661 Power Supply Repair

[sintech]

Nice project for the weekend!

Smaller 20 amp  661, serial 31.. it doesn’t get older than this!  AC on/off switch is at the back.

Melted AC secondaries + shorted bridge:




Awesome adapter kit from the wonderful people Recycled Audio:



Power Transistor bank changed on the bad rail for good measure.






Output Cap re-cap








The 10R resistors are fine.. but the sleeves crumble in your hands!



Replacement Rectifiers



New AC secondaries to replace the melted wiring:


Old rectifiers with crumbling sleeving






New AC secondary wiring in place:


Rails back and voltages look great:




New Front AC switch wiring





I now need to fit fuses, what about these inline blade type?

[kilmister]

Love the idea of inline fuses! They are so much easier to buy than those RS ones which are also relatively expensives.

-Paavo

[Matt Sartori]

Is looking really good!
how did you match the power transistors?

Mattia.

[sintech]

Is looking really good!
how did you match the power transistors?

Mattia.

The transistors came from an SSL PSU spares kit.. hehehe! so I doubt they're matched

What matching process do you use Mattia?

[kilmister]

Transistors don't have to be matched, that's why there are those 10R/5W resistors.

-Paavo

[PMcC]

Keeping the dream alive...power to you!

[Matt Sartori]

I think they need to be matched under stress...

Mattia.

[Audioplatinum Service]

Nice work Andy...

SSL 661 was made very robust,worth to change big caps with new ones..   

I must recapp same psu for our console,now works..so far so good..   

[michaeldtech]

Great work!
I would give those grotty adjustment pots some cleaning/conditioning love as well.  Take pictures of the pot positions, spray with F5, exercise, and return to position.  A word about spraying things- I like to prep the component area to be sprayed like a patient for an operation.  I surround the area with paper towels to avoid getting the spray everywhere.  I use a SC hypo if I can to apply just what is necessary to get into those pots.
 
A full recondition would include replacing them.  You don't want false current trips or fluctuating voltages.  I measure the values of all pots, replace with 10 turn, and adjust to measured values.
Mike
PS: re the fuses/holders I would want the holder to be rated for twice the fuse value.  Since they are automotive they should be robust as they are made for 12 VDC at high currents, but check the rating before using.

[sintech]

Hey Mike, brilliant tips, thank you.

This project is a complete learning curve for me, and have loved every minute of it so far!

Fuse wise, it's this kind of thing or the really expensive Bussmann type.

[xmax]

Nice work! I used the automotive fuse holder during some prototyping
Of my switcher, I thought even the 30 amp type ran very warm, I imagine
Because at around 19 volts the wattage is higher but for 40ch or less they
Should work fine. The power supplies get less fun to work on after about 20 lol!
Happy holidays!
 

[waltzingbear]

very nice work, if you want to maintain the original look of the replacement caps, the BC caps are available from Digikkey, Mouser or Farnell.

While the automotive fuse are a great tool for troubleshooting, they are mostly too fast for long term usage. Read up on fuse types and i think you'll see why the cartridge fuses used by SSL in their upgraded version are a better choice, yes they do cost more.

If you want to match the transistors go ahead to guild the lily, but its not needed. The swamping resistors are there for that purpose. I'm not sure it would make any measurable difference. (or audible)

Cheers and happy solstice.
Alan

[oyanliz]

Hi,

I am interested on this thread, but the photos are not available, because photobucket.com stopped showing the photos.

Does someone have the photos of the post saved? Andy, do you still have the photos?

Thanks in advance.

Regards.

Oihan