Alpha 89
Alpha 89 Fuses – Purchase on our web store by part number:
Micro Fuse, 2 Amp 125V, Part Number FSX-X123
Used on the 89 T/R board (PIN Diode circuit)
Micro Fuse, 1.5 Amp 125V, Part Number FSX-X136
Alpha 89
Documentation
89 User manual | Alpha_89_Operating_Manual |
89 Tuneup | Alpha 89 tuneup |
89 Schematic | 89_full_schematics |
89 Parts list | PARTS_LIST_-_ALPHA_89 |
89 PIN Diode Modification | Alpha 89 PIN Diode Mod |
Alpha Amplifier Production Dates | Alpha_Amplifier_Production_Dates |
Alpha Amplifier Keying Specs | Amp_Keying_Specs |
What is the purpose of the pin diode mod?
If R27 thru R30 are each a pair of tan carbon-film resistors they can fail internally and start arcing, they aren’t rated for the voltage on them. The resistor change across the diodes changes the bias voltage on the receive PIN diodes.