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K 250-4 amp [message #13235]

Tue, 23 March 2010 11:29

Van
Messages: 134
Registered: April 2004

Senior Member

Hi.
Been a while since I've posted here.

Just picked up a black Kustom K250-4 head and 4X12 bottom.
Head works great. Fuzz, tremelo, vibrato and reverb all work.
No foot switch, sadly enough.
The original speaker were gone and 4 12" Celestion Rocket 50 speakers are in their place.
Sounds pretty good though.
Have to do a little repair on the fabric bottom edges and a new pilot light is in order.
Anyone ever replace on of those?

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Re: K 250-4 amp [message #13236 is a reply to message #13235]

Tue, 23 March 2010 11:34

Van
Messages: 134
Registered: April 2004

Senior Member

Here's a pic.

http://i986.photobucket.com/albums/ae341/vandenmike/kustom250.jpg

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Re: K 250-4 amp [message #13237 is a reply to message #13235]

Tue, 23 March 2010 14:26

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

Very nice, Congrats!

Search the board here, we've discussed the bulb replacement issue a lot here before.

The blue plastic caps need to be removed from the switches and a tiny screw in bulb needs to be replaced. The bulb number is 335. A small piece of rubber tubing will help you to get the bulb in and out of the socket.

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Re: K 250-4 amp [message #13239 is a reply to message #13237]

Tue, 23 March 2010 16:22

Van
Messages: 134
Registered: April 2004

Senior Member

Thanks for the info.

I suppose finding the original foot switch and wah pedal will be futile.

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Re: K 250-4 amp [message #13241 is a reply to message #13235]

Tue, 23 March 2010 16:41

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

I've not seen a footswitch for one of those in a few years.

There was (is) a wah pedal on eBay recently for way too much money. Keep searching, you could get lucky!

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Re: K 250-4 amp [message #13242 is a reply to message #13241]

Tue, 23 March 2010 19:01

Van
Messages: 134
Registered: April 2004

Senior Member

It doesn't look like those switches light up.
No wires or bulbs that I can see in there.

http://i986.photobucket.com/albums/ae341/vandenmike/switch.jpg

Also, on the back, from left to right I see the plug in for the switch pedal, something marked "boost pedal", not sure what that is, the speaker out and then a jack with no label.
Any ideas?

http://i986.photobucket.com/albums/ae341/vandenmike/ampback.jpg

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Re: K 250-4 amp [message #13243 is a reply to message #13242]

Tue, 23 March 2010 19:33

Van
Messages: 134
Registered: April 2004

Senior Member

Ah!
Got the blue plastic off and found the 335 bulb.

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Re: K 250-4 amp [message #13244 is a reply to message #13242]

Tue, 23 March 2010 20:55

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

Senior Member

The boost footswitch jack is where the wah pedal plugs in. The boost jack is a stereo jack (tip, ring, sleeve) The unlabeled jack should be a module out that feeds the second cabinet that kustom offered with a power amp in the back of the cabinet. The boost pedal is basically a volume pedal with a return spring in pedal to bring back the pedal.
pleat

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Re: K 250-4 amp [message #13245 is a reply to message #13244]

Tue, 23 March 2010 21:01

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

Senior Member

You can make a footswitch for it. Here is the pin layout
Pin 1 black ground, Pin 2 Red + voltage for the lights in the footswitch, Pin 3 White Trem/vib. Pin 4 Green Rev. Pin 5 Blue Boost, Pin 6 orange Fuzz. Simple SPST switches can be used if your not going to get fancy and try and add the lights.
Pleat

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Re: K 250-4 amp [message #13246 is a reply to message #13245]

Tue, 23 March 2010 21:21

Van
Messages: 134
Registered: April 2004

Senior Member

Hey, thanks for the info!!

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Re: K 250-4 amp [message #13273 is a reply to message #13235]

Sat, 27 March 2010 02:02

Van
Messages: 134
Registered: April 2004

Senior Member

Laughing

Shocked

Aliens are attacking!!!!!!

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Re: K 250-4 amp [message #15596 is a reply to message #13245]

Sat, 07 May 2011 20:32

triceratops
Messages: 7
Registered: May 2011

Junior Member

Hey Pleat,

I have the 1972 Kasino version of the 250-4 amp and 4 x 12 cabinet, the "Little Joe" and I am trying to make a footswitch and boost pedal for it. The amp has a nice schematic glued to the chassis, but the drawings don't include the footswitch or pedal circuitry just the jacks for where they connect to the circuit.

Instead of the 6-pin connector for the footswitch described above for the Kustom 250-4, the connection for the footswitch on the Kasino is by two ring-tip-sleeve 1/4-inch phone plugs. One plug is for reverb and tremelo, the other is for Fuzz and Boost. The boost pedal also connects by a third ring-tip-sleeve plug.

My questions:
1. What is the value of the potentiometer for the boost pedal? Linear or audio taper?

2. What is the correct way to wire the potentiometer to the ring-tip-sleeve jack?

3. Because the Kasino has fewer wires going to the footswitch than the Kustom, I assume the Kasino footswitch has no lights?

4. All the controls on the panel seem to work without the footswitch plugged in except the boost control. Even with the footswitch connected, I can't notice any effect of the boost control. Does the boost pedal need to be connected for the boost control on the panel to work?

5. Is there an owners manual available for this amp anywhere?

Thanks for your help!

http://img823.imageshack.us/img823/7928/img3573u.jpg

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Re: K 250-4 amp [message #15597 is a reply to message #15596]

Sat, 07 May 2011 21:09

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

Senior Member

Very cool amp. They are really a good sounding and loud amp. The amp uses two 2 button footswitches, which are wired as a simple short to ground to turn off the effects. The boost wah pedal, I think uses a 10K lin taper pot and I don't remember how it's wired. It uses a stereo type 1/4" jack and the shield wire is grounded to the case of the pedal. The other two wire are wired to center lug and one of the outside legs of the pot. Hope maybe someone else might have a schematic of the wah pedal.
pleat

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Re: K 250-4 amp [message #15598 is a reply to message #15597]

Sun, 08 May 2011 03:41

triceratops
Messages: 7
Registered: May 2011

Junior Member

Pleat,

Thanks so much for your input--very helpful! I think the tone of the amp is excellent and as you said, it can get seriously loud. The fuzz tone has two knobs: level and effect and sounds great. I wonder if the Ross Fuzz stompbox is the same circuit?

Best regards,
triceratops

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Re: K 250-4 amp [message #15599 is a reply to message #15598]

Sun, 08 May 2011 10:06

zedsalt
Messages: 65
Registered: March 2008

Member

That would make sense. There are likely to be some slight differences due to things like power conditioning, but both the pedal and the onboard effect are worth emulating. There are certainly plenty of boxes claiming similarity to the Ross Compressor, and the Fuzz also tightens things up in the most delightful way, something the initiated like to call "fuzz without fizz".

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Re: K 250-4 amp [message #15602 is a reply to message #13235]

Mon, 09 May 2011 12:11

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

The boost pedal pot is wired across the tip and ring contacts of the 3 conductor cable. The cable must be shielded with the shield connected to ground, as it carries audio signal.

I thought that the value was 50K linear, but I may not be remembering correctly. There was a fellow here on the board that was making and selling clone pedals. Maybe if you search the old posts, you can find him and contact him for more details.

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Re: K 250-4 amp [message #15607 is a reply to message #15602]

Tue, 10 May 2011 03:05

Van
Messages: 134
Registered: April 2004

Senior Member

Here's a pic of the pot I wired. 10 ohm.

Pot and stereo cable bought at Radio Shack.

http://3.bp.blogspot.com/_-svp7Lh69uw/TUHaMeecmAI/AAAAAAAAABE/gq-_o3rv8i0/s1600/boost+wiring.jpg

[Updated on: Tue, 10 May 2011 03:08]

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Re: K 250-4 amp [message #15608 is a reply to message #15607]

Tue, 10 May 2011 11:15

triceratops
Messages: 7
Registered: May 2011

Junior Member

Thanks Van, Bill, and Zed!

Van:
The picture is very helpful!

1. Is the pot actually 10K ohm rather than 10 ohm?

2. Any chance you could shoot a picture of how you wired the plug? In digging through other posts it sounds like it was wired unconventionally with the ground wire to the tip of the plug?

chicagobill:

Same questions as above, and should the ground wire be soldered to the back of the pot also?

zedsalt:

I haven't played with a Ross compressor, but I am a big Byrds/McGuinn fan and I love that compressed 12-string sound. Using a Janglebox right now, which combines the circuitry of a Vox treble booster with a compressor like the one McGuinn built into his Rickenbacker.

[Updated on: Wed, 11 May 2011 07:52]

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Re: K 250-4 amp [message #15609 is a reply to message #13235]

Tue, 10 May 2011 11:36

Van
Messages: 134
Registered: April 2004

Senior Member

>>1. Is the pot actually 10K ohm rather than 10 ohm?<<

Yes! 10k ohm. Sorry. Pesky little "k"! Wink

Wink

>>2. Any chance you could shoot a picture of how you wired the plug? In digging through other posts it sounds like it was wired unconventionally with the ground wire to the tip of the plug?<<

I used a stereo molded plug and just cut one end off.
I'm sure the ground was probably bottom ring.
Anyway, couldn't find a wiring diagram, so I tried various ways until one worked.
I built two of these and wired them both the same way.

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Re: K 250-4 amp [message #15610 is a reply to message #15602]

Wed, 11 May 2011 07:54

triceratops
Messages: 7
Registered: May 2011

Junior Member

The 16 ohm speakers were gone when I got my Little Joe cabinet, so I loaded it with 4 x 12's that I had laying around that were 8 ohm speakers. I wired the cabinet in series/parallel combination that gives 8 ohms total (no way to get 4 ohms total with these speakers). I know the 250-4 power amp is set up for a 4 ohm load, is there any problem running these at 8 ohm, other than less power output? Does an 8 ohm load put any additional stress on the amp?

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Re: K 250-4 amp [message #15611 is a reply to message #15609]

Wed, 11 May 2011 07:57

triceratops
Messages: 7
Registered: May 2011

Junior Member

Van wrote on Tue, 10 May 2011 11:36

>>I'm sure the ground was probably bottom ring.
Anyway, couldn't find a wiring diagram, so I tried various ways until one worked.

Thanks Van! I'll try wiring the plug conventionally first.

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Re: K 250-4 amp [message #15612 is a reply to message #15610]

Wed, 11 May 2011 11:27

Van
Messages: 134
Registered: April 2004

Senior Member

8 ohms is fine. Less stress on the amp, but less power output.

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Re: K 250-4 amp [message #15613 is a reply to message #13235]

Wed, 11 May 2011 11:55

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

As for wiring the pedal, the tip connection should connect to the wiper and the ring should connect to the clockwise end of the pot. Internally the tip is connected to the FX board pin #5 which is ground.

The cable shield can float and connect to the case of the pot/pedal or can connect to the counter-clockwise end of the pot. I would try it both ways to see if there is any difference in the performance of the wah effect and to see if it creates a ground loop hum.

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Re: K 250-4 amp [message #15614 is a reply to message #15613]

Wed, 11 May 2011 18:11

triceratops
Messages: 7
Registered: May 2011

Junior Member

chicagobill--

I am assuming that the clockwise and counter-clockwise references are looking at the pot from the can side rather than the shaft side, correct?

chicagobill, van, pleat, zedsalt, and everyone else--

Thanks so much for all the help guys! Much appreciated by this newbie--this is a great forum!

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Re: K 250-4 amp [message #15618 is a reply to message #13235]

Thu, 12 May 2011 12:24

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

It depends on the pedal. The normal wah effect is treble boost when the pedal is toe down and high cut when toe up. The resistance from the tip to ring should be lowest when the pedal is toe down, so whatever side that is on the pot in your particular pedal.

In general terms, when the CW and CCW designations are used in reference to a pot's shaft rotation, it is based on shaft facing you.

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Re: K 250-4 amp [message #27450 is a reply to message #13235]

Sat, 20 July 2019 13:10

johnnysynth
Messages: 46
Registered: June 2018

Member

Do you still have this amp for sale?

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