| Kustom XII bi-amp [message #23583] |
Mon, 10 August 2015 20:54  |
Iowa Boy
Messages: 767
Registered: June 2014
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Senior Member |
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Help.....just received a kustom XII bi-amp. The amp on the inside to the furthest left has the wires cut that are coming from the two filter caps into that amp. I have no clue as to why its been disconnected and am afraid to reconnect them for fear of something else blowing. Pleat has seen the pictures and says its the power and ground wires that have been cut. What do I need to do to test this amp out?
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| Re: Kustom XII bi-amp [message #23584 is a reply to message #23583] |
Tue, 11 August 2015 06:44  |
stevem
Messages: 4775
Registered: June 2004
Location: NY
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Senior Member |
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Reconnect the wires and install a fuse to replace the likely blown one with a fuse of 1/2 the needed amperage, then turn the amp on, if that fuse blows it's time to check the diode cup on the floor of the amp and start pulling the output transistors and checking them.
If the diode cup checks good I think you can unpower the high amp or the low amp one at a time by its Molex connector, if so then install another low amp fuse and power it up again and if the fuse holds you have pinned down the bad amp section.
It would be my guess that the thing has a bad amp section low amp section will be bad!
Oh wait, let's go back to square one here, the first thing to do is to unhook the power transformer from the diode cup, install that small fuse and then power up the amp to confirm that the PT is not shorted out, and then confirm that the diode cup is good.
Be sure to not let those wires you pulled off touch anything!
It's been a while since I have been in one of these, but if I recall right they have a thermal circuit breaker for each amp section, so both of those need to be checked for being open if the amp does not power up with a good fuse.
Is the crossover / control board in that biamp PC 5258?
[Updated on: Tue, 11 August 2015 06:52] Report message to a moderator |
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| Re: Kustom XII bi-amp [message #23588 is a reply to message #23583] |
Tue, 11 August 2015 13:19 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Let's not get ahead of ourselves here, let's have a bit more information. Does the part of the amp that is still hooked up work as it is? If it does, then the power supply is probably okay.
This thing has a large power amp for low freqs and a smaller power amp for highs and an electronic crossover to separate the signals. If the one power amp is still working, which one is it the lows or the highs?
The amp that was disconnected could be shorted, or it could have not been needed by some former owner and unhooked, or who knows why it was taken out of the circuit. In order to reconnect it, you will need to run a few tests to be sure that it in fact is not shorted.
The simplest test would be to use an ohm meter to check the two power supply line for shorts to ground.
Tell us more about the amp.
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| Re: Kustom XII bi-amp [message #23593 is a reply to message #23583] |
Tue, 11 August 2015 14:45 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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You never answered the basic question, does the amp work as it is?
The red wire is the positive voltage, the green wire is the negative voltage and the black is the ground.
What value or scale was the meter set for when you got the 4.7 reading? If it's 4.7 ohms, that would be a short circuit, if it was 4.7 megohms (million ohms), not so much.
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| Re: Kustom XII bi-amp [message #23594 is a reply to message #23593] |
Tue, 11 August 2015 15:02 |
Iowa Boy
Messages: 767
Registered: June 2014
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Senior Member |
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Bill....I never plugged it in since I had seen wires cut and know now that the plugs have been moved.
The reading was in meg. Rechecking again...the longer I leave the probes on the wires, the values increase as well. Guessing that the battery in meter in supplying the increase.
Since I don't have a schematic to go by, I am also assuming that the Molex plugs are the output.
[Updated on: Tue, 11 August 2015 15:03] Report message to a moderator |
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| Re: Kustom XII bi-amp [message #23596 is a reply to message #23583] |
Tue, 11 August 2015 15:17 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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I don't know how much test equipment you have, but if you have light bulb limiter, I'd suggest using it on this amp when you first plug it in.
People do dumb things. Who know why, all I can suggest is that you get it back to normal if you can. Have you looked for a schematic? That would help in putting everything back to normal.
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| Re: Kustom XII bi-amp [message #23599 is a reply to message #23583] |
Tue, 11 August 2015 16:15 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Well, can you see the pc board numbers? If you at least find the numbers on the power amp boards, that will be a big help. Exactly how many power amps are in this thing? Two 130 watt low freq amps, and two 60 watt high freq amps?
The limiter that I suggested, is nothing more than a standard incandescent light bulb that is connected to the ac line, wired in series with the test amp. If the test amp draws too much current, the light bulb turns on and shuts off the current going to the amp. This will prevent the amp's fuse and internal circuitry from blowing.
I'm sure that if you want to build one, you can find instructions out there. My first one was and old extension cord and a light socket.
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| Re: Kustom XII bi-amp [message #23606 is a reply to message #23583] |
Wed, 12 August 2015 06:10 |
stevem
Messages: 4775
Registered: June 2004
Location: NY
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Senior Member |
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Sorry, I misread part of your first post.
The red and green wires where cut either to trouble shoot the amp, and or to un- power that amp section and be able to use the remaining 2 good amp sections.
In These Amps they stopped using the metal case TO5 type driver transistors that we are use to seing in the silver rectangular heat sink boxes, and switched to the plastic pack TO- 220 types, which if your amp is like mine ( the smaller bi- amp) these transistors are red cased and green.
Mine are RCA brand with one being a 65860, and the other being a 7701.
Neither of them have I been able to cross, but they are just standard audio driver types and not a issue to get a replacement for .
Let's go To back to square one like Bill posted, is the fuse good?
If any of the red wires on the output transistor sockets have a low resistance to ground( under 200 ohms ) then they are shorted.
The best way to get that reading and not have the meter try to charge those big main filter cans is to unhook the red and green wires from the cans first.
Like I posted yesterday, if you do power it up thru the limiter like you are making I would still derate the fuse you install by 50 to 75 %.
Let us know how it goes!
Oh, where did you find the schematic?
[Updated on: Wed, 12 August 2015 06:12] Report message to a moderator |
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| Re: Kustom XII bi-amp [message #23613 is a reply to message #23583] |
Wed, 12 August 2015 16:08 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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A couple of things, have you taken photos of the inside of this amp?
For the limiter, you don't need a 250 watt lamp, a 100 or a 60 will be fine.
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| Re: Kustom XII bi-amp [message #23618 is a reply to message #23617] |
Wed, 12 August 2015 22:15 |
pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi
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Senior Member |
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A few things, have you traced from the speaker jack wires back to each amp? So you know what the center and the other amp is suppose to drive speaker or horns? Are the two remaining amps working?
You said the first amp or left side amp is a low frequency amp the one with the wires cut. The center amp I will assume drives the other low frequency speakers, and the remaining amp is driving the high frequency for the horns.
Since you are hooking up your computer to the input, the signal is going through the electronic crossover first, and the signal is then split or divided into the low power amps and the high frequency amp.
When you hooked up your speakers, did you hook one speaker to the low amp and one speaker to the horn amp? If you hooked both speakers to the horn amp, you won't get much volume as the crossover is only letting the higher frequencies pass on to the power amp. There are two volume controls, Main or master, which has to maxed to get the most volume and then the horn volume control. The horn volume tracks with the master volume control. Turning it down automatically turns down the signal going to the horn amp.
As to the switch always be on, Just tossing this out, the power switch is a rocker type with the center position being the off position. It functions as power and polarity in one switch.
pleat
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| Re: Kustom XII bi-amp [message #23620 is a reply to message #23583] |
Thu, 13 August 2015 01:40 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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It sounds like you are making progress. Do you still have the amp plugged into the limiter? If the bulb didn't light up brightly, then the amp is not drawing too much current and can be powered up directly without the limiter.
Using the limiter will reduce the power supply voltages and will lower the output power. Next step will be to test the power supply voltages with your volt meter. Take the readings at the two power supply caps. There should be plus and minus 40-45 volts at the terminals.
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| Re: Kustom XII bi-amp [message #23624 is a reply to message #23583] |
Fri, 14 August 2015 13:54 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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I've seen the photos now and agree that this has been hacked by someone that shouldn't have been in there.
The transistor that was added to the top of the one board has a different pin arrangement from the original one, so the jumper wire may have been added to connect up one of the pins.
I notice that the driver transistors are the old style TO-39H and not the later versions that used a TO-220 that Steve described.
I can't completely see how the switch is wired, but it looks like a replacement to me. All of the factory switches normally have the two cross connections for the polarity wiring made as part of the switch with flat brass strips. These are added on wires.
If you get a better photo showing how the wires are connected to the back of the switch, I can tell you how to rewire it so that it works correctly.
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| Re: Kustom XII bi-amp [message #23626 is a reply to message #23583] |
Sat, 15 August 2015 01:26 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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In the early days of three prong ac cords, they still used a ground switch and cap, so the original switch would have been a three position center off one.
The light inside the switch is a neon bulb with a dropping resistor. It connects to the two sides of the power line hot and neutral. Nothing should be grounded except for the one end of the ground cap.
What you need to figure out is what terminals the neon light is connected to. My guess would be the two center ones. Is the ground cap connected to one of the center two terminals?
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| Re: Kustom XII bi-amp [message #23627 is a reply to message #23583] |
Sat, 15 August 2015 06:44 |
stevem
Messages: 4775
Registered: June 2004
Location: NY
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Senior Member |
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The problem with those TO-220 transistors as replacements is that the fatter leads will not pass thru the factory lead holes without being drilled out That makes for the need to wire it up with all jumper wires unless you tack solder one or more of the leads right to the top side of the other components it goes to.
This looks like a mess and a tack solder joint is iffy at best!
When I need to go this route I drill out the holes with a .060" bit and hope that the trace is wide enough that I do not have to use a jumper no less on the bottom side.
[Updated on: Sat, 15 August 2015 06:46] Report message to a moderator |
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| Re: Kustom XII bi-amp [message #23630 is a reply to message #23583] |
Sun, 16 August 2015 01:46 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Okay, then the two wires from the transformer should connect to the outer connectors. The two wires from the ac line should connect to the two middle connectors.
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