NSM ES II AMP makes popping sound at end of record

ivanr · by **ivanr** » Sat May 12, 2007 2:00 am

Does anybody know how to fix the popping sound you hear at the end of the record when the mute is activated? It is very anoying. All the NSM vinyl jukebox amps I have seen have this problem. I don't know if it is something that they develop as they get old or they always had this problem. Any suggestions greatly appreciated!

Ivan

Record-changer · by **Record-changer** » Wed May 16, 2007 6:30 am

It could be a leaky input capacitor.

ivanr · by **ivanr** » Thu May 17, 2007 2:52 pm

I noticed that the popping sound can be heard even if the preamp card is removed but made worst when you put it in. I will try and replace the capacitors and see how that goes.

Record-changer · by **Record-changer** » Mon May 21, 2007 8:16 am

If that is the case, somehow the tripping of the record change cycle is getting into the amplifier power supply. Check the power supply electrolytic capacitors. Also check for a bad ground to the chassis somewhere.

ivanr · by **ivanr** » Wed May 23, 2007 3:19 am

I changed all the caps and checked all the grounds with no luck. Is there a way to add a filter capacitor to reduce or eliminate the popping sound? Where would be the best place to do this?

Record-changer · by **Record-changer** » Thu May 24, 2007 6:20 am

Try a .01 uF 600 V capacitor across the trip contacts. But make sure you connect it where it can't impede the pickup arm. It can't be connected directly to the trip finger.

I just realized that dirty pickup arm bearings could cause arcing, which would make the noise.

ivanr · by **ivanr** » Fri May 25, 2007 8:24 pm

That did not work so I am starting to think that NSM amps are just not very good design and perhaps it always made this popping sound. However, this trick did work on my Seeburg LU. Anything else you can think of let me know. Thank you for your help.

Record-changer · by **Record-changer** » Tue May 29, 2007 8:21 am

More possibilities:

- The unit has a magnetic cartridge and the trip solenoid's magnetic field is being picked up.

- Damaged pickup wiring.

- The pickup ground is high resistance, and is being completed better through the trip finger.

- Somehow the arm control motor circuit is causing noise pickup (try another capacitor across the contacts of the arm control motor (assuming it is relay-controlled).

Andymann · by **Andymann** » Tue Jun 12, 2007 2:50 pm

Hi Try cleaning the contacts on the mute relay as over the years carbon can build up on the contacts
Andy