tektroinx 453 repair

[KV8E]

I have a 453 scope that works fine except for the rotary time base sweep knob. it will not go above 50ms position. acts like it has hit the end stop. have looked at the switch best I can through the boards and other things in the way and cant see why it will not turn further. acts like it is hitting something at the 50ms spot. any ideas?? switch does go down to the bottom with no problem.

[huelter]

Try to spray some contact cleaner inside the knob. Other than that, I think you will need to remove it to fix/replace.

[PaulAm]

Is the B sweep locked?  Can you advance the B sweep past the lock point?  It should be able to go to the highest sweep speed.

There may be something in the A/B sweep mechanical interlock that's preventing the knob from going further.  You'll need to open it up to take a look.  With any luck something fell into the switch and you can fish it out.  I haven't looked inside a 453 for a while, but I imagine that it would be major surgery to get that switch out.

I would not spray contact cleaner all over the switch, just sayin.

[joseph nicholas]

I know this is not the place for this but here goes.  If anyone is interested I have all of the boards for this plus a crt, transformer all in working condition.  Just saying.

[particleman]

Does the variable timebase (red knob in center of time base) turn?

[bob91343]

Some of the knobs require pulling out to get past the stop.