Mega Drive Repair

I use a PS2 slim AC adapter for most of my consoles along with a homemade plug adapter (I also use it in conjunction with a splitter for my MD+MCD II setup). It's an amazingly versatile PSU in that it provides plenty of current and just enough voltage to power consoles with a bridge rectifier (which causes the input voltage to drop) such as the NES. Even by itself it makes an awesome replacement PSU for the CDX, Duo-R and Genesis 2 or 3, to name a few.

 

315-5402 do have TMSS but for some reason it's disabled when the JP1/JP2 jumper is set to DOMESTIC (JP1 closed) and enabled when set to EXPORT (JP2 closed).

 

Ah. Ok.

 

Just remembered of something.

I once had a 1988 Juuoki cartridge (Altered Beast) which had 2 8 bit ROMs instead of a 16bit one. That one only worked on non TMSS consoles. So perhaps SEGA made it so the JPN console had no TMSS for 1st gen MD cartridges not stop working ?

 

No. Some games dont work due to the lack of appropriate code which the genesis thinks is not a legit game. Looks like TMSS was concieved before it was implemented in 1989. TMSS was introduced in 1991.

 

No ? I just said the same thing, I just didn't name what it was ? Is it pleasant to disagree or what ?

Edit:I said "1st gen MD games" implying games which released with the console.

Megadrive had a LOT OF PROBLEMS when it released. It even had a patch on the board with three TTL chips to fix a issue with the VDP chip.

 

Didnt seem like it to me. You were describing ROM architecture NOT code. BTW, i didnt know that. Learn something new everyday...

 

SInce I last posted, I have managed to get another 2 consoles to use for parts/testing (Both had faults of their own, but I got them going to a state where I could see the main parts were good).

First thing I did, was remove a CXA1145 from a test/spares console, and install a socket. From this, I found the CXA from my faulty console is working correctly. I have since put this back.

Next, I removed the VDP. I did this destructively by cutting the legs by the IC, as I didn't feel comfortable using my heat gun on such a large chip. I did, however, use a heat gun to remove the VDP from a test/spares console. I hand soldered this into my faulty console, and checked for continuity between the legs and the end of the pads (or vias if I could find them), and it all seemed ok. I also checked for continuity between neighbouring pins to check for shorts, this seemed ok too.

However, the console still has the same issue. It's definitely possible I fried the VDP with too much heat, but I'm wondering if there is a chance the issue lies elsewhere, or whether I should try another VDP?

 

If the VDP is running you should get a black screen. You know, it generates the sync signal when it's running. Even if it received no commands from the CPU.
That causes for example on TVs with that "blue screen" feature to stop showing it.

 

You really don't have a clue who l_oliveira is do you?

 

I don't care who he is? If he's going to give incorrect information, of course I'm going to call him out on it.

 

He isn't one to do so. Furthermore correcting people is fine but we don't take kindly to attitudes.

 

But giving incorrect information is exactly what he did, or I wouldn't have to be correcting him in the first place!
As for the "attitude" you'd have to take that up with him, as those were simply his words tacked onto the end of my post...

 

What incorrect information was given ? I would like you point that.

7805 ICs are rated for half an amp hence why they split the power in two rails.

 

I'm going to leave this at that as this is going off topic.

 

7805's are rated for 1.5amp.. Although I'd be safer running them at 1amp max.

I have no idea why this is continuing, or why APE decided to bring it up when he wasn't even involved to begin with.

 

Modern 78xx chips can do that much. We're talking late 80s chips.

 

They're the same chip :/

 

They're not, (at least internally) because IC process and manufacturing techniques evolved a lot at that time. From 0.5A from the original late 70s design it went to 1.5A we can get from today chips.

Mega Drive was designed in 1987 and released in 1988, it uses about the same number of chips than the Super Famicom but it came three years later (1990) and they managed to make it work with a single power rail, again due to IC design advances affecting the power efficiency.

Etc etc etc.

 

The 7805 in the Mega Drive is rated at 1.5amp, much like the 7805 in the 1980's Commodore 64 supply.

Never were they rated at 500ma :/

The C64 PSU even gets rated at 1.5amps on the 5volt rail, although it will never do it due to the size of the heatsink, however, the C64 do draw about 800ma on the 5volt rail (more than the 700ma the MD1 uses at 5volts!!).... which according to you, is exceeding the regulators rated output by over 50%...
But seeing as its rated at 1.5amps, its not.

Normally if I post incorrect information, and someone corrects me, I'll either accept it, or simply not reply... I'm not sure why you feel the need to continue trying to defend the incorrect information you keep posting.