Test Equipment Anonymous

Arrived today. Packaging top notch. No damage. First picture as received. Surprisingly clean. That calibration sticker is dated last cal August 1966. So I would assume this guy sat on a shelf for many years. We'll see when it's fired up.



Top view and bottom view.




After clean up. Although as mentioned wasn't that dirty but did remove the cal sticker.



The unplated aluminum chassis was very stubborn to clean, even with Simple Green. It's ground in most likely due to heat and would take I feel excessive scrubbing to remove so I left it. But the vacuum tubes were removed and sockets cleaned with deoxit as well as the controls and switches.



Tomorrow get a first smoke test with the Type 535A.

Wow, that's clean! Nice score.

First power up. Decided to use the Type 547 for testing rather than the Type 535A. If compensation adjustments are required the scope has to be turned on it's side and bottom plate removed. The Type 547 is already on the bench while the Type 535A is on a cart and would have to be jackassed onto the bench. Would rather skip that hernia busting operation.

Anyway, could not initially get the trace on screen. Position control and DC Balance ineffective. Changed all the vacuum tubes and replacing V6101 and V6111 (12AU6) got the trace on screen but just barely. DC Balance is completely out to lunch but the vertical gain is good. That 50kHZ square wave shows some tilting so compensation is slightly off. 0.5V range is dead. Other ranges are OK. I'm not totally convinced that the two 12AU6's are bad. There's a severe imbalance somewhere and probably a resistor. So next step is to check some resistance readings and if that doesn't reveal the issue then some power on signal tracing. More later.

Progress with the DC Balance issue. In checking the resistors around the Vertical Position and Vertical Position Range controls found a large imbalance. Centered the Vertical Position control and still had a massive imbalance. Some Gorilla had apparently twiddled the Position Range control. Centered that control and now have a good measured balance with ohm meter. Installed original 12AU6's and after warm up now have a decent DC Balance. However, the Vertical Position control is no longer centered when centering the trace. So the Vertical Position Ranger pot has to be adjusted properly to complete the DC Balance. I have to pull the Type 547 out and remove the covers to adjust it. Follow on activity.

Good progress Med, as always you will get the job done.

Excellent stuff!

It makes me feel guilty. I have a few valve scopes including a Solartron CD1400, which seems to have had very little use. I should fire them up carefully, to keep them aired and stop the electrolytic caps degrading.

More work on this plug-in.

Not liking this tubular crapacitor. Yep, it's leaky.



Much better.



This is the Vertical Position Range that some Gorilla so graciously fucked with. Proper adjustment combined with the DC Balance control has yielded 2 things. Absolutely perfect DC Balance plus trace center line aligned with Vertical Position Control at mid-point. And bonus, all the original vacuum tubes.



Next on the agenda. Why is the 0.5V vertical range dead? Quite simply. One of those bare conductors had been moved and was shorted against the chassis. Easy fix. 0.5V now OK.



Left to do. Vertical compensation. That involves clearing off bench 2 so I can lay the Type 547 on it's side and remove the bottom plate for access to the compensation adjustments. I may not be able to get to that until next week. Stay tuned.

Follow up and completion of this plug-in.

Test set up to perform vertical compensation. Type 547 on it's side. Bottom plate removed for access to the compensation adjustments. Heath IG-4244 Scope Calibrator as signal source through a 50 ohm feed-thru terminator. 1kHz square wave as signal.



All the vertical ranges needed a very slight tweak. After 56 years since the last calibration that's pretty damn good. Here's a 100kHz square after completion. No more tilting of the waveform. This plug-in is now 100% functional.

Looking good now, Med!