| Electronics > Repair |
| Wavetek 2520a 0.2-2,200MHz RF sig gen repair |
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| tautech:
Yep Windows 10. Sent you an email you might like to study. ;) |
| dazz1:
Hi I found the next fault. Another shorted Tant cap. The Wavetek seemingly has hundreds of them (only slight exaggeration). I narrowed down to the main board (there are about 10pcbs) I used the finger test to conclude that none of the voltage regulators were supplying a dead short. This left just 5 candidates, one had already failed and been replaced. After lifting the 3rd cap, I found the faulty one. All of the failed caps have been on the +18V supply. I have now replaced all of the Tant caps on the +18V DC supply. These were all rated 25V. The new caps are 35V. The power supply includes a soft start feature. I am going to see if this is working properly. If it is I will look at modifying it to make it a little softer to reduce the surge current seen by the Tant Caps. Surge current is a known killer of Tant caps. The 2520A has just passed the autocal process. This is a good indicator that the 2520A is functional. The next steps, in no particular order, are to: * make a copy of the eproms holding the firmware. erase and re-burn the eproms replace the NVRam with a DS1225AD modern version investigate the soft start, and modify if required do a full calibration * If there is any interest, I am thinking of doing a video on the repair. Dazz |
| wn1fju:
Almost sounds like Wavetek got a marginal batch of tantalums when they assembled your unit many years ago. I've had a few (non-Wavetek) pieces where there were an excessive number of bad tantalums, all of which suspiciously were the same uF value. It was much more than an isolated bad tantalum that one might expect. Who knows? As I said in my earlier post, I had a big problem with the connector between the main transformer and the rest of the power supply. There clearly was enough arcing going on to burn the contacts. You might inspect your unit just to be sure. So far, I've not had any tantalum failures in my 2510A. But then again, I've probably only turned it on five times in the last year. |
| dazz1:
Hi I suspect that 18V was just enough to kill the 32 year old Tant caps. The same make/value Tant caps on 15V have survived. The only difference is +3V and the 7815 regulators in the path of the surge current. The same tant caps on -18V are OK. There are 2x +18V supplies, and the failed Tants are connected to the same +18V supply. I am going to test the hypothesis that the soft start is only fully active on one of the +18V supplies. Dazz |
| HandWave25:
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 |
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