Though I have been a ROM, I am a new (registered) here.
I think the following information is helpful for you.
I own two 190E 2.3-16Vs. One of them that I have owned more than 10 years had a same problem. I opened the amplifier and found a crack at solder joint. So I fixed it but it was not enough for my amplifier. A lot of electrolysis condensers are used on the board of amp. That kind of condensers are usually exhausted in 7 to 15 years depend on the environment.
I changed all the electrolysis condensers that cost only $15. I think you can purchase that stuff at Radio Shake or like that. (Ifm not sure.)
My amp was fixed in that way. I hope it would help you. Good luck!