Recent content by Alfonsol

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    to recap or not

    It think it sounds better now. more alive than before. now the bass is more precise but still very present, and treble is more present, but less harsh i leave the treble just as before. before changing the caps i felt the need to put more treble, but when putted more treble it sounded harsh...
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    to recap or not

    i went ahead replacing some caps. I started with the output caps because they are very close to the heatsink end they receive lots of heat. when i removed them i found one leaked a little a long time ago (it was not glue). they were rubycon 470uf 25v, i replaced them with panasonic FM 470uf...
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    to recap or not

    Thanks for all the replies. this one is 45 years old and if some caps fail may damage some difficult to get transistors. i think i will replace the ones that may fail in a catastrophic way only. i forgot to mention, this receiver is used sometimes for hours at loud volume.
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    to recap or not

    a friend asked me to repair his receiver, is sony str-230A he used it for years with a dead channel. and it has been in constant use since new. The problem was a broken cable in one speaker. after repairing the speaker and testing it with my equipment so i was positive it was ok i proceeded to...
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    Silver sa-5030

    Hi, yes i fixed it, and is still running strong. the offset on the output was because of a open fusable resistor. check those green resistors ii sounds very good.
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    Hello! Grundig KS 680 U

    It have the magnetic phono preamp and reverb unit!!! I repaired a similar console. If the transformers are good, the repair is cheap in parts, but long, because everything is cramped inside. the turntable lamps is working because this is connected directly to mains. The amplifier( the big one...
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    pioneer sg-540

    i disconnected the power supply for the leds and the noise is gone.
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    Why change so many components unnecessarily?!

    I made some full recaps. some made a big difference, some not. I search for cold solder joints and i clean the pots and jacks. I tend to replace caps that are obviously failing, and then i replace the ones that can damage other components if they go bad. If replacing those make a difference, i...
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    Muskat MPX-20 hum on all inputs

    Didn't had much time to work on the receiver, but i found a picture i took several yars ago. Also i found the power rating of the autotransformer is 30W and the power consumption on the back of the receiver is 50W
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    What is the purpose of this resistor?

    I have the same dilemma with my receiver on another post. I agree with avionic. A the time the receiver was manufactured a ground connection was not so common, so this is a way to discharge the chassis instead of grounding it. But if the resistor is shorted you have 50% probabilities to have...
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    Muskat MPX-20 hum on all inputs

    I looked it again and i think the way the autotransformer is wired should not be more dangerous than it already is with the 2.2M resistor. The real problem and also the source of the hum is the resistor. The hum reduces considerably depending where is the neutral on the plug. The hiss is not...
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    Muskat MPX-20 hum on all inputs

    I agree with you. I always thought it was a transformer until i measured it today. I am thinking where to get an actual transformer. Here when you try to buy a 220v to 120v transformer they sell you an autotransformer. And they swear is a transformer. I am also concerned about the resistor
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    Muskat MPX-20 hum on all inputs

    Thanks, i have an oscilloscope. i not always use it because i have no room on my bench. Today 've been using the oscilloscope and i made some interesting discoveries. 1. The noise is everywhere. even puting the probes on the phono input i can see 50Hz and other frequencies. It just gets...
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    Muskat MPX-20 hum on all inputs

    i forgot to mention the hum now is better. Don't know exactly what i did, but i think it went away when i cleaned again the input selector.
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    dead FM

    i put contact cleaner on the shaft and rotated it several times. it improved a lot. still i have an odd behaviour. when tuned in a place where there are no stations. i can hear a whistle . the pith of the whistle is related to the position on the dial. the pitch at 108MHZ is higer than the...
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