Sansui AU-777A xmas break rebuild

Thanks for the kind comments guys. I've been listening for a couple of days now and I don't really want to go into subjective observations too much but let's just that the sansui this reminds me of the most is the 555A (that's a good thing) but is in the running for becoming my favourite.

Reading back over the posts, I can see that the missing discussion is on the particular component choices (like why I chose a type/spec of capacitor over another).

Something I have been thinking about after my last few rebuilds is how nice it would be to have a clear lid for a sansui. As you can see from my avatar I've made clear lids before. Maybe time for me to start bending some perspex...
 
plexiglass/perspex clear bonnet/cover for sansui au-777 amplifier

I bought some thin plexiglass and some glue. The glue is basically a solvent for the acrylic. The particular product I used was Weld-on 3. It is applied via a tiny needle applicator and what you do is hold the two pieces in place and then put some solvent at the edge of the join and it get sucked in my capillary/surface-tension effect and makes a neat join.

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So the this is a first attempt with this glue for me and a trail run. I will make a cleaner version later after I learn how to work with this stuff.

Also the plexiglass was a bit thin and you have to be really careful to keep your drill speed down as the bit bite through the backside otherwise you get cracks, which I did.

The AU-777A has some airholes above the driver boards so I made an array of holes in the plexiglass. I don't have a drill press at the moment... this took some physical effort.
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Here is a pic with it on the amp. I measured the side chasis screw holes from a 777 I had in the workshop and turned out the measurements were a bit different to my 777A so I could only get two screws in. But hey, I will be remaking a nice version soon anyway.
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The 777A need some feet now, which I don't have handy. I might either add some feet, or on the next version make the sides of the plexiglass longer so the amp can stand up off the ground using the side panels as stands.

Here is a closer pic of what happens when you don't drill carefully.
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You can see the solvent makes neat joins if you use the needle applicator carefully. This side is reasonably tidy (although I'm sure I can do better next time) but the other side i did first and was a bit messier.
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And one last pic. Next time I will try thicker plexiglass which I think will be easier to drill without cracking. Also I might jigsaw or route some lines, instead of making so many individual holes (but I think the hole array look great). Also, I will tweak the dimensions a bit. And, I will not drill the side/chassis holes until i get the cover onto the amp and see how I want it to see, and then mark the positions of the holes for drilling. I might also try polycarb instead of plexiglass.
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A work in progress....but I do like it..
Perhaps a few internal soft glow lights to give the appearance of a tube amp...
 
Try using a wood drill bit when drilling through perspex. Also place a piece of hardwood on the far side making sure each hole you drill goes into the wood and not another hole you've previously drilled. I prefer an electric drill. A router does a fine job as well. Maybe You can find someone with a CNC router. I'd suggest 4mm as the minimum thickness.
 
Interesting. Yes consider some LEDs on strategic places., so that at might you can faintly see the interior.

Regarding an earthed power cord I was advised against it by Echowar. Instead he recommended orienting the polarized plug so that you have the least potential from the amps 'floating' ground to the receptacle's earth.
 
Orientating your plug? So you know which is your hot side? I always wondered how you did that in the US. Can you tell me how you do that?
If you haven't got earth in the mains: well there would be no sense installing the tri core cable option. Still an upgrade can still be as simple as: double insulated 10 amp flex. The downside will be you'll lose the original strain relief. Also have you upgraded your X2?
When was single insulated main power leads outlawed? Sometimes in the early 70's?
 
Furthermore I see you put a dremel over your base. Did you know this is zinc plated?- that is factory corrosion protection. By removing it you have speed up the corrosion process especialy when future dust settles on the surface- not to mention you've lost the patina. I rub with a light oil. That moves white rust as well as moisturizes the metal. But since youre in the hot-rod scene, have you thought about chrome, powder-coating or 2pac auto paint?
 
Beautiful work. For your plexiglass, try 1/4 inch cell cast. Most companies that work with plex will have a CNC machine that will get that hole pattern perfect, and smooth. You can do it though with a plexiglass bit and reasonable care. Google up aquarium filter manfufacturers websites for tips on working with acrylic. Your top perforated piece is more commonly known as a drip plate to them, and there are several of them that would be more than happy to spin one out for you. Weld on 3 is perfect for the 1/4 inch stuff. I'm impresssed with the whole build, showing it off in plex is super cool too.
No affiliation, but I've had lots of work done by these guys... http://gordonsplastics.com/ Top notch.
 
Furthermore I see you put a dremel over your base. Did you know this is zinc plated?- that is factory corrosion protection. By removing it you have speed up the corrosion process especialy when future dust settles on the surface- not to mention you've lost the patina. I rub with a light oil. That moves white rust as well as moisturizes the metal. But since youre in the hot-rod scene, have you thought about chrome, powder-coating or 2pac auto paint?

Now chrome would be loverly...:yes:
The question would be what colour...:scratch2:
 
Try using a wood drill bit when drilling through perspex. Also place a piece of hardwood on the far side making sure each hole you drill goes into the wood and not another hole you've previously drilled. I prefer an electric drill. A router does a fine job as well. Maybe You can find someone with a CNC router. I'd suggest 4mm as the minimum thickness.

thanks for the tip about a piece of hardwood. That makes a lot of sense.
 
Furthermore I see you put a dremel over your base. Did you know this is zinc plated?- that is factory corrosion protection. By removing it you have speed up the corrosion process especialy when future dust settles on the surface- not to mention you've lost the patina. I rub with a light oil. That moves white rust as well as moisturizes the metal. But since youre in the hot-rod scene, have you thought about chrome, powder-coating or 2pac auto paint?

Hi, vinegar and scourer or wire brush are the recommended method of removing white rust. Dremel just speeds it up - the aim is not to remove the plating but to remove the rust in the underlying metal that has already broken through the layer and is not contained by the oxide layer. If there is just patina I, like you, prefer to rub with some oil. When you have deeper spots (not just white rust/zinc-hydroxide) that have already gone through the sacrificial coating it's really best to remove the lot. But at that stage it should really be retreated with a new zinc coating. Maybe it's time to make an electroplating setup for a fresh sacrificial layer can anyone report on luck with zinc spray?
 
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Beautiful work. For your plexiglass, try 1/4 inch cell cast. Most companies that work with plex will have a CNC machine that will get that hole pattern perfect, and smooth. You can do it though with a plexiglass bit and reasonable care. Google up aquarium filter manfufacturers websites for tips on working with acrylic. Your top perforated piece is more commonly known as a drip plate to them, and there are several of them that would be more than happy to spin one out for you. Weld on 3 is perfect for the 1/4 inch stuff. I'm impresssed with the whole build, showing it off in plex is super cool too.
No affiliation, but I've had lots of work done by these guys... http://gordonsplastics.com/ Top notch.

Thanks for the info about the aquarium guys and Gordon. About the CNC, i've been thinking for a while to make a DIY CNC machine but maybe using someone like Gordon is a smarter idea :)
 
I'm sure my next attempt on making the clear lids myself will work out nicer that the previous one, but I started to get curious about how nice it will be if I pay a pro to do it.

I dealt with Chuck at Gordonplastics (no affiliation) which was mentioned by Beanoil. They don't often deal with guys as far as California, but were happy to help me out (even though my job is obviously unusual and small volume). So I sent a vector format figure of what I wanted which I created in Adobe Illustrator. There was a bit of a wait since they were busy, but after not too long Chuck got back to me with a couple of follow-up questions, which indicated he was really paying attention and was going to do it right.

So here is the result. I left myself the job of making the final side screw holes so I could line it up on the actual amp it will go onto. I will take some proper pics with my nice camera later when i get a chance to drill and mount but here is a sneak peak...

First thing to notice is that Chuck went to town on the packing! A good sign indeed.
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And the result is really nice. It's a simple but tidy butt join (looks like a similar glue/solvent to that which I used was employed) which has been polished.
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sorry for the iPhone pics. will take some better ones when i get around to mounting this up, maybe on the weekend.
 
Here are a couple of pics Chuck/GordonPlastics sent to me just before shipping. a bit clearer than my present iphone pics

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Excellent work! We do not see so many extensive rebuilds on AK with this amount of detail all the time. Since you did a 555a to the same extent have you found the 777a to sound the same but just more power?
 
Excellent work! We do not see so many extensive rebuilds on AK with this amount of detail all the time. Since you did a 555a to the same extent have you found the 777a to sound the same but just more power?

Thanks a lot.

The 777a seems more powerful, beyond what the spec suggest. In terms of sound the 555A and 777A sound quite different. Don't get me wrong, they both sounds like sansui of the era. My 777A is not as 'warm' as my 555A. That said, I played around with various output coupling caps on the 555A and these audibly affected the tone a lot. The 777A seems to have a bit more clarity especially in the bass and mid (but this is part of the 555A 'warmth'). The 777A also seems to give a stronger spatial sense of where things are, but this might just be due to more treble output.

I could give some more definitive comparisons when i get around to some A/B with rebuilt 222, 555, 505/555A, 666, 777/777A,999 soon... (plus maybe some receivers).

What is for sure already though, is that the 777/777A are 505/555A are so far my favourite of the bunch. The 555A/505 just have such a pleasing tone and huge soundstage. The 777A has some similar qualities but other characteristics I really like.

The 222 is my current underdog favourite btw. I just fixed one up (not rebuilt) and it sounds great after I did a couple of subs. Amazing little amp and so tiny. I may do a small write-up on it since i love the sound so much - and from such a tiny little box.
 
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