Hartke 3500 Cracking Problem

[BassNGuns]

Hi,
My Hartke is having a problem when where every other note that I play is met with a distorted
clip especially if I play a little hard. Some times a whole note will distort and some times it's ok.
I tried this with 2 other amps (same power) and had absolutely no problem.
I was playing through the same SWR Goliath 4x10 cabinet with the same heavy duty patch cord.
I'm sure it's a preamp issue, but don't really know where to start on an intermittent problem like this.
Any help or ideas would be appreciated. Thanks.

[Enzo]

Doesn;t this amp have either separate tube and solid state preamp volume controls? Or maybe a tube/SS balance control? Turn it all the way one way, then all the way the other, so you play all tube side for a while, then all solid state side for a while. Is the problem only on one? Or on both?

If it is in a rack, pull it out and set it on something sturdy. Turn it on. Ball up your fist and whack the top of it hard. Make any noises? It shouldn;t. If it does, some connection is loose or a component leg is broken or a solder connection is broken.

Apply a signal, doesn't have to be very loud. Have someone play, or just connect a CD player or MP3 player or something with music. Again, whack teh amp hard. Does that either cause or make stop this distortion?

Pop the lid off. Power off, pull the tube from the socket and push it back in a couple times. This will refresh the contact betwen tube and socket. Power up and try again. ANy better? If so, then some socket maintenance is called for.

Power off. All around the tube socket are some little film caps. Seems to me they stand up a little taller than other caps on the board. Flex each one a little to see if any are loose.

Power up, and push on each cap while music plays through the amp. Do any of them make a difference when poked?

WARNING: this is high voltage around the tube, so use something insulated like a wooden chopstick for doing this poking.

And this probably should be checked before the tube related stuff, but better late than never. Look at the main preamp board. ALong the rear endge of it is a row of pins with connectors plugged onto them from the power transformer. Use your insulated stick and push on those connectors while music plays. I suppose you can grasp the connectors with fingers if careful, the conductors are not exposed. If wiggling any of them causes the problem, then they most likely need to be resoldered underneath.

[BassNGuns]

Thank you Enzo.

[J M Fahey]

Cracking amps 101