Vintage Fender Twin Reverb question

[bsco]

Got this unit here and it was all original...Filter caps even had pin holes in the sides and blisters....everything was all original....got it all working except for the two bright switches.....they were very loose and was causing popping sounds when activated.......so I replaced them.....I still have the same popping sounds and i checked for DC on the switches as well and there is none there.....any suggestions or is this issue normal for these amps........
Cheers
P.S. This was made in the early seventies....

[pdf64]

Try 10M resistors across the switches, or from the switch cap leg to 0V. Anything to stop them charging up.
I think it’s fairly normal for them to do that, a quirk rather than a fault.

[Mick Bailey]

+1. Had the same issue the day before yesterday and a 10M resistor fixed it.

[Chuck H]

This qualifies as a "mod" rather than a solution, but I don't like the sound of the Fender preamp without a little bright cap bypass. So I use two caps in series. The standard value for the model and then another that makes the series capacitance close to 50p. So the 50p compound value is in circuit with the switch off. Then the switch closes the added series cap to allow the stock "bright" value activation. I like the tone better and the switch doesn't pop (at least not on my amps).

[bsco]

OK. Picked up some 10M resistors and it did the trick.....I tried it across the switch and also from the cap side of the switch to ground.....same result so I soldered the resistors across the switches....all buttoned up now and ready to go back to the owner.........Thanks guys for that piece of info...got to go and get ready now for some more snow....
Cheers

[Enzo]

The value wasn't critical, it just needs to be high enough that the cap has little effect through it. So if you had no 10M, 4.7M would do, or for that matter so would common 1 meg in all likelihood.

[Chuck H]

Well bsco said that be tried them both 'in series with the cap' and 'across the switch'. And then settled with 'across the switch'. In this case a 1M resistor would probably mess with the volume pot taper a little. But in series a 1M would be fine.

[bsco]

Well bsco said that be tried them both 'in series with the cap' and 'across the switch'. And then settled with 'across the switch'. In this case a 1M resistor would probably mess with the volume pot taper a little. But in series a 1M would be fine.

I chose that one as it was easier to do and didn't require the use of the monster Iron to solder to the chassis....There wasn't any difference between the two as it didn't eliminate the noise completely but it definately made a huge improvement...on a scale of 10 I would give it a 9.5...Thanks for the tip....