AU-999 Restoration & Modification

leray1

Active Member
This is my first undertaking of this magnitude, but after reading all the threads and claims of how easy it can be done, I decided to do it. Stereofun has been a big help so far, but he's probably tired of all my PMs:biggrin:

I ordered all the parts based on stereofun's list and started working on it today.

So far I have the subsonic filters removed. Before moving on, I need help.

Is there an order that all of this should be done to make it easier?

I'm gonna start with the main filter capacitors. How do you get them out of the clamps? Should I remove the driver boards and heatsinks, first? Do the driver boards just plug into the blue strip?

I'm starting to get that "I'm in over my head feeling" in my gut. Can you ease my worries?
 
I removed the driver boards and heatsinks that are around the filter caps to be able to get to the cinch screws.
 

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I removed the driver boards and heatsinks that are around the filter caps to be able to get to the cinch screws.
Just undo the whole bracket from the chassis and pull the cap out with the bracket on it, then remove the bracket, take note of the polarity when you cut the wires off.
 
Just undo the whole bracket from the chassis and pull the cap out with the bracket on it, then remove the bracket, take note of the polarity when you cut the wires off.

Yeh, I was having trouble loosening the bracket mounting screws... felt like I was going to strip the heads, but I got them. The new caps are in place.

I replaced the caps on the driver boards and then called it a day. It's slow going for this newbie, but it's going.
 
Take a few pics of every section that you work on.. this becomes invaluable when you may find a straywire or a component that you needed to desolder and cant remember where it came from.
Download the service manual..check the caps polarity ON the board first,, sometimes the printing on the board/service manual is wrong so I always check this first and take notes of any errors.
Definitely build yourself a dim bulb tester!
We'll be here to guide so try not to make rushed mistakes (hey it happens).. but most of all have fun ;)
 
Finished the filter caps today but this will be on hold until I get the rest of my parts. Should be tomorrow
 

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Practice will differ from person to person but......

I would carefully examine the existing mica washers for any creases or parts broken off. If they appear OK, you can re-use them. Also ensure that you place a couple of dabs of new non-conductive silicone grease under the outputs when reinstating them.
 
Practice will differ from person to person but......

I would carefully examine the existing mica washers for any creases or parts broken off. If they appear OK, you can re-use them. Also ensure that you place a couple of dabs of new non-conductive silicone grease under the outputs when reinstating them.

What you see on the heat sink is all there is. It's not mica but looks like clear film or tape.
 
Just do the check we talked about - where you set your meter to continuity check - then probe outputs metal casing vs heat sink - no beep should be heard. Its such a fast insurance policy to make sure the Mica is doing its job
 
Thanks for starting the thread, I'm going to do my 999 someday. I like the idea of powering up on a dim bulb tester after completing a section, so if a mistake is made it can be isolated to just the work completed. Have fun.
 
This project was on hold for over a week due to another project. A good one though, I put a new floor in my music room. But I'm back at it and I finished the two driver boards after work today.

It went well. I did lift and break half a pad for the same transistor on both boards. The way they bent the leads all the way to the board makes desoldering difficult.

I used isopropanol to clean up excess flux but it kind of dulled the surface of the board. Is this normal?

My next step is to change the rectifier. The replacement (see pic) is different. Do any of you have a pic of how you installed yours?
 

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Coming along nicely now, cant say I've seen the isoprop do that before tho.

I like to triple check that I've put the correct transistor in its location and got the leading correct too. Yours looks tidy, and yeah, sometimes desoldering is really frustrating.

I'd upgrade your trimpots too, sooner the better. I used Bourns multi turn 3296P, the P is important as it suits this vertical board.

2019-01-24 12.52.50.png
 
Coming along nicely now, cant say I've seen the isoprop do that before tho.

I like to triple check that I've put the correct transistor in its location and got the leading correct too. Yours looks tidy, and yeah, sometimes desoldering is really frustrating.

I'd upgrade your trimpots too, sooner the better. I used Bourns multi turn 3296P, the P is important as it suits this vertical board.

View attachment 1396261
Yeh, there is corrosion on the pots. I was planning on trying to dial them in first but will probably just change them.

The isoppropanol is 100%, lab grade. Maybe that's why?
 
Yeah probably why. Ive got 98% I think but I use sparingly. now I only bother to clean around where I've worked using a q tip, think the flux is what gives our gear the vintage aroma when everything is warmed up haha
 
I replaced the outputs and the rectifier tonight. It went well but I should have put the filter caps in after replacing the outputs and reinstalling the heatsinks. The caps got in the way and made installing the outputs more difficult than it should have been.

I drilled a hole in the chassis to mount the new rectifier with a nut and bolt. Looks nice and tidy (thanks stereofun).

I will reinstall the driver boards and build a DBT tomorrow to check my work thus far.
 

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