Junkyard Collector

Testing the PTR gave me these sources:

[toggler id=1 hidden]Blueprints A-G[/toggler]
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• [item=169112] — Sold by the reputation vendor at Honored standing.
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• [item=169175] — Likely a reward from daily PvP chest in the Bloody Grotto. (unconfirmed)
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• [item=169173] — Drop by [npc=152182].
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• [item=168493] — Sold by the reputation vendor at Exalted standing.
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• [item=168248] — Drop by [npc=151627].
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• [item=168219] — Lies on the metal boxes next to the rare mob.
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• [item=169169] — Drop by [npc=152570] and Data Anomalies, such as [npc=152961].
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• [item=167836] — Drop by [npc=151569].
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• [item=167845] — ?
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• [item=167844] — Loot from [item=169471] which is the reward of the daily quest Cogfrenzy's Construction Frenzy
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• [item=168492] — Drop by [npc=151296]
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• [item=169176] — Automatically provided when completing the daily quest Other Interests
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• [item=168908] — Drop off the first rare mob you kill (on at least Neutral standing with [faction=2391])
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• [item=169134] — Sold by the reputation vendor at Revered standing
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• [item=167871] — Drop by Foul Manifestation
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• [item=169168] — Drop by [npc=152569]
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• [item=168906] — Drop by [npc=152961] and probably other Data Anomalies during the quest Large Storage Fragment. This quest is a sequel of the daily quest Discs of Norgannon.
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• [item=167652] — Automatically discovered by completing the fishing quest Build A Bigger Fish Trap
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[toggler id=2 hidden]Blueprints M-Z[/toggler]
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• [item=167846] — Drop by [npc=151625], [npc=154701] and probably other ones too.
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• [item=167787] — Sold by [npc=152321]
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• [item=169171] — ?
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• [item=169167] — Drop by [npc=149847]
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• [item=169172] — Drop by [npc=155438] in [zone=10225]
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• [item=168491] — Available only when Chromie is up in Rustbolt as a visitor. During her quests (while you're in the alternate Mechagon) common mobs can drop this recipe.
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• [item=168490] — Drop by [npc=155583]
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• [item=168220] — ?
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• [item=168062] — Drop by [npc=153226]
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• [item=168063] — Drop by [npc=150937]
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• [item=169174] — Drop by [npc=154153]
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• [item=168495] — ?
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• [item=168494] — ?
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• [spell=302947] — Automatically discovered by completing the quest S.P.A.R.E. Crates
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• [spell=305160] — Automatically discovered by completing the quest Junkyard Tinkering and You
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• [item=167042] — Drop by [npc=150342], [npc=153200], Foul Manifestation and probably other ones too.
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• [spell=300121] — Upon reaching Honored standing [npc=152295] offers the quest This One's on Me. The recipe is automatically discovered upon completing the quest.
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• [item=167847] — Drop by [npc=153228]
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• [item=169170] — ?
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• [item=167843] — Static drop by [npc=150394]
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As of 4th May 2020, [item=169172] is no longer a requirement for Junkyard Collector.

https://www.wowhead.com/news=313893/may-4th-hotfixes-perfectly-timed-differential-not-required-for-junkyard-collecto

heh, this is really a great job. i gave up to compile this list because most rares are available couple of times a day and blueprints don't have 100% droprate, sometimes it feels even like 10% or less. And you have to wait too much for some events to even spawn.