November « 2016 « modelrail.otenko

30Nov/160

Nintendo Famicon + Composite Mod

So, I impulse-purchased this original Famicom from a Recycle Shop next to Higashi-Yodogawa Station in the Shin-Osaka area. I wasn't in the market for a Famicom originally, until I found out that the original A-Train was released for it (as well as the MSX.)

The box didn't have an AC adapter. After a little googling, I purchased one from the stalls under the train station in Akihabara. BE VERY CAREFUL if you're buying an AC adapter for a Famicom, they're non-standard. See further below for potential issues.

Of course, Japan was NTSC back in the day and so this unit outputs an NTSC signal over the RF output. This is no good for TVs in Australia as none of them are capable of decoding an NTSC RF signal. Fortunately, they can decode an NSTC Composite signal, so we'll need to modify this unit to bypass the RF modulator and provide the signal we require.

Outputting a composite signal

I initially thought I'd use this simple modification and bought the required components. At home I realised that I actually had the 1989 version Famicom with Motherboard revision HVC-CPU-GPM-02. Searching further, I found this modification which was stated to work with my revision of the motherboard.

I purchased the required components:

2x 1uf Capacitors (I used Monolythic. The Author says Ceramic, but the picture he shows uses Monolythic caps.)
33uf Electrolytic Capacitor
220uf Electrolytic Capacitor
100ohm Resistor
150ohm Resistor
Two RCA jacks for mono audio and video

There is also a transistor involved. This component is already on the motherboard and does not need to be purchased.

Applying the modification

First, de-solder the transistor.

The next step is to de-solder pin 21 of the PPU and then bend the pin out of its hole. This is to prevent signal noise which shows up as vertical bars in the signal (aka jailbars.) I had issues with the desoldering and so cut the leg at the base with the scissors on my swiss-army-knife. I don't recommend this process as you scratch the crap out of the pcb. Fortunately, there are no tracks underneath, so I fluked it.

Now, flip the board over and scratch the track that 21 was attached to as below. Although you've already removed the signal running on it, all articles recommend that you also scratch the track. Supposedly the thin track next to it absorbs noise from its neighbour. I'm not so sure that the track needs to be isolated, as we've already lifted the pin and therefore there's no circuit... but I did it anyway.

Next, we need to work with the transistor that was removed. Fold one leg horizontal and then solder it to the locations as shown below.

Finally, add the 33uf Cap and resistors. The negative leg of the capacitor is your video output, so wire this (with sheilded wire if possible!) to the yellow RCA jack.

Add the two 1uf capacitors to the following locations to further suppress noise.

The second-last step is to attach the 220uf capacitor for sound output. The sound output comes from pin 46 of the cartridge port, so connect the capacitor there and the other end to the black/white RCA socket. Of course, both sockets also need to be grounded! I initially thought that I could just lie the capacitor on the board and connect the leg to pin 46... turns out that the case presses against this capacitor when closed, so I had to move it and wedge it in the gap to the left.

Now the final step is simply to mount the RCA sockets on the side of the unit. I chose the front right as there is heaps of room behind.

Now... to test...

Incorrect AC Adapter

Nothing... no power... dead... I hadn't actually ever gotten a signal out of this unit; so could it be completed dead? A quick investigation with my multimeter showed that the voltage was backwards on the 7805! Oh shit. For anyone playing at home, the link here gives you all the information you need on the power supply, especially pointing out that the adapter needs to provide negative on the center pin. Of course, I had bought a power supply with positive in the center and had tried to tune the RF for a few minutes. This completely cooked the 'slow-blow' fuse in my Famicom!

See here for more detail on fuses and replacing them. I was unable to find an exact replacement at my local electronics store, so I just shorted it to start with... but there was no way I was going to leave it in this configuration. If you want an exact (or best match) replacement, then search eBay for 'SNES Fuse' and you'll get quite a few results.

Update: The fuse came and was installed with ease. It's actually from a Super Famicom, so looks different, but does exactly the same job.

After this, I reversed the polarity on the AC Adapter.

And then....?

Winner! Nearly...

NTSC vs. PAL

I tried everything to get the picture correct. There's a trimpot, but this didn't help. I also grabbed some tinfoil to shield my video cable to the port, but that didn't help either. After a little googling, I realised that the NTSC timings of the Famicon are slightly out-of-spec and that my TV would never actually decode the signal. I know it can decode a proper colour NTSC signal, so I was a little concerned.

As a final test, I plugged the machine into the big TV.

Muhahahahahaha... and then for the final icing on the cake... (Thankfully I was wearing pants...)

Now to play the game!

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9Nov/160

Installing an AT Motherboard in an ATX Case

I needed an AT case for this naked 386 AT motherboard and hadn't had much luck searching eBay. Little did I realise that I could put the motherboard into an ATX case with minor effort. All AT cases on eBay were way out of the price range, so I went back to the store that I purchased the power supply from for the Compaq and came back with another bargain!

There seems to be a faceplate missing, but I can't complain since I got it for AUD$20. It didn't come with a power supply, so I chose to use the AT that the motherboard came with. Of course, the first problem (it's still a problem, actually) is that the power switches aren't able to be swapped. ATX uses a 'soft power' switch whereas AT runs the full 240v right up to the mechanical switch to control the power feed. This is still currently hanging out the side of the case.

Mounting the motherboard was easy enough. Turns out that the read plate actually has all the required markings for the AT motherboard spacers!

A bag of goodies was included and I quickly got the motherboard into position.

Before going any further, I realised that I'd not put a new battery on the board yet. I cleaned the remnants of the previously leaky battery and mounted a coin-cell holder.

Once screwed down, everything fit back into the case perfectly.

The majority of front-panel wires were still compatible with the old AT style pinout... I just required a quick google to find information on the AT System panel connector.

Of course, the included I/O Panel doesn't fit an AT motherboard, so there's extra ventilation at the back. There seems to be all sorts of hints online to make your own plate, but nothing off-the-shelf that I could find.

I popped the top off to see if I could mount the power switch but there was no room for it. I'll have to work out a better mount for it, as the current answer is to have it hanging out the rear.

After purchasing a PS/2 to AT-style keyboard converter, I was able to actually boot the thing up! Now to get some software onto it...

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2Nov/160

Melbourne – Cup Day 2016

Usually public holidays means very little freight traffic, but everything-and-more was running yesterday! I promised myself to sit in front of the computer, and work on computer-related-projects, but gave up quickly when I looked at the radar and saw that XR554 was leading the Long Island. I ran out of the apartment and just managed to catch the Metro Frankston train in front of the freighter from Hawksburn Station.

Glenhuntly Station - Long Island Steel Train

Glenhuntly Station was chosen as the vantage point. I'd always wanted a shot of the steelie coming round the bend. This intersection happens to be a 'Tram Square' where tram lines cross the railway lines. The catenary has to cross at this point too, and so only one network is energised at a time. There are insulators isolating the crossing wires and, I would assume, there is some large electrical switch that chooses which network is powered into the junction.

I was paying too much attention to the infrastructure and nearly didn't hear the freighter approaching!

The sun came out perfectly for the curve. Very happy to see an XR in the lead.

Two 49s and a Tamper

I was about to head home, and continue that work I promised myself, when saw something strange on the radar. A 49 Class NSW Locomotive heading south into Melbourne. These are sorta like the Victorian T Class, and aren't often down south. Not really knowing a good location, I attempted somewhere new, on-foot. From Albion Station on the Subury Line, I walked over to the curve where the Standard Gauge joins (or re-joins, really) the electrified broad gauge.

Turned out to be a pretty good location! One other on-looker had already been waiting there too. The colour-scheme looks really good on this loco, especially in overcast lighting.

CSR002 - The Sugar Cube

The map indicated that the new SCT movement was coming through next. It wasn't for about an hour though, so I caught the train back to Sunshine and got lunch at the mall. I also purchased an external battery pack for my phone, as the radar does happily trash one's battery. These batteries usually come pre-charged and this brick happily gave me a full charge prior to giving up the ghost. After mucking around and not paying attention to the radar, I realised that I was now running late and that CSR002 was already at Jacana. A quick run from the mall straight to the overpass saw me back in location with around 1 minute to spare.

These sugar cubes get their name from their very boxy shape, and the fact that their class name is 'CSR' (a famous Australian sugar company.) The train hurtled round the bend with 2 vans which it had retrieved from the new SCT depot in Wodonga.

The 49s return home

These two didn't hang around long. After the CSR came through, I ventured back to Albion station and awaited the next Metro train. I just missed one and so the next service wasn't for ~20mins. This was fortunate as the 49s showed up on the radar on the triangle near the LPC in Dynon. It turns out that they were turning around on the triangle; I assume 4911 has the accreditation to run in VIC and 4917 was there as backup.