Hello,
Here's an oldie but a goodie for you:
I have an 8566B SA system that has a power supply problem. I have traced the failure to the series-pass regulator transistor in the +20 V supply. This is a TO-3 case transistor mounted to a heatsink on the motherboard and real panel of the unit. The service manual refers to this device as "A23Q3" with A23 being the motherboard subassembly. However, Q3 is missing from the list of replaceble parts for A23. It also is not listed with the A17 and A8 subassemblies which are the rectifier and regulator sections that it actually connects to. There is no cross-reference to it anywhere in the manual that I can find and it only has what I believe to be an HP part designation on it. It is marked Motorola part "4-618". Does anyone know what standard Motorola part this is or does anyone have a manual that correctly references it? Thanks! Dave
Here's an oldie but a goodie for you:
I have an 8566B SA system that has a power supply problem. I have traced the failure to the series-pass regulator transistor in the +20 V supply. This is a TO-3 case transistor mounted to a heatsink on the motherboard and real panel of the unit. The service manual refers to this device as "A23Q3" with A23 being the motherboard subassembly. However, Q3 is missing from the list of replaceble parts for A23. It also is not listed with the A17 and A8 subassemblies which are the rectifier and regulator sections that it actually connects to. There is no cross-reference to it anywhere in the manual that I can find and it only has what I believe to be an HP part designation on it. It is marked Motorola part "4-618". Does anyone know what standard Motorola part this is or does anyone have a manual that correctly references it? Thanks! Dave
Useful info:
HP part numbers for discrete transistors are in the form "185x-xxxx"
The number you saw printed on the case is just a shortened form of the full number: 1854-0618
http://www.parts.agilent.com says this is a darlington pair, replaced by 1854-0669