Appears to be far from Basic. Basic M2 bias issue.

vsat88

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Hi, Kenwood Basic M2 . When I have my meter across R 86 I have no bias reading whatsoever. I can adjust VR 4 either way with no result. If I use the same meter and probes across R 85 I get a bias reading and can adjust it with VR 3 without a problem. The amp has almost no DC offset. There was no ill reaction on the DBT or ammeter. When I first brought it up. I had been playing it for a long while on test speakers and wanted to check bias before I buttoned it up and went on to another project and found the issue. Anyone care to jump in and give me a bit of schooling ? Thanks.
 
Second night. Swapped TA 2031's side to side with no result. Still no bias reading across R 86. Worth a try I guess. Last night I cleaned the mainboard and checked for bad joints and found none.
 
Still grasping at straws here. Did I forget to say thank you or something ? Removed VR 4 just to check it. Seems fine may swap it out with VR 3 just to say I did. Checked all the resistors at R 50 R48 and and what looks like R49 R47. They are good.
 
Have you tried R84? It's the other emitter resistor in the same channel. Does the amp function now? I have a dead one at home that I can bring into the shop tomorrow to help you troubleshoot as I don't remember what is accessible and what is not.
 
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Have you tried R84? It's the other emitter resistor in the same channel. Does the amp function now? I have a dead one at home that I can bring into the shop tomorrow to help you troubleshoot as I don't remember what is accessible and what is not.
I have tested all the emitter resistors and they all show good/same value. I have not tried the others in order to set bias. Unfortunately I screwed around an broke one of the 500 Ohm pots when I took it out to clean and swap channel for channel. I would have to make a parts order before I can go much farther.
 
I have tested all the emitter resistors and they all show good/same value. I have not tried the others in order to set bias. Unfortunately I screwed around an broke one of the 500 Ohm pots when I took it out to clean and swap channel for channel. I would have to make a parts order before I can go much farther.
Oh, yes. It did function and did not sound bad either. Strange this one..
 
The one I have has bad STKs as it is stuck in the High mode and runs very hot even while not doing anything. This is the first one that I've seen that didn't have bad output transistors so I bought it with plans on doing the DRM mods to it but it's on the back burner now. I also robbed the speakers terminals to fix another one DRM has those too.
 
I had one I bought from Dan a long time ago that was fully Modded out by him. One sweet amp but had to switch to a B&K for my SDA SRS 2's. Needed more current. The one I have now is my original M2 from yesteryear. Gave the one Dan Modded to a friend here local, same guy who got me the SRS's. I think they are a marvelous amplifier I really like them. This one is special to me in that it is the same amp that got me into Hi Fi to start with. Not only that when my Daughter was just a baby we would put on music and she would run and jump up in my arms to "dance". I will never give up on fixing it. The speaker output terminals are in fine condition believe it or not but I can't say that for the rest of it. It's in bad condition as far as looks go and both of the small buttons on the front are broken (hold and level) as well as a toasted power switch. Not too worried about that just want er to him again. I would like to keep it stock however in the end I will do whatever I have to do to get it back up. Thing is I also have had this one on the back burner and if I don't go ahead and try to fix it it will wind up back there again I am afraid. Let me know and I will post back as well. Thanks, you are the only one who has jumped in to help and I really appreciate that.
 
Sorry I'm no help to you.

I just wanted to say that I hope you get your M2 up and running top notch again.
I've only had an M2 for a week after earlier getting an M2A and as you know they're a terrific amp that are well worth keeping

Cheers
Andrew
 
Can't agree more about the amps, they are great amps and definitely worth saving. Just so you know you have been of help because you chipped in with words of encouragement. Thanks.
 
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