The Marconi 2965/6/7/8 are increasingly finding their way into the amateur market and we're seeing more of these in for repair than the ever popular 2955 at present.
The main issues with the 2965 series are delamination of the display window (see picture above), failure of the CRT monitor and failure of the PSU. There are obviously other faults which occur, but those are by far the most common.
The display window can usually be fixed by removing the front panel and peeling back the layers. The inner layer of the window and the screening mesh are cut out and the remaining layer cleaned thoroughly to remove the glue residue. The remaining layers are then glued back together. The lack of screening mesh makes no noticeable difference. We can carry out this work for you, however, it is quite labour intensive and therefore can be costly. It also has the potential to go very wrong and so is done entirely at the owners risk.
The CRT monitor is also unreliable and they regularly start to jump and twitch. Sometimes this can be fixed by replacing the aging capacitors, but it tends to be a continual source of trouble. Like the 2955, the LOPT is also no longer available, so LOPT failure is unrepairable. Fortunately we have developed an LCD replacement kit comprising an off the shelf 7 inch colour LCD screen and driver board. The LCD is held in place by a 3D printed mounting frame, which is secured by the existing keyboard PCB mounting studs. The driver board is mounted on another 3D printed chassis which is secured by screws using the same four mounting holes as the original monitor. The supplied wiring harnesses then plug into the original monitor connector for its power supply and to the VGA output connector on the A5 board in place of the original cable which connects to the rear panel VGA socket. The 2965's VGA output is actually in colour even though the original CRT screen was monochrome, an the result looks great (see picture above). The LCD also negates the loss of the display screening mesh as the LCD has a steel back plate, which will largely 'block the hole' to any RF. The only downsides are that the intensity control no longer performs any function and the external VGA socket is disconnected internally. Brightness/contrast etc can be adjusted using buttons on the internal chassis when the modification is fitted, but are not easily adjustable during normal use, however, many instruments have little or no adjustment anyway.
We are able to fit this modification for you at our normal labour rate, or it can be purchased as a self installed kit.
The PSU consists of two converter boards. One takes the AC input and converts it to 24V DC. The second board takes the 24V DC and generates the various supply voltages used by the instrument. Removal of the PSU is not a trivial task, so if it needs repair, we recommend that all electrolytic capacitors as well as the AC mains filter capacitors be replaced whilst it's out. Once repaired and refitted, your 2965 will be PAT tested to ensure it is electrically safe.