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Disappointing hum with new PS-X7

B

bobspets

Well-Known Member
Just got a PS-X7 had it professionally serviced, aligned and tested with a Grado signature 3 cart and 8MZ stylus.
Played about a side and a half LP and now hum has mysteriously appeared. All connections appear secure.
What might cause this to develop over such a short period of time?
 
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bobspets said:
Just got a PS-X7 had it professionally serviced, aligned and tested with a Grado signature 3 cart and 8MZ stylus.
Played about a side and a half LP and now hum has mysteriously appeared. All connections appear secure.
What might cause this to develop over such a short period of time?
Click to expand...

Was there hum with the same cartridge BEFORE service? If you just put Grado on, it is possible that cartridge is the culprit. Grado are infamous for producing hum. There is a whole page https://docs.google.com/spreadsheets/d/1k_Wr5zx-hcJ0as6wub8wIqsMu2a67DyLhzE8grJp9mc dedicated to that cartridge humming.
 
OK all connections secure and surfaces clean. I unplugged the power cord hum persists I unplug the RCAs with or without power hum is eliminated. This is a new unit for me and I had not played it prior to it being serviced. After service I was assured that all aspects were tested and working properly and indeed when I brought it home I was able to play an LP and a half prior to the issue. I was aware of the Grado hum issue before I bought the unit so I checked the Grado hum database and found that someone had successfully used a Grado cart.
 
bobspets said:
OK all connections secure and surfaces clean. I unplugged the power cord hum persists I unplug the RCAs with or without power hum is eliminated. This is a new unit for me and I had not played it prior to it being serviced. After service I was assured that all aspects were tested and working properly and indeed when I brought it home I was able to play an LP and a half prior to the issue. I was aware of the Grado hum issue before I bought the unit so I checked the Grado hum database and found that someone had successfully used a Grado cart.
Click to expand...

a grado should not pick up emi from the motor on that Sony. you need to check for an open ground. start with checking continuity across the RCAs with cart attached in arm. you should be within a few ohms of what the cart reads across its pins. Check ground wire to arm. should read almost a dead short.

Edit: those generation Sony tables were known for crappy RCA cables.
 
I had two tables that developed a hum and the culprit in both cases was the RCA cables. If I grabbed the cables and moved them around the hum would get worse or go away completely. New cables and ground wire fixed it.
 
grillebilly said:
I had two tables that developed a hum and the culprit in both cases was the RCA cables. If I grabbed the cables and moved them around the hum would get worse or go away completely. New cables and ground wire fixed it.
Click to expand...
Unfortunately there is o change when manipulating the cable
 
marcmorin said:
a grado should not pick up emi from the motor on that Sony. you need to check for an open ground. start with checking continuity across the RCAs with cart attached in arm. you should be within a few ohms of what the cart reads across its pins. Check ground wire to arm. should read almost a dead short.

Edit: those generation Sony tables were known for crappy RCA cables.
Click to expand...
An excellent idea, but beyond my scope
 
Yep its directly above Amp. and hum is equal in both channels. The location of the table has not changed it's in the same place it was when it was working properly
 
bobspets said:
Yep its directly above Amp. and hum is equal in both channels. The location of the table has not changed it's in the same place it was when it was working properly
Click to expand...

That's still about the worst possible place to put a turntable
 
I suppose an easy test as to whether the hum is induced by the amp would be to relocate the table temporarily.

If that helps, have your local hardware cut you a piece of metal to set the table on as a shield?

I'd still lean towards the cables being the problem, especially on an older table. Those have potentially been yanked and twiddled a LOT in 40 years even with the best of care. First step for me would be to clean the connections, inside and out, with D5 and tighten the prongs.

The Signet connector cleaners are right nice, and if nothing else, will eliminate the RCA's as a problem ...

ASIGTOOL.jpg

Could also be cold solder or dirty connections under the table as well. Maybe have your tech look at that if you're not comfortable digging around inside. Or, as I've seen with several tables, broken wires right where the cables exit the table body.

Another common problem is improper grounding. Yes, you should run a ground from the table to your amp/receiver, but don't forget to ground that as well.
 
sKiZo said:
I suppose an easy test as to whether the hum is induced by the amp would be to relocate the table temporarily.

If that helps, have your local hardware cut you a piece of metal to set the table on as a shield?

I'd still lean towards the cables being the problem, especially on an older table. Those have potentially been yanked and twiddled a LOT in 40 years even with the best of care. First step for me would be to clean the connections, inside and out, with D5 and tighten the prongs.

The Signet connector cleaners are right nice, and if nothing else, will eliminate the RCA's as a problem ...

ASIGTOOL.jpg

Could also be cold solder or dirty connections under the table as well. Maybe have your tech look at that if you're not comfortable digging around inside. Or, as I've seen with several tables, broken wires right where the cables exit the table body.

Another common problem is improper grounding. Yes, you should run a ground from the table to your amp/receiver, but don't forget to ground that as well.
Click to expand...
nks
Thanks, yeah I'll move the table and clean the RCAs, but seems unlikely to be the RCAs since it was working properly originally
 
Tonearm wire just on the verge of letting go ... perhaps pinched and weakened by fatigue ... that last auto-return and auto-start did it in? If basic troubleshooting with a digital multimeter is beyond your abilities ... I'd say its going back to the shop.
 
I bought a bunch of these several years ago and divided them up among friends. They clean the inside and outside of phono connectors. Be careful using them on the photo jacks of equipment. Push /pull only. Twisting can damage contact integrity. If you would like one message me your address and I'll send you a new one at no charge.

ASIGTOOL.jpg
 
Bugler said:
I bought a bunch of these several years ago and divided them up among friends. They clean the inside and outside of phono connectors. Be careful using them on the photo jacks of equipment. Push /pull only. Twisting can damage contact integrity. If you would like one message me your address and I'll send you a new one at no charge.

ASIGTOOL.jpg
Click to expand...
Very generous I'll take you up on that
 
sKiZo said:
have your local hardware cut you a piece of metal to set the table on as a shield?
Click to expand...

Unless the hardware store carries Mu-Metal, or soft iron in sheets............plain sheet steel stops low frequency EMF ( the type that causes hum) about as well as air
 
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