| Attachment | Size |
|---|---|
 Without RAM (8MB) | 525.29 KB |
| With RAM (8MB) | 4.35 MB |
I was recently trying to fix my 3.5" floppy drive. Plugged it in and the motor ran endlessly. Unplugged it from the IIGS and turned the IIGS back on and now it doesn't even boot.
Boot screen either goes to purple/green OR shows an endless set of question marks "?" OR shows random scrolling gobbly good.
Please help fix as I just got this ROM 01 IIGS and was so excited to get it going. Everything was working so perfectly. Thank you so much.
Any difference with a disconnected keyboard? If no -- RIP.
Thanks for your help!
No difference. Why would you say RIP when it was just working? Id like to better understand since Im shocked it just stopped. Maybe the ROM or RAM broke?
Is there a beep at all, or does it just go straight to the garbage screen? Will the self test run (hold down open apple and option when powering on)? I know models prior to the IIgs, no keyboard plugged in would trigger the self test, which is possibly why someone else asked. I'm not sure if that applies to the IIgs though.
Nope, Apple-option doesn't work. No real boot chime, as much as I can tell.
Any chance you plugged in the drive while the system was "hot"? Asking because that's amost 100% guaranteed to do what you describe.If not, have you verified you have a good power supply? And a working supply does not mean it's good.
I don't think I plugged the drive in while the systsem was powered on, if that is what you mean by "hot". I have not verified the power supply, but if it really was the power supply then why would it power on at all?
Undervoltage can cause things to partially work. It's an easy thing to check, and usually one of the first things looked at when vintage hardware is acting up. Make sure to check it under load/connected to the IIgs. You should be able to easily check it where the wires go into the plastic plug.
Okay. Could you explain how I would know if the power supply was good or not?
Measure the voltage. Of course, that assumes you have a digital multimeter (DMM) and know how to use it. Which I'm starting to think that was a faulty assumption.
I think I've got a DMM. Just being extra careful before I start poking around with my already-broken IIGS lol
Voltages (not under load):
-4.79
-10.89
11.32
5.14
This switching power supply uses a single high-frequency transformer to convert its primary voltage (around 350 VDC) down to each of the four output voltages. This configuration can't regulate each output independently: the feedback signal raises or lowers them all at once. Since +5 VDC is the most critical output that all the digital logic runs from, it is the most important voltage for controlling the feedback.
When you measure the PSU outputs without a load on +5, the feedback is effectively shut off by the +5 rail rising to its upper limit. In turn, this shuts down the primary side switch, which stops putting energy into all four of the outputs. The other outputs would be expected to be low under this condition.
So you do not think the power supply is the issue?
Impossible to tell without load test
Got it. Results under load:
-5.02
-11.56
11.60
4.91
Also, does seem to do something different when keyboard is disconnected.
The Vcc (+5) is within 2%, which is fine. All supplies are within ±5% which is the spec.
The power supply seems nominal, although this doesn't yet measure noise. If you have a decent TRMS meter you can do the same tests, but on AC volts. It's not an oscilloscope, but it should give an idea of the total noise on each output rail. In this case, closer to zero is better: I would like to see less than 1% of the nominal output in the form of noise+THD.
A problem in the output filtering capacitors would manifest as increased noise.
Does anything different happen on screen if you hold down the "Option" key when switching on?
What does this mean? I'm sure you got a good rundown on the "working" vs "good" power supply. It's something engineers understand and there's many reasons as to why it's true. But... it's also like the battery you test at 1.5V but then try to use it and find it doesn't really work. While loaded/unloaded is the thing there it's more related to available power (function of the transformer, feedback loop and capacitors). Also, the IIGS power supply can be tested unloaded but only really helpful in determining somthing is bad rather thatn good. Glad you got it tested loaded and I think your numbers look fine but I would like to see what happens to 12V when a drive spins up because that drops momentarily and depending how much it can drag down 5V too. If 5V is affected or 12V drops by more than .8V and can't recover in under a second it may signal a problem in the supply. But to see this detail in the power you'd need a scope. And that would also show the noise/ripple mentioned by robespierre.