Tektronix 475 with DM43 - Repair

[Alfons]

Last I bought a whole bunch of partly broken devices. Included was a 475 with DM43. CH1 was dead and the high-voltage eletrolyte cups shown a ripple of about 40VPP. Have then exchanged all Elkos, even if only 2 were really broken.

Ch1 did not work because the vertical channel switch did not turn the signal thru. First thought the hybrid would be broken, until I noticed that there was an error in the logic control. One Resistance was high impedance. After replacing this, CH1 alives. The DM43 showed no plausible values, only 3.3.3.3: in the power supply of the device (hidden under a cover I found a power supply), in which a 12V voltage regulator was defective. A pain to expand the part.

After exchanging some tantalum for Low-ESR electrolytic capacitors (with 100n SMD ceramic between the legs) and normal tantalum, the device works very well. It triggers extremely clean, (much better than my Rigol) the beam is clean and sharp. I'm really excited about the device. Also included was the appropriate Scope mobile.

A 2467B was also there. Is already repaired.

[Alfons]

It was a little difficult to find the right documents for the device. Possibly because of the DMM, the equipment is partly different from the normal 475, it is more like the 475A, but has an input sensitivity of 2mV instead of the 5mV of the 475A. Unfortunately, I find no service manual mached with this device. I wonder why the fixed 12V voltage regulator of the DMM goes defectiv. The device was also unsuccessful repaired earlier. In the power supply of the DMM, i found an newer 5V fixed voltage regulator. Some parts are not from the 70s. In the control of the vertical switch was a 74LS74, which I have again replaced by a 7474. Also one of the Electrolyt-Cups in the power supply has already been replaced. However, the previous owner did not get it up and running and so the device stood idle for many years.

It was my first repair of an oscilloscope and it was really difficult for me to fix such a device. Without fun that makes no sense. All switches had to be cleaned to work properly again.

In contrast, the repair of the 2467B was a breeze.

[lowimpedance]

I have one of these pair in the junk pile as well as the more common (i think!) 475a with the DM44 on top that only gives a burning smell  .
Thanks for the info, all handy when it comes time for a little bit of Tek 'surgery'.
Also always nice to see these old timers kept from the e waste that little bit longer.