My First/Last SX-1010
- Thread starter craxx6969
- Start date
missed the point. ANTENNA GROUND FROM ELSEWHERE....
Use a 300 ohm tee antanna, with NO other grounds connected to the unit.
Just floating FM antenna, speakers and ac power. NOW check hum.
Then use a signal probe on the power line going to the tuner. Looking for hum on the power supply line.
I will follow up on this MTF. Thank you for your help on this. I know you are buried in other issues.
forget the signal probe for now, just test with:
Going BACK to baseline condition to test initial conditions.. You may be inspecting trees rather than looking at the forest.
ONE POWER CORD (reversible)
ONE FM DIPOLE ANTENNAM "FLOATING"
ONE SET OF SPEAKERS "FLOATING"
NOTHING ELSE CONNECTED TO IT- including inadvertent grounds
(like a metal strip on my kitchen counter, 5vac relative to the water faucet and stainless steel sink
OOUUCCHH 
?????)
There is a METHOD to my MADNESS.
UNLESS these were the conditions all along (before the signal probe bupkus). Then please SAY so.
Going BACK to baseline condition to test initial conditions.. You may be inspecting trees rather than looking at the forest.
ONE POWER CORD (reversible)
ONE FM DIPOLE ANTENNAM "FLOATING"
ONE SET OF SPEAKERS "FLOATING"
NOTHING ELSE CONNECTED TO IT- including inadvertent grounds
(like a metal strip on my kitchen counter, 5vac relative to the water faucet and stainless steel sink
OOUUCCHH ?????)There is a METHOD to my MADNESS.
UNLESS these were the conditions all along (before the signal probe bupkus). Then please SAY so.
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forget the signal probe for now, just test with:
Going BACK to baseline condition to test initial conditions.. You may be inspecting trees rather than looking at the forest.
ONE POWER CORD (reversible)
ONE FM DIPOLE ANTENNAM "FLOATING"
ONE SET OF SPEAKERS "FLOATING"
NOTHING ELSE CONNECTED TO IT- including inadvertent grounds
(like a metal strip on my kitchen counter, 5vac relative to the water faucet and stainless steel sink
There is a METHOD to my MADNESS.
UNLESS these were the conditions all along (before the signal probe bupkus). Then please SAY so.
Those conditions are exactly how the system is set up. No more, no less.
describe symptoms, hum on just FM? low level hum?
Current setup
Dipole antenna hooked up as external.
Speakers on channel A, no other speakers hooked up.
Tone switch UP position
All Tape switches in the UP position
Mute – OFF
Light Dim/Bright – Bright
Balance knob – equal position
Hi/Lo filters – OFF position (out)
-20db filter – OFF position (out)
Loudness button – ON (IN)
Mono button – OFF (OUT)
Volume at MIN
Power plug into wall socket no other things plug into this socket.
Turn set on – FM selected, instant hum, scratchy sound both speakers. Scratchy sound quits when station is tuned to FM stereo. Hum still there, no change is hum volume or pitch when receiver volume increases.
When tuned to a FM stereo station HUM increases in volume, same pitch, when tone switch is in the down position, the hum subsides slightly.
When off of a station, the hum volume decreases
Switched to AM, hum is present, lower in volume and pitch
Switched to PH-1, hum still present, when volume is raised, hum does not change, but there is an increase in a secondary buzz, volume pot has been dexoited several times.
Switch to PH-2, same scenario as AM, exactly the same
Switch to Aux, same exact sounds as the AM function
Switch to Mic, same exact sounds as the AM function.
I would say the hum level is mid in the FM mode and low level in the other function modes.
Is the hum 60Hz or 120Hz? you can either be the victim of a transformer hum or a ground loop. Check all the ground connections at the boards and chassis with the meter (set to ohms). Any that show more than an ohm or 2 need to be cleaned and repaired, ideally 0oHms. Some riveted ground terminals will get loose and start corroding, giving you a crappy ground or none at all. So check the tightness of all the terminal strip ground points. You might want to REFLOW ALL the SOLDER Joints on them also (dry solder joints or missed joints). . I googled "60Hz Hum vs. 120Hz Hum in Audio gear" and came up with some threads you might want to read on this. Here are some examples. These may help you determine which and how to Troubleshoot
Online Tone generator. Set to 60Hz and 120Hz (VOLUME DOWN!!!!!!) and listen to the difference. Compare to your 1010's hum. http://plasticity.szynalski.com/tone-generator.htm
http://en.wikipedia.org/wiki/Mains_hum
http://www.google.com/url?sa=t&rct=...DKw0FS-9cMSqH1DYmOkGNWw&bvm=bv.95039771,d.eXY
http://www.google.com/url?sa=t&rct=...LVxU7o8p8a_g_AY2FO5WdPA&bvm=bv.95039771,d.eXY
Larry
Online Tone generator. Set to 60Hz and 120Hz (VOLUME DOWN!!!!!!) and listen to the difference. Compare to your 1010's hum. http://plasticity.szynalski.com/tone-generator.htm
http://en.wikipedia.org/wiki/Mains_hum
http://www.google.com/url?sa=t&rct=...DKw0FS-9cMSqH1DYmOkGNWw&bvm=bv.95039771,d.eXY
http://www.google.com/url?sa=t&rct=...LVxU7o8p8a_g_AY2FO5WdPA&bvm=bv.95039771,d.eXY
Larry
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I'll look over those sites and follow up on it. I have been checking some of the ones on the boards but I'll check again.
Pays to read the post. Looks like it is 120hz hum.
Thanks!!!
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jumpsturdy
New Member
Just a bump to see what happened. Had been following this thread with much interest before it went quiet. Interested to know if the hum/noise issue was ever resolved. I thought the process Mark took you through was very thoughtful and I know I learned a lot. And your perseverance was notable.
elvi
Well-Known Member
Starting with 60HZ, how do you "double" the frequency to120?
A clue might be in the tuner section?
Just a final note to close out this post. I replaced D8 and D9 on the power board with the correct diodes and lo and behold the hum has been removed. It appears I used one diode per location and now I have two of the correct diodes in each locale. Now to paint the bottom cover.
