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Old 8th August 2008, 11:48 AM   #1
joka22 is offline joka22  United Kingdom
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Default just scored kenwood ka-3750

I just bought a kenwood ka-3750 for 15 pounds delivery included in the price from ebay. However one channel is disorted i wonder how you sort this out maybe it caps or needs new transisters. should be delivered by tomorow. any one have servcie manual.
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Old 8th August 2008, 12:10 PM   #2
lineup is offline lineup  Sweden
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Kenwood KA-3750 .. for 15 brittish pounds

That is no bad buy, in my opinion.

The only thing I know about Kenwood,
is that they make/made some real good amplifiers for reasonable money.
you can do a lot worse than Kenwood, if thinking commercial amplifiers.

Unfprtunately my own Kenwood KA-7100 a very good machine!!!!,
has got one broken output transistor. (I made that shorcut blow out myself )
I will try fix that one.
And it will work well again
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Old 8th August 2008, 12:25 PM   #3
joka22 is offline joka22  United Kingdom
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Yeah i know i got a great buy. Time like this it costs 10 to 15 pounds to just have a good meal. So do you think it the transissters that is blown on one channel which why it sounds disorted still waiting to receive the amp then i can explain the problem accurately.

kenwood ka-3750
http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWN:IT&ih=015
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Old 8th August 2008, 12:35 PM   #4
joka22 is offline joka22  United Kingdom
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I remember next to my house there was this large building where on sundays car boot sales were held. I was 13 at the time, there used to be great old skool amps for cheap prices starting from 5 pound. I love pioneers but they seem to have gone dearer.
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Old 8th August 2008, 12:42 PM   #5
lineup is offline lineup  Sweden
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no
if some transistor is blown
there are worse things than distortion (like total silence )

I would start with check out Big Power Supply filter caps.
They may be too old to give any capacitance (at least enough for filtering).

Then I would see if the Volume Potentiometer (either channel) is worn out.
Somtimes can be a worn out carbon pot
that has bad contact surface for the wiper.

Switches can be worn out, with bad contact surfaces.
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Old 8th August 2008, 12:47 PM   #6
joka22 is offline joka22  United Kingdom
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Thanks for the input if the caps are bad on the power supply i will change them for alternatives obvoulsy same value. I got some ncie 80vdc 6800uf caps i wonder which ones will be in the kenwood. Switches are no problem i just re-solder the joints and if they still faulty i got some spare ones from a broken amp which yet to receive its new pcb the gainclone.
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Old 8th August 2008, 12:49 PM   #7
lineup is offline lineup  Sweden
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yes, you do these things.

another simple thing, maybe for a first inspection,
is the wiring

it takes only one bad wire .. or as you say .. one bad solder joint
to possibly cause distorted sound
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Old 8th August 2008, 01:55 PM   #8
joka22 is offline joka22  United Kingdom
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just recived my book from the postman - high power audio amplfiier construction manual by g.randy slone. he suggests 10 percent higher voltage for resovair caps than actual output of the power transformer rating for safety margin, most people use double voltage cap per rail than actual power transformer output. exmple per raild is 30 volts use 40 volt cap per rail recomneded by g slone. most people use double 30 volts power output and 60 volt caps. I think i finally learning something. sorry about spelling mistakes it's the keyboard layout.
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Old 9th August 2008, 07:18 AM   #9
big jim is offline big jim  England
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Hi i have the circuit email me for a copy.


all the best. jim.
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Old 9th August 2008, 07:24 AM   #10
lineup is offline lineup  Sweden
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Quote:
Originally posted by big jim
Hi i have the circuit
email me for a copy.
joka22 will be very happy, jim
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