Seeking help for Otari MTR12

[DavidChampoux]

bump

[Antony Scott]

Hi, I unfortunately do not own the machine MTR-12, but I have a MX-80 (and MX-5050). First you need to check the power transistors/drivers in the circuit of transport control, check the wiring and connectors (visually). Possible mechanical damage to the wiring. But it happens sooo rare. Look for a breaking or damage to any of power elements - transistors, resistors. This should bring you to start of the definition of the problem. But you need a schematic of your mashine and have experience repairing electronics. Then all you get.
Perhaps the reason of malfunction will found immediately. Or you may have to tinker a long time, to then "get on the trail."
Good luck!

[DavidChampoux]

Thanks for your message, I'll check the PSU thoroughly...

[DavidChampoux]

Finally been able to check my MTR12...

PSU is OK, all voltages read what they should. Cables and connections look fine.

Studying the schematics : I think the problem might be in the 'A - transport control' card. Once again, voltages are fine on the test point of this card. I cannot see any damaged parts on the pcb.

As a 10 amp fuse was blown, I suppose I 'should' see some parts with physical dammages? It's a lot of current!

Any hint please??

[Antony Scott]

Hi, you need to check all the power transistors and other semiconductor components on the board of the transport control. It is also need to do on the boards, which are connected with it. You may not see any damaged parts during visual inspection. Need to take a multimeter and check the power transistors for short circuit. Especially transistors, which are mounted on the radiator (heat sink). The fuse is 10A can not be damaged just due to the intervention of supernatural spirits.

[DavidChampoux]

More tests today...

Can't find any power transistor / regulator faulty anywhere in the +24/+30 volt circuit. Even on the boards that use these voltages. There's very few card/circuit using the +30, only Transport Control (A). If I understand the schematics correctly, it's used for solenoids and motors. +24 seems to be for external record sign only... I cannot understand WHAT could have made that fuse to blown, except a faulty card power input regulator, but they are all ok, and provide correct voltage to the specific card. Could it be a problem with some logic control that activates ALL solenoids/motors at the same time, that drains so much current that the fuse blown?

The problem happened when turning ON the machine. Last time I used it, it worked perfectly.

One more interesting thing: removing and re-inserting the card with the power still ON confirm that the motors are working. So is the capstan. Something's funny though: the capstan is ON or OFF independently from the tape sensor. (random state when I turn on the machine). That random state seems to be ordered by the MASTER CPU board cause if I remove it then re-insert it, the state changes randomly... Hope I'm clear... But, there's nothing on the master cpu board that is related to the +24/+30 rail, so I don't get why something faulty on that card could cause a blown fuse.

I'm about to drop this sh** and sell the machine in parts! There's a lot of parts in very good condition on this machine, I would definitely get more $ out of parts than out the complete recorder in its current un-working state...

So before I take my hammer, any other ideas????

[Antony Scott]

Try temporarily disconnect all solenoids and motors from the board. Replace damaged fuses with new ones. Then turn on the power. Without solenoids and motors. Look for damage fuses again.

Unfortunately, I have no schemes. And I have been unable to find them on the Internet. To at least some way to try to help you. Cannibalization for parts - too easy a way out. If the machine need for you as a "working tool" - you'll have to tinker, to repair it.

[DavidChampoux]

FIXED. Problem was with the B 'master cpu' board. Replaced the complete board, machine's runnin fine again now!!

[Antony Scott]

Great news, congratulations!

[DavidChampoux]

Thanks for your help man, let's keep analog tape alive!!!

[Antony Scott]

[Spiritworks]

Good news, thanks for the update. Keep the tape rollin'............

[Antony Scott]

Thank you, the tape is still alive in our hands!

[DavidChampoux]

Can't live without tape, even if it's just the smell of it!!!

[Antony Scott]

I love the smell of RMG 2'' after the morning coffee!