Kel84 input oddity

[bob orbell]

Dave, what do you get when you switch to mute ? all five inputs should be short circuit, but not tape out. Do as snowman al suggests, but I still think it is a the switch indexing, I will dismantle mine and see if I can replicate your findings. Bob

[John Caswell]

Hi Dave,
If you have any IPA (Isopropyl Alcohol) you could scrub the relay PCB using an old tooth brush to remove any solder flux, makes it easier to see the track, joints etc, it will not affect anything on the PCB.

John

[Calorgas]

Thanks Bob, I'll also check the inputs when mute is selected as well.

Originally Posted by John Caswell

Hi Dave,
If you have any IPA (Isopropyl Alcohol) you could scrub the relay PCB using an old tooth brush to remove any solder flux, makes it easier to see the track, joints etc, it will not affect anything on the PCB.

John

No I don't have any IPA John. I have a can of switch cleaner but I presume that's not appropriate to use.

[John Caswell]

Hi Dave,
No do not use anything else except IPA, and definitely WD40.
The only way for i/p 3&4 to be open simultaneously is if the control wires for both are connected together, either a wiring fault or a solder splat on the PCB on both the control lines.

John

[Calorgas]

I think we have a winner!

I did the test with the selector on mute and that was all as expected, then popped the lid and had a close look at that board as snowman_al suggested and spotted a suspicious blobby fella spanning the tracks:



The splat popped off with very little persuasion. So base excitedly screwed back on, plugged leads back in and did a test on the problem inputs 3 (tuner) & 4 (aux) and they're all clear and separate, hooray!

So it very much looks like it's problem solved. Thanks so much to all of you for the help and offers of assistance, hugely appreciated

[snowman_al]

Yes - hooray!
Well done and now enjoy,
Alan

[Calorgas]

Yep, I can now continue to enjoy the amp without that niggling input annoyance.

Next thing I'm considering is attaching some wooden side cheeks as there are a few minor marks that I'd like to hide, but I think I can manage that on my own

[John Caswell]

Hi Dave,
Nicely done.

John

[Mark]

Calorgas,

My KEL84 has vents in the sides. If yours is the same then wooden side cheeks will block them, which will reduce the ventilation. I don't know if that would be enough to cause a problem. Capacitor life is very temperature dependent.

Mark

[Calorgas]

Originally Posted by Mark

Calorgas,

My KEL84 has vents in the sides. If yours is the same then wooden side cheeks will block them, which will reduce the ventilation. I don't know if that would be enough to cause a problem. Capacitor life is very temperature dependent.

Mark

Thanks for that Mark. Yes I'm fully intending to cut openings into the side panels corresponding to the vents so that ventilation will be unaffected.

Cheers, Dave