Not only do I discover that my understanding of the use of my spectrum analyser is probably woefully inadequate, and that my oscilloscope is playing up and needs a service, but now my 2955B test set is on the fritz! Again!
This time, I know im at serious risk of screwing the firmware if I dont fix it. So, its time to open her up.
The 10MHz Oven Compensated Crystal Controlled Oscillator (OXCO) unit, is mounted, horrifyingly, on the same board that generates the EHT for the CRT!
|Rear of the Reference/EHT board|
|Inside the Marconi 2955B. Note the warnings!|
|The 10MHz OXCO...|
|...is bloody complicated inside!|
|On the bench...|
|...and seemingly working perfectly!|
Im now at a loss, but my suspicions center around either a power supply fault, or something as insidious as a dry joint or leakage due to old flux! Where I go from here, im not sure, and ive a ton of work piling up that requires a working test set!