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New Vintage Kustom owner [message #14786]

Wed, 01 December 2010 11:06

dscottch
Messages: 3
Registered: December 2010

Junior Member

I recently acquired a Kustom 250-2 amp and two 2G+1H cabs. The cabs have had the horns removed and a 12 inch speaker screwed into the empty slot. I'm wondering if there is a horn replacement available or suitable substitute to return them to their original configuration. I'm also having issues with the amp; loud humming, no sound. I can sometimes play with the on/off switch and the humming stops and plays beautiful. So Im inclined to replace the switch. I plan to replace the power cord with a ground power cord. If I do, can I use the polarity switch as my new power switch? Thanks in advance guys!

Scott

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Re: New Vintage Kustom owner [message #14787 is a reply to message #14786]

Wed, 01 December 2010 11:30

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Welcome to the place!

I can't think of any failure mode that would include a bad power switch causing no signal and loud hum.

It may be that there is something loose inside the head that is being jostled when you work the power switch. That series of amps has had a lot of problems with the pc board interconnects. If you open up the amp, you will probably find that all of the pc boards are connected by a series of twisted wires. At the end of these wires are small push on connectors referred to as Molex connectors. These are known to become dirty and oxidized and loose from the ravages of time and travel.

I would suggest that you clean all of the Molex connectors with an electrical contact spray cleaner, and re-seat them all so that you know that they are making good contact. The best contact cleaner out there is a product called DeOxit, made by Caig.

And in answer to your original question, yes the polarity switch can be used for the power switch, as they are the same part. If you do need to swap the switches, be very careful when unsoldering the wires, as the switch body is prone to cracking.

Again welcome.

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Re: New Vintage Kustom owner [message #14788 is a reply to message #14786]

Wed, 01 December 2010 12:13

rodak
Messages: 511
Registered: October 2001
Location: Georgia

Senior Member

Was that the White ones on Atlanta Craigslist? Great deal on thos, congrats!

www.combo-organ.com

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Re: New Vintage Kustom owner [message #14789 is a reply to message #14786]

Wed, 01 December 2010 12:19

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

It will be very hard to find a orignal 15" siren to fill those holes back up.
I would say your best bet will be to go to the parts express site and get two 270-302 horns.

These are 12" round models, then the only other thing you need will be two 1" exit 1 3/8" screw on divers rated for 50 to 75 watts, and two 4mfd 100 50 volt caps for the crossover if the originals are gone.
If it where me I wo
uld go for I bit more bucks and get a real crossover network which can also be had from parts express.

[Updated on: Wed, 01 December 2010 12:20]

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Re: New Vintage Kustom owner [message #14792 is a reply to message #14789]

Wed, 01 December 2010 17:32

pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi

Senior Member

Welcome to the site. From the description, your rig has two cabinets. 2x15 and a horn from the factory, and the horns are gone. One cabinet should have a power amp in the back. Is it still there? If it still has the built in power amp, you can send a signal from mixer to see if that amp is still working. The K250 amp is designed to drive one of the two cabs, and you may have some issues if the k250 amp has been ran with both cabs without the power amp in the second cabinet. Those cabs are really brittle sounding with the horns, and you may want to make some new baffle boards, and make it a 3x12 cab, or a 2x15 and 2x10 cab for some versitility. The power amp sections of both the K250 and the built in amp in the cab want a 4 ohm total load.
There was a guy in MS who was selling the horns, drivers, and speakers a few months ago on ebay. Maybe do a search on ebay for completed items and it might turn up the seller. I know they didn't sell, I was trying to buy the horns for a friend. If not, I look on CL and ebay for some altec horn bells.
Let us know how you make out.
pleat

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Re: New Vintage Kustom owner [message #14800 is a reply to message #14786]

Thu, 02 December 2010 07:25

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

Pleat, I may have been wrong in regards to what I posted about replacement horns.
Since he posted that the horns where replaced with 12" drivers I assumed that they where on adapter baffles and the cabs where the early models with the 15" round horns, not the latter rectangular Altec type sectoral horns.

If these are the latter cab`s then the psrt number I posted for the horns will not work, but their are plenty of rectangular after market types that will.

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Re: New Vintage Kustom owner [message #14804 is a reply to message #14786]

Thu, 02 December 2010 11:29

dscottch
Messages: 3
Registered: December 2010

Junior Member

Chicagobill, you called it. The issue is with the Molex connector (the one under the power switch). Even after cleaning it with contact spray, it doesn't make a good connection. It seems the tie down used (screwed through the bottom) has been pulling on the connector for awhile. I currently am using a wrap tie connected to the reverb rca jack to keep it connected to continue testing. Everything seems to be great. Not sure how I am going to ultimately correct this.

rodak - yes, that's the ones. I've been eyeballing these vintage Kustoms for awhile and finally was able to acquire one on a budget.

stevem - yes it is the rectangular horns that are missing, I am new to these and didn't know enough to provide enough info. Sorry for the confusion, but thank you for the help.

pleat - after your comments, the back covers came off. Some 70's toys, an UNO card deck, some old newspaper, and the required 1970's penny were all that was found, no amp. I did test the 12" speaker for ohms (none listed on back) and got 8 ohms. Which I believe means (wired in parallel) is causing 2.66 ohms rating. Now when I was working on the amp I saw it claims to be good between 3 -4 ohms. So it had to be pushing the amp hard. Not sure what I'm going to do about this yet either. Thanks for the reply and any further suggestions.

Scott

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Re: New Vintage Kustom owner [message #14805 is a reply to message #14786]

Thu, 02 December 2010 12:25

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

A question or two needs to be asked here, what you going to use thru the amp/cabinets, guitar/bass or keyboards?
Is your intension to restore these cabinets to use them.

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Re: New Vintage Kustom owner [message #14806 is a reply to message #14786]

Thu, 02 December 2010 13:02

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Did you check to see if the socket on the pc board side has come un-soldered from the board? From your description, this seems the most likely scenario.

If the Molex connectors are at fault, the female side can be tightened up by bending the contact points with a tiny jeweler's screwdriver.

Glad to hear it's sounding good now.

Bill

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Re: New Vintage Kustom owner [message #14808 is a reply to message #14804]

Thu, 02 December 2010 14:44

pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi

Senior Member

Most times it is the molex connectors that cause all the problems. Kustom finally sent out a dealer memo to cut them off and solder the wires directly to the board.
Just so I'm on the same page, you have what Kustom called the 415G+2H K500 amp. Meaning it was a K250 head, one 2G15+H cabinet with two 15" speakers and a rectangular horn. The second cabinet would be the 2G15+H Power module cabinet.
The power module cabinet would have a power module amplifier mounted flush to the back cabinet with a 110V power cord and two module input jacks and redish orange neon pilot light, and would be connected with an audio cable from the monitor out jack on the back of the K250 amp to the module input jack on the power module.
The system was designed as such. the K250 (125 watts RMS) head driving a speaker cabinet with what ever speaker combination the player chose and wired together with a speaker cord.

The second or additional cabinet would be the same speaker configuration and instead of a speaker jack, it would have the power amp module flush mounted on the back panel providing amplification to that cabinet alone. Each power module cabinet provided 125 Watts RMS, so a player could buy more power cabinets and each cabinet would provide more power. Starting out with simple K250 head and cabinet, = 125 watts rms, add the powe module cabinet = 250 watts rms, add a third cab = 375 watts rms. Kustom did this to keep from overloading an amp with too many speakers.
From what I've read your cabs still have the 2x15 speakers mounted and the horn was removed and someone bolted 12" speakers in place of the horns.
It also sounds like your cabs don't have the power module in the back panel of one of the cabs, so we need to know what is in the cabs for speakers, the impedance of each speaker to see what a total impedance load would be to the amp head. That is one reason Kustom only had one speaker output jack, to help prevent adding more speaker cabinets.
Kustom made two versions of the what I call the 2x15 and horn cab. If you count the T&R on the sides, 23 T&R would be the guitar cabs, if you count 27 T&R on the sides, that would be the taller PA version and there would not be any power module in the taller PA cabs.
Kustom offered both short and tall cabs with Standard KEI speakers, Altec and JBL speakers as options.
It's hard to tell after 40 years how the amp, and both cabs came to rest in one spot, especially if they are guitar cabs and missing the power module. Could be someone had a head and cab, and then found a matching cab and tried hooking it all up.

It's alway fun to find what's been stuffed thru the port holes.
I had a 3x15 that had about a foot of broken long necks rattling around the bottom. That was a sticky and smelly mess to clean out.

pleat

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Re: New Vintage Kustom owner [message #14809 is a reply to message #14786]

Thu, 02 December 2010 17:49

dscottch
Messages: 3
Registered: December 2010

Junior Member

stevem - guitar and yes, we intend to use them.

chicagobill - I checked to see if the male (part connected to board) was loose and it was not. I did use a small pick to tighten the female connections. Even took one out to inspect (the crimp did not catch any of the plastic around the wire) but it was secure at the wire. Still had the same connection issue after the above.

pleat - I'm going to give you the numbers on the case.

Head---K250-2 serial # 75311
Cab----2g+1h g serial # 43298
Cab----2g+1h serial # 29198

I am seriously thinking of soldering the wires directly to the motherboard also! There are 23 T&Rs on both, They both have KEI 15 inch speakers (2 each) and a 12 inch green case (s:746-a 67 7435 stamped on the back of the magnet) speaker screwed into the horn location. They are both identical in configuration inside. No amp or evidence of there ever being an amp is present. The KEI speakers are stamped 8 ohms, the other
(12 inch) I measured at 8 ohms. They are wired parallel. I hope I have provided the requested info. And again, thanks for all the help guys!

Scott

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Re: New Vintage Kustom owner [message #14811 is a reply to message #14809]

Thu, 02 December 2010 22:31

pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi

Senior Member

Scott, you have the guitar cabs and not the taller PA cabs with horns. Since the serial number on the cabs are not close together, I'd say they were not sold as the big K500 series amp.
One of the cabs would have the power module mounted to the back panel. It appears your cabs don't have the module or a large hole where the module would have been mounted to.
The KEI 15" speakers are 8 ohm speakers. Wiring them in parallel along with the added 12" speaker, each cabinet represents a 2.66 ohm total load per cabinet. 2.66 is close enough to the 3~4 ohm the amp head wants to see.

Driving both cabinets the way they sit right now would be a 1.33 ohm load to the amp. Way to low to avoid amp damage.

There are some ways around the impedance issue to run both cabs.
I'd remove the 12" speakers, close off the open hole, wire the speakers in each cab in series for a 16 load each cabinet. Wire both cabs to the head and you have 8 ohms, it's better to be above than below to avoid amp damage.

On the amp issue, maybe re-solder the circuit boards under the molex plugs, if that doesn't fix the problem, I'd cut off the plug and solder the wires direct. One less thing to worry about down the road.

pleat

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