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Roberts 778X

Integrated Cartridge and Reel Recorder

Roberts 778X

Description

The model 778X employs the 8-track stereo system on the cartridge. The tape has a total of eight tracks, two of which are used at a time for stereophonic recording or playback. There are four choices of channels for stereophonic recording and playback. When the tape comes to an end, the next channel is automatically set in position for recording or playback.

Recording or playback time for one channel is 15 minutes, and continuously 60 minutes for four channels when using a 300-foot cartridge tape. Any desired channel may be easily selected by manually pushing the cartridge program selector button.

On conventional heads, the signal and the bias are applied to the same recording head. Therefore the components, especially the high frequency component, of the signal being recorded tend to be attenuated or erased by the effect of the bias field.

On the Cross Field System, the signal head and bias head are separate and mounted opposite one another with their centers slightly displaced so the recorded signal is free from the undesirable effect of the bias field. The tape can therefore be modulated over the entire frequency spectrum with maximum fidelity.

The 778X has Hi-Fi stereo sound from a high capacity 12 watt solid state amplifier and high compliance speakers, playable in a vertical and horizontal operation.

Specifications

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

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

Motor: 2 speed induction

Reel size: up to 7 inch reel

Equalization: NARTB

Tape speeds: 1 78  3 34  7 12  15 ips

Wow and flutter: 0.18% (7 12 ips)

Frequency response: 30Hz to 23kHz (7 12 ips)

Signal to Noise Ratio: 50dB

Total harmonic distortion: 2%

Input: 60mV (line), 0.5mV (mic)

Output power: 6 watts

Speakers: 2 x 4 inch extended range

Semiconductors: 19 x transistors, 13 x diodes

Dimensions: 15 x 13.5 x 9.5 inches

Weight: 37.4lbs

Price: USD $429.95

Downloads

brochure (en) - k7sparky

parts list (en) - thegooddoctor

schematic (en) - thegooddoctor

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Roberts Reel to Reels

Comments

re: Roberts & AKAI Reel to Reel Decks

thegooddoctor's picture

Several Roberts and AKAI reel to reel decks use the same basic chassis and transports. In addition the the usual age ware on capacitors, transistors, belts and ideler wheels, "Father Time" works his greatest destructive force on the "white metal" or "pot metal" cams used on the Play/Record and Fast Forward switch mechanisms.

If you have either of these types of decks you should take off the top cover and visually inspect these cams. Stage 1 of the disintegration you will see small cracks appear in the metal. Depending on climate, time and use the cracks expand and eventually one day you go to use the machine and it will not engage because the cam simply falls apart.

If you are thinking about purchasing one of these older decks this is an important point to check since I know of no one who has taken on the task of machining replacement cams out of better materials.

(This is a golden opportunity for someone with the know-how and machine tools to make a few dollars.)

If you know of someone who has already taken on this task please let me know because I see one of these decks almost monthly.

re: Roberts & AKAI Reel to Reel Decks

I recently aquired a Roberts 778X, but have no operating manual. How do I attain all 4 of the speeds the deck is supposed to playback on. I have several old tapes that were recorded at 1 7/8 ips, but cannot figure out how to get the playback speed that low. The slowest speed I can reach is 3 3/4. The tape speed switch at the top of the deck functions and does slow the capstan speed from high to low settings...but does not take the speed down to 1 7/8.
Appreciate any help you can give.
Thanks...

re: Roberts & AKAI Reel to Reel Decks

Older Akai machines were supplied with a sleeve that you remove to reduce the speed, the sleeve was then placed on a small stub, located just above the head cover so that it does not get lost. The Roberts 778X is the same as the Akai X1800 SD and I found the following notes on the subject. Has your capstan got the shaft already installed I guess it is about 1/4 inch in diameter, if so try removing it.

A combination stereo reel-to-reel and 8-track cartridge recorder with the ability to transfer from tape to cartridge.

The Akai patented cross-field recording system plus one micron gap heads gave very good frequency response and low distortion.

A two-speed induction motor was used; three speeds were provided (1, 3¾ and 7½ ips) with an optional fourth speed of 15 ips available with a special capstan and pinch roller adaptor kit.

Other features included: pause control, straight-through amplifier mode, monitoring and input mixing.

Audio output was 4 watts per channel RMS into two internal 4" speakers. Akai also made a matching pair of remote speakers

Hope this helps

 

This website is not affiliated with or sponsored by Roberts. To purchase a 778X please contact the company via their website or visit an authorised retailer.