Yep, this sounds exactly like a failed Z Axis hybrid. I have replaced many of them. They are indeed in the top 5 failures. No soldering required, just remove the 4 nuts. When replacing the part, you m

I think that Tek made instruments like your CA for IBM under contract. If I recall correctly the 454 ( or one of the original 45X instruments) was designed in response to an IBM need. Some of these we

If it's any help, any Tek part number ending in -99 is a non-salable in house test fixture.

Can you post a picture of the CRT showing the problem?

Well, you can see the 1ns markers on lesser scopes. I just did see them on the 2465A I have on my bench. The amplitude and triggering aren't great, but certainly viewable. I have adjusted the TG501 ou

The output circuit may be misadjusted. It requires a good output cable and termination, a good scope, and cre to adjust. Also clean the push button switches.

The fan control circuit in all these model variations have a thermistor to vary the fan speed as the internal temperature increases. The outgoing airflow is mainly directed out the right rear corner,

Martin, I looked today, and I do not have a CRT for your 305. The tube I had in mind is for the 221. Bob

Martin, I think I have one. I will look within the next few days.

Why? Evidence please. The archives are sketchy at best.. Or, just power it up, and wait for a cap to short.

If you want to be really careful, slowly raise the mains voltage with a Variac if you have one. This will allow all those old electrolytic caps to reform slowly. this is about all you can do. You can

I have brand new, factory packed 165-2074-04 for $65.00 shipped CONUS. If interested contact me off forum.

Jim, This seems to be the dreaded bad Channel Switch hybrid. Unfortunately fairly common. Try one from another, any, 24xx analog scope. A replacement will require a recal. Bob

Replace all the PS output caps. I bet the oscillations stop...

The Parametric measurements use the U500. You will need to recal the entire scope if it is to work completely correctly. Jim, contact me off list regarding the cal if you want it done. I have all the

Well, you may not need to change the caps. How many hours on the scope? I know it can be changed, but if they are low-ish, I would just use it.

Ah, OK, the U500 sounds like it is good then. You really need a calibration generator to run the cal's. It needs to be a 1Khz square wave of the correct voltage. Most function generators can't do it.

Jim, You need to run CAL 2 and 3 first. The different Trig hybrid will need different cal constants, plus the bad one probably caused some too-far-afield constants to be generated. If the CAL's don't

I really think it is the trigger hybrid. It is used to make the parametric measurements, so if it is bad, you will get the LIMIT message.

You probably have a bad trigger hybrid. A pretty common failure. You can try running CAL 2, but I don't think that will fix it..