- Do these 'lytics need to be replaced? - 6 Updates
- Oldtimer question (valves/tubes) - 6 Updates
- 16 X 64 SCROLLING LED MATRIX - 2 Updates
| Bob Engelhardt <BobEngelhardt@comcast.net>: May 14 09:54AM -0400 Are these "bulging"? How much bulge is too much? Or is _any_ bulging to much? "If you can see that it's not flat, it's too much"? https://imgur.com/GymXlUb Thanks, Bob |
| Stephen Wolstenholme <steve@easynn.com>: May 14 03:37PM +0100 On Tue, 14 May 2019 09:54:39 -0400, Bob Engelhardt >https://imgur.com/GymXlUb >Thanks, >Bob I had a few years refurbishing old equipment. I routinely replaced power supply electrolytics as they were always suspect. I've found some electrolitics that were not bulging but had no measurerable capacitance. I remember an Italian TV signal and video generator that had banks of electrolytics wired in parallel rather than using high capacitance. It was a good idea as small capacitors lasted longer than large ones. I still changed them all! Steve -- http://www.npsnn.com |
| John-Del <ohger1s@gmail.com>: May 14 08:23AM -0700 On Tuesday, May 14, 2019 at 9:55:17 AM UTC-4, Bob Engelhardt wrote: > https://imgur.com/GymXlUb > Thanks, > Bob Bulging is not an indication of the condition of a capacitor. I've seen many physically large capacitors in power supplies show some bulge and be dead on for value and ESR, and others that looked brand new and were decidedly low in value and high in ESR. Either pull them and test them or at least scope across them (watch for hot ground with your scope). |
| John Robertson <spam@flippers.com>: May 14 09:16AM -0700 On 2019/05/14 8:23 a.m., John-Del wrote: >> Bob > Bulging is not an indication of the condition of a capacitor. I've seen many physically large capacitors in power supplies show some bulge and be dead on for value and ESR, and others that looked brand new and were decidedly low in value and high in ESR. > Either pull them and test them or at least scope across them (watch for hot ground with your scope). In this case (I checked the photo) the bulging is certainly indicative of a dying capacitor. Another clue is the black plastic sleeve has pulled away from the top of the cap. As a matter of course we replace any caps where the sleeve has shrunk - that is an indication of the cap overheating or simply being in too hot an environment. A new cap has the sleeve covering around 25% of the top of the cap, if you can see signs of shrinkage then time to test and likely replace the cap. As an aside, it is interesting that early amplifiers put all the transistors in sockets (pretty reliable devices actually) and yet soldered in the most failure prone part of all - the caps! Only on the odd rare tube equipment did you see electrolytic cans that had an octal style plug. Of course if the caps were in sockets then you would have one more junction to fail (OK two junctions per cap) but at least you could replace them more easily. Ducking. John ;-#(# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
| "pfjw@aol.com" <peterwieck33@gmail.com>: May 14 09:20AM -0700 In general, capacitors are relatively inexpensive such that if one is in any doubt at all, replace them. All and at the same time, an ESR meter is a helpful - but NOT absolute - screening tool. Yes, those caps appear to be bulging Further, the shrink covering on them has pulled down from the top. A typical cap has that covering turning onto the top by some amount greater than what you show. https://media.rs-online.com/t_large/F7152707-01.jpg My guess is that they have gotten very hot, one or more times. Which would explain both the shrinkage of the covering and the bulge. Peter Wieck Melrose Park, PA |
| Bob Engelhardt <BobEngelhardt@comcast.net>: May 14 12:36PM -0400 On 5/14/2019 9:54 AM, Bob Engelhardt wrote: > https://imgur.com/GymXlUb > Thanks, > Bob Thanks for all the prompt and helpful replies. This is my step son's amp and I have decided that I'm not going to do any repair that might not be perfect in his eyes. So I'm going to return it and let him know that the caps should be replaced. |
| Mike Coon <gravity@mjcoon.plus.com>: May 13 06:14PM +0100 In article <MPG.374358d8d2aa025d5b@news.plus.net>, gravity@mjcoon.plus.com says... > Oh, thanks, I might look that up. But the valve tester would certainly > be older than that. It did have a lacquered wooden case, after all! > Mike. See https://www.radiomuseum.org/r/taylor_valve_tester_47a47.html Mike. |
| Cursitor Doom <curd@notformail.com>: May 13 05:45PM On Mon, 13 May 2019 18:14:29 +0100, Mike Coon wrote: > See https://www.radiomuseum.org/r/taylor_valve_tester_47a47.html Very nice, that. You should hang on to it; valves seem to be making a comeback in some areas. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition. |
| Clifford Heath <no.spam@please.net>: May 14 09:13AM +1000 On 14/5/19 12:23 am, Cursitor Doom wrote: > On Mon, 13 May 2019 21:52:09 +1000, Lucifer wrote: > What's worth salvaging from old photocopiers? I vaguely recall there's > some exotic goodies in them somewhere. Perhaps not exotic, but they tend to have a few nice 24V motors. |
| Lucifer <LuciferMorningstar@bigpond.com>: May 15 12:12AM +1000 On Mon, 13 May 2019 14:27:27 -0000 (UTC), Cursitor Doom >I'll have to look into that. I had no idea of such extraordinarily low >plate voltages as that. 9V eh? Wow! Do you happen to remember the type >number of those? I'd be fascinated to check out the data sheet for 'em. I don't remember other that the car radio used transistors for the second audio and the audio output and valves for the rest. |
| Lucifer <LuciferMorningstar@bigpond.com>: May 15 12:24AM +1000 On Mon, 13 May 2019 09:39:11 -0500, Fox's Mercantile <jdangus@att.net> wrote: >> Valves don't need high voltage on the anode for low power >> applications. ><http://www.junkbox.com/electronics/lowvoltagetubes.shtml> Very interesting. Thank you. |
| Mike Coon <gravity@mjcoon.plus.com>: May 14 05:26PM +0100 In article <qbcafc$6ea$1@dont-email.me>, curd@notformail.com says... > > See https://www.radiomuseum.org/r/taylor_valve_tester_47a47.html > Very nice, that. You should hang on to it; valves seem to be making a > comeback in some areas. Too late; assuming they have not thrown it away, it has been at Bletchley Park for several years, hopefully supporting their old computer resusitation projects. Mike. |
| bitrex <user@example.net>: May 13 05:03PM -0400 > I have an arduino mega 2560 and wants to use it to drive a 16x64 LED array but the outputs are not enough, Is there any way i can achieve this? Thank you. You can use an addressable LED driver IC like this one from Texas Instruments: <http://www.ti.com/lit/ds/symlink/tlc5940.pdf> Data is fed in serially and they can be individually addressed with PWM brightness control for each LED, and daisy chained to create larger arrays. They come in different number of output channels per chip, too. there's likely maximum number of individual ICs that can be daisy-chained before clock skew becomes a problem. If you only need on/off then scanning a row/column arrangement with addressable latches would work as another poster suggested: <https://www.nxp.com/docs/en/data-sheet/MC33996.pdf> would also need a high-side driver. Controlling a large billboard-like array that can do colors and full-motion video is a non-trivial project, but a scrolling message board for text doesn't require a high data rate. |
| tabbypurr@gmail.com: May 14 04:47AM -0700 On Monday, 13 May 2019 22:03:59 UTC+1, bitrex wrote: > Controlling a large billboard-like array that can do colors and > full-motion video is a non-trivial project, but a scrolling message > board for text doesn't require a high data rate. If spinning the display is an option you can greatly reduce the electronics. NT |
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