R/E/P > Bruno Putzeys (Designer) - Dave Hecht (Master Tech)

MCI JH-24 Not engaging recording



I have been reading here a lot, but not posting much. I have a session coming, the guys want to do the recording analog, on JH-24. Machine worked fine when last used (before the Corona).
Now it seems everything works, signals are coming thru, REW, FF Play Transport, Audio channels, all good! Machine is in excellent condition.

The problem is, it is not engaging the REC function. I can arm the tracks on the remote, however when I press the REC button on the machine or on the remote, REC light is not turning on and is not engaging the recording, nor the red lights on the channel meters.
My first thought was the Logic board, so I swapped bunch of IC's (IC6, the one after the rec switch, IC7 and all around,..) Checked all the diodes, they seem fine.  Then I re-soldered all the molex pins on the motherboard! 🤦‍♂️ Always stayed the same; no recording. After all this I ordered new logic board from MARA machines, again the same. Tested the Q1, Q2, Q3, and Q4 on the Interface/Lamp driver board with the meter in diode mode, they seem fine... I still have 2N2270 and 2N5783 replacement coming.

I'm kind of hitting the wall of my knowledge and experience with this machine maintenance. I'm sure there are guys who know this machine MUCH better!  (Oh boy, do I miss Steven Sadler in times like this! .. RIP)
Can you please kindly give me any hint as of where to look for a possible cause of the malfunction described above?


You normally hit rec and play in some sequence. Try holding down play and then hit record.


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