New A-960 thoughts and questions

Hi all. Just picked up an a-960 integrated this week, and I'm in the process of getting it in shape again.

I've cleaned out the dust and crud, fiddled with the "Main Direct" switch and sprayed the volume pots with DeOxit. I'm about to set the idle current and DC offset in a few minutes.

That leads me to my 1st question...I get some crackling when I switch between different loads on the phono knob. Is it OK to spray DeOxit on the switch mechanism at the back of the unit? The part that's connected to the knob by a blue 'track' with a metal band inside?

Next question - I notice that when I have phono 1 set to 47k ohms, the right channel is louder than the left. I should mention that I have a HOMC cartridge on my TT right now, a Denon DL-110, and that it sounds balanced between left and right when the load is set to 100 ohms (the manual recommends that setting for HOMC carts). I thought it odd that it doesn't seem to work right when it's on 47k ohms, since that's what a lot of people would have as a MM phono input. Maybe the DeOxit will fix this, but will also try on the 47k phono 2 input.

As for the Main Direct switch...mine wasn't working. It wouldn't stay depressed 99% of the time. I found a thread here recommending a replacement switch for this, but since my desoldering skills aren't that great, I thought I'd try and fix it some other way.

After staring at the thing and poking the switch a bunch of times, it occurred to me that the spring on the outside of the switch shaft might be too strong. I used the tip of a screwdriver to hold a couple of coils so that they weren't pushing with the spring, and what do you know, it stays in now! So I snipped about 1.5 coils out of the spring. It works now, but I'm looking to replace the spring with a lighter one, as the unfinished end of the spring gets hung up on the switch body now and then. Still, it's a quick and free fix in this case.

Has a Yamaha recall on it.There is and x rated Rifa suppression cap across the AC mains line , that burns up. More prevalent in the 220VAC models, but I have seen it in the 120VAC models as well.

http://www.whathifi.com/News/Yamaha-issues-safety-recall-on-amps-30-years-on/

...I get some crackling when I switch between different loads on the phono knob. Is it OK to spray DeOxit on the switch mechanism at the back of the unit? The part that's connected to the knob by a blue 'track' with a metal band inside

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Those switches need to be removed and disassembled to get the deoxit where it will do the most good.:yes:

The problem with the front switches is that the plastic rail wears out so they don't hold their position. You cannot repair this so you need to replace the switches.

As for the Main Direct switch...mine wasn't working. It wouldn't stay depressed 99% of the time. I found a thread here recommending a replacement switch for this, but since my desoldering skills aren't that great, I thought I'd try and fix it some other way.

Click to expand...

The A-750/A-760/A-760II fall in this category as well. Pity. I like them.

I had the A-960 with same problem. Actually all the switches weren't working. Gave it away to a Yamaha collector in Hilversum. Told him about that safety issue as well.

Thanks for the info guys.

Re: the service bulletin, I looked at it and it's not a paper/oil capacitor of the kind I've seen pictured in threads here on the problem (as you said, mostly the 240V models). I'm hoping that's ok? I didn't pull things apart, but I can see a blue component in that area...

Thanks for the tips for the switches. I'm pretty much giving up on the Main Direct switch. My idea of changing the spring kinda worked, but not reliably enough. I'm going to live without that option for now, as I like the sound of this unit otherwise.

Update - I'm pretending the Main Direct switch doesn't exist for now.

The phono section is acting weird. After getting the idle current and DC offset where they should be, and spraying those switches, the left channel seems even more quiet than before, even on the 100ohm setting that I thought was pretty even before (could be wrong though). This is happening if I connect to the Phono 2 inputs as well.

I tried a MM cartridge, and it's the same problem. I went back to my Marantz and everything was normal, so I know it's not a TT/cartridge problem.

I didn't take apart the blue switches at the back to clean them, just sprayed some deoxit from the sides, could that be it? Is there a trick to taking those apart and cleaning them? I gather from another thread that they are fragile.

I could probably do a better job cleaning the phono inputs themselves, but again, it's acting up on phono 1 and 2...

Could it be as simple as hooking up a second TT or putting 'blank' plugs in the empty phono input? My CR-2020 has those in the unused phono jacks.

Nothing looks burnt or anything on the board with the inputs.

Thanks for any ideas to get the phono stage working right. This amp sounds fantastic with my digital sources, but I really wanted to get it running with two turntables for awhile.

Is there a trick to taking those apart and cleaning them?

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For best results the switch needs to be removed from the printed circuit board and the flexi-cable popped off the switch assembly.

I gather from another thread that they are fragile...

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Those cables were inside some Onkyos and Denons from same era...

http://amp8.com/tr-amp/denon/pma970.htm

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Also, read something about this model here (from post #51 on): http://www.audiokarma.org/forums/showthread.php?t=149520

Avionic - do you mean actually desoldered from the board?

Karl vd Berg - thanks for the link, sweet looking Denon too...

Are these switches known for being dirty? They aren't acting like the dirty selector switches and pots that I'm used to dealing with.

Still, I'd rather it be a dirty switch than some sort of issue with a component in the phono stage needing replacement. I'm just about out of my comfort zone messing with this thing as it is.

Guess I will pull out the board and look for bad solder joints too.

Is the fact that it has a quiet channel on phono 1 and 2 a clue to where I should be looking for problems?

So, no bad solder that I could see. I pulled the control board out and soaked the switches in cleaner. If things are still off tonight when I hook things back up, I will consider recapping the phono section, doesn't look like that many caps.

Somebody had a post about a similar problem and found it to be some silver polystyrene caps. It looks like I might have 4 of them (I think) - does anyone know what would be a suitable replacement for that type of cap?

Still very weak in the left channel after more cleaning, it sounds like the highs are missing too, even with the balance to the left and the volume up.

Considering recapping the control board, or hitting the thing with a hammer and burying it.

Sleep said:

Still very weak in the left channel after more cleaning, it sounds like the highs are missing too, even with the balance to the left and the volume up.

Click to expand...

Check for broken copper traces between Balance control and Volume one more time.

This series had a very weak PCB copper traces, and many of them break easily. Sometimes you can't see these broken traces but they are there. Use a flashlite and magnifier. No despair.

Ok, thank you for the tip, I will take a look. Wouldn't that problem affect other sources too though? Still it might be a problem similar to what you describe in the area where the phono stage meets the rest of the control board...

Avionic - do you mean actually desoldered from the board?

Click to expand...

Yes.. Then disassembled. Need to gain access to the actual switch contacts and sliders.

Considering recapping the control board, or hitting the thing with a hammer and burying it.

Click to expand...

None of which will fix the problem.

Thanks for the help so far guys. Looks like this project might gather dust for awhile in the furnace room.

If it's a matter of pulling those switches out, there are just too many legs to desolder with a risk of me damaging something. Maybe if/when I get a better iron or a desoldering station, down the road I can tackle this. Usually if I have a problem with a dirty switch I can tell from crackling or it working briefly in between positions, but there's none of that, so I'm not even sure that's what's wrong.

If it was just a couple of capacitors or something simple to fix I'd be up to it, but seeing as I don't have the skills to determine where the problem is, I don't want to mess around and make this unit worse.

OK. Not ready to give up yet, I was messing around with this thing again.

This time I used a different TT and cart, and headphones instead of speakers.

Still a problem with channels balancing, still only a problem with both phono inputs.

I did notice something odd though. The light for the weird "listening level" slider was lit up solid, even if I pushed it to the right - this was not happening with the speakers, so I figured it's just because I have headphones plugged in - however - when I turned up the volume to a regular level, the protection kicks in and power to the phones is cut, turn the volume back down, and it comes back on.

If I push the balance slider all the way over to the left (weak channel) side, I can turn the volume up to normal listening levels, and the protection does not kick in, also the listening level light behaves normally.

Could this mean that instead of a quiet left channel, I have a really loud right channel?

Also, when the turntable isn't playing, there's quite a bit of hiss through the headphones, I might have missed that through the speakers, and the hiss is louder on the right side too.

Not giving up yet

OK! Possible progress!

At the risk of looking like I'm talking to myself - lol

I checked the back of the board that the phono and selector switches are on again, this time with magnification and a bright light, and I found a lifted/mostly broken trace around the area of the selector switch (Correction - it's one of the big silver/white components to the left side of the phono switch - look like capacitors?). There are 4 similar components clustered around the phono switch area - a big one and small one on the left, and a big/small on the right (when looking from the front of the board). The large component on the left is the one with the trace problems - it's only barely connecting, if at all.

Hope this is it!!! Going to take another look and then see about fixing it.
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