Chris A comment, which is probably representative of many audio systems (although I do appreciate that your company makes fairly "high end" equipment!).
My Yamaha AV tuner amp (RX-V592RDS) is Class II, as is most of the rest of the audio system, but the user manual states that it may be necessary to ground the chassis for noise reduction purposes and provides a terminal on the back for the purpose. I assume that this can be the star point for both the external and the internal earthing since it states nothing to the contrary. There werer certainly noticeable successive reductions in hum/noise on the phono input when, very recently, I earthed first the metal chassis of the (very old!) turntable to the star point, and then connected the star point to a the earth of a spare socket in the mains distribution block. Both of the above connections would be representative of what most people would do - I do'nt think many would star the earths at the mains-distribution block first as this could actually increase hum/noise problems due to increasing the size of the earth loops. Both earths were small diameter (0.5/0.75 sq mm or 20/18 AWG) and I would not expect anyone to use anything much larger unless specified in the installation instructions. The length of the turntable wire is about 2m and it is incorporated as a drain wire in the twin phono lead. The length of the wire from the star point is only some 0.5m as that is the actual distance required. I think these numbers will vary according to the needs to the actual user - OR according to what you state in the installation instructions! Maybe you need to consider real-life situations, make some tests and then specify the actual installation cabling requirements or options in the instructions. Then YOU will have more control of the situation and the pass/fail criteria. Regards John Allen Racal ---------- From: Colgan, Chris[SMTP:[email protected]] Sent: 02 March 2000 09:40 To: [email protected] Subject: RE: Surge Testing per EN 55024/EN61000-4-5 Let's say I'm testing a Class II double insulated CD player - no reference to earth. If the product were stand alone, line to earth testing would be pointless, at least as I see it. It is conceivable that the CD player could be connected to a Class I, earthed amplifier. Through the interconnects, the chassis of the CD player could become grounded (there would probably horrendous hum problems but that's another story). Line to earth tests are now valid but how would I set this up in the lab? A lead from the CD player chassis to the nearest socket outlet earth? A lead to the chassis of my Keytek surge tester? A thin lead, a thick lead? I guess the test should be representative of the real world and repeatable. Any suggestions? Regards Chris Colgan EMC & Safety TAG McLaren Audio Ltd mailto:[email protected] > -----Original Message----- > From: Mike Hopkins [SMTP:[email protected]] > Sent: 01 March 2000 18:32 > To: 'Jim Hulbert'; [email protected] > Subject: RE: Surge Testing per EN 55024/EN61000-4-5 > > > As long as there is no other path to ground, a line to line test would be > all thats required, but keep in mind, if you have other I/O, telecom, > control lines, or anything else coming out of that plastic box, you then > have a potential path back to ground, and in fact, will likely have REAL > ground connections. For example, many television sets have two wire power > plugs, are in plastic cases, but if you have cable tv, the odds are that > coax cable is grounded. Same thing applies if there is a telecom line > involved -- very likely one of the telecom lines is ground. ...... > > Mike Hopkins > [email protected] > > > -----Original Message----- > > From: Jim Hulbert [SMTP:[email protected]] > > Sent: Wednesday, March 01, 2000 10:32 AM > > To: [email protected] > > Subject: Surge Testing per EN 55024/EN61000-4-5 > > > > > > > > > > Colleagues, > > > > EN 55024 calls for surge pulses to be applied line-to-line and > > line-to-earth on > > the AC mains port and line-to-ground on signal and telecommunications > > ports that > > connect directly to outdoor cables. However, if my EUT is encased in > > plastic > > covers and has no direct earth ground connection (class 2 power supply), > > is the > > line-to-line test on the AC mains the only surge test that I need to > > apply? It > > seems to me that performing a line-to-earth test on either the AC mains > > port or > > on signal/telecommunications ports is not warranted since the basic > > standard EN > > 61000-4-5 does not specify placing the EUT over a reference ground > plane. > > With > > no reference ground plane and no direct ground connection how can a test > > be > > applied with respect to ground? > > > > Jim Hulbert > > Pitney Bowes > > > > > > > > --------- > > This message is from the IEEE EMC Society Product Safety > > Technical Committee emc-pstc discussion list. > > > > To cancel your subscription, send mail to: > > [email protected] > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list adminstrators: > > Jim Bacher: [email protected], or > > Michael Garretson: [email protected] > > For policy questions, send mail to: > > Richard Nute: [email protected] > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > ===================================================== Authorised on 03/02/00 at 09:41:53; code 37f48bf3735420B5. ********************************************************************** The contents of this E-mail are confidential and for the exclusive use of the intended recipient. If you receive this E-mail in error, please delete it from your system immediately and notify us either by E-mail, telephone or fax. You should not copy, forward or otherwise disclose the content of the E-mail. TAG McLaren Audio Ltd, The Summit, 11 Latham Road Huntingdon, Cambs, PE18 6ZU Telephone : 01480 415600 (+44 1480 415600) Facsimile : 01480 52159 (+44 1480 52159) ********************************************************************** ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
