Wavetek 3001 signal generator repair

 Got this Wavetek 3001 signal generator just for testing the FM deviation meter since I haven't here my other signal generator and it was the cheaper unit that could generate a signal changing the deviation I could find in the usual online flea market.

Was expecting it to be fully working but unfortunately the listing  didn't matched the reality. Instead of sending it back I decided to try an fix it.
It was not giving any output and the indication meter for the output signal was not moving, also touching the back right panel where the power supply dissipation is, it was getting alarmingly hot after some seconds of power on. Testing the power lines for the + and negative 18V it was showing close to 0V... so either the supply was dead or there was a short. Because it was the two supply lines I suspected initially the output transistors of the supply.

 Looking at the service manual and some web resources was easy to see the 18V power supply lines in short or not working could be due the usual short electrolytic capacitors.

Two great resources I could find with a lot more information than this post are the following ones:

http://k5jxh.com/wave-tek/3006.html from K5JXH for the repair of a similar unit, a Wavetek 3006

and:

http://users.monash.edu.au/~ralphk/wavetek.html by Ralph Llimek on a repair of also a similar unit, Wavetek 3000

In my repair the only hard part was to find which module is the one at fault, if not multiple. That was my approach because looking at the power supply I could not find any fault (top right part vertical PCB).

 

 

My approach was to removed 5 random ones and see. I choose the first 5 on the bottom from left to right. What I did also was to put labels on all the cables for future reference although after unbolting them and turning the box upside down they started to fall with the cabling attached, saving me some time. I was lucky the first time, with 5 modules removed it was back to life, that is, there was no longer a short on the power supply and the output metter moved, then I installed one after the other until find the culprit, it was module M29-2, see bellow.



The modules are easy to remove from the chassis, just unbolt the bottom screen and pull them from the top side.

Inside the module I could see a previous repair had been done on one of the supply lines capacitor because of the two different type, a more modern black on the right and the original one on the left. You can see also the small choke in series to the supply lines, positive and negative.



After measuring, it was confirmed as a plain short, so it was removed and replaced (not the same value but works anyhow):

 In the mean time I bough some more spares for future replacement.

I suspect it's also developing and issue on the 400Hz audio oscillator part, 1Khz is good but that will be for another day. Here's the two oscillators schematic in question:


Have a good day!