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K-150-8 [message #23231]

Fri, 03 July 2015 01:56

ReverbJoe
Messages: 37
Registered: October 2012

Member

Hey guys, I was hoping you could help me find a schematic to a K-150-8 combo. I want to rewire the power switch but don't really know where to begin. Thanks

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Re: K-150-8 [message #23235 is a reply to message #23231]

Fri, 03 July 2015 06:23

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

What do you mean by " rewire the power switch" Do you mean install a grounded 3 wire power cord?

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Re: K-150-8 [message #23244 is a reply to message #23231]

Fri, 03 July 2015 10:59

ReverbJoe
Messages: 37
Registered: October 2012

Member

Well actually, my amp hat it's power switch removed (the amp turns on when you plug it in) and I had previously posted about it, but I didn't want to bring back a three year old thread. So I would like to see how the switch was originally installed and what kind of switch I might need.

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Re: K-150-8 [message #23246 is a reply to message #23244]

Fri, 03 July 2015 13:29

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

This is a SC combo, right? If you go to the technical section the overall schematic has the switch wiring shown.

The original switch was a double pole, double throw- three position - center off toggle switch. It should be rated for at least 4 amps and 125 vac. I commonly see 250 volt, 10 amp versions of this switch at places like Fry's and Radio Shack.

If you change the power cord to a three wire grounded one, you can change the switch to a simple on/off toggle, as you will no longer need the line reversing/polarity function.

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Re: K-150-8 [message #23251 is a reply to message #23231]

Fri, 03 July 2015 20:10

ReverbJoe
Messages: 37
Registered: October 2012

Member

Thanks Bill, I'll give the schematic a look.

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Re: K-150-8 [message #23255 is a reply to message #23231]

Sat, 04 July 2015 06:04

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

I have even seen some local non- big time hardware stores carry such switches!

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Re: K-150-8 [message #23262 is a reply to message #23231]

Sat, 04 July 2015 21:32

ReverbJoe
Messages: 37
Registered: October 2012

Member

Here's the situation. I think those black wires wrapped together are what connect to the switch, but I'm not sure. The switch you see there is the one I bought, Radio Shack guy told me it would work for the amp. Any advice on installing it? Anybody know which cables go where? I also see some white wires wrapped together in the bottom.

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Re: K-150-8 [message #23263 is a reply to message #23231]

Sat, 04 July 2015 23:56

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Okay, first off, do not use the amp until you clean up the wires. Having bare wires that are connected to the ac outlet are stupidly dangerous.

The wires should be connected as follows. The white from the ac cord should connect directly to the white that comes from the power transformer. Either use a wire nut or solder and heat shrink the connection.

The black wire from the power cord should go to the fuse holder and the second side of the fuse holder should connect to the thermal switch that is mounted to the heat sink. The second side wire from the thermal switch should go to the power switch. The other side of the power switch should connect to the black wire that comes from the power transformer.

There is a blue wire that looks like it is connected to the black wires and then goes to the ground cap. If you have installed a three wire power cord, you should remove the ground cap. If you still have the original two wire, you can either remove the cap or you can connect it to the white wires instead of the black ones.

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Re: K-150-8 [message #23264 is a reply to message #23231]

Sun, 05 July 2015 02:51

ReverbJoe
Messages: 37
Registered: October 2012

Member

Thanks Bill, your instructions helped a lot. I was able to install the switch and clean up the wires. The only thing left is the ground cap, I'm not really sure what it is or what it looks like, so I didn't remove it.

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Re: K-150-8 [message #23265 is a reply to message #23231]

Sun, 05 July 2015 07:18

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

It's the cap on the right in that shot the has one end bolted down.

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Re: K-150-8 [message #23267 is a reply to message #23231]

Sun, 05 July 2015 13:52

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Just leave the cap disconnected. It's safer that way.

Is this the original ac cord or a 3 wire one?

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Re: K-150-8 [message #23269 is a reply to message #23231]

Sun, 05 July 2015 14:48

ReverbJoe
Messages: 37
Registered: October 2012

Member

It's the original cord.

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Re: K-150-8 [message #23333 is a reply to message #23269]

Thu, 09 July 2015 11:45

ReverbJoe
Messages: 37
Registered: October 2012

Member

Ok, so I installed a new Jensen MOD 10-50, 16 ohm, where the smaller speaker was, and I left the original Kustom Speaker. I made sure to connect the speaker + to +, - to -. Turned it on and it is working way better than before. Before, the volume would give out or it would fade and then come back. Now, it is working %100. But I am having problems with the quality of the sound. When I turn it up, it distorts, but almost in a broken speaker way, when I pluck a string, it is really high and sounds like the speaker is shot. This only happens when I crank up the three knobs, volume, treble, and bass. Is it normal for it to distort that way? It doesn't sound very loud at max, not as loud as I remember it being. The next problem is the reverb tank, it has a loud hum when turned on, and it gets louder as I turn the knob. I connected the reverb tank, but I might have plugged the two cables wrong. I will try swapping the cables later on today.

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Re: K-150-8 [message #23337 is a reply to message #23231]

Thu, 09 July 2015 12:55

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

How high are you turning up the amp to get this distortion? Does it happen with both channels? Does the chassis get warm or hot around the output transistors?

As for the reverb, is the tank original or a replacement? How is it mounted and how is it oriented in the amp? The end of the tank with the output connector should be mounted as far away from the power transformer as possible.

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Re: K-150-8 [message #23338 is a reply to message #23231]

Thu, 09 July 2015 12:56

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Are both speakers breaking up the same, or just the original one?

Yes, try swapping the reverb cables first.

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Re: K-150-8 [message #23339 is a reply to message #23338]

Thu, 09 July 2015 13:18

ReverbJoe
Messages: 37
Registered: October 2012

Member

chicagobill wrote on Thu, 09 July 2015 12:55

How high are you turning up the amp to get this distortion? Does it happen with both channels? Does the chassis get warm or hot around the output transistors?

As for the reverb, is the tank original or a replacement? How is it mounted and how is it oriented in the amp? The end of the tank with the output connector should be mounted as far away from the power transformer as possible.

I got the distortion when I cranked up the volume, treble, and bass knob all the way. I haven't checked if the chassis gets warm yet. The reverb thank is original, but I'm not sure if I mounted it the right way, I removed it a while ago and forgot how it went. I will check as soon as possible.

stevem wrote on Thu, 09 July 2015 12:56

Are both speakers breaking up the same, or just the original one?

Yes, try swapping the reverb cables first.

It appears that the right side (the new speaker) breaks up a little louder than the original. I have a recording, but I don't know how to post.

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Re: K-150-8 [message #23343 is a reply to message #23339]

Thu, 09 July 2015 15:08

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

One thing I'd check if your original speaker is one with a silver metal dust cap is to make sure it is still glued in solid. A loose dust cap with give a nasty sound when the amp is cranked. I have a K100C-8 with the 4x10 speakers. When I bought it, all four dust caps were missing. The amp didn't sound that great so I removed all the speakers and found the dust caps laying backwards between the grill cloth and baffle board. I had my re cone guy check the speakers and he glued new dust caps. Amp sound wonderful at all volumes after a cheap fix.
pleat

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Re: K-150-8 [message #23345 is a reply to message #23231]

Thu, 09 July 2015 15:32

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Turning it up full blast would probably be distorted, but it would also be really loud. Have you tried plugging the head into a different speaker cabinet?

It may be that the two speakers are not phased correctly. Pull the speaker cable out of the head. Take a 9 volt battery and touch the plug across the two terminals of the battery. When you do this, you should hear a loud thump from the speakers. You should also see the cones of both speakers move in the same direction, either in or out. If both cones don't move the same way, you'll need to reverse the wires on one of the speakers.

Don't hold the plug on the battery too long or you'll kill the battery and you could damage the speakers.

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Re: K-150-8 [message #23349 is a reply to message #23231]

Thu, 09 July 2015 18:27

ReverbJoe
Messages: 37
Registered: October 2012

Member

pleat wrote on Thu, 09 July 2015 15:08

One thing I'd check if your original speaker is one with a silver metal dust cap is to make sure it is still glued in solid. A loose dust cap with give a nasty sound when the amp is cranked.

It does have the silver dust cap, so I will check to see if it's loose. I switch the cables on the reverb tank and it fixed the humming. One thing I noticed is that channel 1 sounds a lot clearer than channel 2. Its almost as if the original speaker is the one that is distorting. And the other thing is when I turn on the amp, there's this 2 second delayed thump, that is really loud. Not sure if that is normal.

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Re: K-150-8 [message #23354 is a reply to message #23231]

Fri, 10 July 2015 06:12

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

That delayed thump is a pretty good sign that the amp needs two new main power supply rail filters.

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