Otari MTR 12 tech help?

Hi there,

My Otari MTR 12 has developed a strange little fault, i was hoping if some one here who knows these machines, perhaps i could email you?

thanks

best

Pete

Have some experience with the otari brand. What type of fault do you have?
AudioFixer ( at ) online.no

EDIT : cant get your email address to work so posted here..

really very good of you to respond,

well, the machine looks in very good condition, all works, records, plays and all sounds good, BUT,

There is a level fluctuation simultaneously every once and a while , for example,

with no tape loaded, using the on board Oscillator, monitoring the input, every now and again, the level jumps 2.5dB up then back down, some times it stays up, but mostly it jumps up and down, once every 5 minutes approx.

with a test (tone) tape loaded, it does the same thing but only jumps 1.5dB, again not very often but its definitely happening.

i have checked all the wiring on the back plane, re-seated all the cards but nothing i can do can make it happen, it just seems to happen on its own accord.

at first i thought it was a bias issue but its happening on the inputs with no tape loaded so now i'm confused a little, thinking it could be component problem, but remember it happens to both channels at once so it has to be common to both,

I look fwd to your reply,

all the best

Pete

[quote author="sinestaraudio"]
at first i thought it was a bias issue but its happening on the inputs with no tape loaded so now i'm confused a little, thinking it could be component problem, but remember it happens to both channels at once so it has to be common to both,[/quote]

hey Pete,

I'm not an anlog tape guru by any means but if it's common to both channels does that not suggest power supply issues? Have you measured the supply and scoped it? Depending on the design a fluctuating power supply might cause these level variations?

Cheers,
Ruairi

yes good good point, i did initially think this but discarded it after finding out that the boards have individual regulators, but i'm no expert either, perhaps it is this...

so ill check my voltages,

thanks for replying, all help is very much welcome..

best

Pete

Hi Audiofixer,

did more tests today, it seems only to happen when the 'REF FLUX' switch is set to 'HIGH' position. When switched to 'MED' or 'LOW' it doesn't happen,

this of course narrows it down, i would say to the AUDIO CONTROL BOARD, looking at the circuit diagram the 'ref flux' switch switches 15v on to three control lines (High,Med,Low) to the main Left and right audio boards.

i'm thinking perhaps its some thing in this switching control, there are a few resistors and capacitors which could be temperamental.

look fwd to what you think,

best

Pete

Do you have these problems when sending an external tone and checking both line and repro recording.. :wink: ?

Hi Audiofixer,

Yes i do.

what i'm going to do is take a look a the components around ref flux switch, i think this is where my problem lies..

unless any one has any mtr 10/12 spare cards lying around?

best

Pete