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> 54502-69501 54502-66501 54502A mother board no atnuatrs
54502-69501 54502-66501 54502A mother board no atnuatrs
This is a 54502A main board. It has been tested and calibrated in a good 54502A. I am selling the board without attenuators assuming that if you have a mother board failure you will simply reuse your attenuators. I do have attenuator preamps in my store watronics92.
Trouble shooting suggestions for the 54502A
If the Power supply module failed... A somewhat common failure. The fan does not run and nothing on screen. No response from the keyboard.
If the High Voltage board failed... Blank screen. The unit appears to power up. The fan runs. Press autoscope and the unit makes click sounds.
A common failure on the 54502A actually is the attenuators. If only one channel of your unit is failing, the attenuator mod is most likely the failed item. The attenuators are easy to remove and install once the board is removed from the chassis. Swap attenuators to validate the failure mode. If the problem can not be swapped, then the main board is most likely bad.
Mother board failure If you have eliminated all else by swapping parts with another 545xx unit then
Sometimes the battery in the NVSRAM chip is dead. When this happens, the unit will work with default cal factors or after calibration, but will not hold calibration when you turn the unit off and on.
Contact me if you wish ****@comcast.net if you need attenuators or check my store Watronics92
NOTE!!!! The 54512-63402 attenuators will not work with the 54502A
Other common failures I see on the 54502A attenuator modules 54503-63401 or 63402.
1. The 50 Ohm input can be blown open (1Meg ohm input works fine. This is not an obvious failure)
2. The FET DC restore path can be blown out. (only passes AC signals. You will not see this failure on HF signals.)
3. There are mechanical switches in these attenuator modules and sometimes the contacts are intermittent.
