Lambda Mikel

Got a new soundchip - problem fixed!

It's believe this is not caused by the caps at all, and the effect that changing RV1 had on the sound was a red herring. I desoldered the sound chip and put a socket in. Waiting for a replacement. Swapping eletrolytic caps never made a difference for me with any machine (with the exception of the SMD electrolytic caps in the Amiga 600); they are generally fine. Guess I was just lucky. I exchanged two electrolytics near the DIN socket, in the audio path, but no difference. So I am not going to swap them. Regarding the caps - well they looked a bit like RIFAs to me, and 2 looked a bit "burned", but that might just be the coloring... Yes, the replacement caps are multilayer ceramic (the small ones) and polyester film capacitors (the orange bigger ones). I don't expect any problems.

Ordered a replacement sound chip now, let see how this goes. Thanks so far. Yeah, I know audio is not the greatest, but none of my other TIs are that bad. So it must be a chip defect I fear. And, the noise is getting louder the longer it is on.

Thanks! Yes, the power is OK. I just did a full recap... didn't change anything unfortunately.

Unfortunately, after 10 minutes when the TI QI heats up, the noise is coming back... now what? New power supply board? And, for whatever reason, I seem to be unable to find the sound chip on board... well it has one, just where?

After a couple of hours and swapping capacitors that I had determined were in the audio patch, with no result. Finally decided to put it back together as is - and in that process I noticed that adjusting trimmer / pot RV1 on the power supply, which is touched by accident in the reassembly process, fixed the issue. So, that was an easy fix! All noise and hissing gone!

Dear all, I have noise on my NTSC new-style motherboard (beige) TI 99/4a. I am just hearing the CPU signals etc. My other beige TI and the silver ones don't have that issue. I also soldered a stereo socket directly to the DIN pins for audio (3 and 2), but same sound as over the DIN socket (so it's not the DIN -> RCA video cable either). How would I go about diagnosing the signal path / faulty component? Capacitors? I can't seem to find any schematics. Thanks

So, in my reply above, replace 28 with 29... see picture. My NTSCP VDPs were 18's. The PAL one is 29A.

Both the beige and the silver had an 18 installed. I checked TMS-RGB first with the 18 in the beige 99er, and got RGB video garbage. Plugged in the 28A and got B&W RGB. Then found the mod, but didn't apply it as it seemed to apply to the black&silver old revision board. I hence reverted the beige into original NTSC condition, and modded the silver TI with the old style board instead. I haven't checked NTSC VDP (18) with TMS-RGB in this one, as it already had failed in the beige with the same 18 NTSC VDP. Hence, I went straight for PAL 28a. Discovered that it was B&W. Applied the TI mod. Got color. Happy I didn't unsolder the DIN socket if I ever want to revert it back to original NTSC, it's easy to do. I added RGB DIN 6 socket for Amstrad CTM RGBs monitor, and an extra mini stereo to fix the audio droning.

I don't think so. The TMS-RGB didn't work with the NTSC VDP for me. Showed garbage on RGB. Also I wanted a PAL TI. So, one can leave the NTSC 5pin DIN installed, but the audio is buzzing. Now, I also needed to route another audio cable. That solved the buzzing and noise issue. Maybe interference from the video or insufficiently shielded cable? I have a 4 RCA socket to DIN5 cable (same I usr for C64 etc.) And was only going to use only the audio line but the video buzzing was very audible. Yes, I used the right line of the cable ? Dedicated mini stereo socket fixed the audio.

Sorted, can be closed. Used an old-style motherboard and applied the TI mod. Without applying this mod, you'll only be getting B&W from an NTSC 99/4a. Simply swapping the VDP and installing TMS-RGB doesn't do it.

PS NTSC composite video is fine without TMS-RGB, as shown here. Insert other media

Hello all, so my new-revision NTSC motherboard got the TMS-RGB, and the VDP was changed for PAL (->TMS 99929A). However, RGB image was black & white only. Please see pictures attached. We also cut wires L2 / L3 near the video DIN socket, but that made no difference (well, composite output was gone from the DIN then). What other mods might be required to an NTSC new-revision motherboard in order to get color? The monitor is fine and works perfectly - and in color - with other RGBs sources (e.g., Amiga 500, Amstrad CPC). Also, I am noticing that the audio is a bit faint and noisy now with that board. This might be unrelated to my failed TMS-RGB installation attempt, but I hadn't noticed this until I put the machine back together. I removed the TMS-RGB for now and put in the NTSC VDP. Color is back. Thanks for any ideas.

So, with my Atari 400 successfully converted to PAL, I am about to take on the 800... anything I should be aware of before I start? I was just planning on swapping the CPU Card, doing the right connections for the Incognito of course, and then the main board crystal. ROM shouldn't matter, as it is coming from the Incognito, right?

Hi all, what's a source for the PAL VDP, 9929A ? Thanks Michael