Renovation of a Revox B77 mk II reel to reel recorder

On May 25, 2024, I purchased a reel-to-reel tape recorder, a second-hand Revox B77 mk II. It is the 2-track HS (High Speed) model, capable of reading magnetic tapes at a speed of 7.5 to 15 inches per second (ips). The recorder had not been used for several years, but was repaired in 2000. The person who sold it to me told me that it belonged to his father, a guitarist in a band in the Montpellier area in the 1980s, who had died some time before. The recorder was used for a long time (the heads are not yet at the end of their life, but they are beginning to be quite worn) and was in need of a major overhaul. It was the model I was looking for, albeit with NAB equalization (I would have preferred a CCIR model, but it can be modified) and the seller asked a reasonable price given the condition of the recorder.

This machine occupied my spare time for several weeks. I really enjoyed working on it as it is relaxing to be able to concentrate on such things. It is a nice recorder with relatively simple mechanics. Moreover, spare parts are fairly easy to source. However, their price is in line with the machine's reputation, which is highly valued by those interested in such things.... The electronic circuits are modular, easily accessible, and based mainly on discrete transistor amplifiers. There are very few components specific to these circuits, which makes the recorder easily repairable, provided you know how to get your hands on it. Overall, this is a solid, well-designed machine that is pleasant to repair and adjust. By the way, this page is not a detailed description of all the work I have done, just a list. Do not contact me to ask if I can repair your tape recorder; I do not offer technical assistance for this kind of thing.

For calibrations I used an oscilloscope for azimuth adjustment (which was already almost perfect) and a Nakamichi T-100 analyzer, which is very useful for this type of measurement. Today my Revox B77 is back in a state that allows me to use it to record my music (have you ever listened to the soundtrack I wrote for my game Silk Dust?). In the not too distant future, I will consider having the cartridges re-polished to their original profile. Unless I can find a set of Revox two-track recording and playback cartridges and in perfect condition at a good price.

The Revox B77 mk II is a very nice item. I tested it with a previously used magnetic tape and am waiting for a new tape. The recording and playback are excellent. There is some background noise and it is sensitive to tape deformation, especially at the speed of 15 inches per second (38 cm/s). I will mainly use it to record my own music. I produce digitally, but I like analog items, especially high-quality ones. I will probably try it as an echo and for loops.

While I did the calibration, I monitored the distortion at 400 Hz with the Nakamichi T-100. On brand new RTM LPR90 tape I could obtain a 0.25% THD+N for a signal at -5dB.

I was pleased to note that it is still possible to find all the necessary recording equipment (new tapes, NAB reels, etc.). However, this is quite an expensive world. Being able to maintain the machine myself and having a 3D printer, I can save on so many things, but the tape alone needed to record at 15 ips represents a small investment.

If you are interested, I described on a Mastodon thread part of the work I did on the machine. Do not hesitate to leave a comment if you wish to!