Revox A77 issue

  • Thread starter Thread starter kip4
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kip4

kip4

Well-known member
The Left channel doesnt have anything like the high freqauncy response that the right one does and the left channel has more hiss too
What can this be?
Can it be fixed?
 
How are you testing it? Playing back an existing tape, or recording a new one? I'm not sure if the A77 has a way to play back from the record head, which would be handy to diagnose problems like this. If you can make it do a direct monitor, does it have the same problem just passing the signal through without any record or playback involved?

If it is a record/playback issue, it could be a number of things. You can try to establish where it's a recording issue by playing a test tape and seeing whether that has the same problem (demag the deck first to avoid damaging the test tape!)
I think you also had a Fostex R8 or something, didn't you? If you don't have a test tape it might be worth putting a recording from that through the machine at a pinch... just to get a rough idea.

Things which may be causing this:
1. Bad capacitors in the audio path
2. Electronics way out of calibration (bias?)
3. Heads out of alignment
 
You can prove whether it is headwear or electronics by making a stereo recording at say 10kHz* at about neg 10 and then flipping the tape inside out.
Naturally the level will drop drastically but the L/R relationship will be preserved.

*I hope you Analogue Only boys do not eschew computers completely because you can generate some very handy test signals in almost any DAW software. Audacity does "coloured" noise but the meters are poor. Magix Samplitude Silver is free, does the tones and has very good meters.

I anyone is ever really stuck, if they send me a few mtrs of tape I could make a test tape (of sorts!) on my Teac A3440 deck.

Dave.
 
Audacity is good for generating signals, but getting them to actually stay at -10 on both channels can be a problem, depending on the soundcard.
 
jpmorris said:
Audacity is good for generating signals, but getting them to actually stay at -10 on both channels can be a problem, depending on the soundcard.
Click to expand...
Can it? I always use Samplitude 8se, now Sam Silver for tones and my M-A2496 is rock solid (but I also have a nice wee Levell oscillator).

BTW Kip. I have a 10 pin remote plug for a 77. PM me if it of any use to you. I have been searching 'web for over a year for the 12pin rectangular jobbie for my Teac. I am presently using panel pins as a kludge!

Dave.
 
ecc83 said:
Can it? I always use Samplitude 8se, now Sam Silver for tones and my M-A2496 is rock solid (but I also have a nice wee Levell oscillator).
Click to expand...

I probably didn't leave things long enough to warm up first. Even so, it's no fun to finish lining up the input amps on an 8-track machine and discover that the reference voltage generated by the computer has been gradually increasing for each one.
 
jpmorris said:
I probably didn't leave things long enough to warm up first. Even so, it's no fun to finish lining up the input amps on an 8-track machine and discover that the reference voltage generated by the computer has been gradually increasing for each one.
Click to expand...
Oooo! Nasty!

I shall check that out with a stone cold P4 XP desktop and a W7/64bit lappy with a DVM in the morning.

I have discoverd that you cannot trust software temperature readouts. Makes you wonder what you CAN bloody trust!

Dave.
 
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