Replacing the two bulbs in the meter for the 651S1. I have just finished replacing the two 6 Volt, type 328, miniature bulbs in my 651S1. The procedure is: (1) Remove meter by unscrewing four small screws that hold the compression mounts for the meter. (2) Use a small screw driver to separate separate the slot/grove holds the meter cover. This is on the back of the meter. Do not remove any screws on the back of the meter. (3) Snap the front cover off the meter. (4) Remove two screws that hold the white plastic meter dial. Slide the dial out from under the meter pointer. (5) Remove two screws from the white bezel that has two holes for the two bulbs. (6) If this white bezel is glued to the black plastic carefully seperate it from the meter using an exacto knife. Watch out for damaging the meter pointer. (7) Set the meter on its back and lift out the bulb holder. Remove the two screws at the back of the holder. (8) You can now replace the bulbs. (9) Reverse the process to preplace the meter. KF4FOR Work:P.A. Bernhardt Home: Paul Bernhardt, KF4FOR Code 6794 5704 Ridge View Dr. Naval Research Laboratory Alexandria, VA 22310 Washington, DC 20375 Tel: 202-767-0196 703-960-9656 FAX: 202-767-0631
Changing the displays in the unit.
Service bulletins651S-1 General Purpose HF Receiver PUB NO. NOTE DATE DESCRIPTION SB 1 10/1/72 Reduction of 450-kHz Leakage From Synthesizer Reference Board A11 SB 2 6/6/73 Change 1 10/15/73 Reduction of Noise Level SB 3 7/15/73 Add Keep-Alive Frequency Memory Function SB 4 7/15/73 Extend Comma and Decimal Lamp Life in Frequency Display SB 5 12/15/74 Minimize TCU Circuit Card Response to Data Link Noise and Failure SB 6 3/1/75 Reduce Intermodulation Level SB 7 2/7/75 Reduce Internal Spurious Signals SB 8 12/27/74 Allow Remote Control Operation With RS-232C Serial Control Interface Card A9 SB 9 2/15/75 Increase Life of Display Tubes SB 10 12/31/75 Revised 8/2/76 4/1/77 Replacing Display Tubes With LED Plug-in Assemblies SB 11 Not Issued SB 12 5/1/78 Revised 7/1/78 Replacing Nonprocurable Integrated Circuits SB 13 10/1/80 Replace Nonprocurable Parts SB 14 11/1/80 Reduce 100-kHz Sidebands SB 15 5/1/81 Prevent Invalid Monitor Responses From the HF Receiver SB A 11/1/73 Change DCFE Filter Switching Diode SB C 1/15/78 Supply KAV Power to DCFE 651S-1A General Purpose HF Receiver PUB NO. NOTE DATE DESCRIPTION SB 1 7/15/73 Extend Comma and Decimal Lamp Life in Frequency Display SB 2 6/6/73 Change 1 10/15/73 Reduction of Noise Level SB 3, 4 Not Issued SB 5 12/15/74 Minimize TCU Circuit Card Response to Data Link Noise and Failure SB 6 3/1/75 Reduce Intermodulation Level SB 7 Not issued SB 8 12/27/74 Allow Remote Control Operation With RS-232C Serial Control Interface Card A9 SB 9 2/15/75 Increase Life of Display Tubes SB 10 12/31/75 Revised 8/2/76 4/1/77 Replacing Display Tubes With LED Plug-in Assemblies SB 11 Not Issued SB 12 5/1/78 Revised 7/1/78 Replacing Nonprocurable Integrated Circuits SB 13 10/1/80 Replace Nonprocurable Parts SB 14 11/1/80 Reduce 100-kHz Sidebands SB A 11/1/73 Change DCFE Filter Switching Diode 651S-1B General Purpose HF Receiver PUB NO. NOTE DATE DESCRIPTION SB 1 - 5 Not Issued SB 6 3/1/75 Reduce Intermodulation Level SB 7 - 9 Not Issued SB 10 12/31/75 Revised 8/2/76 4/1/77 Replacing Display Tubes With LED Plug-in Assemblies SB 11 7/27/76 Prevent Premature Fuse Failure SB 12 5/1/78 Revised 7/1/78 Replacing Nonprocurable Integrated Circuits SB 13 10/1/80 Replace Nonprocurable Parts SB 14 11/1/80 Reduce 100-kHz Sidebands SB 15 5/1/81 Prevent Invalid Monitor Responses From the HF Receiver