I'm hoping someone can help me! I have a Kenwood KR-9600 with a pair of Pioneer speakers. Recently, there has been loud crackling and hissing noises coming from my speakers (usually just one speaker). This happens when there is no input and happens when each input is selected with the selector knob. Any ideas? Suggestions for a fix?
That's a very nice amp, top of the line Kenwood at the time. Definitely worth repairing.
Did this noise just start out of the blue, worked great one day and not the next, or has it been steadily worsening? Has the amp sat unused for any period of time?
I'd start by cleaning all of the controls. Use a cleaner/lube spray, you can get it at Radio Shack. Some brands are Caig DeOxit or Faderlube. Get one with a lube component, not just cleaner. You need to unplug the unit, take the cover off, and using the little straw that comes with the can of cleaner, squirt cleaner into each knob (bass/treble/balance/volume/speaker selector, input selector) and work the knob back and forth about 50 times. Each knob. Then do all the switches. Tape monitor, loudness, subsonic and high cut filters, speaker selectors, each and every switch. Switches that don't get used much (like tape monitor) are prone to oxidation. Crackling occurs as the signal arcs across the oxidized contacts and blows a tiny hole in the oxidation on the other side. The squirt stuff has to get INSIDE the switches and potentiometers behind the knobs where the contacts are... on a few occasions I've actually drilled a tiny hole in the casing if they are sealed. Soaking the outside won't do you any good. Let the amp dry at least 24 hours before you plug it back in.
I don't like the hissing aspect of the noise, noisy switches generally don't hiss. I'd be thinking about a transistor failing, either in the amp or pre-amp. The KR-9600 has pre-out, main-in jumpers on the back, correct? You can take them out and replace them with an RCA patch cord for testing... run the R pre-out to the L main-in and vice versa... does the crackling change channels? If so the problem is in the pre-amp, if not then the problem is in the power amp.
Post back with your results.
Dave
I had a similar problem with a Kenwood KR-V125R. The crackling was always at the same level, and persistent with all operation of the unit. I bought a service manual online. It turned out to be a waste of money because I solved the problem while waiting for the manual to come in the mail.
It was the 15V regulator (A rare type of 7815 that was obsolete (UPC78M15H), and ya the H was very important). I replaced it with a 3A variable voltage one and found that setting it at 15.2 V solved the crackling issue. I fixed it 2 years ago, and the unit is still working great.
I did find that someone had modified the receiver to get more power out if it. I got the proper parts and put it back factory spec. I had thought at one time that was the problem, but after I returned it to spec, the crackling was still there, until I did the regulator swap.
Hope this helps, and good luck with your receiver,
- Tim -
Matt Kissmann wrote in message news: snipped-for-privacy@d42g2000prb.googlegroups.com...
Maybe useful, from my repair briefs
Kenwood KR 9600 monster tuner amp from 1978, 2 x 200 watt Numerous problems due to corroded front panel switches. Intermittent loss of channel,crackles and loss of bass. To access remove wooden case by removing allen bolts from front and through case screws underneath. To slide of lay front face down on a couple of books and slide upwards. Absolutely full of dust settling through top slots. Crackly volume control removed and all switches. Remove bottom steel cover. To recondition vol pot remove final cover ,pull off wiper disk. On levering 4 tags to release next section beware of dedent ball near the 3 terminals. Ball mill in Dremmel to grind the swages back on the end of the Ali shaft to remove the dedent and wiper disk. The switches have to be desoldered from the board (cases not soldered to board) then prize away tags to get to corroded sliders to recondition. Mark the absence of any links that are absent although silk screen printed as present. Alps slide switches of that era had much stouter thickness of the cases so would probably crack the paxolin if forcibly prized off leaving the static lines of contacts soldered to the pcb. Used mole grips (lock -jaw pliers) fixed to front anchor points on each switch and desoldered each in tern with hot air gun . Mark 1 to 6 and 2 way or 3 way. One of the function panel lamps was out,not actually o/c. Bad construction bulb wires soldered to copper wire then touching pins (or maybe failed "spot welds") that are soldered to the pcb,whole covered in silicone rubber. Made proper solder joints after pulling off silicone . Covered stem of bulb (where it touches plastic surround) with PTFE tape. 50mA 7 to 8 Volt bulbs.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
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