- Sansui QRS5500 quadrophonic receiver - 2 Updates
- Difficult customer - 5 Updates
| jurb6006@gmail.com: Jul 02 06:24AM -0700 Wanna buy a Marantz CD-400B CD-4 disk demodulator ? Cosmetically fair, and I checked that is works by injecting a carrier from a generator with a VCG function and modulated it. It was loosely coupled capacitively to the input, a wire near the jacks with the cover off. The signal came out of the outputs. I have a picture of that setup working. Of course I have no CD-4 records, and no compatible cartridge, but I know it works. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Jul 02 06:47AM -0700 > Wanna buy a Marantz CD-400B CD-4 disk demodulator ? https://www.youtube.com/watch?v=9G0EDV07HwU Or, this. I actually own one of these, in working condition. Kinda-sorta like cotton candy or foot-long hot dogs - not something one does every day, but nice on occasion. Peter Wieck Melrose Park, PA |
| Phil Allison <pallison49@gmail.com>: Jul 01 05:33PM -0700 ** Hi, if you do guitar amp repairs for any time at all, you will likely come across someone like the guy in this Vid: https://www.youtube.com/watch?v=ikIDYHna9Dc His Fender Pro 185 ( 150watt rated with 2 x 12inch speakers ) has a small amount of background hum, plus a slight hum in the reverb. But that is NOT how he sees it. Repairers can be expected to fix faults that develop, but something that has been that way since manufacture is another story - often being near impossible or uneconomic to fix. The two repairers mentioned wisely chose not to waste time trying. .... Phil |
| tabbypurr@gmail.com: Jul 01 07:36PM -0700 On Monday, 2 July 2018 01:33:05 UTC+1, Phil Allison wrote: > The two repairers mentioned wisely chose not to waste time trying. > .... Phil Many things are uneconomic, and some customers unreasonable. But fixing background hum from new is often an easy job. If the psu is unregulated, adding lf filtering sometimes sorts it. I used to like CDC filters, capacitor diode capacitor, the D acts as a low R nonlinear resistor. The upside is voltage drop is limited, and the filtering gets better as output volume drops. Of course hum can also be caused by a host of other things not as simple to fix. Reminds me of the guitar amp that had had the wrong transformer fitted, giving twice the wanted voltage. Distorted & cut out often. A rework of the psu configuration sorted it. It's a lot easier if the transformer gives half the required voltage! NT |
| Phil Allison <pallison49@gmail.com>: Jul 01 11:33PM -0700 > and the filtering gets better as output volume drops. > Of course hum can also be caused by a host of other things not as > simple to fix. ** As the background hum in the Pro 185 is independent of control settings, I have a hunch that is due to magnetic field from the AC transformer infecting the earth/ground patterns on the PCB near it. ... Phil |
| Phil Allison <pallison49@gmail.com>: Jul 02 02:42AM -0700 Phil Allison wrote: > ** As the background hum in the Pro 185 is independent of control > settings, I have a hunch that is due to magnetic field from the > transformer infecting the earth/ground patterns on the PCB near it. **FYI: https://en.audiofanzine.com/solid-state-combo-guitar-amp/fender/PRO-185/medias/pictures/a.play,m.898605.html |
| tabbypurr@gmail.com: Jul 02 03:00AM -0700 On Monday, 2 July 2018 10:42:55 UTC+1, Phil Allison wrote: > > transformer infecting the earth/ground patterns on the PCB near it. > **FYI: > https://en.audiofanzine.com/solid-state-combo-guitar-amp/fender/PRO-185/medias/pictures/a.play,m.898605.html I guess one could move it, but the cost/return ratio isn't looking good. NT |
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