Abandoned as an idea for a sticky - too hard basket. - Page 1
Forum section: electronics / repair

author: What_NZ
author_rank: Regular Contributor
timestamp: June 30, 2014, 12:48:17 am
content: Introduction: A suggestion for a sticky.This is not intended to teach or tell experienced Technicians how to repair units. Instead it is aimed at the home hobbyist. Basically what to look for and importantly keeping them as safe as possible. I usually trained technicians and apprentices so it's a little different for me so any help would be appreciated. Also my technical writing skills have suffered since I retired.These are the next 2 (suggested) Steps:----------------------------------------------------------------------------------------------------------------------------------------------------------------Basic Principles of Fault Finding / Fault Diagnosis or if you like, Repairing Stuff -Observation > Confirmation > Disassembly > Re-confirmation > Observation > Resources > Measurement > Repair > Testing > Assembly > TestingAlready covered: First Steps: Observation > Confirmation > Disassembly > Re-confirmationSecond Steps: Observation > ResourcesObservation:- With the unit open and the fault re-confirmed we should now have a look at the general condition inside the unit.Remove the Power cord and/or Batteries. If the unit contains high voltages it may pay to wait 5 to 30 minutes for the voltages to drop down to a safe level. While looking inside the unit try and avoid moving cables, we just want to look rather than remove or move anything. Start a complete visual inspection looking for anything unusual like, charring, arcing, leaking, deformed or overheating of components or the PCB(s) itself, damaged components, corrosion, cracks in the PCB, obvious dry joints especially on heavy components like heatsinks, relays, transformers, large capacitors, front panel switches. Keep in the back of your mind the fault you observed and maybe where inside the unit that fault may be.Resources:- Now could be a good time to gather extra resources you may find helpful and could save a lot of time.The Internet is a wealth of information, Operating/User/Instruction Manuals, Service Manuals, Repair Tips, Electronics Forums and of course the EEVBLOG forums and educational Videos. When Googling for Manuals use the Model Number from the unit, try the Google Image search it may be quicker. Avoid paying for Manuals, most enthusiasts will provide them free. Remember Service Manuals are Copyrighted and sometimes distribution is restricted. Asking the Company who manufactured the product for one, will most likely result in a big fat NO and then advise you to take it to an Authorised Service Centre for repair.When you ask for help on the Forums try to supply as much information as possible, like - the model number, a link to the Manuals, a clear description of the fault, what you have checked/confirmed/done so far and don't be surprised if they ask for clarification, photographs or something else. They are not trying to be difficult, they want to help. Overall be patient, helping to repair something they don't have in front of them is not easy. You may also be in a different part of the world (time zone) than they are.

author: Bored@Work
author_rank: Super Contributor
timestamp: June 30, 2014, 04:59:41 am
content: So now that you have your "own" board you want to dictate the rules and continue to post your made-up "rules"?Well, thanks forhttps://www.eevblog.com/forum/profile/?area=ignoreboards

author: What_NZ
author_rank: Regular Contributor
timestamp: June 30, 2014, 05:26:16 am
content: Quote from: Bored@Work on June 30, 2014, 04:59:41 amYou won't be missed and why not add me to your ignore list too.

author: Kjelt
author_rank: Super Contributor
timestamp: June 30, 2014, 07:57:41 am
content: Quote from: What_NZ on June 30, 2014, 12:48:17 amA bit too vague to my likings, perhaps a suggestion to create a list of products that have this issues and where explicitly to look for and measure the voltages and how to discharge them before going further with the repair.Perhaps even some safety shortcuts, I once saw a tech use a large (1000V insulated) screwdriver shorting all the big caps ("just to be sure") not the nicest way but quick and better safe then sorry.

author: What_NZ
author_rank: Regular Contributor
timestamp: June 30, 2014, 08:30:49 am
content: Yes it was a bit sloppy. How about this instead -If the unit is powered from the AC mains, has a CRT type display or by function uses a high voltage then there is likely to be high voltages inside. You should either safely discharge the voltage or wait 5 to 30 minutes for it to drop down to a safe level.Any further suggestions are welcome.

author: Kjelt
author_rank: Super Contributor
timestamp: June 30, 2014, 09:47:26 am
content: I have not much understanding of CRT tv's hv part but AFAIK in the past when I dared to repair the CRT tv's there was a bare metal wiring around the tube and this wire had a metal pin on it.Before continuing working in the CRT tv I recall I had to manouvre this metal pin on the wire with an isolated plier under the plastick cap with the high voltage in order to discharge high voltage PS. Don't know if this was common for all tv's but the Philips types all had it.

author: What_NZ
author_rank: Regular Contributor
timestamp: June 30, 2014, 10:20:53 am
content: Most of the CRT TV's I worked on didn't have anything so it usually involved using two flat blade screwdrivers with good insulated handles and metal shafts to short the ultor cap pins to the aquadag, the grey graphite stuff painted around the tube.

author: What_NZ
author_rank: Regular Contributor
timestamp: June 30, 2014, 10:42:11 am
content: Actually this is a minefield of issues and best left avoided altogether, it is nearly impossible in a small post to cover every possibility. Maybe someone else may like to tackle it.

author: EEVblog
author_rank: Unknown
timestamp: June 30, 2014, 11:11:23 am
content: Quote from: What_NZ on June 30, 2014, 10:42:11 amSomeone mentioned in another thread doing a video on this, with a general procedure etc. And whilst it would be nice, I suspect it going to be quite a minefield as you suggest. Not to mention a flame magnet