Thomann TA 2400 fault

[philly]

Hi All,

Just came across this site while looking for a schematic for a TA2400 power amp by Tomann.

My problem is that ch B is dead with the clip led constantly on. After inspection I discovered that two FET's ( IRFP 250 ) which I believe are part of a power boost or switching arrangement were faulty. I also found zener diode Z58 ( 15v) short circuit. I replaced all faulty components but I am still in trouble. The clip led now turns off, but the output relay to the speaker does not engage. Before I replaced the faulty components there was voltage on the output to the speaker so I presume that the protection circuit which drives the relay had kicked in. There is now zero volts at this point. The on-board green led does not illuminate either. All the o/p transistors have been removed and checked. All test OK.

Pulling my hair out.

Any suggestions.

[Brian]

Have a word with Blue Room member 'KevinE'.

[paulears]

Only just seen this and mine is exactly the same!!!

[philly]

Hi Guys,

Just got mine sorted yesterday. It gave me a bit of a run-a-round. After replacing the two faulty FET's I found zener 58 s/c. Replacing the faulty zener diode cleared the voltage which was present on the line out to the speaker, however the o/p relay remained in the o/c or protection mode. It seemed that the protection circuit which drives the relay was faulty also, ie (with on dc present on the speaker o/p it should trigger the relay). In the end it turned out to be 'led 10' which is located on the front panel was o/c and causing the speaker relay to remain in the o/c mode.

 

Hope this helps other forum users.

[paulears]

It will! Thanks