jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
I have acquired a K200A-1 amp. and there are two missing transistors in the power amp board PC702. I am hoping someone has this same amp and can identify the missing part numbers. The lower one has a metal heat sink and the upper one is a standard type. Can you help? I have pics of the board with the missing part locations flagged. Please e-mail me achapman@rgv.rr.com
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
Hi, I only have a 703 schematic, but I may have a 200a head I can look at tonight and let you know in the morning.You may also have some bad output transistors, seeing as your board is missing a heat sinked driver transistor.
jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
Thanks a million! I have checked the outputs and had to replace one of them....Just about all transistors in the pre-amps are shorted. Must have been a shorted speaker lead or something......sure did a number on the transistors! Thanks again...Jack
If all of the small transistors in the pre-amps have been shorted, they have probably been subjected to too much voltage. Be sure to check the power supply, and especially the voltage regulator circuits before you power up the amp again.
jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
Thanks for the tip! I am going through everything checking all of the transistors, caps, diodes, etc. Have only found one bad cap, but lots of small transistors that are shorted. I hope to make this dragon breath fire again.
jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
Yes, please. I should be able to figure out what to do with the missing stuff. I will set my computer to accept the fax..........956/423-8866.
Let me know of the phone charge and I'll pay you for any expenses. Thanks. This will be a great help.
jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
Steve,
Thanks for the schematic. It is not very close to what I have, but I think I can come up with something. I have figured out the one with the heat sink......now for the other one. Thanks!
jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
Bob sure was a great help with the missing transistors. Now that I have installed them, I am getting smoking 100ohm resistors near these transistors. Sure wish I could find a schematic and board layout of this amp.....Does anybody have them???????? All the transistors read good on the Sencore tester that I am using.
jackchapman Messages: 12 Registered: August 2005 Location: Harlingen,Texas
Junior Member
Success!!!!! After replacing the burnt resistors and re-checking the driver and output transistors, I found two outputs and one of the driver transistors damaged. After replacing them the amp powered-up without anything smoking or blowing!!!! I found two 3x15 Kustom cabs. in Seattle and when they arrive on tuesday I will be able to give the amp a good testing. Also, I found that the schematics and board layout for a PC704A from a 400 watt amp to be very close to the PC702 in this K200A. Thanks everyone for the tips and help I received. You guys are great!!!!