Kenwood kr 9940 is GO!

[anderslober]

Hello EW.....This is driving me crazy too.......the unit is fully re-capped....all caps have been checked and double-checked. The unit does have output.......good, high output on
RR and LR...strange..........the relays are new.......there are a couple of tr's on the protection board that I have not changed.......I have changed the emitter resistors to brand new 3W/0.47 ohm ones....the main outputs(sd287) all test good..........I am 'conundrummed'.......when the volume goes up on the front channels , the relays click of at '1'.......I don't get it........it is as if the fronts can't take the 'juice' when the volume goes up.

Also, when the unit is in 'mono'........it actually sounds meatier(more bass) and clearer than in stereo/2 ch. The SQ/RM may be the culprit...........the gunk that was spilled in the unit hit this board.........there are a bunch of sc1345's on the board.....you never 1 or 2 of these may have gone dead.................

FM/AM works fine....it tunes stations nicely.

I don't know..............................shucks...it is a nice unit..

 

[anderslober]

EW...check post 3 in this thread:

http://www.audiokarma.org/forums/showthread.php?t=333607&highlight=9940

I was unable to upload due a server problem.......................

 

[anderslober]

I have been testing voltages on the unit......all seem good......

I am thinking to replace all the outputs with new Onsemi's.........I suspect one of the outputs is overloading and causing the relay to disengage.............

2sd287.......replaced with either mj21194 or mj15024.......would either of these do?

 

[EchoWars]

Either is fine.

 

[anderslober]

hello EW...ok...thats good. In an earlier post, you mentioned that it could be 'oscillation'..what would be the cause of this?

Also, a voltage that was supposed to be 40v was almost 45v......would this have any adverse affect?

Thanks...............I will change some stuff and report back........

 

[anderslober]

I changed a bunch of stuff..........resistors and tr's on the power supply, resistors and tr's and zeners on protection board..........all main outputs were changed to mj15024's.
(all the original outputs tested good...I may pop them back in later)...........

The amp still can't get passed '1' on the volume without the relay disengaging.Any advice or ideas is heartily welcomed...........................

 

[EchoWars]

You're flailing in the darkness...you need a scope to light the way.

 

[ManyMoonsAudio]

LOL......What??? When's the last time you slept?

 

[anderslober]

EW...paul79......thanks......shucks...I don't have a scope..........IF I had a scope and it was oscillating....what would need to be rectified/changed?

Funny thing is, when the amp is in MONO and connected to the A or B rear outputs it plays very well...loud and strong. Does selection of MONO bypass the SQ/RM board?



Anyway...back to flailing in the darkness without my scope..........:-(

 

[EchoWars]

Step one is to find out IF there's anything happening at the output of the amp that would explain the behavior and justify the protection coming on. I just don't know how to do that without the proper tools.

 

[anderslober]

ok........my wife will kinda' never accept getting an expensive scope........ouch!

EW....hypothetically......if my imaginary scope was hooked up and was oscillating...what could/may it be?

Anyway.......I have a feeling it is some small thing, that I can't figure.........cap's are new, tr's are new....all tr's and cap's on the power supply/protection have been changed...new relays............

Can the SQ/RM board affect the protection ??

EDIT: EW...scope-wise would this do: ARM DSO Nano Quad STM32F103VC Pocket-Sized Oscilloscope.

 

[EchoWars]

ok........my wife will kinda' never accept getting an expensive scope........ouch!

EW....hypothetically......if my imaginary scope was hooked up and was oscillating...what could/may it be?

http://www.audiokarma.org/forums/showthread.php?p=4621519

Anyway.......I have a feeling it is some small thing, that I can't figure.........cap's are new, tr's are new....all tr's and cap's on the power supply/protection have been changed...new relays............

Can the SQ/RM board affect the protection ??

I do not know enough about the construction and topology to say one way or the other.

EDIT: EW...scope-wise would this do: ARM DSO Nano Quad STM32F103VC Pocket-Sized Oscilloscope.

I've never used anything like one of these, so I can't comment on that either. Bandwidth is the name of the game, and it seems like they are a little timid about revealing this specification.

 

[SicMan]

HMMMMMMMMMM.... sounds like he needs a Japanese Voltmeter ... LOL !!!!!!!!!

Sorry couldn't resist ...

 

[anderslober]

Is there anybody here on the forum that knows where to get 8pdt switches...the old , big, metal cased kind? The switch has 24 pins.
I have googled and googled...................nothing comes close to the switch that I need. Speaker selector switch.

Anybody out there with a kr9340, kr8840 or kr8340 parts unit? thanks.............

 

[anderslober]

Even a kr7340 and kr6340 will do the trick...they have the switch part that I need....

Anyone...............?

 

[anderslober]

bump........thanks.