| k250 Nasty Hum/Part ID. [message #5218] |
Sat, 25 December 2004 00:44  |
OSI7
Messages: 5
Registered: December 2004
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Junior Member |
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Let me start off by saying thanks to all people responsible for this forum,I have become a huge fan of Kustom TNR since I set off to repair a k250-1 that I rescued from a trash pile along with the 2x15 cab with blown speaks. I have read all posts backward and forward many times but alas I am at wits end and I need the help of an expert ,So here goes....
After replacing 2 pre amp transistors ,2 outputs and multiple open resistors I was left with a nasty hum in the form of a sawtooth wave everywhere I touched the probe ,this hum was so bad it produced a puff of smoke from my speaker cabinet within a few seconds.So I of course suspected and replaced the main filter caps ,hum was still there,everywhere,so I disconect the main outputs , still hums , I then unplugged ,clipped and unsoldered everything leaving only the transformer the cap/resistors and what I think is the rectifier ,the sawtooth wave was still there. I come to figure out after much scouring for info on the web that this rectifier is maybey not a rectifier and I'm still uncertain what it actually is . It's stamped IN4436/f and has word Varo on it.I'm guessing it's a variactor? or somthing of that nature.
And thats my long winded story...Soooo can anybody please clear this up?... What is this device? Where can I find one? How can I test it? Is this even likely the problem or could the transformer be suspect also?
I would reeeaaaalllly like to get this unit going so any advice would be very much appreciated!!!
[Updated on: Sat, 25 December 2004 00:58] Report message to a moderator |
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| Re: k250 Nasty Hum/Part ID. [message #5221 is a reply to message #5218] |
Sat, 25 December 2004 11:04  |
rodak
Messages: 516
Registered: October 2001
Location: Georgia
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Senior Member |
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I couldn't say for sure if a blown rectifier could cause those symptoms, but they're pretty cheap and easy to replace, so I'd just do that. Probably don't need to get an exact part# match - I'd think any decent silicon rectifier rated 200PIV/4A or better would do. Are they discrete rectifiers (i.e., are they 2-lead devices, with four of them present)? If so, I'd just replace all four with a full-wave bridge. You can get a hefty 25A bridge for just a few dollars.
www.combo-organ.com
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| Re: k250 Nasty Hum/Part ID. [message #5224 is a reply to message #5222] |
Sat, 25 December 2004 17:05 |
rodak
Messages: 516
Registered: October 2001
Location: Georgia
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Senior Member |
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Wish I could help more, but my amp circuit knowledge is rather limited. I'm sure there's someone else here who could offer advice, though.
www.combo-organ.com
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| Re: k250 Nasty Hum/Part ID. [message #5275 is a reply to message #5255] |
Mon, 03 January 2005 23:16 |
OSI7
Messages: 5
Registered: December 2004
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Junior Member |
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Steve!!! You're the guy I really wanted to hear from and I was actually holding off on making too many more moves till I got a response from you....I have already ordered most of the parts I need for a re-build of the 5065 "Driver" board (I have been calling it the preamp board..my mistake)and both pre-boards (5066 and 5067) and I would very much like to have the scheme before I begin.
I have checked the zeners , and they read ok using my meter on diode check but I intend to replace them either way ,perhapse you could post the values/part number so I could have them included in my next order for the remainder of the parts which I would like to place tonight or tomarrow.Also would like to know part numbers for replacements on the transistors on the drive board 38735 38736 38737 and the diode that clips into the chassis near the outputs also the three transistors on the 5066 pre-board which includes a 4-legged TO-39 case all with numbers from Kustom that don't cross with anything.I figure I could purchase clip on heat sinks for 736-737's. I would like to keep things as close to original as possible and I refuse to use NTE stuff as I have never had good results on audio equipment.
I will have an envelope on it's way first thing in the morning and I will post my progress and results for all that may be interested in the resurection of my "ShytCan System" ,maybe even pictures if I really get bored ,I dunno......Thanks to all who gave advice!!!! and Deb and Steve ...... OSI7
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Took your advice rodak , I leeched a kbh2502 out of an old Ampzilla I've been working on and the buzz is still very much present ,so unless that one is bad also I'm thinkin' the problem lies eleswhere , but where ? the only thing connected is the caps that I replaced the resistors that I'm guessing are to drain the caps and the transformer (blah) . Any other ideas or was this unit in the trash for good reason? Please help prevent this machine from becoming landfill fodder!!!
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