K 8005 b - small output effect

The K4005b is suposed to put out 2x100W in 4 ohm speakers. Well, I do not get this effect because it cuts off before i reache anywhere near 2x100W. when it cuts, it goes away for a few secounds then tries to go back, but fails until I lower the input signal(s).

Ithink it is the current protection for the transistors wich switches off the IC for a few secounds. T1 and T2 cuts at ca 2A, but the motorola TIP142 / TIP147 can handle 10A. now, the fuses blow before 10A goes throug a transistor so can i bypass the current protection by either disconnecting ICpin 7,17,4,14 or connect 4,7 to suply - and 14,17 to suply+ ? Or can i do anything else to get the wanted 2x100W ?

It is not wise to bypass the protection circuit.
What is the impedance of your speakers?
What DC voltage do you have at the input of the amp?

I use a 2x 21V/7,1A 50Hz trafo which means 2x (21x sqare2) -1,2 = 2x 29,1V with 6,3Aslow fuses.
I have two 4ohm speakers.

(just like described in the spesifications pg.2 in users manual)

Most likely speaker impedance drops during operation.
Do your speakers feature piezo tweeters?
How did you determine that the unit does not put out 100W peak? Did you measure the output power? If yes, how?
Are capacitors C1 & C2 15pF ?

I have set an ampheremeter on the collector of T1 and T2. messuring peak 2,2A before it cuts each (4,4A of the 6,3A slow fuses) and i sat a normal ac voltmeter on my speaker terminals(in parallel with speakers) messuring around 3,5 - 4V when it cuts. Yes i belive the speakers can drop impedence (as here around 2ohms calculated). but sholdent i get ut to 3A intead of 2,2A ?

A classic amperemeter and voltmeter are too slow to measure the peaks during music playback.
You could use a generator and supply an e.g. sine wave of 100Hz for more accurate measurements.
If you do not have a generator, a small transforner (e.g. 3VAC secundary) and a potentiometer can do the job.

ok, that makes sense. But i checked the data sheet of TDA 7250, and its sa sound driver for 60W… and the example configuration uses the same resistor and capacitor values as the ones in K4005b… so is it maybe just supposed to go 60W throug it?