Sony MDS-JA20ES / JA22ES or Sony MDS-JB940

[Kame]

Hi Everyone,

I've decided to focus my attention on acquiring ONE model of minidisc deck, but I'll get a few extra as a parts machine.

Right now, I have a Sony MDS-JB940. A British MD technician recommended I focus on this model as its reliable, rather easy to repair.

However, recently I've seen a number of MDS-JA22ES (same as JA20ES according to this site) for sale for approx $250 CAN, which seems OK given that MD decks now seem to be selling at crazy inflated prices.

The MDS-JA22ES was a higher end deck. How does this deck compare to JBS-940 in terms of:

• reliability
• repair-ability and parts
• using the KMS-260A, B, or E laser which is still available.
• sound quality
• build quality and aesthetics

According to Jonathan's guide https://www.jonathandupre.fr/articles/index.php?url=/17-minidisc-md/50-guide-depannage-minidisc-v2/   the JA22ES uses a 6th Generation loader mech with drawer, and the JB940 uses a 7th Generation loader mech, both of which are very reliable.

I am not planning to use MDLP.  To my undiscerning ear, minidiscs sound perfectly fine, but I don't want to push my luck and record my record collection in highly compressed MDLP format.

I'd appreciate your recommendation and suggestions since many of you are very familiar with this now increasingly-rare gear.

 

[NGY]

58 minutes ago, Kame said:

The MDS-JA22ES was a higher end deck. How does this deck compare to JBS-940 in terms of:

• reliability
• repair-ability and parts
• using the KMS-260A, B, or E laser which is still available.
• sound quality
• build quality and aesthetics

The JA20ES (JA22ES) is the top MD deck in my eyes. If you do not need MDLP or PC-Link/netMD, there is nothing that is missing from it. For 250CAD is an absolute "must-buy", if not a beaten piece.

My comparison (certainly subjective, so you can factor it to your taste):

- reliability - I don't see any big differences,  and cannot mention any particular "Achilles heels" either (maybe the sled's toothed rack in the 22ES and the loading belt in the 940QS that may need some attention). My belief is though that a drawer-loading machine gives less chance for human misuse/abuse than a slot-loading one.

- repair-ability and parts - the MDM5 and MDM7 drive families are both good quality, way better than the preceding models. Both are easy to repair, although in the 20ES the drive is deeply "buried" under the loading mechanism and the isolating "armor", means it requires quite some time to access it. The 940QS is just four screws and you already have the drive in your palm. From there, both mechanisms are easy to service. I like the MDM5 a bit more, and as I see the potential part donor models (from the lower leagues) are easier to find and less expensive.

- using the KMS-260A, B, or E laser which is still available - A,B or E lasers are practically the same. With the accurate settings all do the job properly in both drives. B or E lasers are still on the market, A is rare, but there is no particular reason to hunt for it. And laser lifetime depends more on the way of use, than on the suffix, this is my observation.

- sound quality - the ES wins, no question. I have both models, and even my old and dumb ears can hear differences. Of course, if the music is that kind (I would never rely on techno, hip-hop or other similar electronic "music", for a blind test :-) )

- build quality and aesthetics - from design perspective, there happened a slight generation-change between the times of these two models. The 20ES is a classic, beautiful, state-of-the-art machine. The 940 is a clean, minimalist, modern design. I like both, to be honest, though the ES is just more attracting. In build quality, clearly the ES wins, but this is no wonder. The QS is also a superb machine, but more of a "volume product".

You can never be fair when comparing an ES device to a QS, especially if they are nearly from the same age. But as I said above, these days a nice 20ES (22ES) for 250CAD must be a no brainer.

[Kame]

Wow!  Thank you for your fast reply NGY! The careful detail you provide is much appreciated.

I quite like the idea of the slide-open drawer. I've not used one yet, but I would guess it should be more reliable than the pull-in type.
If mechanical parts should ever break, it seems that 3-d plastic printing might offer a solution. I saw a post on Japan Yahoo today of a fellow selling a replacement gear for an MD deck that he had printed.

Based on your description, it seems I can't really go wrong with the 20ES models. I'll try to buy two of the 20ES models and sell my JBS-940 and the Tascam MD-350 decks. They're all in perfect operating condition, but both the Tascam and the 940 are all-black and do not match my silver-faced 70s components. I don't need five minisdisc decks sadly, so I'd better just stick to one model.

I've seen KMS-260A, B, E lasers for sale on Aliexpress for very low prices. Should I buy a few of these as backups?
Also, you'd mentioned laser failure often related to how the unit is used rather than just age? Can you provide some suggestions on getting longer life from lasers?
The MD magician Jonathan recommended on the MDS-B5 decks (using the problematic KMS-210A laser) to make some adjustment to lower the power and thus lower the heat levels which he assumed contributes to the early failure of those lasers.

 

 

[NGY]

1 hour ago, Kame said:

I've seen KMS-260A, B, E lasers for sale on Aliexpress for very low prices. Should I buy a few of these as backups?

My experience with these parts from Aliexpress ("new" printerheads for inkjets ditto), that these are not new, but pulled off of recycled devices. I bought a few a while ago, and although I did not find any faulty ones, it quickly became obvious that all were used to a certain level, some more, some less. (Two examples: the IOP labels said 50,7 and 51,0 mA, and the measured, actual  vales were 53,3 and 53,0 mA respectively. While certainly still within the Sony specs, these are definitely used parts, and the first one will probably have a much shorter remaining life than the second.)

But generally speaking, yes, as backups, they are worth a few bucks.

 

1 hour ago, Kame said:

Also, you'd mentioned laser failure often related to how the unit is used rather than just age? Can you provide some suggestions on getting longer life from lasers?

The list can be long - just a few thoughts here, and others may also add their experience. These things can radically shorten the lasers' life.

1)  heat

- long recording sessions, multiple discs recorded back to back, without letting the laser diode cooling down

- incorrect laser settings ( more of a service thing than user related)

2) focusing/tracking problems

- dirty OP lens, dirty/scratched MD discs

- MD discs not running true (= "hitting" either radially, or axially)

- sled mechanism not working properly - damaged parts, dried out grease, dust/hair/other particles (see some  pictures  below, quite horror, and this machine was in mint condition from outside...)

     

3) silicon ageing

- semiconductors do age, even if it is not obvious or visible. Electronic devices left always on will age their silicons much faster. The laser diode is certainly modulated to be off when not in use, but there is more than just the diode itself on an OP and in the driving circuits, that can age when powered on.

I think you get the idea.

 

1 hour ago, Kame said:

The MD magician Jonathan recommended on the MDS-B5 decks (using the problematic KMS-210A laser) to make some adjustment to lower the power and thus lower the heat levels which he assumed contributes to the early failure of those lasers.

He is very right, excess heat is an enemy. Within the factory recommended range, one can certainly "turn down" the laser power, thus preserving some time for the OP. In any case, it must be done respectively to the diode currents.

[Kame]

On 6/2/2020 at 6:51 PM, NGY said:

My experience with these parts from Aliexpress ("new" printerheads for inkjets ditto), that these are not new, but pulled off of recycled devices. I bought a few a while ago, and although I did not find any faulty ones, it quickly became obvious that all were used to a certain level, some more, some less. (Two examples: the IOP labels said 50,7 and 51,0 mA, and the measured, actual  vales were 53,3 and 53,0 mA respectively. While certainly still within the Sony specs, these are definitely used parts, and the first one will probably have a much shorter remaining life than the second.)

But generally speaking, yes, as backups, they are worth a few bucks.

Thanks for your fore-warning. The site offers a lot of sketchy stuff, but some is quite good. Think I'll buy two backup lasers from the site but hope to avoid used stuff if possible.
But which model of laser should I get?  As I understand, there are a number of models that will all fit into the MDS-JE22:  KMS-260A, B, E models.
Is the KMS-260E a later model, and thus probably superior to KMS-260A?

I found these inexpensive lasers:

https://www.aliexpress.com/item/4001014079414.html?spm=a2g0o.productlist.0.0.32e1134a5GNGJy&algo_pvid=89542bc7-0ed8-40b9-8c21-c8820f491933&algo_expid=89542bc7-0ed8-40b9-8c21-c8820f491933-5&btsid=0ab6f8ad15912900709688694e6cc0&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

https://www.aliexpress.com/item/32793683204.html?spm=a2g0o.productlist.0.0.32e1134a5GNGJy&algo_pvid=de4abf8b-86db-43cb-9535-4361f353a612&algo_expid=de4abf8b-86db-43cb-9535-4361f353a612-10&btsid=0ab6fb8815912889288507052e148f&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

On 6/2/2020 at 6:51 PM, NGY said:

The list can be long - just a few thoughts here, and others may also add their experience. These things can radically shorten the lasers' life.

Thanks for this list too. When I get my "new" JA20ES (JA22ES) deck, should I take it to a tech to make sure the laser is properly calibrated? Do they drift over time?

 

On 6/2/2020 at 6:51 PM, NGY said:

- MD discs not running true (= "hitting" either radially, or axially)

What causes the MD disc to not run true? If a minidisc was warped, surely we'd notice the case was distorted.
Or is this caused by the loading mechanism?  On that topic, can I lubricate the drive mechanism myself? Or is this best left to a shop? I'd prefer to do as much maintenance as I can myself to ensure its done carefully.

 

On 6/2/2020 at 6:51 PM, NGY said:

Semiconductors do age, even if it is not obvious or visible. Electronic devices left always on will age their silicons much faster. The laser diode is certainly modulated to be off when not in use, but there is more than just the diode itself on an OP and in the driving circuits, that can age when powered on.

I did not realize this and in fact thought the opposite was true! I'd read somewhere it was better for capacitors and other electronics to leave them powered on than to leave them off for extended periods. Nothing lasts forever, but if I can keep my MD decks running for another decade or more, that would be fun: I enjoy their aesthetic. They are like mini vinyl records that require careful selection.
 

On 6/2/2020 at 6:51 PM, NGY said:

- sled mechanism not working properly - damaged parts, dried out grease, dust/hair/other particles (see some  pictures  below, quite horror, and this machine was in mint condition from outside...)

When my new deck arrives, I'll open it up to ensure its clean. Those photos are horrible. How on earth did it get so dirty? Was the laser or mechanics damaged from that?

-----------------------------

A final question: I am looking for a loading mech for a Tascam MD-350. I described the situation here: http://forums.sonyinsider.com/topic/30756-looking-for-tascam-md-350-loading-mechanism/

I am guessing that this loading mech was built by Tascam and is not a Sony. Any suggestions on where I can find parts? I've not been able to find anything.
I'm planning to sell the Tascam and replace it with another MDS-JA22. I'll have two JA22. One will be my daily use machine, the other will be a backup/parts machine.

[NGY]

Ha-ha, lot of questions :-)  !

I try my best answering them, but again, I might be subjective (and wrong too) here and there, so I expect others to share their view.

- "Is the KMS-260E a later model, and thus probably superior to KMS-260A?" - This I really cannot answer properly. I guess a Sony engineer would know the "secret". They did the upgrades for a reason, that is sure, but the reason can be just as simple as a new spec diode, for example. My statistical base is small, I can speak about only 100-120 decks I had my hands on for repair. This is certainly not representative, but I could not find any evidences for one type of laser being better than the others. To me, they are all good, and proper settings are the most important.

- "I found these inexpensive lasers" - this was not a question, one note here though: it may worth to double check with the seller, what they actually sell. Most Chinese sellers use the same photos from their wholesalers (or taken from their fellow sellers), as well as titles/descriptions. Most cases they just list all suffixes like compatible versions, but only sell one and only one type. As I saw, most of them sell 260E lasers (funny enough, sometimes pulled from non-Sony devices, as their photo shows), few of them sell 260B (for almost twice as much), and I have not recently seen any 260A versions (not if I wanted one).

- "should I take it to a tech to make sure the laser is properly calibrated?" - It does not hurt to perform a "sanity check" on the laser status. I'd expect though the tech knowing that they do, and having all the necessary test gear.

- "Do they [the lasers] drift over time?" -  Heat can cause some drifting in actual laser power vs. given settings. But this is different from the changes that occur as the laser ages. Over time, the power of the emitted laser beam decerases, this is normal. Checking it regularly - depends on the use. If you record live performances, that are one-time kind, you may want to (as well as to use at least one mirror device recording for back up). If you do your CD or vinyl complations, your deck "will tell", when to replace its laser, and the most you can lose is the very last recording (that you can redo hopefully).

- "What causes the MD disc to not run true?" - Many things, actually. Just to name a few: manufacturing error, disc dropped to the floor, disc left on a hot place for long (car dash, top of the amp), etc. And you bet: it is rare, but drive mechanism can also be a cause - see my post here, for "fun" :-) .

- " On that topic, can I lubricate the drive mechanism myself?" - Sure you can. Do it carefully, and use the proper grease, developed for these fine mechanical devices. There are several known brands and products, the most important thing is that the two main components (the oil that lubricates and the "soap" that carries the oil and keeps in place) must not be separating with time, thus the grease will not dry out and harden. Two more notes: 1) never use silicon grease in these devices, and 2) before applying the fresh grease, always clean the parts completely from any residues of the old lubricants.

- "I'd read somewhere it was better for capacitors and other electronics to leave them powered on than to leave them off for extended periods" - Yes, but let me make some differentiation here. 1) Inside unused caps the chemical complex can change with time, therefore switching unused electronics on regularly might help as these caps sort of "reformatting" themselves, that can limit these irreversible chemical changes. However, leaving the electronics always on will not stop their caps from drying out (it is actually the opposite, especially, if these caps are located close to other parts, that generate heat, like a power resistor, heat sink, etc.). Electrolytic caps do dry out over time, and if left in that state with the device powered down for an extended period, caps can disintegrate (with a "puff" sometimes) when powered on again. 2) What electronics do not really like is frequent switching on and off, for the transients that may cause damage. This much is true (and I did not say one should pull the AC cord after each disc played or recorded). If you never switch off your electronic device, you may save it from these transient shocks (provided the device is plugged into at least a surge protected AC outlet, or running on an UPS). But this will not save them from ageing. Having the "Standby" function on most electronics is exactly there for this reason, it keeps only the least minimum needed circuits running, and shuts of the rest, to save power and device lifetime.

- "Those photos are horrible. How on earth did it get so dirty? Was the laser or mechanics damaged from that?" - I have no idea, I was surprised too. The deck came with "usual" C13 error, and after completing a full strip-down/clean/rebuild circle it worked again flawlessly. I saw a similar one the other time, and that laser was already dying, thought that deck had already run more than 2000 hours, so that could count as well.

- "I am guessing that this loading mech was built by Tascam and is not a Sony. Any suggestions on where I can find parts?" - I am sorry, not only my experience is limited, but is restricted to a few Sony decks only, so no clue here.

Pfhew ... now it begins looking like I was writing a book :-) . If you reached down here with reading, you deserve a beer or your favourite drink :-) .

 

 

[Kame]

 

20 hours ago, NGY said:

"Is the KMS-260E a later model, and thus probably superior to KMS-260A?" - This I really cannot answer properly. I guess a Sony engineer would know the "secret".

Its too bad that we can’t find a Sony engineer to ask the question about lasers. I imagine that MD fans in Japan would know about this- surely an engineer posted about this on an MD forum somewhere.

 

20 hours ago, NGY said:

- It does not hurt to perform a "sanity check" on the laser status.

I will check with my technician to see if he has proper equipment to calibrate the lasers. He works on a lot of CD decks so I assume he should have the right gear.

 

20 hours ago, NGY said:

"What causes the MD disc to not run true?" - Many things, actually. Just to name a few: manufacturing error, disc dropped to the floor,

I have acquired a good number of used minidiscs recently. How can I determine if they are damages or bent?

 

20 hours ago, NGY said:

use the proper grease, developed for these fine mechanical devices. There are several known brands and products,

Any recommendations on brands of grease to use? In the MDS-JA20ES service manual, pages 15-18 shows an exploded view of the drive assembly. I’ve sent JPEGs of the relevant pages in case you or other members might be able to draw on these pages and show where I (we) should apply grease to the mechanism.

Very nice explanation on the pros and cons of keeping electronic equipment plugged in. I use a whole-house surge protector, in addition to a power conditioner/ surge protector for my stereo and computer gear. This should help prevent premature damage.

There are so few knowledgeable people and repair techs around nowadays. This is one of the only forums remaining that provides expert knowledge about Minidisc. Are there any other English language sites? I wish my Japanese reading skills were better- I could do some research on Japanese sites.

Thank you again for taking the time to write a detailed reply. This information will undoubtedly help many other fans of Minidisc.

 

 

[kgallen]

 

Quote

Any recommendations on brands of grease to use?

For plastic gears, the usual recommendation is Dow Corning Molykote EM-30L synthetic grease. Officially this is sold in 1kg tins that cost hundreds of pounds/dollars. However you can usually find a local eBayer who has decanted some to small amounts, say 10 grammes, that can be bought for a small number of pounds/dollars. You only need a tiny amount, I'm still using the grease off the lid of my 10g pot! As mentioned elsewhere on the forum, make sure you clean of any old grease and apply the tiniest amount required using a cocktail stick or similar. This grease can also be used in our applications for metal to metal, since none of the metal parts in our machines are running at high temperatures under high loads (an MD drive is not some huge industrial machine!).

@NGY may have other suggestions, he's clearly an "old hand" at this lark!

[NGY]

I think the EM-30L is a fairly popular product and meets all requirements we would ever need in our applications.

When I was after an appropriate grease, I run exactly into the "1 kg tin only" problem, and had hard times to find smaller quantities. Then I found a Canadian company MG Chemicals, and their "No.8461", a white lithium grease. An electronics grade product, compatible with metals/plastics/rubber, does not contain silicon, has long lasting consistency and also prevents corrosion, etc., much like the Molykote. The manufacturer had a standard 3 oz. tube (~85 g) commercially available. Actually shipping cost more than the product itself.

And as Kevin said, even this 3 oz. tube is a HUGE quantity! I put about 5 ml of it into a small glass pot, and years after and dozens of machines maintaned, I still have a bit of that small portion. I am more than happy to offer anybody such a tiny amount for free, though I feel the postage from mainland Europe might be a lot less reasonable than a UK or US based seller's.

[NGY]

On 6/5/2020 at 9:44 PM, Kame said:

I have acquired a good number of used minidiscs recently. How can I determine if they are damages or bent?

Just simple visual inspection. Take the deck's lid off (*), load a disc and watch it spinning in the drive. Normally you should see a disc as if it was standing still, not spinning. If you see a disc "rocking", that's not so good. Will most probably play/record though, don't get me wrong, the question here is how much extra load this puts on the laser, to compensate for it.

(*) note: on the 20ES it takes a lot more screws, plus another shielding plate to be removed, to have a view into the drive. It is not that convenient, and not really practical either.

[M1JWR]

On 6/5/2020 at 9:29 PM, kgallen said:

 

For plastic gears, the usual recommendation is Dow Corning Molykote EM-30L synthetic grease. Officially this is sold in 1kg tins that cost hundreds of pounds/dollars. However you can usually find a local eBayer who has decanted some to small amounts, say 10 grammes, that can be bought for a small number of pounds/dollars. You only need a tiny amount, I'm still using the grease off the lid of my 10g pot! As mentioned elsewhere on the forum, make sure you clean of any old grease and apply the tiniest amount required using a cocktail stick or similar. This grease can also be used in our applications for metal to metal, since none of the metal parts in our machines are running at high temperatures under high loads (an MD drive is not some huge industrial machine!).

@NGY may have other suggestions, he's clearly an "old hand" at this lark!

i use TF2 lithium grease, it was recomended by a friend who repairs/services cassette decks, he has used it for years, its around £4 for 40g tube and there is a ad for buy 1 get 1 free, will last a lifetime for that much.

[kgallen]

The key question is, is it safe on plastics? A quick google and TF2 is a lubricant for metal bearings, suggested use for bicycles. It’s ‘a packing type grease for bearings’. Sorry I’m not sure about this one. 

[freddyjollo]

if you use an external dac would there be any difference  between them? Surly thats a must do these days with advances in dacs? I use an Audiolab 8200cdq

[M1JWR]

obviously that would be better than the minidisc's dac, although i have heard of people using redundant jb930's etc as dacs for cd players because they are rather good,

ive used the 980 as a dac for a marantz cd 63se and it improves it no end.

[Kame]

On 6/7/2020 at 4:49 AM, M1JWR said:

i use TF2 lithium grease, it was recomended by a friend who repairs/services cassette decks, he has used it for years, its around £4 for 40g tube and there is a ad for buy 1 get 1 free, will last a lifetime for that much.

Thanks! I will get some of this grease and be sure to lubricate all key areas of the drive mechanisms.

I think the Tascam MD350 broke because it needed lubrication. It stopped working after I loaded a disk that would not play. I was unable to eject it after that. I removed the unit's top cover to see if there was a way to eject the disk manually, but I wasn't able to do so. When I took it into the shop, the tech found the loading motor had burned out. He applied voltage to the motor directly and it didn't spin so he's fairly certain its burned out. He's not familiar with dissembling minidisc loading units and so recommended replacing the entire loader.

[NGY]

3 hours ago, Kame said:

I will get some of this grease and be sure to lubricate all key areas of the drive mechanisms.

You probably missed Kevin's point above. If you did not, then my apologies for the redundant post here. It may be worth to check the PDS/TDS of this TF2 first though.

An MD drive is nor a bicycle, neither a roller bearing. "A grease is just a grease" approach might not work here. To the extreeme: there are "white lithium grease" products for heavy duty tractors and other agricultural machinery, for example. Would you just use those in your precious hifi gear :-) ?

As a rule of thumb, better avoid anything labelled "All purpose".

[M1JWR]

what i should have said is that i use it on things like sleds, thats about it, however i dont know how far the tape deck man goes with it, i would say he is doing lots of metallic parts which cassette decks are full of, he did say he used it on the odd cd player sled aswell when he gets to work on those and has done for years without issue, handy man to know if you have tape decks, but his interest in md decks is limited to nil unfortunetly

[freddyjollo]

silicon grease? lots on ebay for not much money? why not?

https://www.machinedesign.com/motors-drives/article/21831576/engineering-essentials-lubrication-tips-for-plastic-gears-and-more-part-2

 

[kgallen]

11 minutes ago, freddyjollo said:

silicon grease? lots on ebay for not much money? why not?

Just get EM-30L. The right stuff, not just any stuff. Also available on eBay as above.

This is what I bought, £3.99:

https://www.ebay.co.uk/itm/Dow-Corning-Molykote-EM-30L-Synthetic-Grease-for-Audio-Office-Plastic-Gears/373078746082?hash=item56dd39e3e2:g:JdIAAOSwBQ1eNyLH

Quote

Molykote EM-30L grease has been specially developed for plastic components such as automobiles , electrical appliances and audio equipment. 

The grease has a long service life and does not contain any silicone, this prevents problems with contact point failures.

Features

• Compatible with most plastics
• Can be used for plastic-plastic contact, metal-metal contact and plastic-metal contact
• Long service life
• Low seepage, so it can be used in places wherein cleanliness is required
• Does not contain silicone thereby preventing problems with contact point failures

 

[NGY]

2 hours ago, freddyjollo said:

silicon grease? ... why not?

Because there are very sensitive optics in very close distances from the lubricated mechanical parts. And if silicon grease gets on those parts (or, "in", actually, like the OP cavities where the mirrors, prisms, sensors, etc. are located), it is very hard, if ever possible at all to remove from there. Just imagine when your glasses (sunglasses) have some fingerprints, how badly it affects your vision (and how far is human retina from the resolution of the CD/DVD/MD players). Same for certain electrical contacts, as pointed out in the quote in Kevin's post above.

Silicon grease is a great stuff for many applications, but is the meanest thing when it comes to how to properly remove it.

BTW, very good article you linked. Explains lots of "why"-s and "why-not"-s, I liked it.

 

[freddyjollo]

1 hour ago, NGY said:

Because there are very sensitive optics in very close distances from the lubricated mechanical parts. And if silicon grease gets on those parts (or, "in", actually, like the OP cavities where the mirrors, prisms, sensors, etc. are located), it is very hard, if ever possible at all to remove from there. Just imagine when your glasses (sunglasses) have some fingerprints, how badly it affects your vision (and how far is human retina from the resolution of the CD/DVD/MD players). Same for certain electrical contacts, as pointed out in the quote in Kevin's post above.

Silicon grease is a great stuff for many applications, but is the meanest thing when it comes to how to properly remove it.

BTW, very good article you linked. Explains lots of "why"-s and "why-not"-s, I liked it.

 

but how does that not aply to any grease

[NGY]

2 hours ago, freddyjollo said:

but how does that not aply to any grease

This applies to any grease (gel, spray, etc.) that has silicon content.

 

[Kame]

On 6/15/2020 at 6:38 AM, NGY said:

Because there are very sensitive optics in very close distances from the lubricated mechanical parts. And if silicon grease gets on those parts (or, "in", actually, like the OP cavities where the mirrors, prisms, sensors, etc. are located), it is very hard, if ever possible at all to remove from there. Just imagine when your glasses (sunglasses) have some fingerprints, how badly it affects your vision (and how far is human retina from the resolution of the CD/DVD/MD players). Same for certain electrical contacts, as pointed out in the quote in Kevin's post above.

Silicon grease is a great stuff for many applications, but is the meanest thing when it comes to how to properly remove it.

BTW, very good article you linked. Explains lots of "why"-s and "why-not"-s, I liked it.

 

This is a great explanation. Its helpful to know the reasons to avoid silicone.
I'll get some proper grease that I'll carefully apply to parts that were formerly greased and avoid smearing it everywhere

[NGY]

I always had trouble with "silicon" and "silicone", which one is the correct spelling in written English, and whether they are actually different in some way. Now I took the time and looked after it. Here is what I found: "silicon is a naturally occurring chemical element, whereas silicone is a synthetic substance."

So actually, there is a difference between silicon and silicone, and it is quite essential. Interesting, as in many languages those two expressions are more distinct than just a single letter (for example in German: Silizium vs. Silikon).

I did not go back and edit all my posts above, but please consider silicone wherever I wrote silicon in the context of lubrication :-) .

[kgallen]

[I did resist my pedantic tenancies to correct, but we all usually know when people say silicon (a shiny metallic semiconductor and the basis of my career!) when in the context they mean some sort of silicone (a compound of some other 'stuff', including silicon probably, often used to seal one's bath tub!). One missing letter in a post of thoroughly good stuff is perfectly acceptable! :-D ]