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Old 29th Nov 2017, 9:45 am   #1
RissyMcG
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Default Aiwa NSX-AV75

I've right now got my old bedroom hifi in bits all over the lounge floor. I'm trying to get it back to a functional state. For years, there has been a problem with it whereby everything seemed to work, but not correctly or consistently. this seemed to revolve around the front face controls PCB just behind the control panel and LCD display on the front. For example, when turning the volume control knob to increase the volume, the volume would either stay still, go up, go down, or be a combination of any of the two/three. Only by turning it really fast, continuously, in the one direction, could you ever hope to get the volume to go up by any margin. Using the remote however, worked fine. So i determined it must be a mechanical issue. Other symptoms of similar confusion would result from the pressing any of the digital buttons to select different modes. You'd press a button and either nothing would happen, or something completely different would happen. Only sometimes would you ever get the proper response from the button you were pressing. Repeated pressing would eventually get you the result you were after.

Right. Now on to my findings after opening up the beasty.

The PCB in question, has all fairly robust looking interface controls. The volume control is quite a solid looking metal POT type spindle, and each of the digital buttons is a nice solid looking tactile microswitch push button. Each has a nice solid click to it when depressed.

I was planning on giving all these controls a good solid spray with some isopropol alcohol. My thinking is that perhaps they've become somehow "bunged up" with the likes of hairspray etc back in the 90's?

Does anyone else here have any experience of such symptoms?

Another issue is tape deck related for the same unit. The belts have completely dissolved into a black gooey mess over the years. I've now ordered another compatible set from Ebay, but i'm in for a challenge in trying to clean all this black rubber belt goo (it's like tar, no joking!) from the pulleys etc.

Does anyone have any tricks or proven chemicals to remove said goo without damaging any of the plastic pulleys which the goo is stuck all over?

I thank all in advance for any help or guidance they can provide me.
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Old 29th Nov 2017, 11:24 am   #2
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Default Re: Aiwa NSX-AV75

Dirty switches are the obvious first thing to check. Servisol 10 will work better than plain IPA (don't use WD40).

Dissolved belts can be a pain to clean off, and the chemical composition varies. White spirit / turps substitute is probably as good a solvent as anything. Ordinary WD40 is mostly white spirit so can be used as a solvent, but apply it using a rag rather than spraying directly, and take care to clean off all residue or the new belts will slip. Acetone tends to attack plastics, so if you decide to try it from desperation try it on a bit of sacrificial plastic first. IPA is safe but doesn't tend to be much use shifting these hydrocarbon deposits.
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Old 29th Nov 2017, 12:06 pm   #3
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Default Re: Aiwa NSX-AV75

Cleaning the switches might help, this includes the volume control which is a simple type of rotary encoder. Contamination of the switches is possible, by dirt (which will clean off easily) or silicone (much harder to remove). Wear can have a similar effect.

I have a Denon system with a digital volume control which is notorious for a similar fault due to the silicone grease they used to give the volume control a nicely damped feel. The lack of surface tension means the grease migrates slowly but steadily until it intermittently insulates the contacts, confusing the algorithms that determine which way you turned the volume Furniture polish containing silicone can do the same ...

Removing silicone is a challenge ...

dc
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Old 29th Nov 2017, 1:35 pm   #4
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Default

Thanks for the feedback chaps! I really appreciate it!

How can micro switches get dirty? They look to be sealed units in their own right!?

They look similar to this type of switch here:

https://www.google.co.uk/imgres?imgu...act=mrc&uact=8

Same really goes for the "rotary encoder"?

It looks similar to this:

https://encrypted-tbn0.gstatic.com/i...A_DdFX0WgQKG3A

I've just checked. I can get some Servisol 10 from Maplin tonight. Can i just spray this all over each of the contacts/encoder in turn, then work them over a bit, and then does the stuff naturally evaporate/dry off, leaving everything clean and dry as if it was never wet?
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Old 29th Nov 2017, 2:21 pm   #5
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Default Re: Aiwa NSX-AV75

The 'dirt' is usually oxidation.

You need to get the Servisol onto the actual contacts, which means finding some sort of gap or hole. Be sparing with it - there's no point in spraying gallons of the stuff about, especially if it's not getting inside. It does dry off over the next day or two, but you should wipe off any obvious surplus with a rag after applying it and exercising the switches.
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Old 29th Nov 2017, 3:10 pm   #6
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Default Re: Aiwa NSX-AV75

It was common for those tact switches to go high resistance or open circuit due to oxidisation over time, a check with a multimeter on the ohms or continuity range would confirm this.

They are best all replaced they don't cost much
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Old 29th Nov 2017, 3:53 pm   #7
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Default Re: Aiwa NSX-AV75

Oh right. Well I can try cleaning them first. How about the encoder pot?
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Old 29th Nov 2017, 4:48 pm   #8
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Default Re: Aiwa NSX-AV75

You may need to dismantle that to clean it properly, but see if you can get some Servisol inside without first.
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Old 29th Nov 2017, 7:15 pm   #9
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Default Re: Aiwa NSX-AV75

I had a similar fault on a tuner-amp I repaired for a friend. The volume would go up normally, but only go down if I spun the control quite fast. The internal battery had leaked and eaten through a PC track, some distance away from the logical location, so you may just have a missing control line somewhere.
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Old 30th Nov 2017, 10:05 am   #10
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Default Re: Aiwa NSX-AV75

I picked up some Servisol 10 from Maplin last night (last can on their shelf). I routinely went round all the microswitches and the encoder, and sprayed liberally, working each in turn whilst wet, twice. Then i dried off the best i could and left everything out to finish drying over night. I'm now waiting for the replacement belts to come before I can reassemble and apply power again to try it all out. In the meantime, I've still go these horrible gooey belt pulleys to clean up. I think i'll use some cotton buds with either WD40 or "sticky stuff remover" on. (I'll admit without referring to the instruction on the sticky stuff remover, i'm unsure at this time if this stuff is safe on the plastics!? It's horrible stuff. It stinks. And you never really get rid of all of it by the time you're finished. I might be able to clean it off with some brake cleaner i have in the garage for doing the cars? I've never tried that before though, although brake cleaner is GREAT stuff!)
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Old 30th Nov 2017, 10:25 am   #11
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Default Re: Aiwa NSX-AV75

Be very suspicious of using sticky stuff remover or brake cleaner, the more these compounds smell the more likely that they will dissolve the plastic. Sounds like acetone compounds to me, like nail varnish remover, another no-no.
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Old 30th Nov 2017, 11:32 am   #12
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Default Re: Aiwa NSX-AV75

If you use WD40 as a cleaner, spray some into a small container such as the aerosol cap and dip your cotton bud or rag in that.

Ordinary white spirit is just as good and much cheaper though. I think Poundland sell it amongst other places. I just mentioned WD40 because most people will already have some.
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Old 1st Dec 2017, 9:54 am   #13
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Default Re: Aiwa NSX-AV75

Ok thanks. I'll stick to the WD40 then. I might even have some white spirit actually. I'll have a look around. I'll probably not get a chance to have a go at this until early next week now. luckily i live on my own, so the fact that there's a 90's HiFi in bits all over the lounge floor is not an issue.
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Old 5th Dec 2017, 10:30 am   #14
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Default Re: Aiwa NSX-AV75

So i've mostly cleaned up my pulley's now. And i've received what i'd hoped was the actual necessary belt kit from an ebay seller for this tape deck (although it was advertised appropriate for other hifi tape decks, not mine (but still Aiwa). I went for it because his pictures looked identical practically, when compared to my tape deck assembly.

His pictures: http://www.dealsan.co.uk/buy/aiwa-cassette-deck

From his ebay shop: https://www.ebay.co.uk/itm/202123771...107&rmvSB=true

Here's another link to a similar stereo which appears to have the same design of tape deck as mine: http://repaircafe.shoutwiki.com/wiki...ystem_NSX_D707

The actual Aiwa NSX-AV75 service manual page (51) showing the exploded diagram of the tape deck with belt routing:

https://www.manualslib.com/manual/69...page=51#manual

(IGNORE pulley's 5 and 6 as these are much lower down and i'm happy with these two)

So the problem i've got, as i've illustrated hopefully clearly enough in the following photos, is that this apparent belt routing doesn't work well as there are two belt pulleys on the motor. The lower groove on the motor lines up perfectly in the Z-axis with pulleys 1, 2, 4, 7 and the lower groove only on pulley 3. The upper groove on the motor pulley lines up perfectly in the Z-axis with the upper groove on pulley 3 ONLY.

BUT, i'm supposed to be putting the TWO belts around the pulleys as illustrated in the specified picture , whereas i can only see it working with THREE belts as illustrated in the proposed picture...!?

The reason for this is, with only TWO belts, and having to use the upper pulley on the motor for the pulleys to the right hand side (3, 4 and 7), means that the belt would be having to be angled down from the motor to both pulleys 3 and 7. To 7 isn't such a big deal, as it's so far away, so the apparent angle isn't alarming, but between the motor pulley and pulley 3, it's much more severe and IS alarming! I think it wont last long before it either slips or gets stressed out with friction.

Because of this concern (and confusion), i've come up with the alternative THREE belt routing as mentioned.

So i'm basically looking for some comments or concerns, or indeed, if anyone has a hi-fi similar to this one, with this same tape deck assembly in it, if they can advise how theirs is routed, as this stumps me. I can never see it working as per the design!?
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Old 5th Dec 2017, 10:44 am   #15
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Default Re: Aiwa NSX-AV75

In the past I have repaired similar decks, and they do only use two belts, IIRC routed as shown in one of your pictures. The explode diagram isn't, in a way, brilliant, but it does show thaat only two belts are used, though not how they are routed. The pictures on eBay aren't brilliantly clear, either.

Last edited by 'LIVEWIRE?'; 5th Dec 2017 at 10:51 am.
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Old 5th Dec 2017, 10:47 am   #16
RissyMcG
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Default Re: Aiwa NSX-AV75

Quote:
In the past I have repaired similar decks, and they do only use two belts, IIRC routed as shown in one of your pictures.
...As would be expected from the Aiwa service manual, BUT, this routing puts a "twist" or "bend" on the belt going from the motor pulley (upper) to the lower groove on pulley 3!? (I may need to take a picture from the side with the motor re-mounted and with the belt fitted to illustrate this to people properly!?)

I just doesn't seem right at all!?
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Old 5th Dec 2017, 12:08 pm   #17
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Default Re: Aiwa NSX-AV75

All I can think of is that, besides the motor pulley having two grooves one above the other, is that the grooves on the two flywheels are in different positions, one nearer the bearing end, the other nearer the spindle end. This is supposed to allow the belts to be routed so that they run correctly. Thus the belt which is routed around the lower of the two grooves in the pulley should go around the flywheel whose groove is lower down, and vice-versa.
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Old 5th Dec 2017, 1:07 pm   #18
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Default Re: Aiwa NSX-AV75

I'm not sure I really understand your post to be honest.

I'll try and get a photo up tomorrow, showing the designed routing and the apparent problem I have with this. But basically the top motor pulley only lines up (is at same height) with the top groove on pulley 3. The bottom motor pulley lines up (is at same height) with pulleys 1, 2, 4, 7 and the bottom groove on pulley 3. So how can I use both grooves on the motor pulley and use only two belts but still wrap around all necessary pulleys without a belt changing height between two pulleys?!
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Old 5th Dec 2017, 3:19 pm   #19
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Default Re: Aiwa NSX-AV75

Close up pictures would definitely help.
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Old 5th Dec 2017, 4:51 pm   #20
RissyMcG
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Default Re: Aiwa NSX-AV75

I'll get some more pictures, or make a video tonight, but until then, this picture might illustrate the issue.

on the left is the black pulley #2
on the right is the white pulley #3

One belt has to go to the left from the motor to #2
One belt has to go to the right from the motor to #3

When the motor is mounted in the middle, with its two mini pulleys in between the black plastic struts in the middle of the picture, the top motor pulley matches the height of the top groove on #3 and the bottom motor pulley matches the height of the bottom groove on #3 AND the groove on #2.

So, since #2 only has ONE groove to choose from, i've been putting a belt on the bottom motor pulley and feeding it on to #2 and on to #1 and back.

That only leaves the top motor pulley free and available for the second belt. So i've been feeding that belt on to the top groove of #3, since where else is it going to go!? If i put it on to the bottom groove of #3, then the belt isn't straight. It's sits diagonal between the motor top pulley and #3!

So now you say "yeah!? well do that then!", but IF i DO, then the other pulleys i've still not mentioned yet (#4, #7), which are at the same height with their groove; are all at the same height as #2 and the bottom groove of #3. If i'm only to use two belts, then how can i go from the motor top pulley to the bottom groove on #3 and then on to grooves on #4 and #7 without making the belt diagonal!?

Using three belts would get around this, but then it wouldn't be as per the service manual?!
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