Clandestine (Chase Tone Secret) noise increases when putting on back lid

[zgrav]

here is a remark from another forum about leaking capacitors that might explain why putting on the back would raise the noise level by trapping the noise that is being picked up in the circuit: Maybe one or more of your caps is picking up noise from your charge pump. Not sure why raising the incoming voltage from 9v to 12v would change anything, but it suggests the charge pump is the noise source.

FWIW, I have seen/heard a hi-fi amplifier with the same symptom. It was the filter capacitors but not what you're thinking. The values measured alright but they had very high ESR and were letting through the switching noise from the high voltage rectifier. The fix was to replace the filter capacitors.

 

[harmaes]

Almost like putting the back on is trapping noise inside the enclosure, which doesn't make any sense.

Never seen this before with any builds.

 

[harmaes]

here is a remark from another forum about leaking capacitors that might explain why putting on the back would raise the noise level by trapping the noise that is being picked up in the circuit: Maybe one or more of your caps is picking up noise from your charge pump. Not sure why raising the incoming voltage from 9v to 12v would change anything, but it suggests the charge pump is the noise source.

FWIW, I have seen/heard a hi-fi amplifier with the same symptom. It was the filter capacitors but not what you're thinking. The values measured alright but they had very high ESR and were letting through the switching noise from the high voltage rectifier. The fix was to replace the filter capacitors.

I also tried changing the charge pump from 1044 to 7660s and it didn’t change the behavior.
I will order some higher than 25v elco caps to see if that changes something. It seems not related to the transistor as I swapped these with no change to the behavior.

Another thing I was thinking is that most people put the orange caps in there using the extended pads. I used the inner pads, not sure if the unconnected/open external pads could be influencing something or pick something up?

 

[music6000]

I have to agree with zgrav with my suspicion still coming back to the 25v electro's, the higher voltage is somehow masking the voltage leaking from them.
I would be looking at 35v minimum, I always use 50v with the 10uf or lower as they are the same size as a 16v Electro anyway.

 

[zgrav]

At this point I would swap out all of the electrolytics and touch up the solder on the other caps to see if it brings any improvement.

 

[harmaes]

I have 50v 10uf but not higher voltage 220uf in my stock.
Can I use 330uf or 120uf?

The Aion Ares uses 100uf before the charge pump and no 220uf at the back. Only 2x 1n5827 with 2x 10uf

 

[Fama]

I have to agree with zgrav with my suspicion still coming back to the 25v electro's, the higher voltage is somehow masking the voltage leaking from them.
I would be looking at 35v minimum, I always use 50v with the 10uf or lower as they are the same size as a 16v Electro anyway.

I don't quite know how the charge pumps work, but could it be that the noise increases to such high frequencies that you can't hear it anymore, when running at 12V?

Another thing I was thinking is that most people put the orange caps in there using the extended pads. I used the inner pads, not sure if the unconnected/open external pads could be influencing something or pick something up?

I'm pretty sure I used the inner pads, at least I used just normal film box caps (and one ceramic).

I have 50v 10uf but not higher voltage 220uf in my stock.
Can I use 330uf or 120uf?

I think both 220uF caps are in the power filtering section, so bigger ones should work fine. Probably 120uF too, but AFAIK larger ones are technically better (or negligible, but at least not worse), and since you're looking to get rid of noise, might want to be safe and go with bigger ones.

 

[harmaes]

I don't quite know how the charge pumps work, but could it be that the noise increases to such high frequencies that you can't hear it anymore, when running at 12V?


I'm pretty sure I used the inner pads, at least I used just normal film box caps (and one ceramic).

I think both 220uF caps are in the power filtering section, so bigger ones should work fine. Probably 120uF too, but AFAIK larger ones are technically better (or negligible, but at least not worse), and since you're looking to get rid of noise, might want to be safe and go with bigger ones.

The first 220uf is before the charge pump so can be 16v or 25v

 

[zgrav]

change out the 10u caps first and see if you get any improvement in the noise. if needed, you can then sub in the 330 for the 220 to see if that helps. also don't forget to touch up the connections on the film caps. you can use your meter to make sure the inner tabs are connected to the outer tabs for those if you want to confirm they are properly in the circuit.

 

[harmaes]

Replaced all 25v+ rated elco caps with 35v and 50v and reflowed the film caps. The noise problem is still there on 9v but now I can safely use it on 12v and will keep it like that.

 

[Robert]

If you're still feeling experimental try removing the 1N4748A zener diode and power it at 9V.

 

[szukalski]

It may be tricky to do with the back on, but audio probe?

 

[music6000]

If you're still feeling experimental try removing the 1N4748A zener diode and power it at 9V.

If he was to try the LT1054, would he have to cut the trace between Pins 1 & 8?

 

[Robert]

If he was to try the LT1054, would he have to cut the trace between Pins 1 & 8?

Nope, the LT1054 will work fine with pins 1 & 8 connected.

 

[harmaes]

It works on 12v so I'm done investigating. Already took too much time.