"noisy" standby switch

[greiswig]

Hi,

I have a Brownnote D'Lite, and the standby switch has recently gotten to be very noisy. Instead of just powering up silently, when it's flipped there is at least a loud POP, and often there is some static for a bit afterward, as though the contacts have gotten dirty or corroded from arcing.

Is this a common problem? Do I need a different type of switch? Is there a way to prevent this from happening to a new switch if I replace this one?

Thanks in advance,

[Funkalicousgroove]

that is not the switch, it is most likeley a filter cap.

[greiswig]

that is not the switch, it is most likeley a filter cap.

Nuts. Okay, sounds like I need to do a search on how to find bad filter caps. Thanks, Brandon.

Would this potentially also explain something odd I'm seeing in the bass? I've been trying to figure out whether it is my cabinet, speaker, or what, but on the clean channel with my Tele on the neck PU in particular, once the input volume reaches a certain point the bass just sounds like it is hitting a wall. It's as if there is a band-sensitive hard knee compressor on it.

Any particular brands/types of filter caps to avoid or seek out?

[greiswig]

Okay, I'm not sure I have a bad filter cap or not. This is in a D'Lite build.

I disconnected the 150k resistor at the end of the dropping string, and put a 50k resistor between the B+ line and the rest of the string. Very little voltage difference between the first point in the chain and the last.

I put things on a variac and brought up the voltage to a bit over line voltage, being careful to keep the voltage below 470 on the 500V caps. Still no real voltage drop.

Is this a decent test? Is "reforming" the caps this way a decent way to make reliable caps, or do I just need to replace these F&T's with something else?

Thanks.

[drz400]

Okay, I'm not sure I have a bad filter cap or not. This is in a D'Lite build.

I disconnected the 150k resistor at the end of the dropping string, and put a 50k resistor between the B+ line and the rest of the string. Very little voltage difference between the first point in the chain and the last.

I put things on a variac and brought up the voltage to a bit over line voltage, being careful to keep the voltage below 470 on the 500V caps. Still no real voltage drop.

Is this a decent test? Is "reforming" the caps this way a decent way to make reliable caps, or do I just need to replace these F&T's with something else?

Thanks.

a very common issue with a lot of Fender amps as well and other amps that use a standby in series. Sometimes you can use a .1uf~1uf/630V from standby switch to ground (not the filter cap side). What I prefer is to use a DPDT and disconnect the secondarys before the diodes ala Marshall style.

[greiswig]

a very common issue with a lot of Fender amps as well and other amps that use a standby in series. Sometimes you can use a .1uf~1uf/630V from standby switch to ground (not the filter cap side). What I prefer is to use a DPDT and disconnect the secondarys before the diodes ala Marshall style.

Thank you for this. Is it just switching AC instead of DC, or is it the somewhat lower voltage that makes it better to do it this way?

[greiswig]

Okay, I'm not sure I have a bad filter cap or not. This is in a D'Lite build.

I disconnected the 150k resistor at the end of the dropping string, and put a 50k resistor between the B+ line and the rest of the string. Very little voltage difference between the first point in the chain and the last.

I put things on a variac and brought up the voltage to a bit over line voltage, being careful to keep the voltage below 470 on the 500V caps. Still no real voltage drop.

Is this a decent test? Is "reforming" the caps this way a decent way to make reliable caps, or do I just need to replace these F&T's with something else?

Thanks.

I screwed up. I put the 50k resistor between the entrance to the dropping string and the hot lead for the OT.

Okay, now when I have 450V on the entrance to the network with the OT disconnected and the 50k resistor in series, the voltage drops to around 220V at the + lead of each of the caps. Is it normal to see that much of a voltage drop for a total of 130uF of cap?

[FUCHSAUDIO]

Put a .01 Ceramic disc or 600-V mylar between the two switch terminals (input to output), which would surpress any arc. It happens when voltages jump across the switch terminals before the terminals actually meet.

This should help with the pop.

[greiswig]

Thanks all for the replies and suggestions. I very much appreciate it!

I ordered new caps from Mouser today, just because I need to have a reliable amp and I'm not sure how good "reforming" the ones I have might be.

I'll also be trying the cap across the standby switch trick. Muchas gracias!

[drz400]

a very common issue with a lot of Fender amps as well and other amps that use a standby in series. Sometimes you can use a .1uf~1uf/630V from standby switch to ground (not the filter cap side). What I prefer is to use a DPDT and disconnect the secondarys before the diodes ala Marshall style.

Thank you for this. Is it just switching AC instead of DC, or is it the somewhat lower voltage that makes it better to do it this way?

yes Marshall style it is switching AC before the diodes on both legs, This is also pre filter caps of course so eventhing charges up slower