What is Insert Coin.
Insert Coin is a diagnostic chat for pinball and arcade machine repair. You paste in a symptom like “left flipper feels weak”, “STTNG resets when I drop the ball”, “Galaga blank at boot”, and get a step-by-step diagnosis grounded in the actual operations manual for that title, cited to the page. If the manual doesn't cover your problem, you still get the likely causes and how to check each one, marked as general repair advice, not from the manual.
Pinball and arcade repair is a closed domain with decent public manuals, deeply specific questions, and a community that already knows the answers. Insert Coin isn't here to displace forum experts. It's here to make the answers they've already given easier to find.
Think of this less like a finished product and more like an open lab notebook. Things move. On our test set of repair questions with known fixes, most answers land on the right subsystem, agree with the fix, and give steps you can act on. How much the manual covers still varies by machine. The honest assessment of where it stands is on the pricing page. The same architecture extends to any machine with a manual: jukeboxes, synths, appliances, test gear. Arcade is chapter one.
How answers are built
1. Ingest. Operations manual PDFs are OCR'd, layout-parsed, and split into page-bounded, heading-aware chunks. Each chunk is embedded and stored in a vector database.
2. Retrieve. Your question gets embedded too. We pull the closest chunks by cosine similarity, scoped to the machine you tagged with #code.
3. Answer. The retrieved sections are handed to the language model as grounding context. It writes a step-by-step plan. Part numbers, fuse values, pins, and procedures come from the manual, cited to the page. When the manual doesn't cover the symptom, it lists the likely causes and the checks for each from general repair practice, marked as not from the manual. Hands-on steps are written for a machine that's off and unplugged.
4. Learn. When you bless an answer, it becomes a verified prior that surfaces on similar future questions. Decades of public Usenet archives get distilled into the same shape. We don't scrape Pinside, KLOV, or any private forum, only public archives published for preservation.