total novice needs advice on zener diodes - Page 1
Forum section: electronics / beginners

author: emmajackt
author_rank: Newbie
timestamp: December 02, 2018, 11:54:54 pm
content: Hi, I am a total novice when it comes to circuit boards and was wondering if someone could help me. I have a Horizon Omega CS treadmill and there was a loud bang when I plugged it in last week and the circuit board had blown a couple of transistors and a couple of zener diodes. As the diodes have blown, I am unable to test what voltage ones I would need to replace them. I am attaching a picture of the same diode that i need and would be really grateful if someone could help me. I have looked online for a diagram of the circuit board with no luckThank you, Kev.

author: FriedMule
author_rank: Frequent Contributor
timestamp: December 03, 2018, 07:47:45 am
content: I am a novice like you so my advice can be the worst thing to do but I would try to locate if there are some place where it says the voltage and then work backward and if that do not work I'll put ZD in with a wary low voltage and then put one with a higher voltage until it looks to work fine.

author: capt bullshot
author_rank: Super Contributor
timestamp: December 03, 2018, 08:00:56 am
content: If you just want to replace the diodes and transistors, you'll have to get some documentation or information from the manufacturer or a very similar unit. I don't have either of these.Otherwise, one would try to reverse parts of the schematic to get an idea of what is the purpose of these diodes, why they were blown and make an educated guess on their value.

author: mvs
author_rank: Frequent Contributor
timestamp: December 03, 2018, 09:49:15 am
content: Quote from: emmajackt on December 02, 2018, 11:54:54 pmZD1 is a Zener diode designator, but D12 is not. If it was also in glass DO-35 package, it might be 1N4148.If you make good photos of the board from both sides, perhaps we can derive components from their functions.

author: emmajackt
author_rank: Newbie
timestamp: December 03, 2018, 08:16:46 pm
content: Hi, thank you for your replies. I have attached a few more pictures of the whole board and a picture of the diodes that I need, from a picture I found online. The treadmill is quite old and not worth spending ££s on it. I really appreciate your answers. I thought it would be a case of replacing the two blown diodes, one blown resistor and the two transistors and hoping for the best, but obviously there's more involved and I cannot find a schematics for the treadmill anywhere.Regards, Kev

author: Johnny10
author_rank: Frequent Contributor
timestamp: December 03, 2018, 09:20:17 pm
content: It looks to me as though you might be able to buy boards and replace.The Omega II manual has pics of PC board but no schematic.http://productload.johnsonfit.com/inc/uploaded_media/ba2e870dabd6373a48f8e138dfc9c56f/service_guide/54c14b21a33d970fb0beb252b7d83034.pdfI don't know your exact Model number but look here.https://www.ereplacementparts.com/horizon-fitness-treadmill-parts-c-201405_201552.htmlOh, But they are over $250 for Motor Controller Boards... OUCH !Sorry, Guess I wasn't much help.Or these guys charge about $75 to do repair.I saw them on eBay.

author: emmajackt
author_rank: Newbie
timestamp: December 03, 2018, 09:53:45 pm
content: Wow!! I think the treadmill is only worth £30. Thanks so much for finding this though. Much appreciated.Regards, Kev.

author: Brumby
author_rank: Unknown
timestamp: December 04, 2018, 12:49:32 am
content: A word of warning ... even if you do correctly identify the failed parts and replace them, the questions still stands: Why did they fail?If the fault condition wasinone of those components that were replaced, then you have a fair chance that the replacements will fix the problem - but if it was not, then the replacement components might also meet an inglorious death.... and you will be back where you are right now.

author: capt bullshot
author_rank: Super Contributor
timestamp: December 04, 2018, 06:33:52 am
content: Looks like this board does some serious mains voltage control. Having small components going bang on such kind of board usually has its root cause somewhere else, not the components itself.

author: emmajackt
author_rank: Newbie
timestamp: December 04, 2018, 11:54:12 am
content: Thank you for all of your advice. I think this repair is beyond my very limited electronics knowledge, so instead of wasting money, I think I will scrap it and look on Ebay for another.Thanks again for all your replies and have a great Christmas.Regards, Kev.