Radarscope: Part 3

So in my last update, I’d removed and socketed all of the RAM chips on the CPU board. This appeared to have fixed the issue with the game hanging on boot up, but now despite coining up and starting it hung after typing out the instruction screen:

After publishing that post, a fellow collector got in touch and told me to check the connections to the sound board as the game waited for a response before starting. Now despite the main boards in this boardset being genuine, unconverted Radarscope boards, the sound board had been modified to be used on a Donkey Kong boardset (as many of the Radarscope boardsets had). The execution of this modification looked brutal:

From lifted legs to “cut” traces, this board had been through the wars. As well as the modifications pictured above, a number of resistors and caps had been swapped for different value ones. I knew that if I had any chance of getting this boardset to boot, I’d either have to reverse this modification or replace this board.

I started off the process by removing all of the additional wires from the rear of the board and measuring up new wires to re-join the cut traces:

I cracked out the soldering iron and got to work repairing these traces. In hindsight, I wouldn’t have cut some of these wires as short as I did, but lessons learnt. After a few fiddly minutes, I was left with this:

Not the neatest of jobs, but really the wire I was using was too thick. Next on the shopping list is more suitable trace wire. With those repairs done, I hooked the board back up and fired it up… no change. To be fair, I didn’t expect much considering I had only repaired the broken traces and not replaced any incorrect value caps or resistors.

The biggest difficulty I had was not having much in the way of reference to help with this “de-conversion”. There’s a great site I was using to diagnose the issues with my boardset and this had a DK conversion reference page, but it’s missing quite a lot. I knew the best way forward would be to source a non-hacked sound board.

Now I don’t know how I missed it in one of my purchases updates (I may not have, but can’t see it…) but I bought a Radarscope cocktail from the US last August. The game was sold (as most are) as non-working with just a comment that the monitor comes on but just showing white, no picture. As this was a purchase from the US, there is always a good span of time between purchase and arrival. Cue many months of waiting (11!) and the cocktail landed on UK soil. A quick trip up and down the M1 and my car was full again:

The cocktail was in lovely condition (albeit the lid being detached from the cocktail itself) and had the all important boardset inside. There is a fan in the bottom of the cocktail, but for some reason it’s sucking air into the cocktail from underneath. This is not really helping cooling the boardset down, more turning the cocktail into a vacuum cleaner:

I stripped the boardset down and set about removing as much dust as possible:

The dust had got everywhere! After cleaning as much dust off as possible, I reassembled the boardset and plugged it in. I flicked the power switch and waited anxiously as the monitor warmed into life. I was greeted with an interesting screen:

Everything appeared correct aside from the coloured bars across the screen. The game appeared to coin up and play, but it was difficult to tell with the coloured bars covering most of the play field. A quick check of my favourite Radarscope site identifed the above issue as a problem with two ROMs one the video board. The two ROMs deal with the background colours. Now the two ROMs in question are the ceramic ROMs below:

These two ROMs appear to have taken the full brunt of the dust, but ceramic ROMs are also notoriously delicate. I pulled the ROMs from the board and replaced them with the newly burnt ROMs from my faulty boardset. I reassembled the boardset and hooked it up to my test bench:

A completely working boardset that’s fully playable and has sound! That’s a massive win as the cocktail was bought as non-working. My belief is that the power supply in the cocktail has failed as it’s one of the earlier PP7A models that are prone to failure.

The next test is to hook this working soundboard up to my faulty boardset and see what happens.

I connected everything up and flicked on the power. Now as mentioned above, I’d removed the two background colour ROMs from this boardset to test the other. I took a chance and put the ceramic ROMs out of the new boardset into this one. Oddly, the board fired up without the same coloured bars issue (I can only assume that the dust had gotten into the sockets and was disrupting the ROMs). The board then ran through it’s normal cycle and after coining up and hitting Player 1, it read out the instructions screen and then started straight into a game! So it was sat waiting for an instruction from the sound board before continuing. I grabbed the controls and started to move the ship side to side and fire, but something wasn’t right:

Its not very clear in the picture above but there are some very minor sprite issues (part of an enemy ship appearing above the point score in the top left):

And there were no “swooping” enemy ships. I was just moving left and right and firing up into the ranks of ships at the top. All of a sudden, the game flashed and I was back to the main score board with no credits and I knew at this point that I must still have a RAM issue.

When I socketed all of the RAM chips, I put the original RAM into the new sockets and it appeared to have resolved the issues I was encountering. So out came the new RAM chips I had (2114s) and I replaced all 6 chips. I reassembled the boardset (again!) and plugged it in and flicked on the power. The boardset worked! I managed to play though a couple of games and even put a score on the scoreboard:

After a couple of games, the boardset wobbled a little and hung. I knew that my trace fix under the socketed RAM chips needed redoing as the joins weren’t the greatest. Also, feeling the RAM chips, the one in the socket above the fix was getting very warm:

So redoing that trace fix is next on the list, but for now, that’s one fully working boardset and another nearly fully working with the exception of the soundboard. I can now turn my focus to refurbishing my upright cabinet ready to take one of these boardsets and repair the lid of the cocktail to take the other.

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