Sansui EIGHT

Kale

Super Member
I decided to show you one restoration job on the Sansui Eight because there are no so many pictures on the internet about that…
So... first one look at the bottom side of receiver after cleaning…

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You see, so many wires, lot of cables…. And what is very interesting, the receiver has in total 12 (!) fuses!!
If you wish to remove that power supply board, you should remove (desolder) all those wires

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… and here it is, already restored…

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One interesting thing about tuner section… complete tuner section is on the one sub chassis, with two connectors (one multi-pin connector and one coax antenna connector) so you can remove complete tuner section without so much problems…

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the only difficult thing could be a dial mechanism, but Sansui engineers made solutions for that: parking pins for dialing pulleys

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That Head Bord is easey-to-remove type, because it is one of three boards with connectors (other two are Driver Boards).

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BTW, Head Bord is just phono preamp board, because it works with very low voltages signals, i decided to remove all those small signal transistors with new ones, especially what old transistor had very corroded legs…
And restored….

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Other side…

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And now hard side of restoration Sansui Eight… cleaning switches and selectors and potentiometers… to do that, you should first remove the front subchassis of receiver…

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But… there is one problem…

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We should to remove that tunning string, but that is very sensitive job, because this receiver has two tuning capacitors (one for AM, and one for FM, something like in TU-X1 for example),

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… and two pieces of dialing strings…

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The first pulley (AM capacitor) is for both dialing strings, second pulley (FM) is for capacitors dialing string only (red color)

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Very sensitive job to do on the right way…
 
The next step is to remove all wires from dial scale lighting board…

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… you should remove all wires from tuner instruments…

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And then finally we can remove complete front side of receiver sub chassis…

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… but we have something more to do to get switches boards out of receiver, we should remove all wires soldered directly to the boards…

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On the next picture, the right board finally removed…

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And, here it is…

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The one detail is something what I wish to say you… Sansui Eight is from beginning of 1970… and at that time, Sansui made two side (!) electronic printed circuit boards with metalized holes!!
But, again, after all those years, you should repair pass through connections points…

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Better view …

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And finally removed from the board…

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Now, I can clean all switches contacts…

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… how it was…

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… and how it is now…

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Balance and volume pot after cleaning (sorry I forgot to take a photo of cleaning process)…

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Nice work!

Looks like you ran into a lot of the same issues I had doing a restoration on my QRX 9001. Pinning the pass through connections on the double sided board can be a PITA, but well worth the effort. State of the art for the time, but they're all cold joints and intermittent as the decades rolled on. If they haven't failed yet ... they will. I'd make that standard practice any time you see one.

One tip on the dial strings ... leave them on the pulleys if at all possible. The green painter's tape works nice as it doesn't leave any residue. You'll notice slack on the lines coming off the pulley to the dial ... the front panel's already off at this point. Goes without saying, you should also make dang sure you have the correct diagrams for string routing on your specific machine and have taken copious notes. There's usually a bunch of ways to string it up, and only one that works!

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- Worth mentioning ... the slide switches can fool some folk. All the electronics are in the back of the switch, so just spritzing D5 in the panel slots ain't gonna cut it. You DO need to dig in, and dig deep, to do it right. Also a good idea to put some phenolic grease on the spring section so they work smooth and easy when done.

- And ya, fairly common to see the tuner sections on these beasts on a tidy little sub-chassis. Kudos to the engineers, as it allows a whole lot better access to what we need to get to on a standard refurb. One caution for folk ... I wouldn't mess with the tuner section unless you know there's a problem. Very sensitive to alignment, and in many cases, components are hand picked to "tune" the circuits, so off the shelf caps and such can cause problems. Re-aligning one of these bad boys properly requires specialized equipment, or at least a boatload of incredible luck - both of which can be in short supply in the average home shop. I'd also be REAL careful cleaning the gang sections, as some chemicals can destroy them - even canned air! A dry rub with soft brushes (pipe cleaners if they'll fit easily) and blowing off the vanes with a mini compressor will usually do the job nicely,

PS ... I see you're another fan of the Elna Silmic II caps ... folk should be aware those can take some time to break in, so it may take them around 50 hours or so for the magic to happen ... it's worth the wait though. :thumbsup:
 
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That looks to me like a jump off a cliff, crazymaking, restore for genius' only. Keeping track of all that wiring would send me to the funny farm. Nice work, by the way.
 
Jump in the deep end ... have fun!

That's where attention to detail comes in. I'll usually snap a bunch of closeups and tag those as needed for reference. Also, good to mark the connectors prior to disassembly.

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Actual point to point wiring gets a bit more complicated. Those get temporarily bundled and marked for a specific board, with matching pics. Be especially careful for multiple wires of the same color. Ground is ground, right?
(WRONG!!)
 
There's usually a bunch of ways to string it up, and only one that works!
I know that, can you believe, I spent almost a one day to do that on the right way, seven times I finished, and it wasnt work as it should, so again (and again) I started from beginning, again and again, seven times!



PS ... I see you're another fan of the Elna Silmic II caps ... folk should be aware those can take some time to break in, so it may take them around 50 hours or so for the magic to happen ... it's worth the wait though. :thumbsup:
Elna Silmic is my choice number one, and I know they need some time to get a full characteristic... I am also using Cerafine and Nichicon KZ, FG and ES, but gain Silmic is my number one choice
 
Nice job, Kale! I just repaired one of these. I want to mention that the protection circuit on this model is a crowbar circuit that basically shorts the output to ground when any DC is detected! On the one I worked on, the customer complained it was lacking in bass, which I confirmed by measurements. When I looked at the coupling cap values in the schematic I saw why. It could never meet it's specs! They intentionally put lower value caps to roll off the low end. I found that if you increase the values of the coupling caps it will meet it's specs, but because of the design of the power amp, it will then have large DC swings on turn on and turn off, and the crowbar circuit detects this and shorts the outputs to ground, blowing the fuses. The solution was to replace the crowbar circuit with a speaker relay circuit that shuts the relay off when DC is detected.
 
Nice job, Kale! I just repaired one of these. I want to mention that the protection circuit on this model is a crowbar circuit that basically shorts the output to ground when any DC is detected! On the one I worked on, the customer complained it was lacking in bass, which I confirmed by measurements. When I looked at the coupling cap values in the schematic I saw why. It could never meet it's specs! They intentionally put lower value caps to roll off the low end. I found that if you increase the values of the coupling caps it will meet it's specs, but because of the design of the power amp, it will then have large DC swings on turn on and turn off, and the crowbar circuit detects this and shorts the outputs to ground, blowing the fuses. The solution was to replace the crowbar circuit with a speaker relay circuit that shuts the relay off when DC is detected.


I suppose the one you repaired had no output relay. Some of the later eights had though, like mine.
 
Nice job, Kale! I just repaired one of these. I want to mention that the protection circuit on this model is a crowbar circuit that basically shorts the output to ground when any DC is detected! On the one I worked on, the customer complained it was lacking in bass, which I confirmed by measurements. When I looked at the coupling cap values in the schematic I saw why. It could never meet it's specs! They intentionally put lower value caps to roll off the low end. I found that if you increase the values of the coupling caps it will meet it's specs, but because of the design of the power amp, it will then have large DC swings on turn on and turn off, and the crowbar circuit detects this and shorts the outputs to ground, blowing the fuses. The solution was to replace the crowbar circuit with a speaker relay circuit that shuts the relay off when DC is detected.
Thanks Doc!
About protection circuit, my unit doesnt has F-1401A board, so there are no any protection relay in this unit, but I have checked at speakers output terminal, just small level drop beginning below 40Hz signal... so, here it seems to me is OK....
 
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And now about power supply capacitors…
First I have to adopt that new Nichicon Gold Tune 1000uF capacitor to old capacitor clamp….

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After that… the main power capacitors…

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As you can see, they are with diameter 64mm but only 70mm tall!
I decided to find a new ones which must have:
- The same diameter
- up to 83 mm height
- The same or little more capacitance
- they should be brand name
- and finally not so important, but it would be good if they are black

After so much searching on the internet, I have found that:

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On the right side is old main capacitor, the left side is a new… EPCOS Sikorel 10000uF 100V, fantastic capacitor, expensive but really HighQ!
The old capacitors had a solder lug contacts, but those new are with Screw Terminal… and here it is the result:

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That slotted screw is because it had smaller height than original philips screws, and why is that important, you will see on the next picture:

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You see that fuse block, it is located over that capacitor contact with slotted srew, and I don’t want some dangerous contact (or very small distance) with some fuse…

And the final result is:

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I have some troubles during working on this receiver, the first was some of small signal transistors on the right channel were out of specifications, and because of that the sound on that channel was distorted but after replacing input transistors with new ones, everything was OK…


The next problem was very specific… because power supply wires connected to the main capacitors are solid core wires, and during crimping those wires to the O ring terminals, one + supply wire was broken, but insolation of that wire still keeping wire fixed to the O-ring terminal, but without electrical contact, you might know what I checked all before I check this….
 
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