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| + | ====== Corsair II - Troubleshooting Weak Receive on higher bands ====== | ||
| + | **From the Ten-Tec Reflector June 8, 2016 and supplemental info from Rick VE3ORY** | ||
| The problem typically presents with these symptoms, as Marco IS0KYB described: | The problem typically presents with these symptoms, as Marco IS0KYB described: | ||
| - | "on some bands (mostly from 15m upwards) I noticed a weak reception when I use the main antenna input. The problem goes away if I switch to the RX antenna. | + | On some bands (mostly from 15m upwards) I noticed a weak reception when I use the main antenna input. The problem goes away if I switch to the RX antenna. |
| No, it doesn't seem to be the RX ant switch :) I cleaned it and operated it 100 times... it doesn't even scratch. | No, it doesn't seem to be the RX ant switch :) I cleaned it and operated it 100 times... it doesn't even scratch. | ||
| - | I believe that the culprit is a faulty switching diode among D1-D6 in the rx/tx switch." | + | I believe that the culprit is a faulty switching diode among D1-D6 in the rx/tx switch. |
| Rick VE3ORY responded to Marco's post: | Rick VE3ORY responded to Marco's post: | ||
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| Like Marco I suspected the problem to be diodes related to T/R | Like Marco I suspected the problem to be diodes related to T/R | ||
| switching, however the problem turned out to be in the High Pass Filter | switching, however the problem turned out to be in the High Pass Filter | ||
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| 3. R6 had been changed from 150 ohms to a 47ohm resistor. | 3. R6 had been changed from 150 ohms to a 47ohm resistor. | ||
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| + | ====== Board Removal ====== | ||
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| + | Below is a jpg showing info regarding layout of the Bandswitch components on TEN TEC, LPF-TR Board 80969. | ||
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| + | The drawing is a bit scattered but it shows some good information on orientation / layout of the bandswitch elements on the LPF-TR circuit board 80969 for the Corsair II | ||
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| + | References to alignment marks on the drawing are my own, as explained below. Before starting I felt I needed to understand layout of the bandswitch elements on the LPF-TR board. The attached drawing is simply a page of notes that I made while figuring this out. | ||
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| + | In order to remove the LPF-TR board from the chassis the bandswitch shaft needs to be at least partially removed through the front of the chassis requiring some disassembly of the front panel. Prior to attempting this I placed the bandswitch at the 28.5 MHz position and used an indelible marker to place alignment marks on both the shaft and the bandswitch wafer sections to ensure that all were properly aligned on reassembly. | ||
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| + | Pulling the bandswitch shaft out from the front of the chassis, I was able to remove it just sufficiently to allow removal of the LPF-TR board. I was then able to temporarily re-install the bandswitch shaft through all remaining segments while leaving the LPF-TR board removed. | ||
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| + | By ensuring that the switch segment on the LPF-TR board was at the proper position to match the selected band (this is where the alignment notes and markings become necessary), and leaving the interconnecting cables connected, I was actually able to power up the Corsair for troubleshooting with the LPF-TR board on the work bench beside the chassis. This afforded great opportunity to check voltages and signal levels on the LPF-TR board that would normally be pretty much inaccessible. | ||
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| + | {{:565lpf-tr.jpg?1000}} | ||
