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Re: Misprint or error [message #16939 is a reply to message #16938] |
Fri, 20 April 2012 20:50 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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Hey, welcome to the place. You're right Kustom amps were very well built. As for your amp, there should be a model number printed on the small metal tag that is pop riveted to the back panel. Something like K200B-1 or K200A-1, etc. Unless your back panel is made from perforated steel, then there should be a small sticker under the perforated panel.
Each version of the K200 head had a slightly different power supply. The original Frankenstein heads had plus and minus 40 and a plus 24 for the preamps. The K200A series had + & -40 and + & -24 volts for the preamps. The later K200B series had + & -40 and + & -8 for the preamps. So when you say that you only have +24, I have to wonder if you have a different model amp than the one that uses the PC703 board.
If you give us a good description of the chassis, we can help to solve your problem.
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Re: Misprint or error [message #16940 is a reply to message #16938] |
Fri, 20 April 2012 21:51 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
reyes61012
Messages: 14 Registered: April 2012 Location: clinton MD
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Junior Member |
![reyes61012%40yahoo.com](/FUDforum/theme/vk30/images/yahoo.png)
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Thanks for the prompt reply. This unit does not have any model or serial number. I have pictures that I can send you. If Kustom has series that have 27 or less volts, then I might be basing on the wrong PC703 board.
How can I send you the pictures so you will see the layout and probably you will know what model is this? I do not kn ow how to attach the pictures on this message.
And do you think the NPN is supposed to be a PNP?
[Updated on: Fri, 20 April 2012 21:53] Report message to a moderator
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Re: Misprint or error [message #16942 is a reply to message #16938] |
Fri, 20 April 2012 22:08 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
reyes61012
Messages: 14 Registered: April 2012 Location: clinton MD
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Junior Member |
![reyes61012%40yahoo.com](/FUDforum/theme/vk30/images/yahoo.png)
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The faceplate of the unit indicates that it is Kustom by Ross Inc. It has four channels each with its own vol. bass, treble, and reverb controls. There are four preamps circuit boards attached at the back of the faceplate. I think the reverb unit is at the bottom just like the power supplies and the filters. At the back are the audio amps output board and two regulator PC boards. The regulator PC board has Ross Inc printed at the back and I think it is PC 105 0r 501.
If I can send you the pictures that would help in determining what model it is. But I don't think I can attach here since it says Max. file size - 0KB. I can attach the image in email though.
The configuration of the knobs are square. The sw in the middle OFF in mid position and ON on either right or left. There are four input jacks. At the back are two speaker jacks on the right side and there is an RCA jack on the upper left and a i/4 jack for foot SW I think
[Updated on: Fri, 20 April 2012 22:15] Report message to a moderator
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Re: Misprint or error [message #16945 is a reply to message #16938] |
Sat, 21 April 2012 00:07 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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Kustom amps were very well designed and extremely well built. They were one of the biggest and best manufacturers for a time there, sorta the Peavey of their day.
From your descriptions, it sounds like a PA model K200A-5. The giveaway is the fact that you say that you have a regulator board. The B-series amps do not have separate regulator boards as they are part of the power amp board.
I don't think that I have the schematic for the reverb/mixer circuit for your amp, but I do have the power amp and preamp circuits.
The two 24 volt supplies are carried by the red and green wires to the different boards. Do you have both + and - 24 volts?
On the back panel there is an RCA jack. This is meant to be used as an output to a tape recorder or other device. Because it is isolated with a cap and connected to the input of the power amp, it can be used to inject a signal directly to the power amp. If you have a signal generator plug it in there and see if the power amp is working to full power. If no generator try an ipod or other device.
You can also test the other way and test the preamps by taking the RCA output to another amp. Once you've isolated the problem to either the preamp or the power amp section, you'll be able to find the problem faster.
I wouldn't be overly concerned about resistor tolerances at this point, unless it's way off. I'd make a first guess that there probably is a bad cap before a bad resistor.
PM me your email address and I'll find the scans of the schematics that I have for your amp.
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Re: Misprint or error [message #16963 is a reply to message #16938] |
Tue, 24 April 2012 11:52 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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OK, I've seen photos of his amp and it definitely is a K200A-5 PA head. I've sent him the correct schematics for the power amp, voltage regs and preamps, but I don't have the reverb mixer board schematic for an A-series PA. Maybe one of you other guys has one that you can send him if he needs it.
Now maybe he can get it working again.
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Re: Misprint or error [message #16975 is a reply to message #16966] |
Tue, 24 April 2012 20:36 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
cassent5150
Messages: 341 Registered: August 2009
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Senior Member |
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yes your right the RCA jacks are for the reverb pan. the jack closest to the front preamp panel is the output to the tank and the rca jack closest to the back driver panel is the input recovery from the tank and I believe the reverb tank has to be grounded to the chassis for it to operate. Steve C
Steve C
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K200 amps is back in operation. [message #17070 is a reply to message #16963] |
Wed, 09 May 2012 18:19 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
reyes61012
Messages: 14 Registered: April 2012 Location: clinton MD
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Junior Member |
![reyes61012%40yahoo.com](/FUDforum/theme/vk30/images/yahoo.png)
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chicagobill
Got my k200 amps working - all 4 channels. I replaced msps 953 on the two chanells with an all purpose NPN transistors that I bought from Radio Shack.
Not a musician, I got a make-shift pick-up and mounted it on my cheap accoustic guitar. It worked but I think I am not getting at least 50 or 60 watts of power. I am using two 8-inch ordinary 8 ohms speakers in parallel to have 4 ohms load. I am now trying to figure where the hiss or noise coming from. I don't think it is 60 cycle hum. I have not tried using my old scope that is sitting in the basement for 20 some years now, he he he .
Now that I have this running, I am thinking of adding a reverb unit if I can find the schematic for it. Is the board mounted flat at the bottom the reverb board? I figured the other jack on the right side is the foot sw. for that purpose.
Considering the age and the condition of this unit (which might have been in humid basement or that sort) still it worked. I will see if I can feed a CD player and see if there any distortion at high volumne.
Any tips regarding the hiss and other noise?
As it is , I only replaced two transistors, a 25 MFD Mallory cap and the 100MFD on one of the tone control board.
Your schematics are a great help. Thanks.
Archie
[Updated on: Wed, 09 May 2012 18:24] Report message to a moderator
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Re: Misprint or error [message #17071 is a reply to message #16938] |
Thu, 10 May 2012 06:43 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
stevem
Messages: 4758 Registered: June 2004 Location: NY
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Senior Member |
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untill you get a reverb pan back in the unit I would make up a shorted RCA jack to go into where the output cable would plug in, with out this you have a open gain stage ( if the gain stage works, see below) and may be picking up noise.
If you plug the cable in this output jack and get a buzz when you touch the tip, then thats good news and means that the recovery side of the reverb board is working and in all liklyhood when you pop in a new reverb pan with a ground to the chassis you will be good to go.
The blue wires in the amp are the signal wires, if you unhook them from the output driver board you can test out the noise level of just this board itself, when all is well these boards are pretty dam noiseless!
I cut the wires at a place where I can just red butt splice them back togethere.
As a matter of course I would replace the first two or three transistors after the input jacks on all four channels, as most times this is the root of alot of hiss and crackle, it takes way less than 3/4s of a volt RMS of signal input to drive these amps to full output, and if a former owner drove any of the channels witha stomp box its all too easy to harm the input gain stage transisor!
If your O-scope still works you can trace back up stream form each channels blue output wire and find any other noisy transistors, or with a volt meter leaky coupling caps.
Once you get it back in good shape I mod I have done with mine for guitar or bass use is you change the tone caps in 3 of the 4 channels for a different frequency range, then with a out board a/b/c/d foot switch that I made, I can switch to different channels for tone and volume changes.
[Updated on: Thu, 10 May 2012 06:50] Report message to a moderator
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Re: Misprint or error [message #17074 is a reply to message #17073] |
Thu, 10 May 2012 19:03 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
cassent5150
Messages: 341 Registered: August 2009
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Senior Member |
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The RCA jack close to the back is your recovery input from the Reverb tanks output and if its working well, stevem is right, could be some of your noise. The RCA closest to the front of the amp is output to reverb tank. "NOTE: THE REVERB TANK NEEDS TO BE GROUNDED TO THE CHASSIS TO OPERATE"
Steve C
[Updated on: Thu, 10 May 2012 19:05] Report message to a moderator
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