Baroni’s Collection

[elbaroni]

Ah, solved one of those mysteries:



Bonus. 

 

[trag]

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.

 

[elbaroni]

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. 

 

[elbaroni]

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?

 

[elbaroni]

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.

 

[trag]

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.

 

[elbaroni]

Trag — a good point. Turns out SIM1 and SIM2 are Bank B, and SIM3 and SIM4 are Bank A. This is...less intuitive than it might be. Unfortunately it also means the broken SIMM socket is in the bank that has to be filled. 

 

[elbaroni]

Swapped the RAM over and...happy chime! Then no video, no sound of booting. Trying alternative video cards. 

Aha! Recognises 820-0198 from 1987, just not the 8•24 from 1990. Makes sense. 

Huzzah!

 

[trag]

Nice progress.   Please keep posting.  You may not get many comments, but folks enjoy others' successes vicariously. 

I like the way you worked TDMS into the photo.

 

[elbaroni]

Thanks Trag - I hope it’s of some interest. Tonight’s problem with the II: won’t boot with the internal floppy plugged in. Not that an 800k floppy is hugely useful, but would be nice to know they’re up and running. Have tried with a few different floppy units, which makes me think there might be something wrong with the chip.

 

[elbaroni]

Having removed the floppy, though: two screens!

 

[elbaroni]

Aaand...now it won’t boot again. Back to powering up, but no chime. Sigh. I guess that means removing the floppy was just a placebo. Still, I got to level 3 in Prince of Persia in the meantime. 

...and another variation: the chime starts, and doesn’t stop. Just holds the note. Slight vibrato. Seems healthy. Intermittent connection in the startup circuitry maybe? Beginning to think 1. this could be quite hard, and 2. maybe wait until my IIfx board is here (to replace the one I posted earlier which I assume is totally munted, although I’ll try). 

 

[elbaroni]

Argh! Thought I’d let out some of my Mac II frustration by trying something nice and new and modern. Quadra 700. All well until *fizz-ZZZZZzzzz* magic smoke coming from the power supply. It kept running long enough for me to shut it down, but kerploding power supplies not a winner. Have plugged it into my IIci supply in the meantime. This should be a lesson to you all - maintain your collections!

 

[elbaroni]

Also, I’d forgotten just how bloated things got by system 7.5. Plugged in a random hard drive with an awesome selection of fonts on it which I want to get off. No Ethernet driver installed. Fair enough - install open transport *and* classic AppleTalk, because I don’t know which will work. Disks 1, 2, 4-8, 10, 11, and a pile at the end. Can’t wait to nuke it and go back to 7.01. 6.08 would be better, but will have to wait until the IIci’s recapped. 

 

[Trash80toHP_Mini]

Love this thread, nice collection. Great two screen setup, but you need to get the monitor off your cooling vents. []

 

[elbaroni]

Thanks Trash — it wasn't there for long!

I bought a cheap IIfx motherboard "in need of repair" — it doesn't boot either, but is in far better shape than my other one. Think I'll practice my re-capping on an LCII, have a crack at my Iici and IIcx, then move to the big box machines. 

In lieu of any real progress, figured I'd post a photo of the disaster that is the old Mac bit of my garage currently. You'll see why I'm feeling a bit overwhelmed about the number of projects (and you can't even see the laserwriters). 

Oh  — speaking of printers, I tried out my ImageWriter II with sheet feeder. Works like a charm, because ImageWriter IIs are indestructible. But the sheet feeder won't take paper reliably. Have tried some rubber roller restorer, but doesn't help much. Anyone got any experience with them? Seems to work electrically. Maybe just needs to be dismantled, cleaned, lubed? 

 

[elbaroni]

Oh, and I did get the Quadra 700 up and running with 7.0.1. That HDD I put in it was haunted. Horrible example of a really crappy era of software — bloated 7.5.5, disk doubler, copy doubler, some godawful fax software that spat up error messages every time it booted, and something which refused to let me copy reliably over the ethernet network and froze the whole OS. 

 

[EvilCapitalist]

In lieu of any real progress, figured I'd post a photo of the disaster that is the old Mac bit of my garage currently. You'll see why I'm feeling a bit overwhelmed about the number of projects (and you can't even see the laserwriters). 

That has to be one of the most organized disasters I've ever seen!  Given the sheer number of machines, and not knowing how many are presently problem children, I can certainly understand being overwhelmed by them.

 

[elbaroni]

Thanks 68k - that minimal level of organisation is new, and there’s still not a lot of empty floor. Getting there. 

 

[CC_333]

I'm very envious of that organized mess!

My collection is in a heap of half-broken storage bins right now :/

c