rpm gauge malfunction

[Barahona Alonso Francisco Javier <javier.barahona@aeasa.com>]

I have a repetitive problem with my rpm gauge. First time, after about 35
hours of working, at full power the indication started to oscillate reaching
even the maximum range. I decided to change de gauge and the problem
disappeared. After about 15 hours of flying the problem has been repeated
with the new gauge.

Has somebody any idea about what the problem is?

Thank you very much

Javier Barahona
Spain
(Classic 187)