 Kasino Club PA Head - Hum & No Reverb [message #15802] |
Mon, 06 June 2011 07:22  |
RobertUI
Messages: 13
Registered: May 2011
Location: Herndon, VA
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Junior Member |
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I've done a good bit of searching, but don't see anything exactly like what I'm experiencing here, but if I'm wrong feel free to point me in the right direction.
I've had this PA head for a few years now, and it has worked without flaw. Most recently the Reverb is not working at all, and there's considerable noise when the amp is turned on. I don't know if these are related, as the noise is not affected by turning the Reverb knobs. The noise is also not volume dependent; if all 4 channels are "off" with the volume all the way down, the hum is still there.
I don't have any pics of the interior, but it looks like this has been through a recap, as the caps look brand new, and there's nothing obviously leaky. I love this thing, and it works well for powering our monitors, so any help would be greatly appreciated!
Thanks
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| Re: Kasino Club PA Head - Hum & No Reverb [message #15807 is a reply to message #15802] |
Mon, 06 June 2011 12:29  |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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Welcome to the place. I'd start by checking the reverb tank and connections, as the two things may be related.
The reverb controls on the front panel control how much signal is sent to the reverb circuit from each of the preamps. Turning down the controls will not reduce any hum that is created in the circuitry itself.
Check to see that the RCA cables to and from the tank are clean and tight. Do you have access to a multimeter?
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| Re: Kasino Club PA Head - Hum & No Reverb [message #15810 is a reply to message #15809] |
Mon, 06 June 2011 15:57 |
RobertUI
Messages: 13
Registered: May 2011
Location: Herndon, VA
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Junior Member |
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pleat wrote on Mon, 06 June 2011 14:29Two things you mentioned, you are running the amp for a monitor amp. Are you sending a monitor signal from a mixer into the chanel input? You may be over driving the input of the preamp and would increase the noise level.
The other thing that I'd worry about is the Kasino Club PA wants a total of 8 ohms for speakers. If your driving a pair of 8 ohm monitor cabs, you have a 4 ohm load and that may be causing the eventual failure of the power amp.
The Kasino Concert PA is the same as a K200-5 and can run at a 4 ohm total load.
Just some thoughts.
pleat
I should have mentioned that my purpose for having this amp is to run monitors w/ my band (2 16 ohm monitors) via a monitor level signal. This is NOT however how I have been noticing the problem... I have recently been using this to just run a vocal mic (w/ impedance changer) or a bass guitar into one of the channels, then into a single 8ohm speaker (seen in the pic) and this is the condition that I'm using it to now notice the hum.
I am certain (from 20 years experience) that this is not an issue of improper use. I don't mind being asked though, as I HAVE done stupid things before, and will probably do them again! 
[Updated on: Mon, 06 June 2011 15:58] Report message to a moderator |
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| Re: Kasino Club PA Head - Hum & No Reverb [message #15811 is a reply to message #15802] |
Mon, 06 June 2011 17:15 |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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If you have and ohm meter, read the resistance across the two RCA jacks on the reverb tank. There should be something like 50-200 ohms across the terminals. If either or both read open check to see if the small wires that connect the coils on the transducers to the jacks have broken or come loose.
I don't know that this is the case, but if you have pulled the tank and cables, the input to the reverb return circuit is wide open. This could cause a hum, kinda like having a guitar cord plugged into the front of the amp without being plugged into a guitar.
If you plug in the RCA cable to the return jack on the amp and touch the tip of the open cord you should hear a buzz through the speaker. Now try grounding the tip of the return cable. Does the hum that you are hearing go away?
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16018 is a reply to message #15802] |
Wed, 17 August 2011 11:48 |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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Did you ever read the resistance on the tank's RCA jacks? If the tank makes noise when you bounce it, the tank's output is ok, but you still need to check the input. Also, be sure that you are plugging the return line into the output of the tank and the send into the input of the tank. The output side of the tank should be physically pointed away from the power transformer.
As for the hum, if it is not changed by any of the front panel controls, then it is a power amp problem, or a power supply problem. Check all of the ground connections in the amp and be sure that the screws that hold down the pc boards are good and tight as well. Some of the boards connect to ground through these screws.
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16020 is a reply to message #16018] |
Wed, 17 August 2011 11:59 |
RobertUI
Messages: 13
Registered: May 2011
Location: Herndon, VA
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Junior Member |
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chicagobill wrote on Wed, 17 August 2011 11:48Did you ever read the resistance on the tank's RCA jacks? If the tank makes noise when you bounce it, the tank's output is ok, but you still need to check the input. Also, be sure that you are plugging the return line into the output of the tank and the send into the input of the tank. The output side of the tank should be physically pointed away from the power transformer.
I did measure the resistance across the tank (sorry, I meant to post about that) and it was around 153 (I will try again tomorrow evening and will post my results).
chicagobill wrote on Wed, 17 August 2011 11:48
As for the hum, if it is not changed by any of the front panel controls, then it is a power amp problem, or a power supply problem. Check all of the ground connections in the amp and be sure that the screws that hold down the pc boards are good and tight as well. Some of the boards connect to ground through these screws.
This is exactly what I was just thinking. Could this be a problem with the power transformer? I am definitely hoping that this is as simple as checking every ground, so you can be assured that I'll be going over all of those. I did absolutely determine last night that the hum is completely independent of ANYTHING that's actually coming through the amp... meaning that if there's no input load, and every pot is turned down to 0 the hum is the same as when I have something plugged into the input and the controls are brought "up". FWIW, the sound coming out of the speakers seems to not be affected by the low hum that's coming out, if I turn it up enough I can't even tell that it's there.
Thanks for the help! I love this amp (have been testing it with my bass, and the tone is just awesome).
- on another note -
From a safety standpoint (I'm new to high powered troubleshooting) is there anything that I can read up on to find out how to discharge caps etc, to make sure that I don't kill myself?  That would be bad. 
[Updated on: Wed, 17 August 2011 12:00] Report message to a moderator |
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16021 is a reply to message #15802] |
Wed, 17 August 2011 17:07 |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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If you want, build a cap discharger by getting a medium value resistor, with a medium wattage rating and soldering an alligator clip to each lead. For use with a Kustom amp, use a 4K7 ohm, 3 watt resistor. To use it, clip one end to ground and then the other end to the powered side of the filter cap that you want to discharge. In a few moments the voltage will be reduced to nothing.
In fact the voltage will drop to nothing by itself if you have the speaker hooked up to the amp, as the circuit itself will use whatever power is stored in the caps after the amp has been shut off. After that, the small amount of residual voltage left in the caps will not be enough to hurt you, but it could possibly in some rare case do some damage to the circuitry if you were to short somethings together. But this is a highly unlikely scenario.
Try this, connect your voltmeter set to read dc across either of the two main filter caps. Turn on the amp and watch the meter reading. It should read somewhere around 40-45 volts dc. Now turn off the amp and again watch the meter. It usually takes only a few seconds for the voltage to drop to around 5 or 10 volts.
Next try the same test, but set your meter to read AC volts. When you turn on the amp you will probably find some low ac voltage reading on the meter. This reading is the residual ripple voltage coming through the power supply. This is a major cause of hum in the amp. The lower the reading the better. Test the second supply filter cap as well. There shouldn't be more than a few ac volts on either filter cap.
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16028 is a reply to message #15802] |
Thu, 18 August 2011 12:20 |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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That's the reason why I asked you to read the resistance across the RCA jacks on the tank. If the wires are connected, you will get a reading, if they are broken you will not get a reading.
At least 90% of all reverb problems are mechanical, just like your tank. Those little wires always break from fatigue. I can't tell if your transducer coils have the little solder terminals or not, but even if they don't, I've had reasonable luck with soldering new wires to the little stub ends of the coil.
Before you do any soldering, I'd suggest that you read the resistance of the coil itself to make sure that it isn't open circuited as well.
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16031 is a reply to message #16028] |
Thu, 18 August 2011 14:14 |
RobertUI
Messages: 13
Registered: May 2011
Location: Herndon, VA
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Junior Member |
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chicagobill wrote on Thu, 18 August 2011 12:20That's the reason why I asked you to read the resistance across the RCA jacks on the tank. If the wires are connected, you will get a reading, if they are broken you will not get a reading.
At least 90% of all reverb problems are mechanical, just like your tank. Those little wires always break from fatigue. I can't tell if your transducer coils have the little solder terminals or not, but even if they don't, I've had reasonable luck with soldering new wires to the little stub ends of the coil.
Before you do any soldering, I'd suggest that you read the resistance of the coil itself to make sure that it isn't open circuited as well.
Great call! I have a similar size reverb tank at home from a VOX Berkely II that I could try (though I'll have to check the values). I didn't have a chance to do any kind of testing last night, but I'll definitely read and report what I find out about the coils. I've got some similar gauge wire lying around, so I should be able to fix this if it's just those wires! This is a cool learning experience for me!
Thanks again!
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16033 is a reply to message #16032] |
Fri, 19 August 2011 11:23 |
C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...
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Senior Member |
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Go back to Chicago Bill's post about testing the filter caps. My bet is on one or both are shot. They are both the same age, even if one fails, the second is close behind. The hum is internal to your amp and not from an outside source. Your tests to this point affirm that. A scope would be handy but if any AC voltage shows up on the caps, replace them. I recommend that you replace them with a larger value, same voltage, higher capacitance. I have gone up to 4 times larger without issue. The main issue is that the new capacitors are taller and smaller diameter for the same size. You may have to install them horizontally instead of the vertical method. This just requires a different mounting. Sticky back mounts with Ty-Raps works well.
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16037 is a reply to message #15802] |
Sat, 20 August 2011 08:10 |
stevem
Messages: 4758
Registered: June 2004
Location: NY
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Senior Member |
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It sounds like your hum problem is in the power supply of the amp and their are two basic sections of all power supply`s that are not of the newer switching types that are used.
Section 1) being everything before the diodes, this is the AC section and as such runs at 60 cycles and bleeds out 60 HZ hum.
Section 2) is from the diodes, and or bridge rectifier on out, which is the DC voltage provider and runs at 120 cycles.
If you have access to a 88 note keyboard you can pin down which of the two hums you have more of than normal, as both are somewhat present in all amps, and more so in amps with reverb.
A low B note is 61 cycles, the next higher B note is 123 cycles.
Bad or weak power supply filters, or way unmatched output Transistors will make for 120 cycle hum. Take a look at the 4 output transistors on the under side of the chassis, are they all the same part number?
Power supply Transfomers and there input or output wires that may not be twisted tight (twisting AC wires phase canceles hum), and or run too close to the units preamp section or output side of the reverb pan will make for 60 cycle hum injection.
A bad ground/shielded cable to the reverb pan can let 60 Hz hum sneak in also.
Hope these tips may help!
[Updated on: Sat, 20 August 2011 08:11] Report message to a moderator |
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16039 is a reply to message #15802] |
Sat, 20 August 2011 09:42 |
stevem
Messages: 4758
Registered: June 2004
Location: NY
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Senior Member |
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White nose type hiss is quite normal for these amps and you notice it more when the speakers used go up higher in frequency.
I hear very few issues about hiss when these amps are used with their original bass type non horn cabinets with drivers that only go up to 3.5 to 4k in responce.
That being said, just replacing the first one or two gain stage transistors in each of the 4 preamp boards and the two input transistors on the driver board with new current new ones can make for far less hiss/white noise and better gain.
Also checking all the electrolytic type caps on the boards with a cap checking meter can revel if any have aged and gone more than 10% up or down in its MFD value, as shifting up in value can increase the gain structure of a given gain stage a lot.
This will make for more hiss and a change in tone outside of what the amp was set up to have.
[Updated on: Sat, 20 August 2011 09:43] Report message to a moderator |
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| Re: Kasino Club PA Head - Hum & No Reverb [message #16349 is a reply to message #16039] |
Sun, 30 October 2011 10:10 |
RobertUI
Messages: 13
Registered: May 2011
Location: Herndon, VA
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Junior Member |
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I wanted to update this thread with the latest on this killer amp.
There IS in fact a significant HUM, and the "white noise" is now almost completely gone due to the new reverb tank being installed.
Due to some health issues that I'm dealing with, I don't have time or energy to complete this repair, so I'm going to be listing this for sale over on the sale section.
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