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Green Wagon

Sansui A-60 Renovation (And repair)

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Well I recon this is probably as good a place to stick this, so here goes :D

 

I was given a Sansui A-60 to work on.

My instructions were, It's been under the house for a year, so it needs a clean, probably a recap, and the volume control might be a bit scratchy.

 

Stage one, Disassemble, clean, replace the obvious, test unit.

Stage two, Repair any faults.

Stage three, Retest, final clean of all internals, reset bias etc as needed, reassemble.

Stage four, Clean face plate knobs panels etc, wire into a system for a long term real world test.

 

Sorry I don't have pics of it when I got it.

I don't normally advertise what I do for others.

Lets just say, is was filthy. Typical finger oils and also full of dead cockies and arachnid webs.....

 

After stripping and cleaning I replaced the speaker posts (as requested due to the originals being broken), did a full recap and replaced the power cord.

It was obvious someone had been here previously. a few caps had been replaced, a crack in the main circuit board repaired, and one channel had been repaired.

On first fire up it was obvious one channel was fubar (45v dc output) yeah that'll ruin your day if you had speakers connected. I didn't. Always ALWAYS bench test with nothing connected first..

Very obvious the output transistors had gone short circuit, so went through it with a mmeter to see what else was gone.

Lots as it turned out......

 

Doesn't help that there are two versions of this board, with minor differences (undocumented) and I won't mention the production errors in part designations between the board, schematic, and overlays.........

Ended up replacing;

~40 capacitors (every single electrolytic)

all four output transistors and their insulators (to match left and right, also updated to higher spec), 

two bias transistors,

two (four in reality) bias resistors,

two bias trimpots,

8 resistors,

power cord (for safety)

and the speaker binding posts.

 

In with all that is a full resolder on the entire unit, go over the board repair to make sure it stays fixed, clean the flux and dirt of all boards.

I'm sure theres more but I can't think of it at present.

Took three goes to get the front panel and knobs clean.

 

This repair ended up consuming well over two weeks (on and off) of time, waiting for parts, trying to work out why the diagrams etc didn't line up.

 

End result, it looks great, and it sounds, well I think its a little bright, but over all not to bad..

 

Here, Have some pics :)

 

Oh yes, Notice anything strange about the speaker posts ?

No wonder it's been blown up two or more times........

 

post-106429-0-95272700-1421986560_thumb. post-106429-0-18998600-1421986570_thumb. post-106429-0-46019800-1421986581_thumb.

post-106429-0-76289700-1421986592_thumb. post-106429-0-82718600-1421986601_thumb. post-106429-0-08205300-1421986613_thumb.

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Nice. Am contemplating a filthy big Sansui-JBL shed system.

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Great work as usual.

@@Green Wagon did a fantastic job recapping a phono stage and preamp of mine, highly recommended.

Edited by Telecine

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The very FIRST thing to do with that model Sanswer er, Sansui and other similar models in the range is to dump that silly steel plate to compress the output devices to the heat sink. The output devices should be bolted or screwed to the heat sink, to ensure proper thermal contact. Poor thermal contact is likely to be the most likely reason for failure in the first place. Additionally and most importantly, I approve of the fitment of higher current output devices in this model. In common with the budget Sansuis of the time, the A-60 uses no VI limiting systems. As a consequence, even the very briefest overload (touching speaker wires for a few milliseconds for instance) will destroy the output stage again. Fuses will not save the silicon. 

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Absolute devotion to the cause Greenwagon. Dedication inextremis and you'll be giving the Grand Poobah and his scion a run for office at this rate.

 

I hope you charged accordingly and didn't lose out on the deal too much seeing as its an A-60.

 

 

*The Green bloke has recently done up/repaired an amp for me. Thoroughness is his first nature and skill his second. Approach with confidence!

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...Dedication inextremis and you'll be giving the Grand Poobah and his scion a run for office at this rate...

 

My word. High praise indeed :)

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To all and sundry, I bow to your words of praise.

It is somewhat my ocd to do my best to make things right.

I do not always succeed, But I try my best.

If you want a horror story of my determination, I'll tell you about the ML summit modules I'm working on.

 

Doing things like this, if you charged a 'normal' rate, the owner would just throw it in the bin.

I did charge more than I would have liked, but this one has sentimental value beyond dollars for its owner.

It covered parts and some of my time. I don't really know exactly how many hours I put into it.

The underlying cause is enough for me to go the extra 1.6 kilometers.

 

Zaph - Yup, I found a forum post (not an english one) where one guy has modified his 60 to reliably output ~100+ wrms.

He outlined all the steps he took, and one was modifying the heatsink.

The previous repairer had already done that. He cut the 'spring' plate and tapped holes to screw the outputs down properly.

You can just make that out in pic 4.

The spring plate is still there, but its sole purpose is to hold the bias transistors in place (Tr09/10 or is that Tr19/20 <- that depends on whether you trust the board, the overlay, or the schematic..........)

 

I did also converse with Skippy on one issue, so thanks should also be directed to him.

 

Luc's probably biased (sorry, bad pun) because I fixed his Burson ha160.

 

In short, I am also a consumer, and like to think I will be treated the same way as I treat others.

Edited by Green Wagon

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Hi Nigel,

Great work on the restoration, and well done on getting rid of those crappy twist lock speaker terminals!

I have an A60 somewhere in the garage awaiting repair, I'll have to find it and get into it.

Cheers

John

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Hey John.

 

Thank you for the kind words.

On the outside the terminals looked fine, but inside, they'd started falling apart with bits of plastic and metal floating around....

 

To be honest, the A-60 is one of the easiest amps I've worked on.

Only real issue I found is to be careful with the main board with the weight of that heatsink swinging around.

Oh, and that brace that runs front to back underneath. Minor nuisance. ;)

 

I learnt very early on that all manufacturers can make good and bad products.

Be it ford holden volvo sony krell akai awa, even rolls royce had a few things that should be killed with fire.

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Zaph - Yup, I found a forum post (not an english one) where one guy has modified his 60 to reliably output ~100+ wrms.

He outlined all the steps he took, and one was modifying the heatsink.

The previous repairer had already done that. He cut the 'spring' plate and tapped holes to screw the outputs down properly.

You can just make that out in pic 4.

The spring plate is still there, but its sole purpose is to hold the bias transistors in place (Tr09/10 or is that Tr19/20 <- that depends on whether you trust the board, the overlay, or the schematic..........)

Good stuff. I couldn't see that the output device attachment had already been done. That should forestall future issues, except shorted speaker cables. That series of Sansui is woefully inadequately protected against stupidity.

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Not to mention the idiotic break from tradition in the speaker connector layout.

And the wonderful non interlocked speaker selector switches.

 

Heck I reckon pushing it hardish into a modern speaker with their low impedance dips would be like playing hopscotch on a highway.......

 

Refer att pic.

Read it, read it twice, think about what its telling you.

How many people have 16 ohm speakers ?

How many will connect left and right in the correct locations ?

 

I honestly believe it's only a matter of time before I see it back with blown outputs again.

 

post-106429-0-90134300-1422433768_thumb.

 

 

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Hi Green Wagon

 

I refer to your post of Jan 23 2015, Sansui A-60 Renovation (and repair) and thank you for your helpful posting.

 

As I am in the process of doing similar, I wanted to ask if you happened to have a Parts List of the Passive Components (in particular - the values)?  I have managed to download a very poor 3 page circuit schematic which does not help me that much.

 

Of immediate issue (for ordering purposes) is the value of the 2 Trim Pots? Also you made reference to all four output transistors and their insulators (to match left and right, also updated to higher spec), can you advise that standard and upgraded spec at all?

 

Sorry to bother you with this but I have been scouring the net for days trying to gather info.

 

Any assistance/data you could provide would be greatly appreciated.

 

Many thanks in advance

Glenn

Gold Coast

 

 

 

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