Revox A77 Calibration - Restoring an EPIC tape delay!

In today's session, Ken 'hiwatt' Marshall walks us through the calibration of a Revox A77. This is old school engineering...from demagnetizing, to bias traps, is there anything more awesome than magnetic TAPE?!?

[@pc_panic]

"we're gonna follow a pretty old-school concept. we're gonna read the manual" the delivery of that was so perfect

[@twitch451]

From Ken's lips to our ears "old school concept, RTFM" Live and learn kiddies! Thanks Ken! ;)

[@neveser]

I feel like I've just sat through an advanced course in electromagnetics and tape delay restoration. Great video Ken! Glad to see it all came together. Can't wait to hear this baby in action!!!

[@Mr666Flake]

Ken, thanks for all you’re Videos, it’s so inspiring and educational. I’m a huge fan of all you’re works, so this is a blessing for the Fans, thank you!

[@TheAmazingSnarf]

Thanks for this, Ken! I'll be using your methodology with my own tape deck, when the time comes for the re-cap and refit. until then, I'm in love with the way it sounds now as a primary recording destination. the kind of procedural focus just sits well with my process. cheers!

[@thereal696969]

This is awesome, thank you! Very jealous of your varispeed mod.

[@Dthebeatsmith]

This is so awesome, thanks for sharing your methodology for aligning the A77! I have one that I just recapped and did the Abbey road mod to. I had a bit a difficulty following the Revox service manual but you cleared some points up for me. I definitely need to get a 7.5ips tape (only have a 15ips IEC tape for another machine). My brake drums need work as well as the cloth has hardened from the adhesive I think.

[@alhug7191]

love everything about this

[@soysos.tuffsound]

I haven't de-maged a tape machine in many many many many many many many many many many many many many many many many many many many many many years!

[@keithmoriyama5421]

Demagnetizing doesn't just accumulate over time. I had a badly magnetized Sony 4 track caused by being placed too close to a JBL studio monitor.

[@hiwattmarshall]

Such great wisdom here @keithmoriyama5421 thanks for sharing 🙏🏻🤟🏻. I'm curious if you were able to archive the material on that tape?!? Different situation, but another great example of how susceptible magnetic tape can be... At Mushroom Studios, we once had a multitrack tape (copy) damaged while crossing the border...the agent insisted on an extended x-ray examination, and when the tape reached it's destination, it was really messed up...all kinds of weird phasing, and wow like half the tape was erased! Thank goodness it was a working copy 😬🙏🏻 Have a great week Keith, stay safe my friend 🙏🏻🤟🏻 -hw

[@joeltaylor2830]

This is a really great resource. Do you find the tape echo is still worth the effort sound and control-wise? I know you like the PCMs for digital, but is it worth the extra mile - in your opinion - to run some tracks through that tape machine you've used for years? I'm fixing up some less desirable Akai 4000D reel-to-reels to bounce to and tape delay and have a Korg 'Stage Echo' - this is really a great resource for anyone working on tape machines. Thanks.

[@tobitweaks]

amazing

[@bkj242]

What about the phase adjustment (fine azimuth). Missed that one.

[@JamesE707]

Good video Ken, I like it! Personally, I prefer the oscilloscope method for azimuth adjustment, but I understand you haven't got all the equipment with you there. I am currently restoring my late 1971 MKIII A77 which I've had since 1979, which was my brother's back in early 1972. Regards.

[@garyspencer1711]

Yes, absolutely. I've had many R2R Decks starting in late '73 with a new Sony TC-780 (ferrite heads). Then, in '82, I purchased a used Sony TC-730 with permalloy heads (1972 model). Lastly, I purchased a used Sony TC-755 with ferrite heads to repair & refurbish (1974 model). Both the 780 and 755 were in mint condition except for minor problems. Azimuth checks and adjustments REQUIRE a 2 channel scope. To debug and detect failure modes in millivolt level signal path in playback pre-amp, you need scope with 10Meg probes so that you don't load down any circuit node(s). I love working on Sony consumer R2R decks. This winter, my next project is to add InfraRed Remote Control for my TC-755. Very easy to do with Raspberry Pi cpu and a few low current relays to "latch" each button-press. Regards, G.S.

[@quangmi3402]

Hello! I'm calibrating for B77. I'm stuck on step 6.4.4 : "Testing the mixing facility with a single channel feed". I have installed the function buttons according to the correct SM, but when controlling them, the VU B77 does not operate according to the instructions. Hope you have some advice and point out which step I might be wrong?

[@JamesE707]

Looks like you got a MKIV version there? If I'm not mistaken, re-lapping the heads is not recommended - they are designed to be worn down to it limits, but I could be wrong?

[@mickynoise]

Great video. is this laquer a nail polish?

[@eduardoandreoli3118]

how often shall you calibrate it?

[@fickfehler3866]

Those MRL's are very pricey indeed. Is it possible to perform this calibration without a test tape ? If a 10kHz signal is fed into it, can the record head azimuth be adjusted 1st and then the playback head azimuth ?

[@miss.wright3035]

Had an opportunity to buy an A77 MK iv for $275 USD with a bunch of original plastic real Revox tapes. Turned it down because it's just not worth the hassle.

[@garyspencer1711]

I agree. Tape deck repair and restoration is a WINTER project. If you don't have test equipment and good soldering skills, there is no point in wasting money on this type of antique apparatus. The price of $275 is a great price ONLY, ONLY, if the unit did not have any scratches, corrosion, dents, or stains. I cannot bring myself to refurbish ANY piece of audio gear if it looks like a Piece-Of-Schitt. The old reels of tape are worthless !!!! Old reel-to-reel tape deteriorates quickly after 25 yrs (Maxell, TDK, Ampex, Sony, BASF, and Scotch). You did the right thing !