MEGA ST 2 - what could this strange add on be?

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MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Thu Dec 21, 2017 10:43 pm

Hi everyone,

currently, I am checking a long stored Mega 2 machine. It has a button on the back and inside I found this little add on glued on one of the chips (well the glue is gone, so I lay it on the side for the photo). It is this white "board" with the black box attached and some "transistor"-whatever sticking out. It is connected to the button on the right (back of case) and has a little round battery it seems. The white cable leads to the modem port and the PSU, green and blue cables lead to the PSU as well and the black and red cable lead to the fan. The fan appears much more noisy to me than on another Mega ST I tried (Mega ST 1 in that case). So it might be just to turn the fan on and off? Any ideas?

I could not detect any changes of the fan or TOS version or any other reactions when switching and well, if this is a battery it would be empty anyway. It would be good to know if I should remove it or the battery or try to exchange it.

Image

Also, this machine has issues running software from disk, e.g. TOS errors or just stopping after a bit of loading demos and things like that. Maybe some chips are loose, I will try to press them gently and hope this helps. This action definitive fixed another Mega ST 1 machine earlier this year.

Anyway, would be nice what this little button is supposed to do and if I should care about this device, maybe its the source of errors. Any hints are appreciated!

Thanks and Greetings!
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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Thu Dec 21, 2017 10:57 pm

The disk errors are now gone and loading software works again. Pressing chips helped. However, that fan now turned off completely. Maybe one of the cables is not sitting properly or so. I wonder if the fan in Mega ST can stay switched off completely or if it will overheat? I read its a problem for Mega STE, but on Mega ST maybe its not necessary?
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Re: MEGA ST 2 - what could this strange add on be?

Postby spiny » Fri Dec 22, 2017 8:10 am

I recall there being a mod that would turn the fan on only when needed, presumably temp related, could be something like that. Instructions are on the vezz site but I'm on my phone so can't look at the archive, will post a link when I'm on a pc

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Re: MEGA ST 2 - what could this strange add on be?

Postby joska » Fri Dec 22, 2017 8:52 am

fiveofive wrote:The fan appears much more noisy to me than on another Mega ST I tried (Mega ST 1 in that case). So it might be just to turn the fan on and off?


Ues, it does look like some sort of "Noise Killer". My advice is to remove it and don't bother with the fan. Under normal circumstances the PSU does not get hot. The fan is there for the power user who adds a graphics card and an internal harddrive.
Last edited by joska on Fri Dec 22, 2017 9:08 am, edited 1 time in total.
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Re: MEGA ST 2 - what could this strange add on be?

Postby spiny » Fri Dec 22, 2017 9:00 am

Link:
http://atari4ever.free.fr/hardware/others.html

my german is a bit rusty but the kit listed -is- for controlling the fan, but for the megafile hard drive. which doesn't have a modem port, so probably not what you have in yours :/

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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Fri Dec 22, 2017 6:47 pm

Thanks for the replies and information, this makes sense and explains why the fan was turned on or off at times. The button functionality is still a bit of a mystery but I will make more tests tonight.
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Re: MEGA ST 2 - what could this strange add on be?

Postby DarkLord » Sun Dec 24, 2017 5:48 am

joska wrote:
fiveofive wrote:The fan appears much more noisy to me than on another Mega ST I tried (Mega ST 1 in that case). So it might be just to turn the fan on and off?


Ues, it does look like some sort of "Noise Killer". My advice is to remove it and don't bother with the fan. Under normal circumstances the PSU does not get hot. The fan is there for the power user who adds a graphics card and an internal harddrive.


Well...it might be useful for someone who runs a BBS and keeps their Mega ST4 on 24/7, decades at a time... :roll:
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Re: MEGA ST 2 - what could this strange add on be?

Postby joska » Sun Dec 24, 2017 11:41 am

Yes, if you consider stuffing your Mega full of dust "useful" ;)
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Re: MEGA ST 2 - what could this strange add on be?

Postby DarkLord » Mon Dec 25, 2017 11:12 am

I usually take the cover off and clean it once a year. Oddly
enough, there's not that much dust at all... maybe I've got
a great housekeeper. :)
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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Wed Dec 27, 2017 5:23 pm

You guys were right. Later on I found there is a poti on the device to adjust the fan speed (off to "megafile kind of level"). Maybe the button is to switch on/off temperature detection, but I could not really get this working in my tests. However, setting the fan speed is pretty useful as allowed me to reduce noise from the machine quite a lot. Very nice :)
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Re: MEGA ST 2 - what could this strange add on be?

Postby 1024MAK » Thu Dec 28, 2017 4:38 am

If the fan control circuit is a simple analogue design (which often uses a variable resistor/preset/pot), the button may just be a test facility, try holding it in and see if the fan speeds up.

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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Fri Dec 29, 2017 6:35 pm

Thanks Mark. Switching / holding the button did not affect anything like speedup. But the temperature detection seems to work in a way that the fan starts after a while when the machine is in use and not instantly when the machine is switched on.
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Re: MEGA ST 2 - what could this strange add on be?

Postby Foxie » Tue Jan 23, 2018 2:13 pm

AFAIK, the fan isn't necessary in the Mega ST (Mega STE might be another story). Mine was a Mega 1 originally and never had the fan. Atari shipped many (all?) Mega 1s without fans. I upgraded to 4MB and still had no fan. Never had any issues but that's not surprising considering it's basically the same hardware as a 1040ST.

The fan could come in handy with a power-sucking expansion board fitted.

Wires going to the modem port makes me think of high speed serial port mods.

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Re: MEGA ST 2 - what could this strange add on be?

Postby troed » Tue Jan 23, 2018 2:31 pm

That was news to me that the Mega 1s came without fans, interesting. I've always thought they were added since "professional computers" had to have fans ;)

The Mega STE PSU (which is where the fan sits) definitely needs one, yes, since the PSU is completely enclosed.

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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Tue Jan 23, 2018 3:03 pm

According to this article in ST Computer Magazine (German) from 1987 first there were only 2 and 4 MB models and 1 MB models that were announced before were skipped. Obviously, this had been changed shortly later on or was a misunderstanding on side of the journalist and Atari delivered a 1 MB version, too. It could be an explanation that Atari wanted to serve the lower cost range with the 1 MB models and skipping an only half-necessary fan added to this intent. Also, I read that the layout of the 1 MB model RAM was different and rather difficult to expand.

As you can read, the models were sold as sets with monitor and mouse. Prices at this point (September 1989) were: Mega ST2 bundle DM 2998, Mega ST4 bundle DM 3998 which equals 1500 and 2000 Euro respectively. No idea what were the costs of the 1 MB version. EDIT: This Dortmund Computer museum page mentions DM 1900 (950 Euro) as price for the Mega 1.

The original intention to offer 2 and 4 MB models is also visible here: http://www.atarimuseum.com/computers/16bits/megast.html
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Re: MEGA ST 2 - what could this strange add on be?

Postby Foxie » Tue Jan 23, 2018 3:16 pm

troed wrote:The Mega STE PSU (which is where the fan sits) definitely needs one, yes, since the PSU is completely enclosed.


That's one of the things that puts me off getting a MegaSTE. It would be a bit noisy in a studio. I wonder if there's enough internal space to fit a silent 120mm fan at an angle and duct it into the PSU? Or I guess the entire PSU could be removed and replaced with an efficient external brick.

fiveofive wrote:According to this article in ST Computer Magazine (German) from 1987 first there were only 2 and 4 MB models and 1 MB models that were announced before were skipped. Obviously, this had been changed shortly later on or was a misunderstanding on side of the journalist and Atari delivered a 1 MB version, too. It could be an explanation that Atari wanted to serve the lower cost range with the 1 MB models and skipping an only half-necessary fan added to this intent. Also, I read that the layout of the 1 MB model RAM was different and rather difficult to expand.


From what I recall, my machine was a later model. It had the small floppy eject lever. Back then my soldering skills were awful so I took the machine to a place in London to have it upgraded. They fitted a board with SIMM sockets to achieve the upgrade. It's been a while since I looked inside, I can't remember how it's wired in.

One thing I do remember being an annoyance with the Mega was the keyboard socket position. If I used a large cartridge like Video Master, you'd have to squash the keyboard cable in between the cartridge and the case. Another annoying feature was the placement of the reset switch. They should have moved that to the back of the keyboard! In the end, I built a monitor switch box which had a reset switch on it (achieved by toggling between low and high res). Of course that didn't work if the program had disabled all the interrupts.

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Re: MEGA ST 2 - what could this strange add on be?

Postby troed » Tue Jan 23, 2018 3:27 pm

Foxie wrote:That's one of the things that puts me off getting a MegaSTE. It would be a bit noisy in a studio. I wonder if there's enough internal space to fit a silent 120mm fan at an angle and duct it into the PSU? Or I guess the entire PSU could be removed and replaced with an efficient external brick.


With a modern 60x60 fan it becomes almost completely silent, see https://blog.troed.se/2016/07/14/mega-s ... -upgrades/

I'm not a musician though, our definition of almost silent might vary, although it's really silent :)

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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Tue Jan 23, 2018 4:17 pm

In my opinion the original harddisk (Seagate 48 MB) is the more annoying part in the Mega STE when it comes to noise. If the machine is running without harddrive or a proper replacement e.g. Ultrasatan, the noise coming from the psu fan alone is not that bad, at least nothing close to the noise produced by a Megafile or similar devices. While I have one installed with the Mega, I never use it on due to the noise. It is a practical monitor stand after all ;) But marketing of the ST as music studio machine and offering Megafile harddrives at the same time stays a miracle to me :)
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Re: MEGA ST 2 - what could this strange add on be?

Postby Foxie » Tue Jan 23, 2018 4:45 pm

fiveofive wrote:While I have one installed with the Mega, I never use it on due to the noise. It is a practical monitor stand after all ;) But marketing of the ST as music studio machine and offering Megafile harddrives at the same time stays a miracle to me :)


Oh yeah, I had a used Megafile for a time and it was deafening. It actually made the machine unpleasant to use like an IBM! It was fast though. Then it crashed, and I lost some data I hadn't backed up. I still have the shell somewhere.

Most music machines I saw tended to be 1040STs rather than Megas - might be for that reason. Also the Mega has some issues accepting certain cartridges.

I think it's crazy they added a fan to the Falcon. That's the worst because you can't hide the machine away in a machine room like you can with a Mega. I wonder if the stock Falcon even needs its fan? The A1200 manages without one.

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Re: MEGA ST 2 - what could this strange add on be?

Postby fiveofive » Tue Jan 23, 2018 6:17 pm

About ST in music studios, maybe simply using discs was very common. Once the sequencer was loaded, as I suppose there was not much to read and write except rather small midi files. Mega was more targeted for offices I suppose. But thats wild guessing :)

These threads cover the Atari Falcon fan topic:
http://www.atari-forum.com/viewtopic.php?t=11230
http://atariage.com/forums/topic/247582 ... he-falcon/
http://www.atari-forum.com/viewtopic.php?t=28044

My conclusion is that you can just remove it / switch it off when you use a CF-Card instead of an internal harddisk. I will do the same as soon as I find time and a way how to do it technically.
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