A3000D - NTSC Screeen Issue

[Tumbleweed]

Hi all,

I have managed to damage my A3000D as a result of foolishly playing around with it - installing a TF4060. The TF4060 is not the problem. The problem is user error, I should just leave things alone.

I foolishly tried to use the TF4060s onboard IDE with a 2.5 inch CF card adapter. The TF4060 needs the INT2 mod to work. The A3000D doesnt have the INT2 mod.

In trying out the CF card adapter with a SD to CF card adapter I managed to damage the RDB on the SD card which I've been using as the hard drive for the 3000D using a SCSI2SDCard. Thinking I had a hardware issue I disassembled the 3000D and after lots of fiddling I managed to install OS3.2 (the 3000d has 3.2 Roms). All good so far.

I then tried to use NTSC Hires-Laced and thats when the problems started. Shuddering video. I switched back to PAL - no problems. Back to NTSC Hires-laced shuddering video.

Also I have a PicassoII card - the pass through from the 3000D VGA became unstable - black screen. Plugging the VGA from the monitor into the 3000D VGA - picture and all good. The PicassoII I think is ok but I have not tested it in another Amiga. My B2000 has the same card and I'll use it to test the one from the 3000D.

I have read that shuddering video can be a pain to track down and requires lots of tech I dont have (good quaility oscilloscope etc).

Is there anything simple I can try first? Ive checked jumper settings. Cleaned the board with isopropy alochol; pressed down on chips etc etc.

Tnaks in advance.

Weed

[Tumbleweed]

Hi Kolla,

I hope you're right - unlikely Ive damaged something. Ive tried the switch - Amber on / Amber off. Last night I changed the setting on J200 - was on pin 2-3; I changed to 1-2 - made no difference. Changing it back again - also made no difference. My thinking was to default it to NTSC - looking at:http://amiga.serveftp.net/a3000_hardwareguide/jumpers.html J200 switches between NTSC and PAL.

Just had a thought - maybe I dmanaged the pins in the VGA port. But if I had I would have though the it would also have impacted the output when set to PAL.

AGNUS is 8372A - 318069-03 [which is PAL]; DMAC 390537-02 and Ramsey 390541-04; Buster is 390537-02. The DMAC / RAMSEY combo looks to be ok based on: https://www.retroisle.com/commodore/amiga/Technical/Firmware/customchips.php

Thanks for your help.

Weed

[Tumbleweed]

Have managed to find some time to do more testing.

Symptoms:

Fuzzy / unstable video after switching to NTSC from PAL. Video is stable and clean when in PAL mode.

While cleaning the board with isopropyl alcohol (A3000D switched on) the fuzziness improved. Soaking the area round Amber removed the fuzziness entirely. I then waited for the broad to dry and switched it back on - fuzzy video again. This time I soaked the area to the left of Amber, round the resistors R484, R454 and R477) remioved the fuzziness entirely. Checking the resistors I get 10 Ohms on R484, 3.4 k on 454 and 33.1 ohms on 477. Looking at Chuky's Component Locator Chucky 1.41 R454 should be 10k. My board is a Rev 7.3. Any ideas why resistance would be less than 10k - I measure its less than half.

Bypassing R484 and/or R454 removes the fuzziness. I'll try replacing these two resistors and see what happens.

Weed

[Tumbleweed]

Thanks Castellen.

I hooked up my 1084 to the 15KHz and it looks to be ok. There is flicker visible but not the phasing I can see on the VGA port hooked up to my LCD. There is no visible sign of corrosion from what I can see (see pics).

What sort of scope would do the job? These can be pricey and Ive looked at obtaining one previously but the price has always put me off.

Thanks.

Weed

[Tumbleweed]

Pushing down on VC470 seems to have sorted it. Switched off. Fitted my Picasso II and the pass through is working.

Weed

[Tumbleweed]

Thanks Castellen.

I'll replace VC470 and also look at replacing the other compoents U481 and the OKI buffers as per the link in your other post. Second hand scopes maybe not as expensive as I thought. I found this:
https://www.ebay.co.uk/itm/326366618527?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=z6DJe-b4TpW&sssrc=2047675&ssuid=&widget_ver=artemis&media=COPY

2 Channel up to 100 Mhz.  For less than £100 roughly US$80.

Thanks for your help once again.

Weed

[Tumbleweed]

Thanks Castellen. The low prices look suspiciously low vs prices from other sellers which are at least double. I'll may be seer clear. I had a l ook at some low cost Chinese ones on Amzon.

https://www.amazon.co.uk/OWON-Oscilloscope-SDS1102-Professional-Generator/dp/B0B4294BY1/ref=sr_1_23?dib=eyJ2IjoiMSJ9.nSpJY7iLmlMuSujMS8NT6xUVn7dLYzQBQGvgAHn0FNA3ycm3MZqIQ_rTLORJNm4t-QYEuGgGI5TJdCes1jnxDg0vmO6wMaiYSk4UkTZVaK-WUN0wqNvvO9b1I-ONkRnXI-6k-NyODdFeRCrn_bH4C2wfiU3QsuuNT9Ve-CtE-9HeiYKj7-aeJhZ4ckG4tydEzf4tJ-a0AxzTrrSvo6fvzF1Y_E0Dc2GG7DrmIf9po4Iuu35PRIkLAfzsnv-ecj0Cn49z1QJfkGYktBMQ0f5gOtjBhAX1ETpnBIpyxSTeA2lM26uraIo5oEnpIFznqxu8zIQPCvtY7oqaALiwX4_Bd2bbSsyIib6v2lhr71YgBeN28XLxrHPNyQ7J0XDFUKqeB4E8edxslGOlYtG4Pc4aj8c9dywyHIEnlXOf1t6imQ5GhSn2PnjchsVEY6t02Om3.tT5RrPyRgUK2wbVqGxuZijtiH9bOO15rzv-Domgvp2A&dib_tag=se&keywords=oscilloscope&qid=1738743042&sr=8-23

Also thanks for the test software. I'll have ago at running it when I can get a chance. Loosk like it will be the weekend again before I can some time to look at it properly.

Weed

[Tumbleweed]

I opted for the one of Amazon in the nd. Arrived today. Ive desoldered V470 and replaced it. That said I may have used the wrong size. What is the capcitance of V470? The one I removed is blue and the one I relaced it with is white.

I hooked up the scope to pins 2-3 of J483 with and put the jumper on 2-3 on J482. I adjust V470 (plastic trimmer tool) and no matter how many turns I cant get the clock to be much more than 10 mhz. 

Think Ive got a few options:

1. Ive not set the scope up correctly. (I am a newbie - but think I ve got it set to read frequency correctly forllowing the guide that came with the unit)
2. Ive used the wrong size replacement part. I'm thinking likely as th eone I removed is 'blue' and the one I replaced it with is 'white'. Since ordering the part Ive learned that they are colour coded. White has a higher max pF (10 pF) than blue (7 pF). But thinking if its more than blue then I should still be able to set it correctly - just don't turn is to the maximum setting. 
3. Ive bodged the soldering. Checked connectivity with my multimetere and all ok. Part is fitted the right way round and matches the layout on the board.
4. Something else is wrong elsewhere on the board?

[Tumbleweed]

4. Something else is wrong elsewhere on the board?

Forgot to put the jumper (J482) back!. Once I did that - all looks to be ok.

Think that's my Miggy working.

Thanks for all your help (again) Castellen. Thats three miggy's you've helped me fix over the years (my 3000T, 4000D and now my 3000D).

Best.

Weed.

[Tumbleweed]

Probe wasnt grounded properly. 

Weed

[Tumbleweed]

The only issue I still have is with the Picasso II which has scrambled video. While I had the case open I swapped it out for another Picasso II that I have in my A2000. All working ok in the 3000D. Looks like I knackered the PII in the 3000D. I'll have a look at it when I can find time and see if I get the same result in the 2000D, but I'm happy with the 3000D.

All this cause I wanted to upgrade my 4000D to a 060. Swapping cards between different Amiga's to test without due care and not appreciatingt these machines are now 30+ years old is a lesson I wont forget.

If there are any positives to come out of this debacle - I've learned some new skills and acquired some new tools (Ossilloscope).

Weed

[Tumbleweed]

Hi all,

Does anyone know where I can source schematics for the Picasso II?

Im trying to fix the PII but I dont really know what Im looking for. I have two PIIs - a v1.4 (which is the one that is no longer working) and a v1.6 which was in my A2000 (working fine in my 3000D). Ive spent some time probing around with my scope on both. The only difference I can see between them is the voltage on the crystal. The v1.4 is less than half that on the v1.6; frequency is the same 14.33 mhz.

Could the crystal be bad? or some other fault?

Weed

[Tumbleweed]

Thanks Castellen. Probe is in x10 mode and I've measured on the same side of the crystal on both boards. If its case of trial and error I was thinking of the following:

1. Replace the crystal
2. Replace the caps - there's not many of them - and my desoldering/soldering is good enough to remove / replace.
3. I can swap out socketed chips. Was nervous about doing so in case there is a fault on the board that damages them and then I end up with two broken PIIs
4. Replace the relays
5. Replace resistors
6. Replace the GD5428 (think I have one in my box of PC boards) - replacing this will push my soldering skills (I'm not very good with drag soldering)

There are a couple of PII clone projects on git hub and I've seen a repicasso II board (but I cant find schematics or other details for it)

Weed

[Tumbleweed]

Thanks Castellen. Youre comment re soldering made me laugh 

This is what I was referencing:

https://www.bing.com/videos/riverview/relatedvideo?q=drag+soldering&mid=AB87A33CCDDB449C0B31AB87A33CCDDB449C0B31&FORM=VIRE

I'll swapt the chips form the good board at the weekend.

Weed