need Kenwood KA-990EX service manual

[tino96]

Hi, from some years i'm searchin' schematic or service manual of vintage Kenwood KA-990EX.
Someone can help me?
many tnx in advance
pc161368.jpg

[K-amps]

Thats an underrated amp... very tight bass for a small amp. Try and your hands on the KA-1100, 2200, 3300. (all 150wpc).

[tino96]

Originally posted by K-amps
Thats an underrated amp... very tight bass for a small amp. Try and your hands on the KA-1100, 2200, 3300. (all 150wpc).

yeah.. it's a very good amp, 10/20 W in pure A class and abiding 100 W. rms pc ...but without schematic or servce m..

p.s.
were I can take schematics of KA-1100, 2200, 3300?
bye

[K-amps]

Is the amp broken or what?

[tino96]

Originally posted by K-amps
Is the amp broken or what?

Hi K-amps, the amp is now broken...
tree times broken..
tree time repaired by technical centre of Kenwood, but make back same problem.

now I want replace the final stage with this...
(and I don't want give more € to Kenwood... )


http://users.swing.be/edwinpaij/ampli_mosfet_simple.htm


but I need schematic or service manual...

[K-amps]

That is one amp that is not good for mods. (I may be wrong but it has a DLD (class-H) output stage right?

Meaning if you replace it with another OP design, the existing heatsink will not be adequate.

Post a Picture of the heatsink and surrounding components and I can confirm if that is the case. I know all other Kenwoods of that era were class-H. i.e KA-880, 1100, 2200, 3300 etc.

[tino96]

Originally posted by K-amps
That is one amp that is not good for mods. (I may be wrong but it has a DLD (class-H) output stage right?

Meaning if you replace it with another OP design, the existing heatsink will not be adequate.

Post a Picture of the heatsink and surrounding components and I can confirm if that is the case. I know all other Kenwoods of that era were class-H. i.e KA-880, 1100, 2200, 3300 etc.

U'r wrong, it has 2 powerpacks, no PWM, no oscillators....
.......and very BIG heatsink .....

[Nigel Goodwin]

I've got a paper manual, it's a SERIOUSLY complicated design, the actual output devices are KAB01's, which includes four power transistors, two run off +/-35V, and two off +/-64V - they are fed in turn by two driver IC's, TA2030. The TA2030's are fed from what looks almost like a complete amplifier in itself (with 18 transistors), except the emitter resistors are 150 ohm, and outputs are taken off both emitters.

It's got a pretty nice spec though!

[K-amps]

Originally posted by tino96



U'r wrong, it has 2 powerpacks, no PWM, no oscillators....
.......and very BIG heatsink .....

Based on Nigel's details, Tino it seems YOU are wrong.

I may be no EE or expert but in terms of hours logged on these DLD Kenwoods, I have a bit.....


The TA2030's are class-H switchers, the dual rails also confirm it is like all other of the same era. They are used in the KA-880, 1100, 2200, 3300, M1, M1a, M1d.

I tried to rebuild an M2a (220wpc) making it a monoblock and removing the switching circuit (TA2031) . The amp lasted 15 beautiful minutes and the sinks were over 90C with very little bias I had used 16 2sa1943/ C5200's Thermal runaway was very quick. That heatsink is rated for class-H, not regular class-B.

The M2a had +/-91 and +/-56vdc rails and used the higher V rated TA-2031.

The KAB01's are like the Sanken DAT's the other models use. Paralleled trannies in once package to save space.

[tino96]

I have the amplifier... i'm not wrong...

this ampli is 25 years old....

how old are U?

p.s.

weight..... 13.9kg

do U've never seen a 100+100 w H-class amplifier??