bluesboy Posted February 16, 2009 Share Posted February 16, 2009 I've got a Fisher X-100 tube integrated amp that does not have a ground post for a turntable. I ran the ground wire frome the tt to a couple of different chassy screws but I'm still getting a huge hum from the tt not being grounded. Anybody got any ideas to rectify the situation? Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 16, 2009 Share Posted February 16, 2009 This is just an initial thought, hopefully more to come if it doesn't work. Is the hum in just one channel? Jiggle the leads between the tonearm and the preamp to see if the hum cuts in and out. If so, the grounding shield may be broken at one end, and need resoldering. Is there a "pop" if you move the selector switch between phono and another input? Also, are the jacks pushed firmly in at both ends and making good contact? Did the hum change when you tried to attach the ground wire to a chassis screw? Are the leads well attached at the back of the cartridge? Others will have other good tests to try to track this down. Quote Link to comment Share on other sites More sharing options...
Blvdre Posted February 16, 2009 Share Posted February 16, 2009 I found a schematic on the web (scroll down). It looks like all of the grounds are the same. Schematically, it's depicted as earth ground (I assume this unit has a three pronged plug?). I wouldn't rely on a chassis screw for a good ground, I'm sure there's a better place to ground your table. I don't know what the 100 looks like under the hood, but I'm sure someone will have a suggestion. Quote Link to comment Share on other sites More sharing options...
bluesboy Posted February 16, 2009 Author Share Posted February 16, 2009 This is just an initial thought, hopefully more to come if it doesn't work. Is the hum in just one channel? Jiggle the leads between the tonearm and the preamp to see if the hum cuts in and out. If so, the grounding shield may be broken at one end, and need resoldering. Is there a "pop" if you move the selector switch between phono and another input? Also, are the jacks pushed firmly in at both ends and making good contact? Did the hum change when you tried to attach the ground wire to a chassis screw? Are the leads well attached at the back of the cartridge? Others will have other good tests to try to track this down. The hum is in both channels. The tt works just fine through my HK 630 which has a grounding post on the back for a turntable. So there are no issues with arm or the cartridge. What I'm going to try next is run the tt through my Haggerman phono pre amp to the aux inputs on the Fisher and see how that works out. Quote Link to comment Share on other sites More sharing options...
bluesboy Posted February 16, 2009 Author Share Posted February 16, 2009 I found a schematic on the web (scroll down). It looks like all of the grounds are the same. Schematically, it's depicted as earth ground (I assume this unit has a three pronged plug?). I wouldn't rely on a chassis screw for a good ground, I'm sure there's a better place to ground your table. I don't know what the 100 looks like under the hood, but I'm sure someone will have a suggestion. Thanks for the link. Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 16, 2009 Share Posted February 16, 2009 A vintage unit would likely have a 2-prong cord. If it grounds well on another unit with a grounding post, then it seems to me it would ground well under a chassis screw IF it has good, direct contact with the chassis metal. Perhaps reverse the plug and then try for a screw that has good contact with a non painted part of the chassis? I'm out of ideas other than those. Well, maybe see if any of the connections are bad on the backside of the phono jacks inside the chassis. Quote Link to comment Share on other sites More sharing options...
Blvdre Posted February 16, 2009 Share Posted February 16, 2009 A vintage unit would likely have a 2-prong cord. If it grounds well on another unit with a grounding post, then it seems to me it would ground well under a chassis screw IF it has good, direct contact with the chassis metal. Perhaps reverse the plug and then try for a screw that has good contact with a non painted part of the chassis? I'm out of ideas other than those. Well, maybe see if any of the connections are bad on the backside of the phono jacks inside the chassis. You're right, it is two-pronged (just checked the schemo). I assumed it was three because the ground is drawn as an earth ground - that symbol gets abused a bit. In any case, it shouldn't be too difficult to spot a ground under the hood (Is it point to point wiring?). If you have a multi-meter, you can measure for continuity from ground to a chassis screw. If you're getting continuity, you should be able to ground there (scrape any paint from around screwhole). Larry's idea is a good one. You may have a bad connection at the phono jack, or maybe a bad jack itself. Weird that unit doesn't have a phono ground. Quote Link to comment Share on other sites More sharing options...
daleh Posted February 17, 2009 Share Posted February 17, 2009 I’m not sure if mine is an x-100 or x-101 but I found the best grounding point to be the top of the pre tower. It’s located behind the left side of the face plate and has two tubes mounted horizontally. There is an exposed grounding wire connected to these two tube sockets and I used closest screw to this point to ground my TT. Your unit may not be the same as mine though. Also, if you haven’t done so, try reversing the power plug in the outlet or a different outlet if available. Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 17, 2009 Share Posted February 17, 2009 Also, if you haven’t done so, try reversing the power plug in the outlet or a different outlet if available Also try reversing the TT power cord if it's non-polarized (i.e., both prongs the same size). Quote Link to comment Share on other sites More sharing options...
flaming eye Posted February 17, 2009 Share Posted February 17, 2009 If all ells fails get a phono pre-amp Quote Link to comment Share on other sites More sharing options...
bluesboy Posted February 17, 2009 Author Share Posted February 17, 2009 A vintage unit would likely have a 2-prong cord. If it grounds well on another unit with a grounding post, then it seems to me it would ground well under a chassis screw IF it has good, direct contact with the chassis metal. Perhaps reverse the plug and then try for a screw that has good contact with a non painted part of the chassis? I'm out of ideas other than those. Well, maybe see if any of the connections are bad on the backside of the phono jacks inside the chassis.Yes it does have a two prong chord. I'll try reversing the plug. Right now I've got it hooked up with a phono pre to aux. Sounds ok but doesn't seem to have near the gain as when the tt and phono pre were fed through the Kailin amp. Quote Link to comment Share on other sites More sharing options...
bluesboy Posted February 17, 2009 Author Share Posted February 17, 2009 I've got a Fisher X-100 tube integrated amp that does not have a ground post for a turntable. I ran the ground wire frome the tt to a couple of different chassy screws but I'm still getting a huge hum from the tt not being grounded. Anybody got any ideas to rectify the situation? Are you certain you are making connection with the chassis metal? Chassis that are painted or anodized can be tricky to simply ground with a screw. You may want to try grinding the area with a dremel. Try to take your ground to the point on the Fisher where the electrolytic can capacitor lugs are twisted to the chassis. Thanks Mark, I'll try that next. Quote Link to comment Share on other sites More sharing options...
bluesboy Posted February 17, 2009 Author Share Posted February 17, 2009 I’m not sure if mine is an x-100 or x-101 but I found the best grounding point to be the top of the pre tower. It’s located behind the left side of the face plate and has two tubes mounted horizontally. There is an exposed grounding wire connected to these two tube sockets and I used closest screw to this point to ground my TT. Your unit may not be the same as mine though. Also, if you haven’t done so, try reversing the power plug in the outlet or a different outlet if available. Thanks guys for all of your suggestions. I guess I better get to work. Quote Link to comment Share on other sites More sharing options...
bluesboy Posted February 17, 2009 Author Share Posted February 17, 2009 Thanks, daleh. I grounded it just like you explaned. It's totaly silent now. Quote Link to comment Share on other sites More sharing options...
daleh Posted February 17, 2009 Share Posted February 17, 2009 [Y] Quote Link to comment Share on other sites More sharing options...
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