Is using an external fan needed with a Mac Plus?

[Mac128]

I use my 512Ke much less than I should wish to do simply because it is fanless. The bucket above the analogue board is not louvred ...

I have accepted that I may as well also make another hole in the bucket for a 12-V fan exhaust, and make slots in the bucket above the FBT.

equill, are you saying your 512Ke does not have the same rear bucket the 128K, 512K & Plus have? i.e. vents on the top left & right side of the handle and vents in the top rear chamfered corners? Traditionally the fans added to a 128K-Plus go in the corner opposite the analogue board. The bucket you are describing sounds more like a Classic with vents only under the handle.

a few of his decisions have caused engineers and consumers more than a bit of grief.

Tom, you neglected to mention the original anti-fan heat debacle: the Apple III, which overheated to the degree that the chips expanded and popped out of the logicboard and Apple actually suggested consumers drop the computer on the floor to re-seat them. I guess Jobs figured if there were no sockets in the 128K, they couldn't expand and pop out from the heat, so no worries.

 

[JDW]

Traditionally the fans added to a 128K-Plus go in the corner opposite the analogue board.

Yes, that is where my HyperDrive fan is located, as shown in this photo.

 

[equill]

equill, are you saying your 512Ke does not have the same rear bucket the 128K, 512K & Plus have? i.e. vents on the top left & right side of the handle and vents in the top rear chamfered corners? Traditionally the fans added to a 128K-Plus go in the corner opposite the analogue board. The bucket you are describing sounds more like a Classic with vents only under the handle.

Verily that is what I wrote, but it is not the case (pun accidental). The chamfered corners have horizontal slots. The top side edges are indeed provided with (seemingly) pressed-in louvred panels, rather than the same kind of open slots. This press-in could have been Apple engineers' desperate late response to the fiat against an internal fan, as raised by tomlee59.

When I first held the bucket to the light some days ago the louvres appeared simply to be translucent plastic grooves. However, your question prompted me to go back to where I have been handling the bucket intermittently for several days, and to look with an angled light source. Sure 'nuff, there are slotted openings at the rear edges of what I had wrongly taken to be mere incuse grooves. The bucket defiantly displays the Apple press-in logo. and the legend 'Macintosh 512K', as well as the moulded-in P/N 810-0374- and stamped-on 630-5139-A.

With the acute vision that hindsight engenders, the intended internal fan's position could be thought to be reflected in the moulding of the bucket, but in a position closely analogous to that of the SE/30's fan. The signatures in that part of the bucket would have been casualties of the fan's positioning, as the signature of Steven Jobs near the centre is already (and perhaps, ironically).

de

 

[Mac128]

The top side edges are indeed provided with (seemingly) pressed-in louvred panels, rather than the same kind of open slots. This press-in could have been Apple engineers' desperate late response to the fiat against an internal fan

Whew! For a minute there I thought you had some kind of late model variant to the 512Ke!

As Tom Lee correctly points out, Jobs always intended the Mac to be fan-free ... it is the engineers who attempted to defy him with expandable logic-boards boards and fans ...

As for the top vents, I don't believe it was ever a last minute decision as Jobs always intended the Macintosh to be convection cooled and fan-less. I would need to double check, but I'm pretty sure that's what I recall from various sources. Actually a lot of thought went into the deign by Apple engineers to make Job's vision possible. The top vents are one such example. Jerry Manock, responsible for the overall industrial design language at Apple up to that point, as well as specifically the rear bucket, took great pains to come up with a design which would both adequately vent the heat (notice I did not say optimally), but also keep small children (present in the households of the target consumer) from sticking things into the top of the Mac which could easily come in contact with lethal electronics. If a child stuck a paperclip into the bottom grille, at worst it would short your logicboard. But nobody would die. All this is explained in Kunkle's Apple Design and other sources. My guess for the vent inserts, versus moulded directly into case is that it was too complicated a mould for the technology of the day to do in one piece ... it is also the only aspect of the Macintosh that doesn't conform to Jobs' other mandate that the Macintosh be as close to a single moulded unit as possible with no seams. Obviously he compromised his vision for safety. You'll note the vents in the chamfered corners are equally resistant to inserting something, but were obviously accommodated by the mould.

 

[Mac128]

Traditionally the fans added to a 128K-Plus go in the corner opposite the analogue board.

Yes, that is where my HyperDrive fan is located, as shown in this photo.

I had forgotten that picture. Excellent example. The Dana has that auto-on thermostat too, a nice touch back in the day. Larry Pina shows the exact procedure and a similar picture as well for just the fan. If you don't have one already, Macintosh Repair and Upgrade Secrets is a MUST have for the Vintage Mac user and fairly easy to come by these days.

FYI, adding a fan requires adjusting the voltages to accommodate the added power requirements.

ALSO: The SE sold an optional floppy drive plastic shield back-in-the day as an "option" to reduce the amount of dust sucked through the floppy drive opening and eventually clogging the works. You would be well advised to create a similar enclosure around your Plus floppy drive to avoid future problems there, especially considering the venerability of these early drives to mechanical failure. Hard to believe it was an option based on the grotesque conditions I have found many of these drives from SEs which were never cleaned.

 

[Bunsen]

I wonder - some kind of homebrew heatpipe soldered to an external heatsink out the back of the case for silent cooling?

 

[equill]

Positive fan ventilation, so as to reverse the direction through the FDD? Maybe even improve the airflow past the power/sweep board?

de

 

[JDW]

Mac128, since you mentioned the required analog board voltage adjustment after adding a fan, I thought it best to mention one more thing. The fan in my HyperDrive 512 also passes it's power wires through a filter, as shown in this photo. EMI filters and chokes are technically not required, but if you see "snow" on your CRT after adding a fan, you will need to add such filters to clean it up. As a result of having these filters (which are external and separate from the secondary PSU that accompanies the HyperDrive), there is no on screen noise when the Hyperdrive and cooling fan are running. The screen is just as clean as my other Mac512 which is stock (no fan, no hard drive).

 

[Mac128]

Positive fan ventilation, so as to reverse the direction through the FDD? Maybe even improve the airflow past the power/sweep board?

It's worth a try ... however, it does not sound as efficient. The entire configuration was designed to maximize convection, i.e. the hottest components located near the top to draw cool air up. Forcing air down through the Mac would actually send hot air down into the case.

As for the reverse airflow through the FDD, that would not eliminate dust build-up. In fact more dust might be drawn in from the top than gets sucked in from the bottom. Either way, without a dust shield, the FDD is going to get filled up with dust bunnies no matter which way the air flows. Apple finally added a slot cover to the Superdrive around the Colour Classic era to prevent dust from getting sucked-in through the drive. These drives were almost fully enclosed as well.

 

[equill]

'Positive' in this connection may have meant something different to you from what I intended, which was maintenance of a positive static pressure within the case, as opposed to the negative static pressure during air extraction by an exhaust fan. I envisaged that air be blown into the case by the fan, and therefore that it follow (more-or-less) the path intended for convected air over the power/sweep board and out through the top vents. How much dust ingress there might be would depend on the point of air input, and the presence or absence of a filter at the input. Having air flow through the FDD from heads to insertion slot could well be an improvement over the reverse direction of airflow, although that is at much slower flowrates during convective cooling.

de

 

[Mac128]

equill, no i got what you meant. picturing the intake fan in the same location as for exhaust, you will be forcing hot air from the top of the case down through the case, regardless of how cool the outside air is, you are working against physics to push the hot air generated at the top of the case down through the bottom. Since dust generally is stirred up in the air and settles downward, pulling air through the top will also pull in more dust. Therefore, I doubt the flow direction of dust-infused air will matter much.

Now if I follow what you are saying now, I take it you mean to install the intake fan near the bottom vents. That is certainly preferable, but somewhat challenging. I suppose the fan could be mounted parallel to the metal chassis over the large opening behind the FDD above the logibcboard. This is similar to the Classic/II fan with the air scoop drawing air in from beneath the case. I would still seal up the back of the FDD to prevent airflow through the bulk of the drive as well as the other openings in the chassis deck to maximize the draw of cool air through the bottom vents and minimize hot air recirculation. But trust me, you'll still be drawing air in through the bottom vents and my 512Ke that had used a Kensington System Saver had a thick carpet of dust coating the logicboard. That more or less confirms an equal amount of dust is likely to cover the FDD, regardless of which direction the air flows.

None of this is particularly destructive either. As long as we're making changes, I had always thought mounting the speaker on the analogue board face down on the chassis would improve the speaker sound by sending it unobstructed through the bottom vents. With the addition of a fan, it could be mounted face up through the front top grille opposite the analogue board.

 

[equill]

Your view of mechanical air replacement may be a tad jaundiced, perhaps from experience with clogged vents or the like? The SilenX IXP-34-08 Ixtrema fan that I have on the way is rated at 10cfm, or roughly 10 replacements of the internal air each minute. Even at half that throughput I suspect that few calories generated by the electronics will hang about for more than a moment, and the airflow's turbulence will prevent formation of any dead-spots anywhere inside the case.

Although the pudding has yet to be eaten—and I am prepared to experiment with directing the airstreams by judicious masking of the case vents—I have no fears about the outcome of forced ventilation. I am no stranger to airflow patterns, having spent four years at one time in the development of a method to produce high-activity dry yeast from compressed yeast, using air-lift dryers.

de

 

[bigD]

equill - it's funny how I have to shift my brain every time I read your posts. It's like going from day to day conversation to all of a sudden reading some Dickens, or something. LOL - it's not a knock, just an observation.

 

[equill]

No offence taken. Be assured, though, that the relationship between my screen name, avatar and occupation is far from accidental. And the use of MacDraw for the avatar is also no accident.

de

 

[Mac128]

Although the pudding has yet to be eaten—and I am prepared to experiment with directing the airstreams by judicious masking of the case vents—I have no fears about the outcome of forced ventilation.

Uh, right. I do not recommend masking any external vents. I mean to direct and maximize the cool air flow from the bottom vents in much the same way as the engineered Classic/II does (which by the way returns the vent to the handle area previously removed from the SE). Meaning using duct tape, or the like to cover the openings on the deck of the metal chassis for all but below the fan's mounting. Then likewise use duct tape to cover the back of the FDD to minimize airflow through it. Otherwise I am in complete agreement that there will be substantial turbulence inside the beasty to keep it cool.

That said, I still prefer fanless, blissful silence. I think the M0001 was brilliantly engineered and is as elegant a solution as Mr. Jobs demanded. My perspective as to its well-documented failures has more to do with sub-standard components for the design (presumably to to maximize profits). Either way, it's hard for me to imagine using my M0001 for such extended periods as to overwhelm its engineering resulting in accelerated failure. Of course most of my boards have been upgraded with the more robust parts recommended. As I have stated elsewhere, I have a late model Plus (1990) which was used extensively over the years, in a hot poorly ventilated office space for many hours at a time and has never once been in the shop for repairs.[/u]

 

[dbraverman88]

I have read a rumor that Apple changed the design of the Mac Plus power supply at some point. When users began to install 4MB of RAM in the Plus, the power supply would overheat. Apple examined the issue and installed a better power supply in later Mac Plus units. Mac Plus computers with the second type of power supply were not as likely to overheat.

As I have stated elsewhere, I have a late model Plus (1990) ...[/u]

It could be Mac128 has had success without active cooling because his Mac Plus was manufactured later in the production run. Perhaps only the earlier Mac Plus computers with the inferior power supplies require active cooling to prevent overheating.

Is there any truth to this rumor? If there is, when did the change in power supply occur? My Plus has a date of 1988 on it.

--David

 

[JDW]

David, it would be VERY helpful if you could open your Plus, remove the analog board and shoot some photos for us. Seeing the numbers on the analog board is what we're mainly after, although I wouldn't mind seeing the flyback and other components used on your board.

You can see my analog board photos here.

 

[trag]

Do some research on the Mac Chimney...supposedly the best way to cool them. Mac Bible should explain it for you if you get an earlier edition. It's basically exactly what the name says--a big chimney for the top of the Mac to cool it down!

Here's the one I built back around 1990:

http://www.io.com/~trag/Chimney/Chimney0.JPG

http://www.io.com/~trag/Chimney/Chimney1.JPG

http://www.io.com/~trag/Chimney/Chimney2.JPG

http://www.io.com/~trag/Chimney/Chimney3.JPG

It'snot the professionally die cut one, but it worked for several years.

 

[Mac128]

trag, LOL, I LOVE that! I had seen that picture on the net before ... now I know it was you! It's like some kind of Wizard of Oz Mac.

JDW & dbraverman88, I had posted my analogue board info here: http://68kmla.org/forums/viewtopic.php?p=26919#26919

The 820- numbers are the key, not the 630- numbers. It would appear that Apple figured out real quick they needed to update the board (if that's the case) as my June, 1990 "820-E" board is copyright 1986. This is clearly the last US domestic 120v analogue board produced since the Plus was discontinued in October 1990. JDW, it would be great to get the 820- number from under your 661-0462 replacement board's vinyl cover, since yours should be the late model also and identical to mine based on its 630- number. You already have the B & C boards, so all I may need to do is cover the "D" board pictorially since I think you have the E. We need to get stevep to document his late model International board more thoroughly as well.

JDW, with your existing Excel spreadsheet data and pictures from the missing "D" board from your collection, excluding any undocumented modifications, you should be able to catalogue an extremely specific and detailed upgrade history for the M0001 analogue board components.

 

[tomlee59]

I have read a rumor that Apple changed the design of the Mac Plus power supply at some point. When users began to install 4MB of RAM in the Plus, the power supply would overheat. Apple examined the issue and installed a better power supply in later Mac Plus units. Mac Plus computers with the second type of power supply were not as likely to overheat.Is there any truth to this rumor?

I have not done an exhaustive tracking of what was changed over time (but I suspect JDW has, and will chime in shortly). I do know that the flyback was upgraded fairly early on, so incidents of HV failure dropped quite a bit. However, the yoke connector problem (triggered by heat) was pretty much a constant over the life of the Plus. The basic switching supply topology did not change (AFAIK), and there were no component upgrades that made much of a difference in efficiency. So, the amount of heat produced likely remained constant. Improvements in longevity mainly came from component upgrades aimed at reducing their sensitivity to the heat.

If JDW (or anyone else) has specific knowledge of power supply changes during the life of the Plus, I'd love to hear from them.