HD dimmers predated RD dimmers, and were manufactured by LMI in the early 80's. ETC still stocks some parts for this rack. ETC can also perform board level repairs on the clock cards and dimmers. As each of these touring racks and installation racks were custom built, there are no manuals.
Looking from the top of the dimmer module down: (Figure 3)
Backside of dimmer (Figure 2)
If you remove a module, you will see a small toggle switch on the PCB. This switch is to determine whether the slot has a dual 1.2kW or a single 2.4kW module in it. The rack pictured is a 1.2kW. You should not change this, as it may damage the modules.
Rack (Figure 1)
The chokes for the dimmers are in the rack -not on the dimmer module. On the rack assembly for each row of dimmers (each row is a phase) is a control section. This section has test points for the Neutral, Line voltage, Clock signal, and control common. There is also an LED that indicates power to the clock card. The fuse provides protection for the clock card behind the small screw panel. This clock card takes the 0-10Vdc control signal and modifies it to a pulse-width signal based on the voltage zero-crossing per phase. On the back side of the Rack are breakers and output connectors; generally Socapex.
Note: Most of the below parts are not currently in stock and the availability is limited.
Connectors J313 CON 10M TERM BLK SOC EV Male (module) small stock available J312 CON 10P STRIP Female (rack) none in stock
1050A1002 ASSY;DIMMER MODULE, 1K none in stock Q107 TRIAC; Q6025P 25A 600V F101 FUSE 10 AMP SC-10 CB102 CIR.BREAK;SP, SLOW, 10A X102 FUSEHOLDER; HPS-EE 1050A1001 ASSY;DIMMER MODULE, 2K Q109 SCR; 63A PACK F106 FUSE 20 AMP SC-20 X111 FUSEHOLDER; HPF-JJ
Note: Most of the parts are not currently in stock and the availability is limited.
HD Dimmers are analog dimmers. Originally they had a digital patch built into them but the patch was removed on all of them. Some may have been retrofitted with either EC-24 cards or a Response 96 out card (most likely the former).
There were two versions of the rack. One had the ramp/trigger cards on the side panel, the other version had them behind in a little door to the right or left of the modules (there were left and right had units) They both worked the same.
There were three versions of the trigger cards. All interchangeable but some had better trigger/zero crossing circuits.
There were both dual 1K and single 2K modules. There were two version of these too. Basically the same but the driver that controlled the bar graph went obsolete so it was changed to a different circuit.
The biggest problem they had was that they would slip out of the tray during shipping and have to be pushed back in at each sited. Version II had a retaining bar.