Building VU Meter Bridge - Please Help

[djnmonte]

Hi,

I am building a VU meter bridge for my Sound Workshop Logex 8 console out of the meter panel from an Otari MTR 90 mkII. The challenge i am faced with is trying to figure out what the supply voltages were to the circuit boards that drive the VU meters in the MTR90. i have searched hi and low for the MTR90 schematics and have had no luck. Does anyone here have these schematics or have a line on where i might be able to acquire them? if not does anyone know what the supply volatges were for the MTR 90's meter panel. The MTR90 had 3 rows of 8 meters. Each row of meters had one long circuit board associated with it. There were six power lines that came into each circuit board. Two of the power lines fed the voltage regulators, so i looked up the part numbers and figured out that the regulators need +23V and -23V. Another 2 wires were to power the meter lamps, i haven't been able to figure out what this voltage should be yet. The last two wires i havent' been able to figure out anything yet, at first i thought they were to power the record lights but i'm not so sure now.

Any help anyone can give me on this would be greatly appreciated. If i can't get my hands on the schematics how would others here at gearslutz go about figuring out the voltages?

Thanks Guys

Nick

[JohnRoberts]

VU lamps are generally 12V. But you may want to confirm with a variable supply.

JR

[KingDaddyO]

You might try pulling a lamp or two and see if the voltage is stamped on the casing. The supply is probably of a serial design, meaning that the voltage is static but the current draw is where you need to provide more than enough capacity.

There are often any number of service documents available on eBay, for all types of devices:

otari mtr90 service manual - Google Search

[djnmonte]

i was finally able to track down the schematics.

i need + and - 20V for the voltage regualtors which feed + and - 15V to the meter drivers.. i also need 6V and 0V AC for the lamps (they are 8V lamps that otari purposely under powers).

it was suggested that i could add a resistor inline with each meter and run the lamps off a DC supply. can any suggest how i would go about building/configuring a power supply to suit my needs. i looked into triple output 'power-one' power supplies but the highest they go up to is 15V. should i just bypass the regulators and send a regulated + and - 15 volts directly to the circuit board? sorry for all the dumb newbie questions.

nick

[KingDaddyO]

Originally Posted by djnmonte

i was finally able to track down the schematics.

i need + and - 20V for the voltage regualtors which feed + and - 15V to the meter drivers.. i also need 6V and 0V AC for the lamps (they are 8V lamps that otari purposely under powers).

it was suggested that i could add a resistor inline with each meter and run the lamps off a DC supply. can any suggest how i would go about building/configuring a power supply to suit my needs. i looked into triple output 'power-one' power supplies but the highest they go up to is 15V. should i just bypass the regulators and send a regulated + and - 15 volts directly to the circuit board? sorry for all the dumb newbie questions.

nick

Good luck finding them 0V replacement bulbs. I tried once but m' still searching.

[djnmonte]

funny