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#1
07-13-2006, 09:11 PM
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Hum in Magnavox Astro Sonic
I bought a Magnavox Astro Sonic console stereo with am/fm and phono. The model # is 2st686. It dates from 1965. It is a huge thing,6 feet long and weighs a ton. It works good except it has a hum. The hum gets worse as you turn the bass down. It has 2 brown electrolitic caps above the power transformer. Would those be bad? I know filter caps are what usually cause hum. Also it has a control called timbre and one called squelch sens. What are those for? I have never had a stereo with those.
John. 
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#2
07-13-2006, 10:50 PM
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9/10 times a constant hum is caused by poor AC filtering. I definitely suspect those caps. If this has a solid state rectifier, I would test that as well.
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Jordan
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#3
07-14-2006, 05:29 AM
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Astro Sonic hum
It is totally solid state. Those two caps are 1500 uf at 35 volts. Where would I find caps that big?They have a light brown paper covering though they may be cans under the paper. I dont think Justradios has them that large.
John.
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#4
07-14-2006, 07:18 AM
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The timbre control is just a tone control that controls the highest frequencies and the squelch sensitivity is for quieting the noise as you tune between stations just like a squelch control on a two way radio. Do you have the hum with the volume turned all the way down? Do you have the hum on all functions? If the problem is the filter capacitors the hum will be present with the volume turned down. The replacement filters you get now will be physically much smaller than the originals, I've been buying nearly all my electrolytic capacitors from www.mouser.com they do not have a minimum order and the prices are very competitive.
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"proximo satis pro administratio" KAØSCR
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#5
07-14-2006, 04:27 PM
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Hum in Astro Sonic
Yes it hums on all functions and also with the volume turned all the way down. Would replacing those 2 caps above the power transformer be all that would need to be done to fix the hum or are there other parts that could contribute to it? They are both single section electrolitics the same size 1500 uf,35 volt. The new ones could be mounted under the chassis so it would still look stock. The timbre control is also the power switch for the amp. when the phono is on its switch powers the amp.
Thanks,John.
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