-
Hello MLAers! We've re-enabled auto-approval for accounts. If you are still waiting on account approval, please check this thread for more information.
Baroni’s Collection
- Thread starter elbaroni
- Start date
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.
Last edited by a moderator:
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?
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?
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.
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.
Last edited by a moderator:
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.
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).
...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).
Last edited by a moderator:
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!
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.
Love this thread, nice collection. Great two screen setup, but you need to get the monitor off your cooling vents. [
]
]
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?
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?
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.
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.
Similar threads
