There are several reason I have decided to stop doing upgrades. The most important reason is just simply the time it consumes. I have a full time job, 2 baby girls, a wife and child #3 on the way. (Yes! We have now figured out what makes this happen;-).
I get about 2 or 3 nights a week after the girls go to bed to mess around with my arcade hobby. A typical upgrade will take me one full late evening. The time to unpack, test the boards, upgrade the board, re-test the upgraded board, pack it and ship it. It is amazing how much time is consumed that is not part of the physical upgrade of the board.
Anyways, I want more of this time back to work on other new kits (like my DK/DKjr/DDK high score save kit, the millipede/centipede switcher and the asteroids/deluxe switcher). I've been saying I'll do these now for a year.
Other reasons include the the hassle involved in receiving boards that are not fully working. Sometimes the people are unaware a particular sound or something is not working, other times the people know indeed that the board is not totally functional, and then there is the "it was working before I sent it to you" hassle.
Lastly, the price of bi-polar proms has tripled in the last 6 months. The upgrade requires 3 new proms, at minimum, I would need to raise the price to cover this cost.
There are a few people that have expressed interest in taking over building these games after I stop making them. At this point I cannot guarantee that there will be an alternative supplier, if (hopefully) so, expect the price to rise considerably.
I have not yet decided if I will make the design public or not. Keep in mind, there is no great secrets behind this upgrade. Besides the modifications to the board itself, it requires replacing (doubling) 10 eproms and 3 proms. It requires a special daughter card that contains a custom PLD circuit to deal with the digital sound circuit differences between DK and DKjr. There are some minor code modifications required to both the game code and the music processor code, and lastly the 13 eproms and the daughter card need to have a select wire that attaches to all of them spanning across both cards.
Part of the decision to make it public or not will depend on how much work will it take to fully document the hack, and how many emails will I get asking questions etc. Remember the main reason to stop is to free up time. Secondly, if someone else decides they want to offer upgrades and sell them, then the design would not be made public to help protect their investment.
I will continue offer support help and repair assistance for any Double Donkey Kong game that I built.
On occasion, when/if I happen to obtain a working JR board I may upgrade it and sell it as a complete unit. This is yet to be decided, plus it seems like it is more and more difficult to locate DKJR boards at what I would call a fair price.
Again, I appreciate all of the positive comments I have received about the Double Donkey Kong, and hope I have provided a valuable service. With the extra time I hope to start offering some new kits to keep those classic games going and enabling more features.