Electronics > Repair

Wavetek 182A repair

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dirty_glam:
Hello to you all,

This is my first post, so thanks to everybody for having this forum. I read some random topics and I'm glad I ended up clicking the link to this site on Google because I can see that I can benefit from your experience and I hope I can help others with the little bit I have.

Being said that, let's get to the point...

I live in Spain and I few months back I bought this wavetek 182A function generator from a seller in Indonesia. I had a LOT of problems in the Spain customs department because the seller didn't especify the charges correctly and I ended up paying big bucks for an instrument that I later found out it's not working (returning it would cost me more than keeping it and accept I was ripped off  :( )

The thing is, it came with the fuse blown, I purchased a new one put it in, selected the 230V (Spain) switch and when pressed the on/off button it turned on for 0,00000something milliseconds and then went off again, checked the fuse, blown, put a new one, same thing all over again.
Opened the generator, couldn't find anything blown, burned or suspicious to me, but since I'm thinking I have a short somewhere I did some research and I came up with the idea that it might be the transformer, so I took it apart, put a 100W light bulb in series with the main transformer and connected it to the wall and it seems to work fine. I have 25,6 or so Vdc in two of the three secondary transformer wires and 2,something in the other.

Then I thought it could be the electrolytic capacitors since it is an old unit, so I de-soldered one of the capacitor in the rectifier area and it seems to work fine, but I only could test it with a digital multimeter that its capacitance range goes only to 20microF and the one tested is 1000microF. So I could only check if it charges and discharges "correctly" using the resistance meter.

So...HELP!!!! Please
Any suggestion, usual suspect, any advice. I would like to repair it myself instead of taking it to a tech, so, let's see if I can do it with your help

Thanks very much

Vgkid:
Have you checked the resistance of the primary transformer

dirty_glam:
Ok thanks, I'll check that as soon as I find some time and let you know what I find

Khashoggi:
Schematics-
http://bitsavers.informatik.uni-stuttgart.de/pdf/wavetek/182A_Mar86.pdf

Power supply section looks straightforward. As suggested, check primary winding and then filter caps and bridge rectifier and regulator.

dirty_glam:
Hello guys.

Today I received and ESR meter I bought on eBay and measure the two 1000microF 35V filter capacitors and they give a resistance of 0,161 and according to the "worst case" table for this cap it should be 0,07, so, it's obviously bad, right?

The resistance in the primary of the transformer gives: blue cable to chasi or brown cable to chasi more than 2Mohm and blue cable to brown cable 185 ohm. That's ok, right?

And finally the 4 diodes of the rectifier give an impedance of 0,580 ohm in one way and infinite in the other, so, they are fine.

Since I don't have a dc source I don't know how to test the voltage regulator, but with these results I give you is it possible that the short that's blowing up my fuses is caused by the bad filter caps???

Thanks again

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