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Messages - Detech

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1
Tape Tech / Otari MX 7300 Schematic
« on: March 19, 2017, 07:46:45 PM »
Have been asked to look at MX 7300 Otari.
Even though the owner has a manual, it's missing schematics for Transport cards .and interconnect.

Am happy to pay for any costs if required .

Des

2
Tape Tech / Studer A807, A happy ending
« on: March 15, 2017, 09:14:18 AM »
Dear Ki and Tape Project Forum,

Thanks for help with my 2 dead Studer A807's
Got one of them going, after finding another 3 faults on cpu board.
But the other machine will have to be put away for the moment.
Strange addressing faults . Starts in rew most of the time. Will not go into play, even via RS232 and causes 38Khz noise in repro and sync playback.
Was required for archival capture at 96Khz. So Captures were being rejected.

But I'm very happy all the same.

Best regards,
Des



3
Hi Tom.
In  brief, if you wish to set to original playback level.
adjust replay level to Approx +3 vu.
However that standard is the original Ampex operating level.
Dating back to the early 1960's.
Tape stock improved greatly over the years.
In the last days of professional recording always being done on tape.
Ampex and other manufactures produced tape stock that could record at operating level 9 db above "Ampex"spec'
And still maintenance same distortion figures, but increasing signal to noise level to a point to compete with Digital recorders .
For machines like B77 , pr 99 etc . They should be able to operate  at 250 nW at 7.5 i.p.s.
Problem will be record drive and or Head saturation in record. So you loose front end on any sudden transient.
I use to have to do the calculation to convert test tape level to desired operational level all the time.
You can calculate the db difference in the same manner you calculate the difference in voltage.
20 log (Flux ratio)
20 x log(185/250) =2.61db.
I think I would be trying to get machine to record at 250 nW/m if I was in your situation.
Just one question, if you play back the test note, adjusted back to 0 VU, is it distorted ?
I think I had some machines, that the replay head would distort, in my case 320 nW/m .
I  that case for me, the tape machine was not suitable for the task required.
For you, just go back to manufacturer spec.

I hope that help somewhat.
Des

4
Tape Tech / Studer A807 software
« on: February 23, 2017, 06:36:00 PM »
I know this issue has come up in the past on this forum,
But can anyone help me by providing bin files for eproms for A807 version 40/87.
It is ic 15 that programmer tells me is faulty.
Can do hardware changes to go to another revision is available.
All the Best
D

5
AnalogRules.com have a reasonable copy for 8 track.
can be cleaned up in Gimp.
But change resolution to 200 to 300 dpi when importing pages.
Then you can adjust the contrast of the image to allow you to read.
Otari tape machine manuals were always always horrible to read from the start.
Use to have to make photo copies and write notes on them all the time.
D

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