Mitsubishi Heavy Industries Heat Pump (outdoor unit) SRK35ZJ-S PCB repair - Page 1
Forum section: electronics / repair

author: max.wwwang
author_rank: Frequent Contributor
timestamp: January 20, 2025, 03:46:47 am
content: Got another job – a broken PCB of a heat pump. Photo attached.According to the attending tradesperson, it appears the hedge plants had overgrown and intruded into the unit and somehow caused the damn damage to the board. I'm considering whether this board is repairable.Another option is to buy a new replacement board (this is also being explored). But if the existing one can be repaired it would be great.One difficulty is that I actually don't have access to the unit, and have not received the board yet.Hoping someone out there has similar experience and insights to share anyway. (If anyone spotted one on sale online please also let me know.)Coincidentally, as someone who had no experience whatsoever in repairing heat pump before, I recently picked up some boards from scrap yard that I only suspected were from heat pumps (this thread). So that at least gives me some elementary (and first-hand) preparation for this job. Not a bad Omen.I've located itsservice manual.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: January 20, 2025, 03:53:42 am
content: I found one for sale oneBay. I'm a bit confused. I assume it is ONE board (rather than two), but one of the photos is green colour but the rest are brown (like typical old single-layer boards). Do you think these are photos of (two sides of) the same board?(Unfortunately, this one does not ship to where I am.)Answering my own question. These are probably two boards. Typical arrangement, just like one of the two that I salvaged. There is a photo of the two boards on p69/162 of the service manual (attached).

author: BradC
author_rank: Super Contributor
timestamp: January 20, 2025, 04:06:29 am
content: That's a normal single sided board. Green resist on the copper side, just plain silk screen on the non copper side.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: January 20, 2025, 04:09:08 am
content: Quote from: BradC on January 20, 2025, 04:06:29 amAh, that's also possible. On sale on eBay is probably ONE board. But I'm not sure really. (I'm actually a bit confused by the photo in the service manual, noting, of course, that it is for multiple models.)

author: indeterminate
author_rank: Regular Contributor
timestamp: January 20, 2025, 08:14:21 am
content: It looks like high voltage has been applied to one of the temperature sensors that is connected to CNTH on the PCBchances are that the cpu is toast.

author: Whales
author_rank: Super Contributor
timestamp: January 20, 2025, 08:15:29 am
content: Your photo with burn marks:the PCB looks conformal coated. This means the burns here are not from something touching those exact spots, but instead because of high voltages being placed on that board from somewhere else. Unfortunately this means there is a high likelyhood that many of the ICs on that board are invisibly dead.EDIT: Ninja'd by indeterminate.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: January 20, 2025, 09:19:30 pm
content: Quote from: indeterminate on January 20, 2025, 08:14:21 amQuote from: Whales on January 20, 2025, 08:15:29 amThese are invaluable input. Much appreciated. This means the likelihood of preparing the board is fairly low (if ever possible). It also means replacing the entire board (if replacement is available) or the whole machine are probably the more viable and realistic options.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: January 20, 2025, 09:24:41 pm
content: I've managed to get hold of a spare parts supplier who has the new board but only sells to partner companies. I'm in contact with a local company who has the privilege to buy from them and awaiting a quote.The part supplier is however so kind and helpful that, upon my pilot request, they provided me with two photos of both sides of a working replacement board (to potentially help my repair endeavour). Attached. These confirm that the board's one side is green the other brown, i.e. on sale on eBay is ONE board not two.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: January 20, 2025, 09:25:24 pm
content: The other side (due to attachment size limitation).