I dearly love the 400, but I just don't mess with anymore

[ACML]

The last two 400's I bought needed some TLC and I forgot what a pain in the butt and how temperamental 400s can be. The 400 was my first computer and that's what keeps drawing me to them when I see a good deal. Its fun to fix them and marvel how small the 400's footprint is, but in the end, I always move on to my 1200XL or 800. I got one now that has great video, but it resets itself, about a half second of static on screen, then reboot. It does it even sitting static on MEMO PAD. I takes about 5 minutes after being turned on. Anyone have any ideas what is happening?

 

 

[russg]

The last two 400's I bought needed some TLC and I forgot what a pain in the butt and how temperamental 400s can be. The 400 was my first computer and that's what keeps drawing me to them when I see a good deal. Its fun to fix them and marvel how small the 400's footprint is, but in the end, I always move on to my 1200XL or 800. I got one now that has great video, but it resets itself, about a half second of static on screen, then reboot. It does it even sitting static on MEMO PAD. I takes about 5 minutes after being turned on. Anyone have any ideas what is happening?

I'm no expert. It seems like an intermittent power source. Maybe a capacitor is shorting out. You could check your power brick, maybe try another.

[ACML]

I really don't think its the power brick as I've been using it routinely on my 1200XL and used it afterwards on a 1200XL and 850 without incident. I should clarify that once it fails the first time, take 3-5 minutes once its been off, it will fail if left on in just a few seconds or certainly less than a minute. Sounds like a heat issue on a component. It does make the screen go to static for a split second. Does that sound like a capacitor or could it be an ANTIC or GTIA going bad (i.e. static screen), then reset?

Edited August 24, 2014 by ACML

[+bob1200xl]

Sounds like the power is going off and then on. The regulator may be overheating and shutting off - cooling a bit - turning on - overheating....

 

Not the brick, the power supply components. Something on the output of the regulator drawing a lot of current. Since the 400 runs correctly for a short while, a passive component like a filter capacitor. Can you swap out the power board?

 

Bob

[russg]

I really don't think its the power brick as I've been using it routinely on my 1200XL and used it afterwards on a 1200XL and 850 without incident. I should clarify that once it fails the first time, take 3-5 minutes once its been off, it will fail if left on in just a few seconds or certainly less than a minute. Sounds like a heat issue on a component. It does make the screen go to static for a split second. Does that sound like a capacitor or could it be an ANTIC or GTIA going bad (i.e. static screen), then reset?

I'm thinking more a power supply problem than a Antic or GTIA or other motherboard chip. The 400 and 800 have separate power supplies to provide DC 5v to the motherboard. You say you have more

than one 400. You could narrow down the problem if you swapped the power board with another. There are large capacitors on the power board. I have a capacitor checker, but don't know how

to use it. A good capacitor, when you test its' ohmage, will briefly show low ohms, then quickly climb to a very high ohmage. If you reverse the probes on your VoltOhm meter then it might repeat.

Capacitors pass AC and block DC. If you get a steady ohmage, that could be a shorted capacitor. I don't know if capacitors tend to short or go open.

With the capacitor still attached to the circuit board, it will effect the ohm readings.

Edited August 24, 2014 by russg

[ACML]

I'll have to try it with another PWR board. The other 400 is temperamental. If you just look at it sideways, it acts up. I finnaly got it together and working and I'm reluctant to mess with it.

[ClausB]

Have you examined your power board for cracked solder joints? Or maybe just resolder all the joints.

[ACML]

Have you examined your power board for cracked solder joints? Or maybe just resolder all the joints.

Quick update: Thanks to ryanr256 helping me out with a parts 400. I was able to identify the PWR board as the culprit. I don't think I'll mess with trying to fix the old PWR board as buying new capacitors would quickly exceed the cost of a whole new PWR board ($15). Anyway, the PWR board ryanr256 sent me has replaced the bad one. This unit will now be sporting a 48K upgrade and low_budget's 5200/400 svideo upgrade board. Now it will have a 5 pin DIN with composite, audio, and Y/C separate video. Just need to muster the nerve to drill a hole in this 30+ year old brittle plastic so I can install the 5 pin DIN.

Edited October 5, 2014 by ACML

[Rybags]

You could probably just route a short cable through where the RF normally goes and put a female DIN plug hanging off the machine.

The RF cable can be unplugged just like the later ones, difference being it's inside the machine itself.

[Faicuai]

That's how I precisely remember my 400... After some time, I remember pressing "Reset" and the whole system would lock-up... Not even continous editing in Basic would be guaranteed. Very strange problem, though.

 

It alwas made me look toward the wonderful 800 and even the 1200xl (!)... It was severely frustrating. That, combined with the not-so-appealing aesthetics of the machine, made me froget it rather quickly (it was just my experience, though, and not necthe reflection of others, though).

Edited October 5, 2014 by Faicuai