Looking for some Hafler XL-600 Amp service/repair references

Hello all, I have a pair of Hafler XL-600's. After intermittently needing to warm up one of them recently stopped playing, it does power up but no output. Amps are bridged Mono. Any idea's for some troubleshooting and/or some repair references would be appreciated. Especially in the Colorado area, Colorado Springs. Thanks in advance!!
Call Rockford Corp and ask who was doing their Hafler warranty repairs, closest to you: 800-669-9899
Did you check the speaker output fuse ? I believe, in mono it is a 10 amp fast blow fuse that is recommended from the manual ( I owned these amps ).
There are also fuses on the driver boards(one each, at the top) and a, "Protective Relay", that can be visually observed, with regards to operation. Of course: if that relay’s not closing(or the fuses blew), there could be other, valid reasons. Are you experienced?
btw: If your speaker fuses are still good: you might try swapping the amps, between channels, before opening up the suspect. It’s possible that the problem is upstream. ie: No signal on that channel. Also: DC at the input, would keep the XL-600’s Protective Relay from closing.