Testo 550 digital manifold guage repair - Page 1
Forum section: electronics / repair

author: jkloepping
author_rank: Newbie
timestamp: January 31, 2017, 07:58:01 am
content: Here is an obscure repair that I recently did. If any of you work on HVAC equipment, you may know that modern pressure gauge sets are digital. Thinking I would upgrade from my old manual set, I grabbed a Testo 550 from eBay cheap with the message "EEP fail" on power up.After tinkering a bit, turns out the onboard 24FC256 serial flash is corrupted. Unfortunately, there's no way to get a good flash image, and the people at Testo want an outrageous amount to repair the unit. So, taking a chance I ordered a working one from eBay, figuring I would fix both and then resell one of them. Eureka! The repair worked. I couldn't reprogram the flash in circuit, so I did have to desolder the chip to actually reprogram it, but the repair worked and I now have two working 550s.I've attached the good flash image file.

author: Muttley Snickers
author_rank: Unknown
timestamp: January 31, 2017, 08:36:33 am
content: Nice work and well done.Slightly off topic alert, If you wouldn't mind I am interested to know roughly how old your original Testo 550 was as their web site currently states a five year warranty for that particular product, yet when you go to the product registration page it states a two year warranty plus an additional year once registered making a total of three years.The reason I ask is because I was looking at purchasing one of their 760-2 multimeters but fortunately came accross a recent video showing where they are prone to magnetic fields so I've decided at this point to give it a miss until they can properly address the issue. I've never owned a Testo product before so am somewhat guided by others in regards to their products quality, reliability and perhaps more importantly what their customer care and support is like.

author: ace1903
author_rank: Regular Contributor
timestamp: January 31, 2017, 08:55:55 am
content: Could you please post teardown pictures? I was thinking to buy one but can not decide between different models that are offered.Would like to see what is inside and build quality.

author: noidea
author_rank: Unknown
timestamp: January 31, 2017, 02:37:13 pm
content: +2 Yes please post some pics of the teardown, repair if you can.I must admit I'm still of the old school and prefer to watch an actual gauge when looking at a system that's playing silly buggers! After doing it for 30 years you sort of know when somethings up just by looking at the trend of the needle. I guess it's the same as an old analog multimeter.

author: jkloepping
author_rank: Newbie
timestamp: February 01, 2017, 05:47:21 am
content: Sorry for the lack of action shots, as I couldn't imagine that there would be any interest in such an obscure device! I'll attach some pics here later so you can get the general idea, it's pretty simple. Just remove the six screws in back, remove the battery cover and batteries, flip out the rubber temperature sensor covers and then carefully pry off the back cover, making sure the battery terminals slip through the holes in the case and don't get torn off.Once inside, see the pic that shows the flash in the middle on the left (with the manifold connections down). I used Chip Quik (1st time, worked great), and my MiniPRO TL866A to flash a new chip. I didn't attempt to reuse the old chip, but it may have been fine.Once verified, I simply cleaned up the board as explained in the Chip Quick directions and resoldered the flash. Super simple. Reassemble in reverse order and you are good to go.As for the date of my unit, I vaguely recall asking about warranty status when I called the mfg, so I don't think it was covered, but I might have been boneheaded about that...