Production of the Rola "77" Mk III early 1962 and continued till the 1970's. During this time there were quite a few revisions to the schematics and most of this information can be on my Revision History page. Some new features made the Mk III technically better than the Mk II but in my opinion there is something about look, the symmetry that I really like about the Mk II which was lost in the later Mks. The new features in the Mk III are:
1. The winding speed is now continuously variable in either direction.
2. Elapsed time indicator.
3. A capstan fast start switch added to the operator controls
4. Metering of internal circuit voltages.
The weight of the 77 Mk III had increased 55 lbs, making it 10 lb heavier than the Mk II series. The Rola 77 shown here was still in service when occupational health and safety rules were introduced in the 1980's, note the heavy lift symbol on the side of the case.
The Rola "77" Mk III Deck
Apart from some improvements in the construction of the deck which further improved the performance of the tape transport over that of the Mk II , there were three new features which made the machine more convenient to operate. First was the replacement of the "SHUTTLE CONTROL" with a continuously variable winding control called "SPOOL". At the centre of travel of the "SPOOL" control a small and equal amount of tension is applied to the tape by each spool motor, with the control fully anti-clockwise maximum rewind speed is achieved while the fully clockwise setting is maximum fast forward. The "SPOOL" function is engaged with the "SPOOL" push button and stopped with one of the two "STOP" switches or the tape run-out switch.
The second new feature was the inclusion of an elapsed time indicator. Time is indicated on an analogue dial, one rotation is 30 min or 15 min for 7 !/2 ips or 15 ips respectively with the smallest divisions being ten or five seconds.
Thirdly a "FAST START" switch has been added to the deck controls. The purpose of this function is to allow the operator to switch on the capstan motor prior to recording or playing so that the capstan is at operating speed when the transport is started.
Like the Mk II the Bias/Erase oscillator is located on the deck and a 12BH7 tube is used for this circuit.
The Rola "77" Mk III Amplifier
This gives you a close-up of the amplifier controls.
The amplifier panel has all the functions and features that were available in the Byer "77" Mk II plus one additional feature originally in the Byer "77" but dropped in the Mk II then reintroduced in the Mk III. This feature is a meter function switch, it allows the operator to select the input to the meter. Normally the audio signal is selected however, other system voltages can be monitored. The voltages that can be monitored are: AC filament supply, DC HT, Record bias, and Cathode bias on most of the amplifier tubes. Indication of each of these voltages is scaled so that 0dB on the meter represents the nominal voltage.
The tube complement of the Rola "77" Mk III amplifier is:
1 x 6GW8, 1 x 12AU7, 1 x 12AX7, 1 x 12BH7, and 4 x EF86.
"77" Mk IIIs at 3UZ
"77" Mk III Console Configuration
|The 77 Mk III had originally been supplied in a transport case and if required it could be rack mounted. By the late 1960's a console style case was made available for table top use and a roll-around stand was also available. A complete machine was sold in this configuration or you could purchase the console cabinet separately with or without the stand.|