Hello. I have a amplifier K4005B and i’m testing it on power supply 2x 21VAC. I don’t know what is wrong with it. The amplifier is working normaly but when i put on the input 40mV/100Hz i get on the output/speaker (bridged) 15mV/100Hz something like that. But when i change the input frequency to 1KHz/40mV on the output i get normaly amplified signal. The amplifier is going like high pass filter. I don’ know what should be wrong. I checked my work but it is OK. I mesured IC1 (TL072) and the signal is OK. On IC2 (TDA7250) is like high pass filter. Can you please help me…?
Most likely a wrong capacitor value.
Check you assembly.
I’ve rechecked all capacitors, TDA7250, TL072CP, 2x TIP147, 2x TIP142 and they are working correctly. On the input of the TDA7250 is the signal OK but on the output there is a problem (high pass filter…). I’ve changed the TDA7250 but i still have this problem. What can be possible wrong?
Sorry, we do not have experience with this problem.
Maybe there is an interruption somewhere, which acts as a parasitic capacitor?
If you want, you can return your unit for inspection/repair to:
Velleman Projects Tech Dept.
Legen Heirweg 33
9890 Gavere
Belgium
or return it to your Velleman distributor.
How many days do i have to wait to get it back? I have a serious problem because this amplifier is my school project and it must work in the next week…
Turnaround time is usually 1-2 weeks.
Today i have tested the K4005B and put it on stereo 2x 8ohm on 2x 30V and the amplifier worked normaly. Then i put it on bridged 1x 16ohm 2x 30V and it was working normaly. So i decided to test it bridged 1x 8ohm on 2x 30V and the amplifier was working normaly. In assembly manual there was a specification that the K4005B on 1x 8ohm must be connected to 2x 21V. But on 2x 21V was not working right but only on higher voltage 2x 30V. Is this ok? I tested the amplifier on two (2) power supplyes 30V and 30V. Could this destroy the amplifier or it is ok that the amplifier is connected to 2x 30V when he is on bridge 1x 8ohm?
Supply voltage for mono: 25 to 30VDC.
These specs can also be found in the manual.