TL;DR: Mint-condition Canon EOS-1N won't power on. Multimeter shows 260 µA in LOCK (should be ~40 µA per service manual) and 0 mA when selector goes to A. Traced through the manual to E1ON brown-out protection actively killing DC/DC1 on startup - likely a degraded cap or leaky component on the VDD rail. Camera that "barely got used" is probably suffering from age-related electrolytic degradation. DC/DC1 is a swappable module so I'm taking it to a tech with a donor body for transplant. Full diagnostic trail below in case it helps anyone Googling similar symptoms.
Hey everyone,
Most 1N threads here are about BC errors, sticky mirrors, or shutter issues. Mine is a bit more interesting - and I've spent a few hours digging through the service manual to narrow it down. Posting the full diagnostic trail in case it helps someone with similar symptoms.
The camera: Canon EOS-1N, serial 117573 (early production, ~1994). Cosmetically near-mint - no scratches, no wear on buttons, all screws still have factory paint, no signs of moisture or corrosion anywhere. Looks like it barely got used, which (spoiler) is probably part of the problem.
The symptom: Camera is completely dead. No display, no beep, no mirror twitch, nothing.
What's interesting - multimeter on the battery line shows this:
- Battery in, selector on L (Lock) → 260 µA idle draw
- Battery in, selector on A or beep → 0 mA, completely flat
Reference values from the Canon service manual:
| State | Product standard | Typical actual | My patient |
|---|---|---|---|
| LOCK | 75 µA | ~40 µA | 260 µA ⚠️ |
| Standby | 150 µA | ~50 µA | - |
| SW1 ON | 400 mA | ~100 mA | 0 mA ⚠️ |
So the LOCK draw is 6.5x higher than normal (something is leaking ~220 µA somewhere even with MCU asleep), and instead of waking up and pulling current to power the DC-DC, everything collapses to zero.
What I've already ruled out:
- Battery: fresh 2CR5, tested in a donor 1N (beat-up body, sticky mirror, but electrically alive) - boots fine. So battery and contacts are good.
- Power selector switch: it's switching electrically, since current changes between L and A. Not a dirty-contacts issue
The diagnosis (from service manual section 13.2 "Battery Installation"):
Power-up sequence is roughly:
- VBAT reaches DC/DC1 (VIN1, VIN2)
- VIN1 feeds a regulator → 4.7V VDD for LCD Driver, MPU, RESIC
- LCD Driver generates 32.768 kHz clock and wakes the MPU
- MPU pulls /E1ON low → turns on TRDCON → starts DC/DC1 proper
- DC/DC1 outputs E1, E2, VDD (all ~5.5V) to the rest of the camera
- When E1 reaches threshold, RESIO goes high, MPU starts operation
And critically, the manual states:
>
This is a brown-out protection circuit. And it explains the 0 mA reading exactly - when I flip the selector to A, the MPU tries to start DC/DC1, but VDD can't reach its target (probably due to a leaky/degraded component on the output rail), the E1ON IC sees VDD < 3V, and actively kills DC/DC1. Hence the perfect zero current draw, not just "dead".
Most likely root cause: dried-out or shorted electrolytic cap on the DC/DC1 output rail, or a component with elevated leakage somewhere on the VDD/E1 line. The 6.5x elevated LOCK current supports the leakage theory - something is already drawing extra in standby, and that same path probably collapses the rail when DC/DC1 tries to ramp up.
The "barely used" camera detail is consistent with this: electrolytic caps actually degrade faster in unused gear than in regularly used gear - no thermal cycling to keep the electrolyte healthy.
The good news for me: the service manual parts list shows DC/DC1 as a single replaceable assembly (part CH3-0109-000, DC/DC CONVERTER1 ASS'Y). This means a tech can swap the entire module from a donor instead of doing component-level repair on the main board. Excellent serviceability - Canon designed this well.
The plan: I'm not comfortable going past the top covers myself, so I'm taking it to a tech. With the donor body available for transplant, this should be a relatively clean fix:
- If swapping DC/DC1 module revives the camera → confirmed: dead module, case closed
- If it doesn't → problem is in the surrounding circuitry (E1ONIC, TRDCON) or somewhere on the VDD/E1 rail itself, and we'll need scope work on the start-up signals
Questions for the hive mind:
- Has anyone seen this exact failure mode on a 1N before? MCU alive in L, brown-out protection killing DC/DC1 on wake?
- Any known weak components inside the DC/DC1 module specifically? Particular caps that fail?
- Anyone successfully swapped a DC/DC1 module between bodies? Any gotchas with the SDC Flex desolder?
Camera is too clean to give up on. Even if my patient can't be revived, posting the diagnostic trail here so future Googlers find it.
Cheers, and thanks for any input.
