secure the Caps in place and there is no excessive use of the glue that is typically present on most of the Sansui units I have seen. The Power Amp Modules have no Cap Glue on them at all and the Filter Caps are original with no sign of being re-soldered, these might get replaced in the near future.
The F2778 Regulated Power Supply board seems to have the most Cap Glue of all and it is hardly even visible and doesn't flow over to any neighboring components that might cause alternate signal paths(see photo) and what little there is, isn't baked to that dark color. Also, in checking the Caps I find they are at or within 5% of nameplate value, yet I know this is no guarantee to their future reliability.
I have been very lucky so far with this acquisition as I feel it is in much better condition than I expected it to be.
I have it working on the Bench and have gradually increased operating time and temperature in order to catch any anomaly that might arise before I connect to my regular Speakers.
Something that I have noticed is an RF signal signature present on both channel outputs. Centered around 1.5Mhz, it is very low level, slightly higher on the right channel, but definitely present. I have tested for outside sources but feel this is internally generated by the amp. I have traced it back to the Flat Amp and discovered that if I operate the Jump Switch, which removes the flat amp from the signal path, the RF signal disappears. I also discovered that if I back down the Power Amp individual level control just a slight amount, like from 0db to -2db, that the RF is reduced significantly, around 6 to 8 times lower. Reducing the Power Amp level control this slight amount is almost not detectable while listening but I think very important in reducing possible RF in the Power Amp. so for now I am going to use this method to keep the RF signal out of the Power Amp. until I can determine for sure if it is internal or external source.
That's all for now, I will Let you know the progress.
The F2778 Regulated Power Supply board seems to have the most Cap Glue of all and it is hardly even visible and doesn't flow over to any neighboring components that might cause alternate signal paths(see photo) and what little there is, isn't baked to that dark color. Also, in checking the Caps I find they are at or within 5% of nameplate value, yet I know this is no guarantee to their future reliability.
I have been very lucky so far with this acquisition as I feel it is in much better condition than I expected it to be.
I have it working on the Bench and have gradually increased operating time and temperature in order to catch any anomaly that might arise before I connect to my regular Speakers.
Something that I have noticed is an RF signal signature present on both channel outputs. Centered around 1.5Mhz, it is very low level, slightly higher on the right channel, but definitely present. I have tested for outside sources but feel this is internally generated by the amp. I have traced it back to the Flat Amp and discovered that if I operate the Jump Switch, which removes the flat amp from the signal path, the RF signal disappears. I also discovered that if I back down the Power Amp individual level control just a slight amount, like from 0db to -2db, that the RF is reduced significantly, around 6 to 8 times lower. Reducing the Power Amp level control this slight amount is almost not detectable while listening but I think very important in reducing possible RF in the Power Amp. so for now I am going to use this method to keep the RF signal out of the Power Amp. until I can determine for sure if it is internal or external source.
That's all for now, I will Let you know the progress.
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bobrown14
Super Member
You're gonna love the RICH CLEAR sound hooked up to your EV speaks. I've got a lowly AU-D11 II hooked up to some EV Sentry IIIs and love the sounds. I'm big on separates, exception being the Sansui big'uns. You're price for admission is mighty fine. I was watching that amp on Eprey and thought the seller was a hoax so I passed. Dang.....good on ya.
Cheers,
Bob
Cheers,
Bob
fuelie
New Member
Thanks Bob, and I thank you for not picking up on the X1, but if you did I am sure it would have found a good home. , as it is I am getting very excited about this huge gem - I hooked it to the EV's today and can hardly believe the difference.
I was able to do some comparable listening between the 2102 and the X1. The X1 immediately has more presence and separation, but what most impresses me is the improved tightening of the bass. I have always thought that my AU-919 had better Bass Response and control over the 2102, but did not expect that the X1 could overcome the lack of the loudness control that is also missing on the AU-919. I switched out my 919 with the 2102 because of the 2102 pre-amp having this feature, the meters are neat too, but I always felt that the 2102 was missing something, the something that the 919 easily fulfilled. With the 2102 I was always fiddling with the parametric equalizer and switching the loadness off and on to match with the main volume setting. I can tell you now that with this AU-X1, even though it does not have the loudness option, it doesn't need it and I ain't gonna miss it! It's just incredible how much difference there is.
Maybe the difference here has something to do with the fact that the AU-X1 with 80,000uf main power filtering is more than double that over the 2102 and 919.
Had I known how good it is and how huge a difference there would be, I would have invested in an AU-X1 a long time ago.
Thanks, and here is a pic of the EV's, - let me see your EV's.
I was able to do some comparable listening between the 2102 and the X1. The X1 immediately has more presence and separation, but what most impresses me is the improved tightening of the bass. I have always thought that my AU-919 had better Bass Response and control over the 2102, but did not expect that the X1 could overcome the lack of the loudness control that is also missing on the AU-919. I switched out my 919 with the 2102 because of the 2102 pre-amp having this feature, the meters are neat too, but I always felt that the 2102 was missing something, the something that the 919 easily fulfilled. With the 2102 I was always fiddling with the parametric equalizer and switching the loadness off and on to match with the main volume setting. I can tell you now that with this AU-X1, even though it does not have the loudness option, it doesn't need it and I ain't gonna miss it! It's just incredible how much difference there is.
Maybe the difference here has something to do with the fact that the AU-X1 with 80,000uf main power filtering is more than double that over the 2102 and 919.
Had I known how good it is and how huge a difference there would be, I would have invested in an AU-X1 a long time ago.
Thanks, and here is a pic of the EV's, - let me see your EV's.
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dr*audio
Fish fingers and custard!
I am glad you thought to hook a scope up to the output, because this model is prone to oscillating. That causes the outputs to heat up and self destruct. It looks like the power amp in yours may be ok, and the flat amp has issues. One thing you can try is see if there are any of the "black flag" capacitors in the falt amp, and replace them if there are. They are small black caps, used as Miller caps to stabilize the amp. Echowars says they go bad.
dr*audio
Fish fingers and custard!
I don't have an AU-X1 but I have repaired them successfully. I have a AU-9900 and a AU-11000. These are my favorite Sansui amps.
reggaenaut
Addicted Member
Great thread. I envy your skills.
BTW I know even my wife would not oppose those EV speakers.
BTW I know even my wife would not oppose those EV speakers.
noveltone
Active Member
Great thread guys! I am sure this is a dumb question, but I'm trying to understand something. If the 1.5MHz signal is found to be internally generated by the flat amp, is this considered oscillation?
This amp has RF chokes, which I have not seen on many amps, so depending on the corner frequency of those (probably pretty high, since there aren't many turns) wouldn't they help attenuate external RF?
Thanks.
Oh yes, I think so.
They might but that's not what they are there for AFAIK - something to do with on-load power amp stability?
rabbit
Well-Known Member
ricohman
Adventure Rider
I had good success with cotton swabs dipped in laquer thinner (very little) and dental pics.
But it can be a real pain.......
fuelie
New Member
Warren, I like the AU-9900 & AU-11000 too, they definitely have beautiful cosmetics and wonderful sound. I still have one AU-20000 that needs a re-build and is also missing one board - not sure if I will ever find it, I may have to make it.
When you worked repairs on those AU-X1 - did you perform or consider doing any modifications to reduce the possible internal oscillation issues? or is that only a concern on early vs late production date?
When you worked repairs on those AU-X1 - did you perform or consider doing any modifications to reduce the possible internal oscillation issues? or is that only a concern on early vs late production date?
I have not seen the schematic for the flat amp in the X1 but have have played with the one in the 919 extensively. On the 919 there are a number of the "black flag" caps in various spots. First you could try replacing these with similar value but new Mica caps. Also many of these are low pF values in base to collector spots - if the flat amp is oscillating replace the compensation caps first and see what happens. If it still oscillates you can try increasing the value of some of these guys in the critical spots to reduce the bandwidth slightly that may well fix it. If you are listenting to it with the Flat amp engaged and it is oscillating I suspect it could sound a lot better.
fuelie
New Member
I just started to compare the Flat amp tonight in the X1, and it is very similar to the 919 with a couple differences. The Front Diff amp appears to have two current sources, one below and above, maybe this is for better stability. The finals and drivers are different devices, maybe having slightly higher current capability, but most interesting is that there is only one compensation cap used at each driver. I don't see any compensation for either final device like in the 919.
2000zx12r, have you had 919 oscillation issues?
I will put the X1 back on the bench and check all the caps in the flat amp and if they are OK I will try a small compensation on the finals. We'll see what happens!
2000zx12r, have you had 919 oscillation issues?
I will put the X1 back on the bench and check all the caps in the flat amp and if they are OK I will try a small compensation on the finals. We'll see what happens!
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dr*audio
Fish fingers and custard!
If you search here for AU-X1, there is a thread here where I list all the mods I did on the AU-X1 for stability.
Kale
Super Member
For that job I am using lacquer thinner, small brush and small slotted screwdriver, that glue I get softer by lacquer thinner, by small slotted screwdriver I remove glue, but you should apply two or three times lacquer thinner over glue that you can remove it...
+1... it gets softer each time - 3 times is all you should need.