Kasino Concert 120

[Tennerondack]

Hey All,

This is my second project, My first a Fender M80 was a great success with the help I got here !

I have this Kasino Concert 120 I want to restore. It powers on, and produces sound.
The left channel, which has a remarkably good bass tone.It hisses loudly, and will give out with a loud hum which can be stopped by hitting the case, until it comes back.

The right channel seems to be fairly issue free, but seems more voiced for guitar, and I want to use it for bass.

From what I can determine, these use the same boards as the Kustom K-250 heads.

Anyway, before I dig in too deep, are there common problems with these boards I can try to fix first, or information I can share to get started ?

Any help greatly appreciated !

[galaxiex]

I have a Kasino PA head that had an intermittent reverb.

Thumping the cabinet would make the reverb work.

It was a simple bad solder joint. Simple, but not so easy to find.

I suggest the chopstick method.

Pull the chassis and power up and take a wood chopstick and wiggle, tap,
and probe wires and components with the chopstick until you find the loose/bad connection that causes the hum.

Be careful in there with the live circuit.

The hiss may or may not be related to the hum noise.

[Tennerondack]

Thanks Galaxie, I opened the case and will try your suggestion.
Not that I am knowledgeable, but I cant get over the two big honkin' filter caps compared to the ones in my other SS amps!

Here are some pics. Like all old USA stuff, this thing is built like a tank !

[Tennerondack]

I took Galaxie's advice and went exploring, here's, what I found :

I cured the temperamental loud blast by wiggling the connector from the input jack on left channel to board, corroded no doubt, making a loud blast just like an open cable plugging into the bass with the volume up.

I poked around and got no noise or pops from anything anywhere. The right channel is fine, if I turn everything down to 0 on left channel all noise goes away. It's not a hum, a white noise hiss that is totally affected by EQ adjustments.

I pulled the cable that connects the two pre-amp boards with both channels turned up and the noise disappeared, except for an open ground hum from the disconnected cable, which nearly disappeared when I took my hand off the cable and let it lay. Reconnect, noise returns.

Am I safe in saying it is probably narrowed down to the left pre-amp board ?

What next ? All components seem to be original and solid, nothing looks burned, one small wafer cap near the top left of the board looks a little green on top but ?

The power amp seems fine, it cranks up good and loud.

The right channel has far more gain than the left,  I have to crank up the volume to about 8 before losing headroom on the left, right goes to about 3 before losing headroom.

I used a jazz bass to test the amp, and it has passive pickups with not a lot of punch.

It sounds pretty good for an early solid state, I'd like to get it up to speed, I only paid $50 for it.

Thanks for help !

[galaxiex]

Great, you found something. 

Yes, probably the left preamp board.

Can you give us a good,clear, in focus picture of that board, both sides if possible.

Also a schematic would help.

The hiss may be a part dying, or just poor spec, noisy transistor(s).

[Tennerondack]

I will thanks.

[Tennerondack]

https://docs.google.com/file/d/0B1FxxpOmGO8vckY3MG93XzZIZW8/preview?pli=1&rm=demo

Schematic and board layout.

This is it, I am quite sure. PC5066  Kustom K250-4 series. The knobs on the Kasino are laid out volume clarity bass treble, but the board components are right on.

4

[galaxiex]

Possibly Q1,Q2 are the source of your hiss.
IDK, just a guess.

Can you read the numbers on the actual transistor, not the Kustom numbers from the schematic.

Those 739 op amps are obsolete. check here...

https://www.ssguitar.com/index.php?topic=1605.0

Also check voltages as per the schematic.

Report those please.

[Tennerondack]

Transistors f23567

I found this as well.


http://www.vintagekustom.com/FUDforum/index.php?t=tree&th=1612&goto=21289&rid=0&S=4a8612fdd754885caeadd8be0f19f85a

[Tennerondack]

Thank you galaxiex for your help so far on this project.

I think I have decided to abandon it in favor of something else a little more useable in my "studio".

I am thinking of parting the Kasino out to those who are dedicated  Kustom buffs who might benefit from the parts.

Didn't want to neglect to say thanks ! This forum is great and I have other relics I am tinkering with.