AU-717 Deadly Glue

[dr*audio]

Yep. We actually tried that at my work. Detuned the circuit more than we liked so we ended up using silicone. Still detunes the circuit but it stays workable longer so you can tweak the coil.

 

[SansuiSamRI]

I think that glue does something resulting in galvanic action. It's like two dissimilar metals coming in contact and a small electric charge takes place even when the gear is turned off. Resistors are epoxy coated and I think the resistor lead and internal metal tab inside the resistor rots away, eating the resistor from the inside out. Same with cap where it was used. I've seen eat away a board etch that was routed under the cap too.

 

[EchoWars]

I don't care what it is, but it has to go... FWIW, I see the corrosion on every one I've ever done. Sometimes it's just starting, sometimes it's pretty advanced, but I've never seen one where the glue wasn't busily chewing its way through the leads of all that it was in contact with.

Next step...remove ALL components that are contaminated. If the glue touches it, it goes.

This one has been stripped of all contaminated parts.

 

[EchoWars]

The Dremel with a wire brush attachment does the lion's share of the work.

 

[EchoWars]

After the brush, there will be places where the glue is still tacky, and the brush just pushes it around. I stop after I have it as clean as I can get it, and then I use Q-Tips dipped in acetone to get the rest.

Acetone is not a carcinogen or fashion-conscious women all over the world would be dropping like flies...it's the main solvent in fingernail polish and polish remover. But I don't recommend breathing any more of it than necessary...

 

[scottrt]

Hey EW...In the thread asking about the AU-919 diodes ss-3 and ss-3r, those are the diodes shown in your pics on this thread labelled D01 and D01...the BIG white rectangular jobies. I dont know if this will help you answer the fellows question. I am assuming they are unobtainium? (the Au 717/517 uses the same as the 919 apparently)

Scott T.

 

[EchoWars]

Welp...I asked WTF and he never replied, so - far be it from me to help those with little interest in helping themselves. FWIW, those diodes are nearly indestructible. If one actually failed, I'd rip 'em out and replace 'em with a bridge.

OK...last step in glue removal repair...repopulate the damn board. This one required:

10 rectifier diodes
2 Zener diodes
9 transistors
12 resistors
and 23 electrolytic capacitors

 

[Kegger]

Hey that looks like a new board! LOL!

I see the dremel deal works pretty nicely, then a little cleanup to get the rest!
Got it!

 

[scottrt]

Hey EW: any chance you'd have 2 spare MJE15032's to sell? The 33's are in stock, but not the 32's. That board looks new indeed!. Even the relay could pass as new....do you open them up and service them, or do they stay nice looking except for the contact pads/surfaces? Did you replace ZD602? I cant find an equivalent for that guy either..

Or better yet...howzabout I send you MY 2663 board and $5 and you send me that one in exchange? ;>)

Scott T

 

[dr*audio]

When I worked at Hughes Aircraft, they gave us training on hazardous substances, and they told us acetone is a carcinogen. Here's a link to the MSDS.
http://www.bu.edu/es/labsafety/ESMSDSs/MSAcetone.html#anchor891201
It says "...investigated as a tumorigen, mutagen, reproductive effector." So maybe it is suspect but not proven. It's nasty stuff anyway.

 

[stabist]

Hi,

as I'm in a search of a AU517/717/719 - is this glue stuff used only at this regulator/protection board or at all boards??

Because now I'm in a crossroad:
- to buy (still) operating amp and make a recaping job + glue cleaning (but the amp itself costs 250-350Eur with shipping costs) and those extra job will add another 100-150Eur or
- buy one with blown out outputs etc (for 50-100Eur with ship.costs) and renew it ...
As I understand - in both cases it's recomended to clean this glue, to recap the amp, etc ...

Right now I'm quite interested in one "dead" AU-517 - the seller says it powers on but after protection mode time - no sound - so I guess the trannies and the mechanics are good - and that could be a nice amp to get rebuild into life again ...
If I'll buy it - I'll need to do total recaping and transistor replacement, cleaning the glue away and that should be it ...
Are there any transistors that are very hard to get for AU-517??
What is the PSU voltage? (I guess PSU caps are 15.000uF/63V as in 717 or not?)

Thanks for any advices and opinions

 

[EchoWars]

Hey EW: any chance you'd have 2 spare MJE15032's to sell? The 33's are in stock, but not the 32's.

Digikey will be stocking more, but you'll have to wait. I only have four of them, and I'm betting that I'll need more before they replenish their stock. Are you sure your TO-220's are bad? It's nearly always the small signal transistors and the Zener...

That board looks new indeed!. Even the relay could pass as new....do you open them up and service them, or do they stay nice looking except for the contact pads/surfaces?

Yep...I open them up, and use a tiny folded strip of #1500 sandpaper on the contacts. I also use soap and water on the clear cover.

Did you replace ZD602? I cant find an equivalent for that guy either..

No need. ZD602 is a 6.2V 500mW Zener.

Or better yet...howzabout I send you MY 2663 board and $5 and you send me that one in exchange? ;>)

Scott T

God help you to get that board completely out. What a mess...

Warren...I've had upwards of 20 HAZMAT courses...I could probably teach the bloody things (but I have to admit, acetone isn't a common chemical used in semiconductor manufacturing, so I don't believe it was ever discussed). Acetone, even if it was just suspect, could not be used in consumer products, and certainly not cosmetics (and you know the Great State of California is on this chit like white on rice). Perhaps the verdict is not in, but if they have to spend 10 years giving mice and rats a headache with the stuff to induce some tumor or blood disorder, then I'm not gonna sweat having to deal with the stuff a couple times a week. I'd have to say that its volatility is much more of an immediate hazard than any long term medical issues it may induce. Common sense still says to avoid skin contact as best you can, and work with good ventilation.

http://en.wikipedia.org/wiki/Acetone

 

[scottrt]

Yeah, removeing that ps board completely would be alot of work. I presume you do just enough to slip it out the bottom side of the chassis?

Regarding the TO-220's: Mine are probably fine, remember I'm the guy with the start-up 120 hz buzz till warmed up. I guess its most likely just one of the electrolytics causing the issue. But since I will be 'going in' I thought freshening those TO's wouldn't hurt. But if it wont actually help improve anything, and they aren't age sensitive, I will just leave them alone if you advise me to.

If the corrosion has gotten to a few diodes and a few of the smaller transistors, would it be wise to replace all the similar ones on each side of the board just to keep things symetrical? I also see you replaced ALL the small resistors with new 1/4 watt 1%ers. I will assume thats a wise move...wether or not they are glue contaminated. Right?

Scott T.

 

[Redcatcher199th]

Looks nice EW ..........ok whos unit was that ?? maybe a hint lol

Welp...I asked WTF and he never replied, so - far be it from me to help those with little interest in helping themselves. FWIW, those diodes are nearly indestructible. If one actually failed, I'd rip 'em out and replace 'em with a bridge.

OK...last step in glue removal repair...repopulate the damn board. This one required:

10 rectifier diodes
2 Zener diodes
9 transistors
12 resistors
and 23 electrolytic capacitors

 

[EchoWars]

Yeah, removeing that ps board completely would be alot of work. I presume you do just enough to slip it out the bottom side of the chassis?

Six wires have to be desoldered...a black, red, and blue on one side of the relay, and a white, grey, and yellow on the other. A bunch of wires have to be moved around a bit, and a couple of wires that go to the driver boards have to be unplugged and pulled back through the maze...and a bunch of wire bundle ties get cut...then the board can be slipped out through the bottom.

Regarding the TO-220's: Mine are probably fine, remember I'm the guy with the start-up 120 hz buzz till warmed up. I guess its most likely just one of the electrolytics causing the issue. But since I will be 'going in' I thought freshening those TO's wouldn't hurt. But if it wont actually help improve anything, and they aren't age sensitive, I will just leave them alone if you advise me to.

You can get to these transistors with the board mounted in place, so if you discover later that you need to replace them, you won't have to do the complete removal again.

If the corrosion has gotten to a few diodes and a few of the smaller transistors, would it be wise to replace all the similar ones on each side of the board just to keep things symetrical?

If you want to be anal about it, I suppose, but likely nothing to gain.

I also see you replaced ALL the small resistors with new 1/4 watt 1%ers. I will assume thats a wise move...wether or not they are glue contaminated. Right?

Negative. There's a ton of resistors on that board, and I only replaced the contaminated ones...that was only 12 of the 75 or so on the whole board.

Looks nice EW ..........ok whos unit was that ?? maybe a hint lol

Not yours...belongs to a local guy who's been waiting a hellova long time for my slow ass to get a move-on.

 

[scottrt]

Geez, EW...the sun must not set in Kansas City, your are certainly a Nite Owl!

Thanks for the continued guidance. PM sent to you.

Scott T.

 

[Redcatcher199th]

lolol EW man I am in no hurry .................ya right lol I was just being a smart azz

lol I have the other one ready to ship to you can you take it now or should i put it on hold ?

EW I have seen your handy work and you my respect 150% and then some

my 7070 cuts out and the meter light also at the same time ??

then tap the glass lightly then ok any clue ? power short ?

the relays dont reset just lights go out and sound goes away i will check the wires

Look for a paypal transaction its burning a hole in my pants lol thanks EW for all your advise I sure do appreciate it

Brian :thmbsp:

 

[scottrt]

I Live in CA and just looked at a can of acetone I bought at Ace Hardware. Indeed, it has NO health warnings o the label of any kind, except for the usual dont breathe the fumes...
No Prop 65 warnings, which, by the way, adorn every gasoline pump in the state.

Just thought I'd share....
Scott T.

 

[fabvsix]

EW:
Could this have been my unit ? :scratch2: :scratch2:

 

[Redcatcher199th]

EW:
Could this have been my unit ? :scratch2: :scratch2:

Originally Posted by Redcatcher199th
Looks nice EW ..........ok whos unit was that ?? maybe a hint lol

Not yours...belongs to a local guy who's been waiting a hellova long time for my slow ass to get a move-on.
__________________
lol i am sure more than a few was thinking the same thing ......patience is a virtue;;;;;;;
folk that lol