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Rola 77 Mk III Revisions |
The Rola 77 Mk III like other products was revised during the life of this model, 1962 to 1972/3. All of the advertising refers to the machine as a Rola 77 Mk III however, there are two versions Rola 77 Mk III and Rola 77 Mk IIIB. There are at least four public releases of the schematics, amplifier drawing number 12-0072, revisions "F", "N", "R", and "W" and the transport drawing number 12-0073, revisions "A", "H", "J", and "O".
Note: Not all schematic versions are currently available for download, please contact me if you need a specific schematic.
Unfortunately, apart from one revision I've not found any other records relating serial numbers on tape machines to drawing revision numbers, however, we do at least have dates for the revisions. You may be asking yourself what is so important about these circuit changes? If you want to correctly restore a machine or if you want to use a tape transport with an amplifier that have different serial numbers then you will need this information. It is important to note that if a 77Mk IIIB amplifier is used with a 77Mk III tape transport then record amplifier mute circuit can be damaged when the machine is placed in record mode. The best course of action is to check the transport circuit and upgrade it to the revision "E" schematic or later.
AMPLIFIER REVISION HISTORY
| REV | DATE | COMMENTS |
|---|---|---|
| 28 Dec 61 | Initial drawing release | |
| A | 12 Feb 62 | C3 was 47nF now 22nF |
| A | 12 Feb 62 | C12 was 100pF now 68pF |
| A | 12 Feb 62 | R35 was 390k now 240k |
| A | 12 Feb 62 | R52 was 2k2 now 1k5 |
| B | 9 Apr 62 | C11 was 47nF now 100nF |
| C | 10 May 62 | Mains indicator added, F1 deleted |
| D | 16 May 62 | CT2 was CV1, CT1 was CV2, CT3 was CV3 |
| D | 16 May 62 | Functions added, C.N. 88 |
| E | 24 May 62 | R86 and R87 were 220R now 150R |
| F | 22 Aug 62 | R45 was 1M now 100k, R46 was 680k now 270k |
| G-M | No information | |
| N | 15 Dec 64 | Redrawn, no alterations |
| O | 4 Feb 66 | C46 was 22pF, deleted |
| P | 13 May 68 | C3 and C13 were 22nF now 47nF |
| P | 13 May 68 | C20 was 100pF now 47pF |
| P | 13 May 68 | C22 was 56pF now 22pF |
| P | 13 May 68 | Major revision to record eq circuit refer schematic |
| Q | 17 Jan 69 | Chang of earth point for R91 1k2 |
| R | 27 Mar 69 | C12 was 68pF now 100pF |
| R | 27 Mar 69 | C46 added now 100pF |
| R | 27 Mar 69 | R34 was 180k now 390k |
| R | 27 Mar 69 | R53 was 3k3 now 2k7 |
| R | 27 Mar 69 | R85 was 150k now 220k |
| * | 27 Mar 69 | Added C50 220pF, C51 56pF, R102 47k, R103 470k |
| S | 23 Feb 70 | C25 was 5n6F now 10nF |
| S | 23 Feb 70 | C29 was 25uF now 50uF, 25V |
| S | 23 Feb 70 | C50 was 220pF now 330pF |
| S | 23 Feb 70 | C51 was 56pF now 180pF |
| S | 23 Feb 70 | C52 added 56pF between C12 and RV3 |
| S | 23 Feb 70 | C53 added 22pF between C15 and RV2 |
| S | 23 Feb 70 | C54 added 56pF across R63 |
| T | 14 May 70 | MB10 bridge recifier was 4 x 10B1 |
| U | 16 Nov 70 | C55 added 100nF, 160V |
| V | 23 Feb 71 | Position of C55 corrected on the schematic |
| W | 15 Oct 71 | R13 was 56R now deleted |
| W | 15 Oct 71 | R18 and R19 was 10k now 100k |
| W | 15 Oct 71 | R4 and R5 was 270R now 1k2 |
| W | 15 Oct 71 | R4 and R5 are now in parallel across R18 and R19 |
* The components are on drawing Rev R but are in listed in the change record.
TAPE TRANSPORT REVISION HISTORY
| REV | DATE | COMMENTS |
|---|---|---|
| 16 Jan 62 | Initial drawing release | |
| A | 10 May 62 | C35 added 0.1uF |
| A | 10 May 62 | R35 added 22R |
| A | 10 May 62 | Pole 2 added to SW1 |
| A | 10 May 62 | FAST START EDIT LAMP WAS "MAINS IND" |
| B | No information | |
| C-E | Major circuit revisions | |
| C | 31 May 63 | No information except C.N. 269 |
| D | 26 Jun 63 | No information except C.N. 293 |
| E | 24 Jul 63 | No information except C.N. 294, applies to: |
| E | 24 Jul 63 | S/N 1771, 1772, 1803, 1811, 1812, and from 1838 inclusive |
| F | 17 Dec 63 | No information except C.N. 321 |
| G | 29 Jan 64 | R33 was 1700R, 20W now 1000R, 20W |
| H | 24 Feb 64 | Rectifier diodes were 10B1 now 10B2 |
| J | 16 Dec 64 | Redrawn, No alterations |
| K | 18 Jun 69 | R23 & R25 were 400R, 20W now deleted |
| K | 18 Jun 69 | R42 was 1k5, 10W now 2k 10W |
| K | 18 Jun 69 | R46 700R, 20W added |
| L | 14 Apr 70 | 0.5uF, 400V capacitor added (no info as to where in the circuit) |
| M | 14 May 70 | Rectifier diodes were 10B2 now EM402 |
| N | 27 Jul 70 | R15 was 220R, 1W now 150R, 1W |
| O | 27 Jun 71 | 0.5uF 400V deleted |
| O | 27 Jun 71 | C31 2uF, or 2.5uF for PAPST capstan motor |
| O | 27 Jun 71 | R33 was 1k, 20W now 2k, 20W |
| O | 27 Jun 71 | R42 was 2k, 10W now 1k5, 10W |
| O | 27 Jun 71 | R46 was 700R, 20W now 1k, 20W |
| O | 27 Jun 71 | R47 400R, 20W added for PAPST capstan motor only |