- CRT peel - 3 Updates
- Panasonic PV-4800 VCR Timer Recording Issue - 1 Update
- audio buzzing after PC is turned off - 1 Update
| Rob <nomail@example.com>: Jun 14 09:00AM > Zerox (ok, it was Savin then) copy of the service manual, but it says nothing > about this. Yeah, it's nostalgia and prolly not worth the effort. But would > appreciate any tips from anyone who has done anything like this before. Of course the service manual does not mention this, it was either not known at the time it was made or the service was not intended to cover that long of a lifetime. There will likely be other things wrong with it, like dried-out electolytic capacitors or other components that decay over such a long time. I would recommend consulting someone with experience in refurbishing such equipment, like "Curious Marc". |
| Lucifer <LuciferMorningstar@bigpond.com>: Jun 14 11:10PM +1000 On Sat, 12 Jun 2021 02:10:09 +0000 (UTC), >Zerox (ok, it was Savin then) copy of the service manual, but it says nothing >about this. Yeah, it's nostalgia and prolly not worth the effort. But would >appreciate any tips from anyone who has done anything like this before. I have a 45 year old CRT colour TV! |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Jun 14 07:25AM -0700 > about this. Yeah, it's nostalgia and prolly not worth the effort. But would > appreciate any tips from anyone who has done anything like this before. > -- The CRT is considered a single replaceable component. Removing the bonded safety glass is very dangerous and something no manufacturer would recommend. John Robertson's advice to wear armored clothing and eye protection is a good one if you want to attempt to remove the safety glass. I've used a heat gun and piano wire stretched between a couple of pieces of wood dowel to slice the glue to remove the cataract safety glass, but both the tube and safety glass were indeed glass. If that's some sort of plastic on the HP, I don't know if the same procedure would work. |
| Lucifer <LuciferMorningstar@bigpond.com>: Jun 14 11:22PM +1000 >problem, it's so unlikely to find a replacement clock/timer board these days >and probably priced at 10x what the machine is worth, there really is no >other solution except to replace the whole machine. I still have a working VHS VCR. It has a stereo sound decoder, Hi-Fi sound, half speed record and playback, NTSC playback on PAL TV, G-Code programming, and on screen programming. However, if I play a five hour tape it folds the top of the tape over!(?) Three hour or less works OK. |
| dplatt@coop.radagast.org (Dave Platt): Jun 13 04:54PM -0700 >everything is on, but when the desktop is turned off I am getting a >buzz/ hum from the speakers and loud enough that I power them off. Why >is this and how to remedy? Thanks. When the PC is powered on, there's DC power going to the sound-card output circuitry. The output amplifiers (when powered on) should have a relatively low output impedance - typically a couple of hundred ohms for a "line level" output, quite possibly less. Since the speaker set's input circuitry has a high impedance (at a guess, 47k ohms or higher), the voltage on the signal conductor will be dominated by the output amplifier - and when you aren't playing music, it'll be right about at zero volts ("dead silence"). When you power off the computer, the sound card loses power and its output amplifiers shut down... they go to a "high impedance" open-circuit state. At this point, the sound card isn't holding the signal line at zero volts. Instead, the signal line will start acting like a simple antenna, picking up 60-cycle buzz and hum from magnetic and electrical fields around the PC. With its high input impedance, the speaker set will be sensitive to even small noise currents and it will amplify the resulting voltage. If you were to unplug the cable from the PC, and touch the end of the plug with your finger, you'd get a similar (possibly much-louder) buzz. If this really bothers you, you can probably make a "noise stopper" device, wired between the sound-card output and speaker set. You would need a small (sensitive-coil) 5-volt-DC double pole, double-throw relay. The relay coil would be wired to a USB plug which would go into the PC, so that the relay would be energized when the PC was turned on. You would wire one set of the normally-closed relay contacts, and a 47-ohm resistor, across each of the two audio signal lines and audio ground. When the PC is off, the relay would be in its normally-closed position, connecting the 47-ohm relay across the audio signal. This would silence the audio, muting the buzz. When the PC is on, the relay would operate, opening the normally-closed contacts, disconnecting the resistors and unmuting the audio. A similar unmute-upon-power-on system is used in many commercial audio components (e.g. tuners and preamps). |
| You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com. |
No Response to "Digest for sci.electronics.repair@googlegroups.com - 5 updates in 3 topics"
Post a Comment