Looking for Scematics [message #15111] |
Mon, 17 January 2011 10:22 |
JoeT
Messages: 13 Registered: December 2010 Location: Wynantskill, NY
|
Junior Member |
|
|
Hi Guys, Picked up a 150-6 Bass combo in fair condition. Looking
to rebuid. Unfortunately someone in the past had removed the power amp board and intalled different power amp. Cannot identify what the amp is, but its a small module on a heat sink with date codes of 1971. Whomever did the mods, do a decent job. Combo plays and sounds OK, but obviouosly with mods that drastic not confident in the reliablity and its power output.
Looking to see if anyone has schematics for the K150-6 bass combo, and if anyone has an amplifier board or old chassis they are willing to part with and for how much.
Someone had sent me schematics for a K100-1 I bought a couple months ago. Head would not output at all. Checked every component in the amp and could not find anything definitely bad. When I received the drawings I notice the drawings which were a Revision 3, had some 1% resistors indicated when my unit had 5% carbon. Checked those 2 resisitor and found they had drifted so far out of spec that they shut the amp down. Replaced with precision resistors and amp sounds great. Thought you repair guys might find intersesting.
Thanks
Joe Treiber
|
|
|
|
|
|
Re: Looking for Scematics [message #15138 is a reply to message #15137] |
Sun, 23 January 2011 22:47 |
pleat
Messages: 1454 Registered: June 2004 Location: Belding, Mi
|
Senior Member |
|
|
Joe, the Self Contained SC series K150-6, K150-7, K150-8 used the PC5032 power amp board. The newer slant metal faced K150 guitar and PA used a different power amp board, I think it is a PC5034 but it would still be a 75 watt rms board, and those amps are not that expensive used. I'd use any slant face amp as a donor to get a plexi face amp back up and running. The +8 and -8 voltage is part of the slant face amps.
The amp that you have now that clips easily, since I don't know what the amp is or what impedance it wants to see, it may have a mis matched speaker that the amp is driving. Just guess work on my part, I'm not a tech, so I'll let the experts give advice on why you are having issues. My thought is to use a slant face donor amp to get your plexi going.
pleat
|
|
|
|
|
|
|
|
Re: Looking for Scematics [message #15150 is a reply to message #15111] |
Wed, 26 January 2011 17:04 |
JoeT
Messages: 13 Registered: December 2010 Location: Wynantskill, NY
|
Junior Member |
|
|
Hi pleat, you know I was thinking the preamp boards were the same, but I wasn't considering the reverse image thing. Makes sense now. Yes, some one did go to a lot of trouble. You would thing it would have been eaisier to repair the bad board but it might have actually burned up quite a bit. They did replace the bridge rectifier and the caps. Not nice computer grade but but circuit board types. The dc buss reactor looks to be original though, so it didn't fail. The Altec 418 seems to be in real good condition and the tuck and roll can be repaired. Most of the damage is to the 2 cross pieces that should be easy to replace and may not show to bad if I use new naugahyde (silver). For some reason I'm attracted to this amp and probably will spend some money and get up to playing condition. I play bass in 60" girl group band. Thanks for the info on the boards. If I can't find drawings I might try and make a set myself on AutoCad. These boards are pretty simple, not a lot of components.
I don't know if you have looked at any these new class D ampliers you can buy now. Fairly small, extremely efficient.
Might stick one in this amp to get more power and reliability. With two premp boards and a good amp should be pretty reliable.
Thanks
Joe Treiber
|
|
|