- VCR plays color tapes in B&W only? - 2 Updates
| Chuck <chuck23@dejanews.net>: Jan 17 03:19PM -0600 On Tue, 16 Jan 2024 22:28:09 -0500, Usenetist <carg121@usenet.com> wrote: >>> Thank you in advance for your help. >> Those old Akais had lots of electrolytic caps that get weak with age. Try heating the signal boards with a heat gun to see if the color returns. If it does, you're going to have to recap that unit if you intend to keep it. >Can you explain the heat gun technique for bad caps... how does it work? When you heat up a bad cap, the ESR goes down and the capacitance goes up and sometimes the problem goes away. You then replace the cap you were heating when the symptom went away. I would suggest buying a cheap esr meter on EBay. It is a quicker and more certain way of finding bad capacitors. |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Jan 18 06:48AM -0800 On Tuesday, January 16, 2024 at 10:28:13 PM UTC-5, Usenetist wrote: > On 1/9/24 12:24, ohg...@gmail.com wrote: > > Those old Akais had lots of electrolytic caps that get weak with age. Try heating the signal boards with a heat gun to see if the color returns. If it does, you're going to have to recap that unit if you intend to keep it. > Can you explain the heat gun technique for bad caps... how does it work? When I suspect a lazy/weak/ electrolytic capacitor as the cause of a failure, I take my heat gun and warm up the board in question. I get the board pretty hot but not hot enough to melt connectors, ribbons, or indeed the shrink wrap on the capacitors. If the device now performs correctly or even if the symptom changes, an electrolytic becomes a strong suspect. MOST weak capacitors improve with heat, but you'll find the occasional one that actually responds better to cold, but that's as about as rare or more so as finding an open silicon diode (most short). The heat may also affect defective semiconductors so if heat fixes it, it could still be anything on the board that's become heat sensitive, but most circuits that come back to life with applied heat will have a bad capacitor(s). Once I identify weak dried out capacitors with heat, I'll either shotgun the device if it's old and I want it to be long term reliable, or I'll take out my ESR meter and go over the board when the board cools down if it's a board with a crapload of caps where shotgunning is time consuming. One way to get all the weak ones identified is to put the board in question in the refrigerator (or outside if it's cold), as even capacitors that work well at room temperature and not causing any immediate issues may fail at very cold temps. Capacitors that are in good condition won't be bothered by the cold, so it's a good way to ferret out the ones that will fail next. Caps that work at room temp but not in cold temps are on borrowed time. |
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