Radar Scope: Part 1

So you may have seen in my last purchases post that I picked up a Radar Scope boardset. I purchased the boardset off the same eBay seller that I got HeliFire from, but this one arrived in a much different state.

As is always the way with eBay, reading the description is key. All of the boards he was selling were marked as “Spares or Repairs” due to the nature of this 30+ year old kit (you don’t want to advertise something as working for it to take a knock in transit and end up with faults or worse!). The listing stated that you’d need to make up a loom to run the board, which is fair enough, but it missed out one key fact. When the board finally arrived, I excitedly open up the package only to be met with disappointment. The boardset was a Radar Scope as described, but would need more than a loom to get it up and running:

It was missing all the ROMs and CPUs so making up a loom to connect this up was going to do ‘diddly squat’ whilst it was missing all of these key components.

This led to the purchase of the necessary ROMs for a Radar Scope boardset, which involved a bit of googling and a tiny bit of guesswork as the only reference I could find online was for the original TRS board (and not the TRS2 boardset revision). I bought the blank ROMs off eBay and put the message out for some assistance in burning the necessary files, which was picked up by a fellow collector. I posted off all of the ROMs and received them back a few days later (with some blanks as I’d managed to over order…).

Now 10pm after a long day at work was probably not the best time to start trying to insert old ROMs (with delicate legs) into a boardset. After a few attempts (and lots of cursing!) I had all of the ROMs in the correct places. The only ones I wasn’t sure about were the colour PROMs in the CPU board as the filenames that were put on labels didn’t give a clear indication of location for these. I knew they both had to go in the CPU board (as apposed to the Video board), but there were two sockets and two chips… 50/50!

I ‘borrowed’ the two CPU chips from my TKG2 boardset and wired the board up in one of my Donkey Kong cabinets:

After double and triple checking all connections, I asked my Mrs to watch for smoke or flashes and flicked the power switch… We had signs of life, which was a step in the right direction:

Despite the chaos on the screen, the colours didn’t quite look right and we appeared to have a lot of off yellow. I was in constant communication with my friend and fellow collector Paul at the time who agreed that maybe the PROMs were the wrong way round. I powered off the cab, pulled both PROMs from the CPU board and swapped them over. I powered the cab up and we were met with the same garbled screen, but much better looking colours:

So, next step was to check a great reference site I’d come across (the same site I’d used to work out what ROMs I’d need) to start to diagnose. This site is a collectors reference site for all things Radar Scope: www.ostermayer.ch. There is one section to the site for troubleshooting and lists known issues and faults along with screen shots to help identify the area of the boardset that may be causing the issue. A quick scan done this page brought me to a picture that looked very similar to what I was seeing. The title of this picture was “cpu does nothing at all”. So, out came the boardset and I pulled the CPU from a board I knew was working (as the TKG2 boardset I had was untested…) and put this CPU in the Radar Scope board. With everything back in the DK cabinet, I powered it up and was met with this:

Things are looking better, but I was a little concerned that we’d landed straight on this screen with no attract mode showing. Now unfortunately, the cabinet I was testing this in is at the start of it’s restoration journey and the wiring loom for the control panel is in a bad state. I pushed the service switch and shorted the P1 switch to try and coin up the game and the “1 OR 2 PLAYERS BUTTON” disappeared and the “1UP” in the top left began to flash, but that’s all that happened:

Nothing else happened. I tried shorting out all of the other buttons to see if I could move it on at all, but it was stuck fast. So I went back to my trusty resource and started scouring the pictures to find something similar. The screenshot above the “cpu does nothing at all” was showing exactly what I was seeing and had the title “defective ram / picture contents missing”. I knew that was as far as I was going to get that evening as I’d need to find out what RAM the boardset used to try and “piggyback” some RAM chips onto the board to see if we could get any further.

The last thing I did was to see what sounds we were getting. I thought we had nothing, but turns out I hadn’t checked the volume knob in the monitor… once turned up, I powered up the cab and was greeted with a looping sound. This didn’t surprise me too much as the potential RAM issue is causing the game to stick, but also I believe the sound board has been converted for use on a DK boardset at one point in its life. I’ll add it to the investigation list.

All in all, a good evening of tinkering. The boardset was bought from eBay in an undetermined state and my hope lessened when it arrived with no ROMs or CPUS. I’m quite happy to get to this point and I’m confident we’ll have the boardset up and running without much trouble.

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