There is a ghost in my Kenwood Basic M1D home stereo power amplifier.

Thread Starter

lipsk1

Joined Jun 1, 2020
1
Hello,
I have a home stereo power amp Kenwood Basic M1D. I am having trouble with it working fine and then cutting out. I have checked every variable i can think of, including power source, testing different speakers and making sure the speaker wire is the right gauge and equal length, testing the speaker wire terminal ports (A vs B), changing the fuse, searching for miscolored resistors, and checking for overheating and good ventilation. It just really confuses me because it will work fine all day and then the next day it suddenly it will click off with a pop in the speakers and the "protection light" starts blinking. I have a little background with electronics but this is beyond me.
 

drc_567

Joined Dec 29, 2008
844
If the unit has been used for a sufficient number of hours, it is possible that moisture has infiltrated certain switches, variable controls, or adjustments. One product to try out is electronic contact cleaner, available in spray cans with a straw like applicator. Try to direct some of the cleaner spray into parts and assemblies that seem to be movable, or have different positions, as you exercise the switches and controls. Be sure and mark positions for anything that might be an important adjustment. Allow a few hours for everything to completely evaporate and dry.
... If following this procedure doesn't actually fix the original problem, it may serve to provide a more precise description of the malfunction.
... Any further troubleshooting will likely require a schematic.
... Suggest only spraying large variable resistors and control knobs at first, since the cleaner spray is actually a solvent that may erase any written marks that have been made on important adjustments.
 
Last edited:

dl324

Joined Mar 30, 2015
10,747
Welcome to AAC!

I can assure you that no ghosts are involved.
It just really confuses me because it will work fine all day and then the next day it suddenly it will click off with a pop in the speakers and the "protection light" starts blinking. I have a little background with electronics but this is beyond me.
That's the nature of how things fail. They work for a long time and then stop working.

The blinking protection light is a clue. Do you have an owner's manual? They usually have some basic troubleshooting guides, but blinking protection light will probably just tell you that the unit requires service by trained personnel.
 

drc_567

Joined Dec 29, 2008
844
Another approach sometimes used without actually knowing what is wrong is to 're-cap' the unit.
Basically, this method sometimes works for units that are several years old and have parts called electrolytic capacitors that are subject to a form of aging, where a liquid electrolyte inside the capacitor either leaks out or dries up. The electrolytic capacitors are readily identified since they are cylindrical or can-like, and have + and - polarity marks printed on the side. A few sharp photographs of the circuit board can sometimes identify a faulty electrolytic capacitor.
 

dl324

Joined Mar 30, 2015
10,747
Before you start blindly replacing capacitors, make sure your soldering skills are up to the task.

This thread has a lot of people blindly replacing capacitors and some of them found that even that wasn't as easy as they thought it would be.

If there are electrolytic caps that have bulging tops they're candidates for replacement. I replaced some on a motherboard and it didn't help. I replaced some in my DVR and it fixed the problem. YMMV.
 

abrsvc

Joined Jun 16, 2018
35
Given that this appears to be heat related, I would suspect that a transistor or two are breaking down due to heat and allowing DC voltage through to the output stage. It is also possible that the protection IC is failing (UPC1287HA). With the unit in protect mode, check voltage levels at the following components and report them here:

IC3 (UPC1287HA)
Q9/Q11
Q10/Q1`2
Q4/Q8
Q2/Q6
Q1/Q5
Q3/Q7

Obtain the service manual (a quick search for the service manual should egt you to the Electrotanaya site which allows the download for free) and reference the above parts. Verify the voltage readings with those in the service manual.
 
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