Hello, The upper right bnc only affects the delayed signal. Why not try the one for the A time base, at the lower right? A simple 1-volt p-p signal works fine for a trigger level. Also, try using Line

The diode addition is around Q664, half of the slope comparator pair of transistors. (B-time base) There is also an extra resistor. The soldering looks very neat, as if it was done at the factory, but

Hello Barry, Metal film could be better, I agree, and I am not committed to carbon film. As I recall, carbon comp had lower inductance than the other two types, but of course they can drift in resista

Thanks Ozan -- I will look into R1003 and 3F too. The last time I checked (a while ago) all of the power supply voltages were good. But when I open it back up I will double-check. Except for the odd s

Hello Mark, Thanks for the advice -- I will try it soon. I will probably put in 1/4W 1% carbon film to replace the broken ones. That might be over-kill, but the cost difference should be small. I usua

After checking through most of the circuit involved with the Ext Horiz function, and finding the signal going through all the way to Q824, and still no trace, I figured out what was wrong. After switc

R646 is okay. It will be awhile before I can dig into it further.

Thanks to all for the advice, and I am not offended. I measured them in-circuit, and thought they were isolated enough to do that when viewing the schematic. My plan was to find replacements in my sta

The EXT HORIZ function of my Tektronix 453 does not work, and I found some resistors that were way-out of specification. They are: R634 (reads as 550, should be 11K) R644 (reads as 4k, should be 10K w

Hello, The TekScopes articles mentioned earlier are a great place to start. If you lost track of them or cannot find them, contact me at <mmerigATsilverstarDOTcom> and I will send you pdf's. If I reme

Not sure about mods, but I would really make sure that the problem is with the tunnel diodes in the unit you have. It seems strange that all four of them would have failed. There are other parts of th

Hello, The first one in Charles Phillips' series was in February 1969. This is the volume when Service Scope was renamed "TEKscope", which in turn includes Service Scope. The look changed somewhat as

The Tektronix "Service Scope" publication had a series of articles by Charles Phillips. At least two of them maybe helpful: Troubleshooting the 453 Troubleshooting Trigger Circuits I think the Tekscop

What's wrong with mentioning the IEEE? I know a little bit about it (a good friend of mine is a past president, and we talk about it sometimes). Just curious, as a non-EE person. This is already off-t

As a non-EE, maybe my take on this could be useful, because the OP was looking for a non-technical analogy or explanation. But it should still be accurate. The kids going into the house example does n

Hello Dennis, Good luck to your wife, and I hope your cooking skills improve fast enough to avoid disaster. Once in a while I get email bounce messages from tekscopes.io, that sound like what you are

Hello, Earlier today, you said: "ALL the low voltage supplies test ok and have no ripple whatsoever. That, of course, applies to the 55V as well." Then why would you replace the cap(s) on the 55 v sup

Okay, you did all of the tests, but it was hard to tell given the reporting. For example, is the 55 VDC supply okay as far as ripple goes? I am not the only one to ask about this. Also, using "ripple"

Hello Stephen, Although I don't have a 465B, I have been following this thread because line-frequency noise can be so hard to track down, in many types of things, and was curious about how this all wo

There may be a loose grounding screw. There is a document on cleaning the switches in 4xx scopes, and within it is this: "One OTHER thing to check: (I'm not sure, at the moment, if this is only for th