blackswan

Hi, I'm selling my Atari TT030/4 on eBay. Please find the details there. http://r.ebay.com/zIBWbh Regards

Hey Guus, that's what I'm expecting (and posting in the atari-forum.com). Have a look the schematic: I totally agree with your finding, that's why I'm thinking about "isolating" pin 4 of the video plug (to prevent the MONOMON line from being grounded). If that would solve the problem, then I expect a short circuit somewhere inside the video plug or inside the monitor). By the way: Can you tell me about the "known problems" with the MC68901? Blackswan

I already did: http://www.atari-forum.com/viewtopic.php?f=15&t=25290&p=234809

Thanks for your advise, I'll be very careful and I'll do it will my wife's father. He's also familiar with eletronics. There's another idea flashing across my mind: Would it be possible to feed 5V into this line without causing a short circuit? Maybe the monitor switches to color mode (50/60 Hz) - which implies that I'm believing that it is in "monochrome / 72Hz"-mode causing the weird picture and the awful sound. Blackswan

Hi guus.assmann, I was measuring pin 29 with the monitor attached: 0,3V (the same at pin 4 of the Atari's monitor socket, which should be the same). I guess I have to proceed my investigations inside the monitor (may be first at the cable and the solder joints of the cable). Blackswan

I found an interesting site: http://www.retrocomp..._monitor_st.htm I'll have a measurement on pin 4 while SC1224 is connected. Hopefully it is not 0V...

I don't know how to do that...

Hi GadgetUK, sorry for confusing this... I found some interesting specs about the SC1224: First, there have been several versions (two or three) of this monitor. My one is the one with the fixed video cable. I cannot detach it from the monitor. Second, the mono mode (I used before with the SM 124) provides 640x400 @ 72Hz. This is what I can see, when I connect the Atari 1040 STE to my TFT (with a special cable from ebay) and display the informations about the resolution. Third, the monitor I own does only support 50 or 60Hz (source), maybe the Atari still tries to display mono mode, which would not work. By the way I don't really understand, how Atari and monitor do "negotiate" a graphic mode (low/mid/high)!? I'll give this a try! Blackswan

Hi Stargunner, thanks for your advise. I've found a service manual for troubleshooting a SC1224 at http://dev-docs.atariforge.org. Maybe this can help you (or others) to give another hint. I'm also not familiar with repairing tube monitors but familiar with working with electronics in general (current flow, metering, etc.). Blackswan SC1224_Service_Manual.pdf

I've recorded a video: http://youtu.be/C0IQtGf9VeY When you turn up the volume in the video, you can hear the whistling. Hope someone can solve this! Blackswan

Hello everyone, I've bought a used (so-called functioning) Atari SC1224 for my 1040 STE. Before I was using an Atari SM124 (monochrome). I switched it on and the screen got a little brighter and white diagonal stripes were moving from top to bottom but no desktop appears. I didn't modify the switches on the back for sync or size. In addition the monitor is whistling at high frequency. Any ideas what happened to the screen? I'll try to make a photo of it. Blackswan