Kam amp repair

[Wayne Phillips]

Kam mixer type amplifier repair...

Blown output stage on right channel due to shorted bass speaker.

This amplifier was in a bit of a mess with protection relay holding off the left side channel, the owner over powered a 150w speaker at this years new years party and the smell off the bass diver well nasty.

Not much on the net regarding this amp so it was using the working channel to trace it out and use it has a voltage ref point.

Sometimes we come across amplifiers that need time spent tracing them over with out the circuit diagram to hand.

 

[kellys_eye]

Precise make/model?

 

[Wayne Phillips]

Precise make/model?

I will look over my notes and post...think it was a ka karaoke type with built in effects circuit..some of the ic's had there numbers scraped off..

Precise make/model?

Kka300 the model of this karaoke amp

 

[kellys_eye]

If this is a 'commercial repair' might I suggest it being beyond economic? Given the price of used equipment on Gumtree......

https://www.gumtree.com/p/audio-dj-...-pa-disco-karaoke-mixer-amplifier./1241523118

It will take upward of 2 hours to fix imho......

 

[Wayne Phillips]

Some folk's may not want to buy second hand units and instead want there equipment repaired.

I always look over an item to see if it's been looked at before as it can be a real pain if you have to spent to much time doing to many faults.

 

[kellys_eye]

I take it you're familiar with the standard repair/fault location methods for audio output stages? If so then the repair could be done in a couple of hours (maybe even 3) at whatever rate you charge but if your skills are lacking then a second hand unit may be useful for 'board swapping' - potentially a lot quicker and ultimately a 'guaranteed repair' with the bonus of having a box full of spares there after.

If a repair takes 2 hours at £50/hour and a 'swap out' takes 30 minutes plus £75 for the 'spares' the difference in cost is negligible and the repair is (almost) certain. Bonus spares too.

It's all in the maths. As I said, any other route may be 'beyond economic repair'....

 

[Wayne Phillips]

Hello thanks for your reply..

I've been in the electronics service and repair for many many years covering tv/video to pa system and valve audio design.

Most moden cheap audio like you say is pop it in the bin and buy new or second units.

Mmm even board changing can save time in order for quick turn around.

It does many me smile when folks watch on line video clips on you tube, and take the back of the family tv..

Most of us did not have such "how to do vids" when we did our training..

The only time my scope get's powered up is to trace them signal's.. you may do the same.

Helping newbies to the world of electronics can be interesting.

 

[kellys_eye]

I agree with helping newbies and showing them the pitfalls as well as the satisfaction of fixing something.

My own policy is to always 'have a go' - but then, I'm not constrained by financial needs so my time is (effectively) free which is something legit businesses can't discount and makes for the larger part of any fees charged.

Equally I'm more inclined to fix stuff that has some 'appeal' - black box stuff, not so much, but recent so-called vintage stuff, heck yeah. I don't fit with the modern disposable society either and try to buy with a view for genuine longevity - even if this means purchasing something that is 'old' to begin with.

But today it's all about the bottom line - and if the price isn't right then the job simply isn't worth doing. But that's all down to the customer.