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K200A-1 head, no output to speaker cab [message #22430] Wed, 11 February 2015 05:47   ToddMcD Messages: 2 Registered: February 2015 Location: United States Junior Member I have a K200A-1 head that isn't output to a speaker cab. I've owned it for 17 years or so, it hasn't worked for the last 10 or so. It blew fuses. I checked the transformer, rectifier, and capacitors. They were OK, put them back in and now it doesn't blow fuses anymore. Now it doesn't have any output to a speaker cab. There's a buzzing but no other sound. Any ideas or some schematics for it would be great. Report message to a moderator

Re: K200A-1 head, no output to speaker cab [message #22432 is a reply to message #22430] Wed, 11 February 2015 06:25   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member Hello and welcome! Your problem in the first place with the amp is a issue in the driver / output stage born out by the blowing fuses issue! The first thing you need to learn about anything electronic is that the blowing open of a fuse is never a fluke, there is a underlining issue that has to be fixed, so your replacing of the fuse only made for more damage! Why the amp currently does not blow fuses if that's what you mean I could not say for sure without getting my nose into it, but one thing is for sure your likely to need the repair services of a electronic tech to get it back up and running! We can help you if you have a good ability to solder well and have a good volt / ohm meter on hand. Report message to a moderator

Re: K200A-1 head, no output to speaker cab [message #22433 is a reply to message #22430] Wed, 11 February 2015 13:14 chicagobill Messages: 2005 Registered: April 2003 Senior Member Welcome to the place. Agree with Steve, usually fuses don't blow for no reason. If you go over to the Technical part of the site, you will find some schematics for the K200A series amps. You should be able to at least find the power amp and the preamps. If you have any other questions feel free to ask. Report message to a moderator

Re: K200A-1 head, no output to speaker cab [message #22434 is a reply to message #22433] Wed, 11 February 2015 17:07   ToddMcD Messages: 2 Registered: February 2015 Location: United States Junior Member OK,I do have a good multimeter and am a decent solderer. I also have a better one at work. Now on the pc702 board there are 4 Memcor 1 ohm resistors. 3 of them read 1.2- 1.3 ohms, the other reads 550 ohms. Where can I get a replacement for it? I do know that blowing fuses isn't good which is why I was suprized when it didn't blow after I checked the transformer, rectifier, and capacitors. Report message to a moderator

Re: K200A-1 head, no output to speaker cab [message #22435 is a reply to message #22430] Wed, 11 February 2015 18:07   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member Yiu are reading over 500 ohms because that 5 watt resistor is open and that bring open also means you have at least one bad output transistor and may be also a bad driver transistor. The first step is to remove that bad 5 watt emitter resistor and replace it, but while you are at it you may as well replace all 4 as newer ones will be much closer to the resistance that they should be and then we can help you repair the rest of what's wrong! Do not power up the just because you have replaced those resistors! Report message to a moderator

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