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Author Topic: A4000D - Yellow screen  (Read 1376 times)

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Offline cehofer

Re: A4000D - Yellow screen
« Reply #14 from previous page: January 13, 2023, 05:15:52 PM »
FYI,

Even after I fixed all the continuity of the traces and before I replaced the chips, it still didn't fix my problems.  I was really discouraged at that point.  It wasn't until I removed, cleaned and replaced the 3 chips that it fixed my problems.

I purchased my solder/heat gun station 4 years ago on ebay for around $250 US.  I did because I had 2-A4kT, 3-A4kD, and a CD32 to recap as well as their power supplies.  I wanted nice heat control to be able to recap the smd caps.  I am still not fully confident on using a heatgun to remove chips.  I purchased an IR table to preheat. 
There is a guy in NZ who is highly recommended and not cheap.  There is pretty much nobody in the US that does it that I am aware of.  I am scared that my stuff would get lost or damaged if I shipped it all the way to NZ plus the shipping would be outrageous.

The solder station was a good investment.  I have used it to repair a lot of other stuff too besides my Amigas.
« Last Edit: January 13, 2023, 05:48:08 PM by cehofer »
 

Offline TumbleweedTopic starter

Re: A4000D - Yellow screen
« Reply #15 on: January 13, 2023, 08:15:53 PM »
I might just incur the cost of getting a proper rework station. The guy in New Zealand fixed my A3000T a couple of years back. Top job too. Board looked brand new when I got it back and he helped me when I had a couple of teething issues when I re-installed it in the tower - I messed up refitting the ZIPs.

Ive got a 2000 & 3000D that need recapping and a A1200 thats 'dead' - black screen no sign of life so might just might be able to justify the cost.

Weed.
A3000T, Cybervision64, CSMKII 060; A3000D, PicassoII, Z3 Fastlane; A2000D, 040, PicassoII; A4000D, A1200, Blizzard 030 MKIV  (not working - next project)
 

Offline cehofer

Re: A4000D - Yellow screen
« Reply #16 on: January 13, 2023, 10:30:55 PM »
« Last Edit: January 13, 2023, 10:32:33 PM by cehofer »
 
The following users thanked this post: Tumbleweed

Offline TumbleweedTopic starter

Re: A4000D - Yellow screen
« Reply #17 on: January 14, 2023, 08:08:50 PM »
That look like it will do the job. Its similar to one I was looking at on Amazon. I'm in UK so found this one on ebay:

https://www.ebay.co.uk/itm/255844036734?hash=item3b917e307e:g:K-oAAOSwHYZjfx3f&amdata=enc%3AAQAHAAABEA41IEMvOn9XcvsOaMj3kN%2BRAxMpMmTBHG%2BJjzGnUpSiyWivfuos5YsCm3xI4ue7fmGCnuRtb2%2B2J%2Bz3YP1x0Lgv0cqwu%2BBssT%2BlHKkq2BIE84Wqw8t40r9wpSttl8jseh9%2BAXRFnbExZfdr2WrlQDNard78AK8fVDkeEw7ezk6jzaE7ybpEQrf0BNYmv6fmLPZ5LN3fiVkDVg47KfAKr7be12f0i1kMidjFMfJ0vknCbKoV6Sc8pc7Fwd9bE7mhiDg%2F8txI4hvQPoFPS4W3xq%2BW0z9tjJEIT7%2BuB4arSZHdRWJuMEWjB8f0oy4C4VYbdTWHfe%2BxJLI25vVWoRvrEXVWjEabCVnHaGgG3%2BOkYS4b%7Ctkp%3ABFBM4sCpm7Zh

The one on Amazon I was looking at was this one:

https://www.amazon.co.uk/Soldering-Temperature-Stabilization-Function-Electronic/dp/B08YD66SXZ/ref=sr_1_2?crid=2VUX6G0U65A6I&keywords=YIHUA+862BD%2B+SMD+ESD+Safe+2+in+1+Soldering+Iron&qid=1673725925&sprefix=yihua+862bd%2B+smd+esd+safe+2+in+1+soldering+iron%2Caps%2C74&sr=8-2

Both look similar. Think I might go with the one you suggested if it does the job and it is more within my budget.

I checked all the traces from U975 and U976 respectively. U975 connectivity was all good. U976 wasn't (least Im not sure).

U976 Pin 14 to the resistor R989 ok; resistance 4.68 ohms; voltage 4.77v (Amiga PCB explorer puts resistance at 4.75 ohms and voltage at 5v). My readings look ok compared to that (?). Connectivity from R989 to J975 Pin 11 - none. No connectivity at all. Is this ok? And also what is header J975 for?

U976 Pin 10 to the resistor R992 on the underside of the board ok; resistance 4.63 ohms (that seems a tad low Amiga PCB explorer has it at 4.75 ohms). Voltage I measured at 4.9v (Amiga PCB has it at 5v) that seems ok. However no connectivity to J975 pin 5. None. Is that ok?

And I made a discovery when I turned the board over to check R992 - there is no capacitor at C177. One of the Pads has gone too.

Nevertheless I have been able to play with it - have got the OS installed and hooked up a Iomega ZIP100 to it that I got off ebay this week. I have it connected to the net using my plipbox (borrowed from my 3000D) however it seems temperamental. Sometimes it works sometimes it doesn't. Could be a problem with the parallel port or me being dumb in setting it up.

Cheers for your help.

Weed

« Last Edit: January 14, 2023, 08:12:44 PM by Tumbleweed »
A3000T, Cybervision64, CSMKII 060; A3000D, PicassoII, Z3 Fastlane; A2000D, 040, PicassoII; A4000D, A1200, Blizzard 030 MKIV  (not working - next project)
 

Offline TumbleweedTopic starter

Re: A4000D - Yellow screen
« Reply #18 on: January 15, 2023, 03:02:15 PM »
I dug out an old soldering iron, not a quality modern one, and was able to address some of the the things I had identified.

R994 had lower than expected voltage.  My multi meter measured c2.4v when Amiga PCB showed it should have been closer to 5v. There was no connectivity between the resistor and the 5v rail. I fixed  it by adding a blob of solder between Pin 1 and the via #1795. Multi meter now reads +5v.

R975 (underside) wasn't connected to ground. I fixed that by adding another blob of solder between Pin 2 and via #11570.

Booted up and still only 16 colours in WB; ATK shows I still have probs with Alice - 'AGA Alice with bad Lisa ID'. So still some ways to go.

Weed


 
A3000T, Cybervision64, CSMKII 060; A3000D, PicassoII, Z3 Fastlane; A2000D, 040, PicassoII; A4000D, A1200, Blizzard 030 MKIV  (not working - next project)
 

Offline TumbleweedTopic starter

Re: A4000D - Yellow screen
« Reply #19 on: January 22, 2023, 10:02:12 PM »
Hi all,

After a lot of connectivity testing, de-soldering, resoldering I got my A4000D back to booting with full AGA. The intial non-boot I reckon was down to a knackered Buster. I replaced the Rev 09 on the board with a Rev 07 one from my A3000T. Machine booted but no AGA. 16 colours only. I ordered a Buster 11 and installed A4000D booting happily into WB but still no AGG. Amiga TestKit reported "WARNING: AGA Alice with bad Lisa ID".

Lots of googling later I narrowed possible cause down to U976 by following "Chucky" A4000D repair guide. I ordered replacement parts for U975, U976 and U177 plus some 4.7K resistors and some new ceramic capacitors.
   
Lots of youtube later I de-soldered U976. Checked connectivity - the vias under the chip. Hmm not all good. Long story short after checking all connectivity from U976 and repairing broken traces on the top-side and the bottom-side, replacing a resistor and a cap along with U976 Ive got it working with AGA. its been almost 10 years' since this machine worked and I thought it was gone for good.

Wife will be happy too as she can now get the kitchen table back!

Weed

A3000T, Cybervision64, CSMKII 060; A3000D, PicassoII, Z3 Fastlane; A2000D, 040, PicassoII; A4000D, A1200, Blizzard 030 MKIV  (not working - next project)