Haven’t posted in awhile and need to show a lot of work that has been done. The Kenwood KA-8006 had the remainder of it’s refurbish completed but there is still a short issue in the power supply. Originally the issue was the right channel was cut out and C9 on the power supply was blown which was easy to point a finger at seeing it is related. The two transistors on the power supply check out good and the resistors are in spec. Next, it is on to the diodes to make sure they are not shorted. Here is the schematic of the power supply and you can find C9 between the two transistors. This shows the use of a dim bulb tester in powering up vintage gear of unknown condition. I will show how a DBT works in another post, but there is a ton of info out there about them. Soon as the short is found this amp will be ready for testing and break in.
Im hoping you can help me, My father passed away recently and left me his sound system which is the one you refurbished, Kenwood KA 8006 Solid state stereo intergrated amplifier with matching speakers, My problem is that lately the sound becomes distorted then when i increase volume the sound becomes clear for a short while and then distorts again, have no idea what to do, I love this system and have loved the sound it gives since i was 11, please this would mean a great deal to me
thank you for your time
Hi Brendon,
Sorry to hear about your dad. I’m sure it would be great to get the Kenny running right again. There is many possibilities as to what is causing the problem your describing. Most distortion is caused by dirty controls or leaky transistors. The former being the easier to repair.
I would start by trying to clean all the control pots and switches including the switches on the rear of the receiver with Caig Deoxit D5 cleaner / lube. This is done by removing the bottom of the case to gain access, spray into the body of the pot, and working the control many times. Let dry for 20 min or so and then apply Caig Faderlube to the control pots. Both products can be purchased online or many music stores like guitar center.
Ultimately, your amp is about 35 years old, replacing all electrolytic capacitors would be a good idea before cap failure. If you need help feel free to post a reply or email me mike@hudsonvalleyhifi.com
Good luck!
Did you ever find the short in this Kenwood KA-8006? I have rebuilt the power supply, and both driver amp boards and it still will not come out of protection. I am using a DBT and it lights up bright when turned on but fades all the way out after a few seconds. There is no relay click. Any ideas? I put new transistors in Q1 and Q2 and two new resistors a 680 ohm and 820 ohm. Still does the same thing. No relay click. Diodes check OK. Any ideas?
Hi Davey, there actually was not a short. Someone rigged up a pair of resistors in series they thought would replace a higher value resistor which was not good. I replaced it with the proper resistor and it came right out of protection. I would replace the diodes regardless since diode testing is not always 100%. Do you know why it is in protection? High offset?