Это видео недоступно.
Сожалеем об этом.
Amiga 4000: Repairing Extremely Dim Video
HTML-код
- Опубликовано: 6 авг 2024
- My Amiga 4000 developed a VERY dim display during the recording of my recent video on the Fastlane Z3 SCSI/Memory card. A day after that video dropped, my Amiga 4000s display was down to maybe 5% of its normal brightness and HAD to be fixed.
Follow me, as I work through all of the candidates that could cause the problem. Was it simply a monitor on its way out? Or the LISA graphics chip? Maybe resistors between the video DAC or the DAC itself is where the problem lay? Watch and see how things shake out.
PCBWay Affiliate Link: Use this link to order, get $5 credit and also help Retronaut grow
pcbway.com/g/0aMj5i
PCB Explorer
amigapcb.org/
TheRetroChannel: How to improve the video output from retro systems
• How to improve the vid...
• Help the channel to improve & grow by supporting us on Patreon: / membership
• Drop us a tip, & support us on Ko0-Fi: ko-fi.com/retronauttech
00:00 - Intro
02:30 - How Dim is Dim?
05:20 - Is it the Monitor?
07:45 - Is it the LISA Chip?
08:53 - Could it be the DAC?
09:09 - The ADV7120 DAC
11:11 - The Chips RGB I/O
15:41 - The DAC's Controls
16:19 - The COMP
19:16 - The Vref
21:01 - The FS Adjust
23:38 - Final Checks
25:17 - Ordering Components
27:59 - The Repair
31:04 - Conclusion
#amiga4000 #retro #retrocomputer #amigas #computerrepair
That was a very nice walk though and is helpful for those who have the same problem or are interested in learning to repair Amigas.
Glad you enjoyed it
liked & subscribed. I love to see new channels covering stuff I like.
Great vid and good learning! Nice to see the process of diagnostics as it can be daunting trying to work out where to start. Ta!
Yes, I guess first thing is, DONT PANIC. Its usually diagnosable. Sticky part here was measuring items in circuit. The resistor read exactly as is, but they can return false values. The capacitors though, were all over the shop and could only really be measured once removed from circuit. So, unless you do that first, to pinpoint the issue, do what I did and hedge your bets with your parts order. TBH I want to build up a supply of components, so ordering 30 when I need one, is not much of an issue. But you may as well do that, as the part cost £0.20 whilst postage was £6.50+ :/
Excellent job - thank you very much for sharing! (I like your nice calm an clear way of explaining things)
Glad you enjoyed it!
Cool vids dude
Most components have a tolerance value, and it is rare for cap values to be particularly critical. Of course 100 to 5 is more than a bit out of spec!
As you found it is usually very difficult to measure caps in circuit, and while resistors are sometimes easier, they can also easily show misleading values in circuit because of the interaction with other parts.
I agreed that the digital side was very unlikely to be the fault, and the gradual way the brightness faded made me immediately suspect a capacitor.
Good tracking nonetheless.
Yes, in hindsight, it becomes more obvious that a capacitor was more the likely issue. But I'm still a relative noob at diagnosing issues like this. I made this video, because watching videos on A4000 battery damage and what it can cause, was very helpful in fixing my own A4000. So this is passing it on, if someone else's DAC circuit has issues in their A4000 or A1200 (quite similar setup) this video should help them I think.
They put two 100+10 nF caps in parallel because they have different ESR spec. And not because they wanted to put 110 nF.
Ceramic caps also do fail. They are very fragile and sensitive to mechanical stresses.