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reverb issue [message #13053] Tue, 23 February 2010 09:38   cassent5150 Messages: 341 Registered: August 2009 Senior Member I got a K-100-5 and the volume goes down when reverb is turned upward. As the reverb is turned up it decreases in volume until halfway then increases in volume to full open back to volume you start with. I have good readings on red green and blue wires. Green= -9.8 Red= +10.1 and blue +.6. Overall output on the amp seems to be weak although a gentle finger touch to Q-900 at the emmiter will blast the room. My question is, if the driver board is that aggressive at Q-900 would the overall volume weakness be from the preamp side (mainly the PC-803)? Has anyone dealt with this issue that could addvise me in a solution to fix this problem. Thanks Steve C Steve C Report message to a moderator

Re: reverb issue [message #13056 is a reply to message #13053] Tue, 23 February 2010 12:12   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member Unhook both reverb cables from the circuit board and see if the amps volume comes up, as the pan may be plugged in reversed. Report message to a moderator

Re: reverb issue [message #13059 is a reply to message #13056] Tue, 23 February 2010 20:08   cassent5150 Messages: 341 Registered: August 2009 Senior Member I unhooked the reverb pan. Reverb control at 0 signal is there but its not punchy like it should be. turning up the reverb control the sound takes a dive down and as I go past 5 the volume starts to come back and at reverb control at full we have a punchy signal (not as punchy as I think it should be, but a whole lot stronger than when the reverb control is at 0 ). Keeping in mind that the reverb pan and wires are completely removed during this test. Any thoughts? Steve C Report message to a moderator

Re: reverb issue [message #13060 is a reply to message #13053] Wed, 24 February 2010 06:39   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member I would be suspect of any of the caps being leaky or bad like C1522 on the emitter side of Q1509, or any of those 2 2n5033 FETs on that gain recovery side of the pan after Q1510. Q1505 FET on the input side of the pan could be toast also. Report message to a moderator

Re: reverb issue [message #13061 is a reply to message #13060] Wed, 24 February 2010 09:21   cassent5150 Messages: 341 Registered: August 2009 Senior Member Thanks stevem, I'm gonna check all the resistors, replace any leaky caps and bad transistors and keep it for a spare. I went through my parts collection, cause I thought I had a PC-803 board I salvaged from a Kasino 100 PA last year, and just replaced the PC-803. That totally eliminated the problem. She'll pack some punch now, this baby ROCKS!! I did notice that there is a lot of white noise (SHHHHHHHHH)with some hum with the reverb pan and wires removed, but quieted down the minute I hooked the pan and wires up, should I be concerned about that? Steve C Steve C Report message to a moderator

Re: reverb issue [message #13062 is a reply to message #13053] Wed, 24 February 2010 10:19   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member Sorry, that info I gave you is wrong kind of, as I forgot you are working on a -5 head, and I was looking at my schematic for a k100 combo amp. I will have to get back to you with different suggestions. Report message to a moderator

Re: reverb issue [message #13080 is a reply to message #13053] Wed, 03 March 2010 06:40   stevem Messages: 4733 Registered: June 2004 Location: NY Senior Member What is the board number that your reverb cables go to on that k100-5? Report message to a moderator

Re: reverb issue [message #13081 is a reply to message #13080] Wed, 03 March 2010 14:36   cassent5150 Messages: 341 Registered: August 2009 Senior Member That board is a PC-803. I'm not positive but I think all the 4 channel K-100 and 200 PA heads use that same board. I had a good board I salvaged out of another amp and that solve the problem with this amp. Still am curious what would cause those issues with the amp so I can fix this 803 board and keep it for a spare. Steve C Report message to a moderator

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