The M79 Logic Board is the 'brains' of your M79 recorder!

But these boards are very old now, after 30 to 40 years of service, and the logic comonents are usually in dire need of service or replacement!

The logic circuits that control your primary transport and other important machine functions, are made up of 'old technology' discrete analog transistors! This is NOT to say this older technology is 'bad' at all, but these dozens and dozens of transistor circuits need some good TLC to keep the M79's running in top form!

In our rebuild of the logic board, we remove all of the discrete transistors in the logic circuits and their associated resistors and capacitors and we replace them with new, updated parts.

This service is VERY thorough! Nearly every part of the logic board is replaced. The complete process takes over 60 hours, including auomated burn-in testing! So YES, it is expensive!

The transistors are replaced with NEW units that have better specs and higher reliability. The transistor bias resistor values are 'tweaked' to provide even better transistor logic switching reliabilty.

We also replace all of the trim pots on the logic board, which by now are usually very sloppy and hard to 'trim' to an exact resistance. much less HOLD a setting for any duration!

We also replace the drive transitiors in the Bias Oscillator circuit and 'tune' the Bias Frequency to exactly 234 KHz. We also update the Bias circuitry to allow for higher bias Voltage so you can use your M79 with more modern, higher level tapes.

We also add all of the Factory Recommended Modifications, if your Loic Board does not already include them..

We then thoroughly clean the logic board in an industrial ultrasonic cleaner and then we apply contact preservative to all edge connector contacts.

Next, the entire Logic Board is placed in our 100 degree F Hot-Room for 24 hours in a special test jig that cycles the Logic Board through ALL functions. Then after the 24 hour burn-in, we re-test the Logic Board again to make sure that all finctions are operating correctly before shipping it back to you.

We warranty your rebuilt logic board for 1 year, parts & labor (excluding misuse, user modifications, water, flood, liquid damage, powerline & lightning voltage surges, abusive environmental temperatures extreemes). Shipping charges, not included.

Once you have placed an order for this service, please send in your M79 Logic Board to us via insured UPS or Fed-Ex.

Be sure to DOUBLE BOX your shipment using plenty of packaging peanuts. And be sure to INSURE your shipment! GRS Systems is NOT responsible for damaged shipments and UPS and FED-EX will not pay damage claims on poorly packaged shipments!

We will let you know when we receive your Logic Board and we will give you an initial performance report on your Logic Board by email.