Hello,
So I have a trio kenwood ka6004 amplifier, but no left channel. However, when i switch off or power down the left channel prouduces sound then fades away. Why and how to fix please
So I have a trio kenwood ka6004 amplifier, but no left channel. However, when i switch off or power down the left channel prouduces sound then fades away. Why and how to fix please
All I can do is give your thread a bump and point you towards a service manual: https://archive.org/details/manual_KA6004_CD_KENWOOD_EN
You can zoom in to the schematic to your heart's content, bazza, while you wait for an amplifier repair expert to chime in!
You can zoom in to the schematic to your heart's content, bazza, while you wait for an amplifier repair expert to chime in!
Could be the output relay RL1. There are also other speaker switches after the relay.
Try cleaning all contacts on these.
Try cleaning all contacts on these.
Thanks, I've been zooming in and out of the service manual all day...one thing is bothering me is that previously someone took the relay out so with 2 cables there is fuses spliced in and a 3rd loose cable that I can't find anywhere, must have fell out!!!
Dunno, just mite sell it instead, I have the ka8004 and 4004. Hoarding!@@
Dunno, just mite sell it instead, I have the ka8004 and 4004. Hoarding!@@
Cleaned the switches and still nothing. But why when I switch off do I get sound from the left fading out? I've wriggled all the switches and knobs, gave it a shake and still nothing...
Can you use a scope to check for signal before the relay contacts?
While you are in there, also check the 0.47 ohm resistors for value.
While you are in there, also check the 0.47 ohm resistors for value.
Sorry Rayma I don't have such tools. Do have a multimeter so I can check the resistors bit where are they?
So when you switch it off with music playing, you don't just hear a thump, but you hear music from the left channel for a second or two?
Hypothesis: maybe some defect in the left channel messes up the bias point somewhere along the signal path to such an extent that there is no signal coming through anymore. At switch off, all DC bias voltages change and it temporarily passes through a bias point where it is functional.
If any of this is true, you should be able to find a big difference between the left and right bias points (with everything on) when you compare the output DC voltages of the various stages.
Emitter voltages Qd6 and Qd5: both about 23 V?
Emitter voltages Qi1 and Qi2: both about 29 V?
Collector voltages Qi3 and Qi4: both about 17 V?
Collector voltages Qs1 and Qs2: both about 12 V?
Emitter voltages Qu1 and Qu2 about the same?
DC voltages at the left and right loudspeaker outputs both close to zero?
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MarceldvG has good points to check.
Also - try to divide and conquer the circuits a bit. Check if both Left and Right are present on the pre-out jacks.
Also check if both channels are available on the headphone Jack.
Also - try to divide and conquer the circuits a bit. Check if both Left and Right are present on the pre-out jacks.
Also check if both channels are available on the headphone Jack.
Or you could take it out of the case to access the printed circuit board and look for cold solder joints and remake them. One possibility is there is a cold solder joint in the negative feedback circuit where there is arm that decouples the signal to ground. This consists of a resistor in series with a capacitor. If there is a cold solder joint at that point such that there is no connection to ground the closed loop gain of the amplifier will reduce to one.
have not looked at this circuit however I repaired a Kenwood amplifier a few years ago which had a circuit that used a turn on delay that produced a loud hum at switch on in one channel. There were no relays in this amplifier these are dearer to buy than a handful of transistors. I did take the trouble to lubricate all moving part connections.
Re the fuses in the pictures these should be housed in proper housing. One should not solder wires onto the ends of fuses as these rely on heat to blow the solder looks messy . You could well have a colder joint with one of the fuses. This looks like a DIY fix that doesn't work. You should buy proper fuse holders to make replacing these if they blow. You can solder the holder without the fuses in place and fit them when the solder sets