Dual 1019 pops LOUD on power off

[beatcomber]

I am completely at a loss.

I've just burnished the mute switch sleds with some superfine sandpaper folded in half and shot some contact cleaner on there... no change. Every time the mute circuit switches on or off, I get a thump through the speakers. It's especially loud when the motor powers off at the end of the side after the arm sets down.

Now what do I do... anyone? @NoTransistors ?

 

[Nashou66]

How about the two solder lugs that are connected to the Switch? Parts 155 ?
Are they making a good connection and check where the wires go from that switch and their connection points, Are those making a good clean contact? Recheck all your grounds as well.



Nashou

 

[beatcomber]

How about the two solder lugs that are connected to the Switch? Parts 155 ?
Are they making a good connection and check where the wires go from that switch and their connection points, Are those making a good clean contact? Recheck all your grounds as well.

View attachment 986495

Nashou

Thank you! I'll check that.

 

[Omegaman]

Do you have a florescent light near by causing it?

 

[beatcomber]

Do you have a florescent light near by causing it?

Nope. And it did it in two rooms, in different systems.

I'm suspecting the switch is at fault.

 

[beatcomber]

In case anyone reading this thread is struggling with the same issue, the former Assistant Service Manager at Noresco -N.Q.I.-Dual of Canada,
Klaus Adlhoch, gave me a very detailed response on Vinyl Engine, which I have pasted below. I can't say that I fully understand what needs to be done - this is a bit over my head - but it appears that there is some stray EMF causing the problem.


Hi,
Cleaning the muting switch contacts is a good idea but this does not influence back EMF noise/pop, generated by the power switch. Let's separate the two sources of noise.
The power switch for the 1019 and units of that era used this switch slide:



As can be seen in the picture, the "fingers" need to be re set as outlined in order to give proper pressure to the main switch lever (item 128).
Keeping the contacts clean also reduces the back-EMF spark. As for the cap, it is a good idea to uses a combination RC unit that has a 100 ohm resistor in series with the 10 nF capacitor. This should also be an X2 rated safety item. The combined resistor/capacitor will reduce the pitting on the switch points. The cleaner to points, the less noise ensues during switching.
It is also possible to reduce the noise by using a different power socket/outlet for the changer as opposed to the amp. The pop noise (a spike created in the power line) is further distanced from the amp by this method. Keep in mind, the preamp is very sensitive, so any noise in the power line can work its way into the preamp stage.
Now the muting switch. Cleaning that is a very good idea which also reduces pops in the audio line. This muting switch has a priority function, which is not sound related. The muting switch fingers have, as a first job, to place the cam in a null or home position. In order to accomplish that, the fingers that touch the cam must also be re-stressed. The secondary mute finger are then adjusted to open and close (short) the sound path, as the cam is either rotating (sound mute) or at the home position (sound open).
It is also important to clean the power contacting tips on this rail as well as the contacting tips in the power box:



Unfortunately, there will probably never be a total silent switching, because of the amount of power that is involved and the back EMF it creates. Back EMF can be seen in light, power switch or brushes in a motor. It is simply the resistance to change and follows the laws of inertia. These are simple ways to reduce this unwanted by-product.
Regards,
k

 

[jlb2]

For me it was a bad capacitor in the power switch [...] I used a 10000pf 1kv capacitor on my 1229 and fixed it right up.

I just replaced the spark suppression cap with a .01MFD 630v

VERY IMPORTANT SAFETY REMINDER here: this cap is on mains and is required by law to be a an X-type capacitor and nothing else, not to bother you but because any other type can (and does) catch fire, no matter the voltage spec. REMOVE IT NOW and don't change it for anything else than a X-type capacitor, which is designed and tested to be safe. It is a VERY bad move to use just any cap with the right value and voltage there - in fact, it is better to have no capacitor at all there, than to have the wrong type of capacitor.

This should also be an X2 rated safety item.

No, not should, MUST!

I wonder how many times we will need to say this on this forum For a better understanding of the problem, just google "X-class capacitor".

 

[beatcomber]

VERY IMPORTANT SAFETY REMINDER here: this cap is on mains and is required by law to be a an X-type capacitor and nothing else, not to bother you but because any other type can (and does) catch fire, no matter the voltage spec. REMOVE IT NOW and don't change it for anything else than a X-type capacitor, which is designed and tested to be safe. It is a VERY bad move to use just any cap with the right value and voltage there - in fact, it is much better to have no capacitor at all there, than to have the wrong type of capacitor.



No, not should, MUST!

I wonder how many times we will need to say this on this forum For a better understanding of the problem, just google "X-class capacitor".

Thank you! I was not previously aware of what the distinction referred to! I'll head back to the electronics parts store and pick up the correct item!

 

[beatcomber]

After two months of head-scratching and poking around, I've concluded what the source of the problem is: the metal contact "fingers" on the start/stop switch and/or the blades on the power plate were pitted. I burnished the surfaces with 200 grit sandpaper followed by contact cleaner on a Q-Tip, and the popping noise has been reduced to the point where it's no longer a big deal.

I'd like to be able to get it to the point where it's totally eliminated, but I'm not sure that's achievable.

 

[dmadmc]

After two months of head-scratching and poking around, I've concluded what the source of the problem is: the metal contact "fingers" on the start/stop switch and/or the blades on the power plate were pitted. I burnished the surfaces with 200 grit sandpaper followed by contact cleaner on a Q-Tip, and the popping noise has been reduced to the point where it's no longer a big deal.


I'd like to be able to get it to the point where it's totally eliminated, but I'm not sure that's achievable.

Thank you for your detailed and thorough expanation about this thump noise on dual 1019, which I have experienced before.
I gave up and put aside the 1019 table due to this annoying noise.

I am going to try to do the same steps as you suggested here.

 

[stereofisher]

Spark capacitor goes bad on these. Seen on Duals and several BSR 810s Replaced and and all quiet!

Eric