| Electronics > Repair |
| Wavetek 2520a 0.2-2,200MHz RF sig gen repair |
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| dazz1:
--- Quote from: HandWave25 on June 16, 2021, 07:01:46 am ---I am going balder by the minute with a Wavetek 2505 (.1-550MHz) Sig Gen. I am guessing it is similar to the 200MHz one. I have a "tripped" text on the "Level" display and I get no RF out. Can it be reset somehow? or where do I look to fix? Can't find a manual anywhere on-line. :-( rodg --- End quote --- Hi I don't have any info on a 2505 but if the circuit is similar, then the attached may help. The reverse power relay should be reset by cycling the power. Wavetek give away an on-line book with all the Operator manuals https://www.wavetek.org/. Probably only of some value to you. Dazz |
| dazz1:
--- Quote from: dazz1 on June 16, 2021, 03:14:32 am ---... I am going to test the hypothesis that the soft start is only fully active on one of the +18V supplies. Dazz --- End quote --- Hi Testing shows that both soft start circuits are working properly. The RC time constant is 39ms, which is slow enough to make any surge current more like a crawl in electrical terms. I have looked at the Wavetek 2520a output on the spectrum analyser and an initial look indicates the 2520a is functional. Dazz |
| tautech:
Cool. All that remains is to backup the EPROMs then so will see you next weekend to help with that. :) |
| dazz1:
Hi I have been looking at the output of the 2520a to see if it is working OK. This is really the first time I have used the spectrum analyser connected to the Wavetek. All of the faults found have been well within the freq range of my ancient oscilloscope. The output looks like it is well within factory specs. In all cases looked at so far, it exceeds specs. In all cases, there is a 10dB attennuator between the 2520a and my spectrum analyser. I have found another fault. The nvram does not retain memory. The one good thing about this is that the failed nvram has not bricked the 2520a. It appears that the calibration programs generate everything stored in the nvram. Without nvram, there is no point in doing a full calibration. The settings would be lost on power down. So the next step is to buy new eproms and a new nvram. Dazz |
| dazz1:
Hi One of the calibration routines steps the control voltage on the 4x VCOs. The nvram then stores a lookup table. When the user selects an output frequency, the control system does a look up to get the rough frequency, selects the right VCO and sets the control voltage. This is open loop control. The DDS then uses closed loop control to fine tune the output frequency. The spectrum monitor output shows the No.19 routine stepping through the control voltages to generate the lookup table. Dazz |
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