Kerett Electronics

UC8000 Backboard (or motherboard).

The majority of problems with the JEL system stem from the poor power supply filtering and noise suppression on this board. Additional suppression is always added during repair. This dramatically improves the reliability of the whole system.

There are a couple of components that have become obsolete on this board and for these we have produced adapters to allow the use of later devices as replacements.

PMB CPU module.

One of the most common problems is the failure and leakage of the Ni-Cad backup battery. To solve this we have devised a method of replacing them with large capacitors (memcaps) which is done irrespective of the condition of the battery.

There are two main versions of this, the PMB4000 and PMB5000. There is also a variation of the PMB5000 that uses a 12MHz. crystal and is not compatible with some front panels, so the correct type/version must be specified.

CM2500 Communications Module.

These fail for all sorts of reasons but can usually be repaired.
Alternatively, we have developed a more robust replacement which is compatible with the original in all respects. In addition, it allows you to communicate with other units over the JelBus using either a JS4000 or a front panel.

UC8600 Front panel.

These units suffer from ageing LCD backlights which I replace with LCD modules with LED backlights. Membrane switch panels can also fail and I have developed a proper ‘touch panel’ (not membrane) replacement.

AO8000 Output module

Apart from the usual transient susceptibility, these boards will not tolerate the outputs being shorted to 0v. Unfortunately there is not much scope to modify these for a proper fix.

To overcome this we have developed a new AO8000 that will survive this. It is fully compatible with the original.

AD8000 Expansion board

The analogue output section has the same problems as the AO8000 above. They can be repaired but we have not as yet, produced a replacement.
There are two versions of this board. They are functionally the same but the most important difference is the wiring. To save you time diagnosing problems with the replacement and re-working the wiring, please specify the version (A, B, C, etc.) you require. (See picture for version location.)

AI1600 Input expansion module

These suffer the same problems as the analogue section of the UC8000. They are repaired and noise suppression added.

Analogue scaling modules

These modules are potted during manufacture and cannot be repaired. However we are able to supply a compatible module (repairable) with ‘A’, ‘B’, ‘C’ or ‘V’ inputs in any position. Other input scaling is ‘work in progress’

SC5000 Backboard

As with the PMB modules during repair, the battery is replaced with Memcaps. In addition, this modification provides a +5v supply to allow the use of Coherent Technologies EC24 modems without an additional power supply. The modification fixes the main problem with this and other modems which result in the communications being locked up.

MZ3000

This is a ‘compilation’ of the original JEL boards rolled into one! It suffers most of the faults of the original and can be repaired in the same way.

Micro 2000

These have a few problems. There are obsolescence problems with a couple of components but we will do our best!

The unit is repaired as a complete unit (front and back boards).