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Roberts Electronics 770X

Three-Speed Reel to Reel Tape Recorder

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Roberts Electronics 770X


The Roberts 770X uses a cross-field bias technique for recording, which results in extended high frequency performance.

Features include two separate amplifier units resulting in easy identification of channel controls, built in monitor speakers with on/off switch, the recording light is driven from the erase circuits, very positive lock-out to prevent accidental recording, sound on sound facility; dubbing from left to right, pause button which may be locked in either run or pause mode, and a tape tension idler with built in cleaning pad.

In addition, the end of tape can be set to either automatically stop the mechanism or turn off the entire machine.


Track system: 4-track, 2-channel, stereo/monaural system

Heads: 1 x playback/record, 1 x erase, 1 x bias

Motor: 2 speed hysteresis synchronous

Equalization: NARTB

Tape speeds: 1 78  3 34  7 12 ips

Wow and flutter: 0.15% (7 12 ips)

Frequency response: 40Hz to 20kHz (7 12 ips)

Signal to Noise Ratio: 45dB

Total harmonic distortion: 3%

Output power: 6 watts

Speakers: 2 x 4"

Valve complement: 2 x EF86, 1 x 12AD7, 2 x 12AX7, 2 x 6X4, 1 x 6AR5

Dimensions: 20 x 14 x 9 inches

Weight: 48lbs

Note: optional 15 ips conversion kit



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Reviewed Jan 06th, 2020 by

The Roberts 770X is the same RTR deck as the AKAI M-8 (both the internals and front user controls). The only difference is that the 770X's power chord stores differently on the back panel outside the deck where the AKAI M-8 has a side of case power plug storage compartment with a stainless closing clasp. The only other difference is that the 2 x 4 output Speaker placement on the 770X is on either sides of the deck(left and right sides). The output speakers on the Akai M-8 are both on top of the decks cabinet if standing upright. Note : there needs to be a correction to the entry on Hifi engine for the tube complement which should read for Roberts 770X: Tube complement (all tubes made by NEC and Masushita)
2 x EF86/6267, 1 x 12AD7, 2 x 6BQ5/EL84 , 2 x 6X4, 1 x 6AR5 (The left channel preAmp contains 5 tubes and the Right channel 4 tubes (as there is only one 6AR5 tube). Both of these decks are very reliable and where actually modeled very similar to the commercial professional Ampex 600/601 model.



re: 770X

I recently acquired a 770X in pristine condition, however upon further investigation have found that the play/record cam has simply disintegrated. It looks like it was made out of compressed powder, and simply crumbled. Does anyone have a spare they'd part with, or know of a source for one. Alternately, does anyone have a drawing for the part, or even a part that shows what it's supposed to look like. Any help would be greatly appreciated.

re: 770X

I am restoring my 770x ,looking for any parts or whole units not working.

re: 770X

I've got one out of the duct bin. Looks like amps and all working but play cam gone. Replaced it this afternoon. but while I was putting it back together a small spring fell out. Have no idea where this goes. Looking for a service manual that might shed some light.

re: 770X

I don't know if you are still working on this project, but I am also restoring a 770x and I have a couple of other Rheem/Roberts RTR recorders (lower models with similar construction) I've been using for parts. Let me know if you're looking for anything in particular and I can tell you if I have it to spare.

Fritz23's picture

re: 770X

I'm about to get into mine. I was wondering if you could give me any tips. Thanks
Scott in Cincinnati
Are there belts in these??

re: 770X

I have one in good shape but of course the forward play cam is toast!

Roberts 770X ready for the scrap heap

Dug my 770X out of the closet this morning to try and dub an old reel-to-reel tape. Waited too long: Belts are probably too old and capstan/pinch roller no longer meet to drive the tape.

Was going to consign the deck to the trash men next week, decided to Google it, and found this web site.

The last time I powered up the recorder was probably 10 years ago; everything worked at that time. Based on this, I assume the electronics are still OK, but the mechanics would need work to make it functional again.

If anyone is interested in the deck, please send me an e-mail. If someone is willing to cover the cost of shipping, I'd consider sending it to you. May not be cheap; we know this things weigh 50 lbs!

Would rather NOT attempt to part this out as it's not obvious how to dissemble it (and this isn't my area of expertise). As you know this is OLD technology; no easily removed modules, circuitry is point-to-point wiring (haven't seen this since the 60's), and the case is made out of wood (wood!).


re: Roberts 770X ready for the scrap heap

I am interested in your roberts reel to reel. I live in selah, washinton. thanks, Paul

re: 770X

I recently acquired a used 770x. It plays great but I can't get it to record on either channel. The record indicator light comes on but there is no response on the vu meters. Microphones have been tested and they do work. Have the same problem with the line-in
jacks. Any suggestions?

re: 770X

Have you cleaned the two slide switches that switch the amplifier from play to record? Also, you may need to replace some capacitors in your Roberts.

I love these machines.


Does anybody know where I can get various knobs for this unit. I have a Roberts 770x and I am missing the play/record, FF and rewind switch and 2 volume and 1 tone knob.

re: 770X

The pot metal around the pot metal portion of the start switch of my 770x has deteriorated. Does anyone have one? A parts list? a service manuel?
Thanx David Lynch

re: 770X

I have the same problem. I just joined this group this morning so I am a newbe.

Roberts 770X Capstan Bushing

Finally, after many years obtained a 770X. I love it, but have to find the capstan bushing to play 7 1/2 speed. So far, I can only locate a new one for $42.00. Any other ideas? I could rough out the dimensions, and take to a machine shop, but that's a bit hazy. Many thanks.

Play and Rewind SLOW DOWN after Approx. 15 Minutes

I just received a used Roberts 770X Reel to Reel Recorder.

When I test the machine, PLAY and REWIND both function very well until machine has been powered "ON" for approx. 15 Minutes.

Around the 15 minute mark, there is a "beep, beep, beep beep beep" noise in the speaker and the PLAY Slows Down and the REWIND pretty much stops -- however the reels move freely so I can "hand rewind".

With this "beep, beep, beep beep beep" noise and the 15 minutes of "heating up time"...I'm wondering if this is a simple matter of lubrication or bad fuse, etc.

Thanks for your help! I really look forward to recording with my new, used Roberts 770X.

re: Play and Rewind SLOW DOWN after Approx. 15 Minutes

I know this is an old stream, but I just got my old Roberts out of the closet and the same thing is happening, minus the beeps. I suspect all the caps in the thing need to be replaced, but wonder if there was any information on this line to the earlier problem?


The ROBERTS "CROSS FIELD HEAD" were designed by AMPEX, manufactured in Japan and to be sold in the
U.S.A. as Ampex units.
Negotiations fell thru, thereby the units manufactured in Japan and sold under the ROBERTS name.

Roberts Crossfield models

Actually Roberts were Akais, not Ampexes. Each Roberts model had an identical Akai counterpart. The USA still had a bit of an 'anti-Japanese' (remember Pearl Harbour?) sentiment in the early 1960s and as the brand-name 'Akai' looked and sounded a bit Japanese, it was decided to license and re-badge to a more 'American' sounding comany. See attached comparison of a sampling of 1960s models...

re: Roberts Crossfield models

Essentially - semi-correct.

Roberts approached Akai with their own recorder designs looking for a manufacturer. If Akai would manufacture the designs Roberts retained the profits for units sold in the USA under the Roberts name, while Akai got the profits from the non USA market sold with Akai branding. That relationship continued into the early 1970's, at which point Akai decided to enter the USA market under their own brand name. While it lasted it was a collaborative relationship, but it was initiated by Roberts with Roberts designed machines - not the other way around.

re: Roberts Crossfield models

I have a akai M8 and today bought a 770X Roberts are not only similar, are identical!


Very much appreciated your comments -now, able to understand the "looks" similarity of these two brands which are one. Think I half- procured this unit because of staring for years, at an old ad I have with gorgeous Julie London sitting in front of her "Roberts". Yes, I remember Pearl Harbor, and the scrap metal & rubber drives my Dad and Uncle carried out. Also, gas and meat ration booklets.

Roberts 770X

Believe it or not I am trying to find the switch that enables the external speakers to play. Help!

owner's manual Roberts 770X

I am looking for an owner's manual for a Roberts 770X

re: owner's manual Roberts 770X

I have the manual that came with my 770X but, also have the 770X still working very well but, you can have a copy I am in Canada

Roberts 770X manual

Hello..I have a original owners manual for this. Do you want it?

george parker's picture

re: Roberts 770X manual

Hello, I also want a manual, schematic for my Akai M7 or M8 reel to reel tape recorder with a Roberts mono block amplifiers. Please advise. geo

Roberts 770 X SS

I'm looking for a Service Manual for this model so I can learn how to take it apart & repair it. Also need the following parts:
Belts. Motor & Capacitor. Any help would be appreciated

re: Roberts 770 X SS

I am searching for the same, if I have any luck finding a service or repair manual I will let you know. I have the original Operators Manual for the 770 x. Let me know if you want a copy.

This website is not affiliated with or sponsored by Roberts Electronics. To purchase 770X spares or accessories, please contact the company via their website or visit an authorised retailer.