Tek 465B Diagnosis Comments Requested #photo-notice


 

Glad to hear that you fixed the problem!

The sheet metal cover is easy to assemble incorrectly, and a number of 475s that I have handled (whose construction is almost identical to the 465) had their sheet metal covers assembled in various wrong ways. I don't entirely understand your fix, but you may have simply restored the cover to its correct configuration. It certainly should NOT have been pressing on the attenuator blocks.

These scopes can be operated with both 1X and 10X probes, which is why they have a probe readout sense ring (you're cheap Chinese probes almost certainly don't have a readout sense pin, so the vertical gain range lamps will be lit incorrectly, but that's merely an inconvenience). However, a 1X probe (or a 1X/10X probe in 1X mode) has very different bandwidth characteristics than a 10X probe (or a 1X/10X probe in 10X mode). In almost all cases you will want to have your probe set to 10X, unless you need the increased sensitivity of 1X mode, and can accept the drastically lower bandwidth.

-- Jeff Dutky


 

Thank you. But this response came too late. I have already buttoned up the project, calling it finished. Now that I know those little rectangular white plastic blocks are actually easily removed, I "fixed" my problem another way. I had already cleaned the contacts, best as I could with those blocks in the way. Here was the problem: I noticed that both channels behave more or less the same way when my cheap chinese probes are set to 10X, when the sheet metal cover of channel 1 was off. But as soon as I tried to put the little sheet metal cover back on, the trace would get pointed and noisy again. That cover is a snap-on arrangement, and it was squeezing together the metal sides of the attenuator mounting bracket. So what it did was bend one of the flanges of the cover outwards out so it didn't squeeze and snap on. Now it is only held in place by the 5 little screws. Now both channels behave almost perfectly identically. What i also learned was this scope doesn't like when you set the switch the probes to 1X. Apparently the correct way to operate this scope is with the probes set at 10X all the time. I believe I like this scope better than my 2215, even though my 2215 is light as a feather and works absolutely perfectly. This 465B has the DM44 volt/ohmeter on top. From what I read, it has a 10meg impedence on the voltmeter, which means you can use it as a VTVM. Is that true? Thank you. PS: this 465B is a sweet machine.


 

It sounds like the attenuator blocks have dirty contact pins. The solution to this is to clean the pins of the attenuator blocks with a cotton swab and isopropyl alcohol. The procedure is fairly simply: one at a time, remove each attenuator block, clean it's pins with the swab dipped in anhydrous pure isopropyl alcohol, and reinstall the block. You should only remove one block at a time so that you don't get confused about which block goes in which socket. This is a known problem with the 465 and 475 scopes. It also happens to the socketed transistors and ICs elsewhere in the instrument, and those can be fixed by the same procedure.

The attenuator board does not need to be removed. You can unseat each attenuator block from the top using the same access you currently use to "press down" on each block. You can gently rock the block back and forth lengthwise to unseat it from its socket. You might want to use a small tool to gently lever the block out of its socket incrementally from alternate ends.

-- Jeff Dutky


Dave Peterson
 

I'm not familiar with the 465B yet, but my first examination of the innards shows it is very close to the earlier 465.

Review the Maintenance section of the Service Manual available on Tek Wiki (make sure you're accessing the correct manual for the 465B, not the earlier scopes). The Maintenance section of the 465 (earlier) gives a good description of the removal of the vertical assembly on the left side of the scope. I'd be surprised if the 465B SM didn't give a similarly good disassembly procedure.

The 465 procedure involves unsoldering the input capacitors (the small metal cylinders inside the attenuator shields). Then behind those caps are 4 1/4" nuts that have to be removed. They are what hold the board to the face. Aside from taking off the volts/div knobs, you don't need to disassemble anything from the face. The BNCs are attached to the vertical board, not the face.

Otherwise it's bits-n-pieces that should be apparent to disconnect the rest of the board. You'll probably have a few small wires to unsolder to free the board. Along with screws and connectors in plane sight.

Good luck!
Dave

On Tuesday, May 4, 2021, 09:22:08 PM PDT, henryfinley <tomsradio@gmx.com> wrote:

I have a problem on my Tek 465B. On channel 1 the square test wave doesn't display right until I tap or push down on the rectangular white plastic adjustment blocks on the attenuator board. Every time I change the VOLT/DIV knob, I have to tap or push down on one or the other of the first or second block (counting from the front of the scope), to get the squate wave to display correctly. I suspect possibly a bad solder joint on the underside of the board. but I can't figure out how to get the attenuator board out, aside of taking odd all the knobs so I can get the front panel off, so I can get to the bracket screws, so I can take out the attenuator board. Certainly there has to be a better way. Thank you.


 

I have a problem on my Tek 465B. On channel 1 the square test wave doesn't display right until I tap or push down on the rectangular white plastic adjustment blocks on the attenuator board. Every time I change the VOLT/DIV knob, I have to tap or push down on one or the other of the first or second block (counting from the front of the scope), to get the squate wave to display correctly. I suspect possibly a bad solder joint on the underside of the board. but I can't figure out how to get the attenuator board out, aside of taking odd all the knobs so I can get the front panel off, so I can get to the bracket screws, so I can take out the attenuator board. Certainly there has to be a better way. Thank you.