Calibration tapes,tools etc.....

  • Thread starter Thread starter j.harv
  • Start date Start date
Aplogies if I have mentioned this before but two factors cropped up when I re-visited this thread when it popped up in the Sats' newsletter.

"Rms" digital meters. Most of them are not, much, despite what it might say on the tin.
Yes, for mains frequency waveforms they give a good rms indication but for nolse or signals past about 400Hz do not trust them!

Then, mention was made of measurements ref 400 or 1000Hz? This interval is JUST where cheap (and not so cheap!) DMMs give dodgy readings. A meter might be "flat" ref 50Hz up to 400Hz (but some not even that) but be 3dB down or more at 1kHz.

If you have a decent sig genny check the DMM against that or use tone derived from a PC. You can also build a very flat, wideband analogue meter around a VU movement using 4xOA91 and a TL072. Easy peasy to incorporate a "0dbu" and +20dB gain switch, or whatever suits your kit.

Dave.
 
Well I have decided I really want this done right. And I have just located a local tech who specializes in vintage recording gear.
He's booked solid right now but I still have to get an MRL tape.He told me when I get the tape,he'll book me in.
I figured Im not gonna try and mess with the head alignment, I'm just not comfortable with that step,so I might as well get someone experienced to go over the whole thing.
So thanks to all who guided me through some of the steps and recommendations. Really appreciated.I was starting to really get into it,it was kinda fun.
Who knows, when I get this 388 back and set up in my little studio, I'll most likely start to tinker with my first 388 and try to dig in deeper with that one. I just want one that is running smoothly and set up pro,just for piece of mind.
 
j.harv said:
Well I have decided I really want this done right. And I have just located a local tech who specializes in vintage recording gear.
He's booked solid right now but I still have to get an MRL tape.He told me when I get the tape,he'll book me in.
I figured Im not gonna try and mess with the head alignment, I'm just not comfortable with that step,so I might as well get someone experienced to go over the whole thing.
So thanks to all who guided me through some of the steps and recommendations. Really appreciated.I was starting to really get into it,it was kinda fun.
Who knows, when I get this 388 back and set up in my little studio, I'll most likely start to tinker with my first 388 and try to dig in deeper with that one. I just want one that is running smoothly and set up pro,just for piece of mind.
Click to expand...

First job, after you get everything back bang on the money is to make some reference tone tapes that you can use on a daily or weekly basis to line up and check the machines.

Dave.
 
Offer to UK persons ONLY and also only those with some electronics skills.

I have a "spare" Levell microvoltmeter mod #TEG0128. It works ok but has a bit of a problem on the 500mV switch position, could just want a spray! The large, sexy meter is calibrated in dBu and volts and the unit is the dog's danglers for tape line up. You will find it easily on Google along with a schematic.
Free to a good home.

http://www.vintage-radio.net/forum/attachment.php?attachmentid=28304&d=1251469455
Dave.
 
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