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elbaroni

Baroni’s Collection

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Right. I’ve had a lot of these for a while, but I’ve only now caught my breath after having twins and moving house (in 2010...ahem) to start looking at them properly. First off is my Mac II upgraded to a IIfx. I don’t think this is very healthy. B72C8B8B-2368-4561-AD81-3E143E1FC3E0.thumb.jpeg.acdd6d14ec08daa6a88d9e9dfc2dc6fd.jpeg

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Gack - I reckon around the RAM slots is where the pain repairing is, as they're so hard to clean and check I find.  Good luck with the repair!

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Yeah. That doesn't look to good. 

 

At a minimum, those RAM slots should probably be replaced?

 

c

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Moving on - my IIci. This one powers on and runs well, but won’t power off regardless of the rotation of the power switch and has no sound. 

 

Odd artefacts on the screen when using built-in video on a portrait display at 16 colours. They seem to disappear when I change the desktop background, so perhaps just a CLUT issue. 

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Edited by elbaroni
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Artefacts.

 

Bad RAM or CLUT? Thought it was linked to instability for a while, but then discovered my FloppyEmu was riddled with WDEF-A, which apparently has a bug on IIcis. 

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Needs new caps.

 

There might be more damage in the power management circuit which prevents it from turning off correctly.

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In short: bugger. Time to learn to solder. Seems to be the surface mount ones rather than axial, but guess I should get them all. 

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Okay, so I find I need the following for the IIci (thanks to maccaps - the mm measurements are mine):

8 - 47µf - 16V - SMT — 6.4mm wide

3 - 470µf - 16V - Axial — 21.5mm wide

2 - 10µf - 16V -SMT — 4mm wide

1 - 220µf - 16V - Axial — 16.3mm wide

 

I can’t find anything specifying the ESR I need though. Tantalum ones in the right (adjusted for down rating) voltage and capacitance range from 40 mOhms to 1.2 Ohms. 

 

I see the caps Trag is offering Here are 800 mOhms (This one), but I’d like to understand how to determine this. 

 

As as may be obvious I know nothing about this stuff. Any advice gratefully received. 

 

 

Edited by elbaroni
Typo

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@elbaroni I used to be in the same boat as you not too long ago.  This is what I've come to understand about recapping and capacitors:  capacitance is what matters: the µf (microfarads) part.  So you want to make sure that one is equal to what you need.  The Voltage part is the rated tolerance.  This one can be equal to or greater than what you need.  So it's OK to put in a higher rated capacitor such as 47µf 20V in place of a 47µf 16V.

 

ESR isn't specified because it probably doesn't matter too much in this case.  From what I've read, the lower the better.

 

Next is to just make sure that it's the right type of cap.  Tantalums are good replacements for surface-mount caps.  Axials are for a couple of the horizontal through-hole caps, and radials for the regular through-holes.

 

I just can't remember the type of capacitor, but there's one that LOOKS like an old electrolytic surface mount, but they're more reliable.  They're also more expensive, but they'll keep the old-school look of the motherboard without using tantalums.

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I think the ESR only really matters when you're dealing with heat-sensitive stuff.  According to the Googles, the lower the ESR, the lower the amount of energy is dissipated as heat.  So I would imagine that would make a difference if you're trying to make an efficient power supply and keep the heat levels down.  Or if a device operating in a temperature controlled environment.  That kind of stuff.

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This has been a good morning. A LaserWriter I, a LaserWriter IIf, a LaserWriter IIg, and a 13inch trinitron monitor. 

 

The seller (near Bathurst in Australia, so not much use to most of you) has a massive array of apple stuff - at least four SE/30s with Ethernet cards, at least six complete Mac plusses, LC580s, apple IIes with monitors, PowerMac 6100, 5400ish, image writer IIs including one sheet feeder, several Inagewriter Is and a LaserWriter IIntx. All in a decrepit old house that’s being renovated. No power, so can’t test, but certainly worth checking out. 

 

https://www.gumtree.com.au/s-ad/bathurst/computer-accessories/apple-vintage-computers-equipment/1217771713?utm_campaign=socialbuttons&utm_content=app_ios&utm_medium=social&utm_source=ios_social

 

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Finally got to trying the LaserWriter IIs. The IIg has the two red flashing lights which the service book tells me means new laser assembly. The IIf boots fine, shows up on a network, and prints...kinda...but with some paper feed issues. 

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And finally got to the Laserwriter I. Don’t know yet if it’s a plain I or a plus (or what version of the plus) but it looks super clean inside apart from one spider corpse. I’ve ordered a new toner cartridge because the foam on the old one has liquidated. Turned it on and it made all the right noises, identified correctly that there’s no paper (although there is a paper tray!), but I turned it off before the green light stopped flashing. Dunno about that serial port though. Still, found a db9 appletalk kit for $5 which is cool. It and the toner are en route. 

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On 5/15/2019 at 11:10 AM, olePigeon said:

I think the ESR only really matters when you're dealing with heat-sensitive stuff.  According to the Googles, the lower the ESR, the lower the amount of energy is dissipated as heat.  So I would imagine that would make a difference if you're trying to make an efficient power supply and keep the heat levels down.  Or if a device operating in a temperature controlled environment.  That kind of stuff.

 

ESR can matter in a time dependent circuit.    The time a circuit takes to change is usually proportional to RC where R and C are resistance and capacitance in the circuit.    

 

As R gets higher, the capacitor is slower to charge and discharge.    When capacitors are being used as bypass (power smoothing) this doesn't matter very much, as long as it is not extreme.    You want your caps to react quickly and discharge during low voltages and absorb charge during high voltages.   However, that is why there are many sizes of capacitors used.

 

The tiny ceramic caps close to chips have capacitances in nanofarads, typically, and react very very quickly to voltage fluctuations.  However, they can only balance small fluctuations, because their capacity (capacitance) is tiny.    Larger caps are slower, but have more capacity for larger fluctuations.

 

This works okay, because large fluctuations take more time to occur than small fluctuations.   If the preceeding isn't true, then you have a large current excursion somewhere and there are bigger problems...

 

Also, if ESR is too low, in theory, the current to the bypass (balancing) capacitor could overshoot and cause ringing in the power circuit.

Edited by trag

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Wow this stuff’s complicated. I guess most things are when you’re two weeks into learning about it, but yikes. Thanks all for your replies. I’ll let you know how I go. Might practice on a Performa before I break something a care about. 

Edited by elbaroni

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Continuing my saga of failure, tonight I tried out my Mac II. Dead as a doornail upon initial attempt, multimeter on the batteries indicating they were dead. Unsurprising given they're 32 years old. What was surprising was that they hadn't leaked. 

 

Soldered — amateurishly — a new pair on. Cheapies from the local electronics store, but I'm impatient. 

 

Now: Partial success! Hit the power key with no monitor or video card: HDD spins up, no beep, no booting.

With a monitor and video card: sad Mac chimes. Power gets to monitor, but nothing shows up. 

 

Discovered one of the RAM slots is missing a plastic tab, so one of the SIMMs was wedged in place with one of the machine's rubber feet (which you can see in this pre-soldering image). Took the right hand SIMMs out — now no sad Mac chimes, but back to HDD spins up, no beep, no booting, power gets to monitor, no image. 

 

Can't see any sign of capacitor leakage. Known good monitors and video cards x3 and x2 respectively. 

 

AFAIK: Speaker good (sad Mac chimes) power supply good (HDD spinning up; monitor power); ROM good (sad Mac chimes) RAM good (no sad Mac chimes when half removed). There isn't a RAM jumper is there?

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And examining my Aunt's old SE I find the RasterOps ClearVue SE card in it — I fear I threw out the two-page monitor a million years ago. Foolish, foolish. 

 

I see from this archived post at Mac Gui that "This adapter has a high-res frame buffer, selectable for 1024x768 or 640x870 with an integral 16 MHz 68000 accelerator." Now that I look at the insert in the back of the SE I see that next to its current 9-pin port it has a blank spot for what I would think is a standard Mac DB15 monitor port. I found a site in German which Google Translate advises me says "The supplies with TTL level on / HSync (pin 23) and on / VSync (pin 22). It depends on which type of driver chips between the TMS34061 and the SubD socket are." Uh huh. 

 

I wonder if it's possible to find the pinouts anywhere, or build the cable from the internal port to a DB15 port — would be super cool to run on elf my portraits off an SE. Another project. 

 

Also, of course it boots to a vertical line on the screen, so analogue board repairs are in order.

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Edited by elbaroni

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No RAM jumpers on the Mac II, but you should check for rules about which RAM bank must be populated if only one is populated.  There are also some oddities about which bank must have a larger capacity if two different sets of RAM are installed in each bank.

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