Disauda Posted March 12 Posted March 12 3 hours ago, brodricj said: My MC70 has been repaired. Total cost = zero. It was an effort in time to get it out of the rack and open it up. And a bit tricky to get the lid aligned with the holes in the chassis to button it up again. The key point here for MC owners is to use the HRAS diagnostic software tool. In this case HRAS said my +5V supply was good but the +12 and +72 A/B were not. This is an odd indication. With this fault all LYRUS modules will shut down. On inspection a broken +12V wire was found and this was entirely consistent with the HRAS diagnostics. Without the +12V supply you won't have the +72V, but you will have the 5V. That is great that your were able to fault locate on the unit!! It has invigorated me to setup HRAS and see what logs have been recorded on my amp! I know I know, should've done that first... It may well be this simple for my unit...
bob_m_54 Posted March 13 Posted March 13 On 12/03/2025 at 1:02 PM, brodricj said: I found the fault with my MC70. The +12V (red wire) solder joint attaching the power supply to the back plane was broken. Without +12V the +72V circuit will not be powered. This explains why there was +5V but not +12 and +72A/B. Easy fix. That's an odd way to attach the wires to the connector. Only relying on the solder, with no mechanical connection whatsoever. Be checking the other joints too, I reckon.
brodricj Posted March 13 Posted March 13 15 minutes ago, bob_m_54 said: That's an odd way to attach the wires to the connector... I thought the same thing. The power supply board outlet is the male half of a phoenix connector. The wiring harness has a phoenix female on the other end which attaches to the back plane. It really should have a phoenix female on both ends of the wiring harness instead of bare wire being soldered to the power supply board. It would make replacing the power supply easier. Anyway, I'm back in business with it. 1
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