7L5/Repairs: Difference between revisions

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==Intermittent Rotary Encoder==
The "Dot Frequency" and "Reference Level" rotary encoders can become faulty to the point that they either do not work at all, or just cause random unpredictable changes when operated. The good news is that they are mechanical switches constructed from hard gold contact traces on the front panel PCB, and all elements are held together by screws. They can be accessed by separating the front panel from the 7L5 and removing the front panel overlay. Simply cleaning the gold traces on the PCBs with isopropyl alcohol and carefully bending the contact fingers slightly outward to reestablish contact force will restore operation. See the figures below.


==Front Panel Disassembly==
The [[7L5]] is constructed of two main modules and the front panel assembly. The left module hinges outwards once a few screws are removed, and with further screw removal the complete front panel assembly comes off. When further disassembling the front panel, note the unconventional "Frequency Span" and "Time/Div" switches that need to be removed to be able to lift off the front panel overlay. These are entirely built into the particular knobs and can be pulled off from the front panel as a complete unit after removing two fasteners at the back. Note that the "Time/Div" switch has very thin metal contact fingers that fit into a socket at the front panel PCB. To guide installation, there is a little plastic spacer with conical holes for those pins. Make sure to install this spacer in the right orientation before attempting to reinstall the "Time/Div" switch, as shown in the figures.


==Front Panel==
==Pictures==
===Front Panel===
<gallery>
<gallery>
7L5_Frontpanel_PCB_back.jpg|
7L5_FrontpanelOverlay.jpg |Front panel Overlay (Military version without B-(save A) )
7L5_Frontpanel_PCB_back_inframe.jpg |  
7L5_Frontpanel_PCB_front_inFrame.jpg | Front panel with overlay removed in frame
7L5 Frontpanel PCB back Ref Level disassembled.jpg |  
7L5_Frontpanel_PCB_back_inframe.jpg | Front panel backside in frame
7L5_Frontpanel_PCB_back_Ref_Level_part_disassembled.jpg |  
7L5_Frontpanel_PCB_front.jpg | Front panel frontside
7L5_Frontpanel_PCB_front.jpg |  
7L5_Frontpanel_PCB_back.jpg|Front panel backside
7L5_Frontpanel_PCB_front_inFrame.jpg |  
7L5_Frontpanel_PCB_back_Ref_Level_part_disassembled.jpg | Front panel backside with Reference Level switch partially disassembled
7L5_Frontpanel_PCB_front_Ref_Level_part_disassembled.jpg|
7L5 Frontpanel PCB back Ref Level disassembled.jpg | Front panel backside with Reference Level switch removed. Parts of switch with sliding contacts shown below.
7L5_FrontpanelOverlay.jpg
7L5_Frontpanel_PCB_front_Ref_Level_part_disassembled.jpg| Front panel frontside with Reference Level switch removed. Switch gold contact traces visible
7L5_Span_and_time_div_switches1.jpg
7L5_Span_and_time_div_switches1.jpg| Span and Time/Div. switch backsides
7L5_Span_and_time_div_switches2.jpg
7L5_Span_and_time_div_switches2.jpg| Span and Time/Div. switch sideview
TimeDivSpacer.jpg
TimeDivSpacer.jpg| Front panel with Time/Div. switch removed. Note plastic spacer on the right
TimeDivSpacer_installed.jpg
TimeDivSpacer_installed.jpg|Front panel plastic spacer for Time/Div. switch installed in correct orientation, ready for switch installation.
</gallery>
</gallery>


==Left Module==
===Left Module===
<gallery>
<gallery>
7L5_left_module.jpg
7L5_left_module.jpg
Line 26: Line 31:
</gallery>
</gallery>


==Right Module==
===Right Module===
<gallery>
<gallery>
7L5_right_module_front.jpg
7L5_right_module_front.jpg
Line 33: Line 38:
7L5_right_module_top1.jpg
7L5_right_module_top1.jpg
</gallery>
</gallery>
[[Category:Instrument repair reports]]

Latest revision as of 02:46, 7 January 2023

Intermittent Rotary Encoder

The "Dot Frequency" and "Reference Level" rotary encoders can become faulty to the point that they either do not work at all, or just cause random unpredictable changes when operated. The good news is that they are mechanical switches constructed from hard gold contact traces on the front panel PCB, and all elements are held together by screws. They can be accessed by separating the front panel from the 7L5 and removing the front panel overlay. Simply cleaning the gold traces on the PCBs with isopropyl alcohol and carefully bending the contact fingers slightly outward to reestablish contact force will restore operation. See the figures below.

Front Panel Disassembly

The 7L5 is constructed of two main modules and the front panel assembly. The left module hinges outwards once a few screws are removed, and with further screw removal the complete front panel assembly comes off. When further disassembling the front panel, note the unconventional "Frequency Span" and "Time/Div" switches that need to be removed to be able to lift off the front panel overlay. These are entirely built into the particular knobs and can be pulled off from the front panel as a complete unit after removing two fasteners at the back. Note that the "Time/Div" switch has very thin metal contact fingers that fit into a socket at the front panel PCB. To guide installation, there is a little plastic spacer with conical holes for those pins. Make sure to install this spacer in the right orientation before attempting to reinstall the "Time/Div" switch, as shown in the figures.

Pictures

Front Panel

Left Module

Right Module