Another piece of Jaycar garbage bites the dust... - Page 1
Forum section: electronics / testgear

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 17, 2013, 12:21:22 pm
content: I just walked away from my bench for a minute and heard a bang and really loud high pitched squeal from the other room. I ran back to find my scope (one of those Digitech 2 channel analog scopes) displaying just a dot in the top right quarter of the screen. Awesome, just what I needed while totally broke and up to my ass in projects.I think this is officially the only piece of equipment I've bought from there that made it past a year old and still worked (somewhat... it's always had some intermittent trigger problems and generally been a clunky piece of crap that I always regret buying). I got a whopping 2 and a half years out of this one, so I guess I got lucky.Anyway, I don't know the first damn thing about troubleshooting/fixing scopes, and I don't think I have the tools or knowledge to go troubleshooting the high voltage section (I did take a couple quick reads of some low voltage sections and they all looked fine though). I can't see any damage visually, nothing scorched or anything. The only signs I have to go off are the massive high pitched squeal coming from the power supply section and the screen only displaying a dot. I can move the dot up, but not sideways, so I'm guessing it's an issue with the horizontal section. But again, I don't know much about scopes, I don't have a schematic, so I don't know what to look for and don't feel like sitting up all night guessing and trying to figure out how it works. The guys at my local store are really helpful and I'm sure I could take it in and get it sent away to their repairer or something but I really couldn't be bothered dealing with the process. I assume it's well past warranty, and it'd probably be gone for ages, and I don't really want to pay for repairs on one part of it when I'd bet dollars to donuts another part packs it in a month or two later.So here's the question- does any of that info give anyone some ideas of what might have bitten the dust, and if so, is it even worth bothering fixing? If I can get this thing back up and running on the cheap I will because I don't like binning usable stuff, but I'm so sick of goddamn Jaycar stuff blowing up that I'm tempted to just bin it, call it the final straw on buying equipment there and start saving for something made with at least some level of quality.Thoughts?

author: madires
author_rank: Super Contributor
timestamp: June 17, 2013, 12:53:54 pm
content: Not a scope expert either, I think you're right with checking the section for the horizontal. Since you got a nice dot the HV stuff is working, no worries there! You could start with checking the low-voltage outputs of the power supply. The horizontal is basically a sawtooth generator with variable frequency and a trigger circuit to re-start the sawtooth. Another scope would be quite helpful :-)

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 17, 2013, 01:16:13 pm
content: Quote from: madires on June 17, 2013, 12:53:54 pmHahaha that thought did cross my mindCheers

author: metalphreak
author_rank: Frequent Contributor
timestamp: June 17, 2013, 01:22:49 pm
content: I bought one of those little stereo PA amps. Left channel was dodgy/broken. Replaced it with about 3 different ones all with the same problem before I lost the receipt and gave upWas jaycar ever known for quality?

author: madires
author_rank: Super Contributor
timestamp: June 17, 2013, 01:37:28 pm
content: Quote from: metalphreak on June 17, 2013, 01:22:49 pmDid they sell it with 50% discount?

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 17, 2013, 01:44:12 pm
content: Quote from: metalphreak on June 17, 2013, 01:22:49 pmNot to my knowledge. When I first started getting into this stuff a couple years back I was too naive to realise the stuff was junk, and since I've figured it out I've bought a couple things just because I was there and it was available and I REALLY needed whatever then and there. Never again though, I'm done with these experiences. The place is fine for some resistors or heat shrink etc., but the tools and test equipment really are about as bad as you can get from my experience. Which sucks, because there's a store literally within walking distance from my house, and the customer service is tops.

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 17, 2013, 01:56:21 pm
content: Hmm... Just noticed I can wiggle the core of what I assume is a flyback transformer for the CRT in there. That doesn't seem good. I did wonder if that high pitched noise was coming from a transformer, I might have been right.

author: Fraser
author_rank: Super Contributor
timestamp: June 17, 2013, 04:19:24 pm
content: Capacitor failure in the power supply I suspect.The capacitor becomes a heavy load on the SMPSU output and the SMPSU complains by squealingWhat normally follows is the destruction of the switching transistor due to excessive load.Check all of the smoothing capacitors and decoupling capacitors inside the oscilloscope. If no deflection, X or Y, is possible you may have lost the approx. + and - 200V plate deflection voltage supply.Good luck