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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
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7th Nov 2018, 11:53 am | #61 | |
Banned
Join Date: May 2018
Location: Norwich, Norfolk, UK.
Posts: 605
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Re: Revox A77 calibration.
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7th Nov 2018, 12:14 pm | #62 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Revox A77 calibration.
A known good test set is good for tape deck setups etc if you do a lot of them, back then the Ferrograph RTS2 was a popular choice, I see you are aiming for one of those, that's the type I used, you can just see the left hand end of one set into the bench panel in the photo, that was my old bench at Sony, the 'scope was nothing special (single trace B&K) shortly after the photo was taken I upgraded to a better spec dual trace job in preparation for Sony Betamax servicing as the Betamax had just been launched, needless to say there were scorch marks behind the two dummy load resistors shown in the photo.
Lawrence. |
7th Nov 2018, 12:19 pm | #63 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
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Re: Revox A77 calibration.
You can set up tape recorders with all sorts of instruments.
I prefer an oscilloscope as my first look at anything because it allows you to see everything that's going on. DVMs are more accurate on voltage, but can be misleading if something funny is going on and stuff usually winds up on my bench only if other people have failed to find problems. For setting up tape bias on 3-headed machines, I use an HP 3580A audio spectrum analyser. Set to slow sweeps and a wide resolution bandwidth the it's tracking generator is still within the analyser's bandwidth even after the tape delay and I have the luxury of looking at updating frequency response plots as I adjust. It's a new area to you and you're still finding your way around, so you may be best sticking carefully to the printed setup routines to start with and then getting more adventurous when you have a bit of spare time on a machine of your own. THose adjustment routines are usually well written and carefully thought out, they don't usually explain why some things are done the way they are, but the Sony ones suggested above make informative reading. Those adjustment procedures weren't handed down on tablets of stone, someone had to design them. Someone had to pick operating levels and bias levels by looking at the effects on flatness and on overall distortion and then pinning the tail on the donkey by picking a good compromise bias setting and planning out how someone in a service centre with limited test equipment can arrive at that level. David
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7th Nov 2018, 12:21 pm | #64 | ||
Banned
Join Date: May 2018
Location: Norwich, Norfolk, UK.
Posts: 605
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Re: Revox A77 calibration.
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Last edited by NorfolkDaveUK; 7th Nov 2018 at 12:35 pm. |
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7th Nov 2018, 2:06 pm | #65 |
Banned
Join Date: May 2018
Location: Norwich, Norfolk, UK.
Posts: 605
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Re: Revox A77 calibration.
BTW , these are all my machines , I have about 12 - 14 at the min . I dont do work for other people incase you got the impression I did , when I say "customer" i refer to the person that buys the machine when its all finished and I always let them have a good pl\ay with it before selling them and never had one back . I didnt want people to think I was taking money for doing shoddy work on other people machines . When I sell them I sell them as part calibrated and state clearly that I`m no expert just a hobbiest and the machine will more that likely need tweaking .
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