[RTTY] Alpha 89 question

[Fabi va2up]

Hi all,
since there is an ongoing trend on aplifiers I take the opportunity for shooting a question to the group out of the dark. 
I have 2x Alphas 89s and they have given me nice service for the time I have used them , I don't like nor do I see the need for running the amps over 1K, normally between 500-800W sometimes less. 
I have an intermittent problem that one of them developed last december. Without warning the amp will go on 'WAIT' mode as if he's trying to protect himself. After some head scratching I had beefed up the air debit of the auxilary fan and the problem went away. It came back though last weekend and we were unable to make it work for more than 5 minutes before it would again go into WAIT state. What happend then is that after sitting pretty for a day or two the amp starts working normally unless I use it without the aux blower on for a long period. 
Has anybody come across this before and/or any ideas from the amp gurus out there? Thanks.
 
73, 

Fabi  va2up
http://sites.google.com/site/va2upcontesting/