Yes, I followed the service manual directions, loosened the nut on the collet, held my breath and pulled twice at 90 degrees rotations. The second pull let go and the fan came off clean. Guess I was living right today. I cna take pics if it will help anyone. I would try to make impression molds if someone wants to model this for a 3D printer.
I also got a chance to measure voltages and rough measures of ripple on J119, the test point for the main board. All values are almost in spec except for pin 11 the -8 volt supply to the channel 1 and 2 inputs. There I found the voltage at -6.4 volts (as I reported before) with a triangle waveform riding on top of over 150 millivolts. I am convinced this is the same waveform that corrupts the Ch1 and Ch2 traces. Now I have to separate cause from effect (is the power corrupt because its overloaded or is the regulator faulty). I also measured the voltage supply at U160 and found this tringle wave on the DC power. Overall, good progress for today.
I think my next step will be to tear down the LVPS to repair the fan and inspect the -8 volt regulator while its apart. My goal is to correct the power supply before replacing all the electrolytic and film caps.
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--- In TekScopes@..., "Tom Miller" <tmiller11147@...> wrote:
There are no brushes in that motor.
There is an end play adjustment on the rear bearing but it requires removal of the pc board to get to.
Did the fan just pull off the shaft?
T
----- Original Message -----
From: machineguy59
To: TekScopes@...
Sent: Sunday, March 10, 2013 6:14 PM
Subject: [TekScopes] Re: New here with a 2465 to clean up
I will post my experience repairing the fan when I have it completed. But for now, the fan and squirrel cage appear to be intact. The collet is functional although I have not taken the jaws out of the sleeve yet. I was careful removing them and it all looks good to me.
I suspect either the motor windings (not likley I think), the motor "brushes" (more likely), or the drive transistors (what I am hoping for). I will keep my fingers crossed.
--- In TekScopes@..., "Tom Miller" <tmiller11147@> wrote:
>
> We will be interested in how you resolve the fan problem.
>
> it is a well known issue. Most likely the plastic fan collet has broken.
> Hey, I wonder if this part (or something similar) could be made with the 3D printer?
>
>
> Tom
>
> ----- Original Message -----
> From: machineguy59
> To: TekScopes@...
> Sent: Sunday, March 10, 2013 2:05 PM
> Subject: [TekScopes] Re: New here with a 2465 to clean up
>
>
>
> You guys are super. Thanks you again for the warm welcome and helpful advice. I finally got some time to apply some of it and want to give you a status update.
>
> First, I dismantled the front control panel and cleaned everything. There was a minor amount of residue from an old spill (I feared it would be worse) but overall the inside is remarkably clean. I did find that someone had previously glued some knob covers to their inserts and they broke during tear down. I plan to order replacements but I CAN glue them back if necessary.
>
> Second, I built a heat sink for U800 by modifying an old heat sonk from a computer video board. It was messsy to cut notches for adjacent parts but it was worth it. I have a heat sink that fits well and seems to work well. It screws to the same screws that hold the U800 but I was careful to no overtighten. I can post or mail pictures if anyone is interested.
>
> Third, Patrick, your advice to measure voltages on J119 (the test point for regulated low voltage on the mainboard) is spot on. The -8 volt supply is only at -6.4 volts (a 20% error). Also, several voltages have ripple that is far out of spec (I didnt record actual values but will before repairs are started). My review of the schematics shows that -8 supply only feeds the two vertical pre-amps (U100 and U200) and the op amp that sets paramters for VAR gain and DC ballance (U160). My conclusion is that you were right, the -8 volt supply is failing (probably the output filter cap) and this drooping voltage causes the vertical pre-amp gains to be off and variable. Alternatively, one of the preamps or the op amp is overloading the supply but this seems unlikely since other preamp functions are working.
>
> Fourth, I ordered new caps for the entire LVPS (both boards). The spead sheet posted at Tekarc was very helpful and still relevant. All parts are still available at Mouser. I verified this list with the service manual for the 2465 and found I need two additional caps (C1112, and C1050). I also chose to order replacements for the ceramic caps but will probably not change them out since ceramics seem to have a long life expectancy. I apprecaiate any advice on this decision.
>
> Fifth, I found that the case fan is not running. The shaft turns freely and feels to run smoothly but the fan does not turn. If I give it a spin by hand it just stops with no apparent self motivation. So I have a fan to repair. Its one of the "original" designs with a separate transistorized drive board. These were very quiet fans so I will try to restore this one.
>
> So work continues in my spare time. I expect a complete restoration will be possible. I will post updates of my progress along the way. But I wanted to post this thank you for the excellent help I have received from this group. I would not take on this project without your advice.
>
> Mac
>
>
> --- In TekScopes@..., "Patrick Wong" <patwong3@> wrote:
> >
> > Hi Mac,
> >
> > I recommend that you add qservice.tv as a favorite in your browser because you can get lots of useful information about Tektronix scopes there.
> >
> > For example, you will see that the part number for the 2465 low voltage power supply has a slightly different suffix compared to the LVPS for the 2465A and 2465B. Therefore I would not assume that a parts list compiled for a 2465B will work 100% for your unit. It might be 95% correct, or might be further off.
> >
> > When I worked on the LVPS for my 2465A and 2467 I found small differences between the capacitors. There were a few non-polarized electrolytics in the 2465A power supply. Both scopes were built in mid-1988. Therefore, even within the 2465A/2467 generation, you cannot count on the LV power supplies being identical with regards to capacitor content.
> >
> > I also recommend you replace the two AC X2 line filtering capacitors as you will probably see the yellow transparent plastic body has lots of cracking. This is a potential failure area especially in Europe where the AC line voltage is 220V or more.
> >
> > With regards to the CH1 and CH2 gain problem, I doubt the preamp hybrids are the problem. Assuming the 2465 has similar circuitry as 2465A in this area, I suggest you look at U160, a quad op-amp which controls the gain and DC balance for U100 and U200 (see schematic #4 which shows the vertical attenuators and preamp section.) U160 is powered by the +15V and -8V power supplies (see the power distribution diagram) so a problem with either of those two may help explain the gain problem you noticed.
> >
> > Meanwhile the CH3/CH4 hybrid is powered by the +5V and -5V supplies.
> >
> > Does your A5 board have a lithium battery soldered to one end? If so, that maintains calibration constants.
> >
> > Assuming the battery is original, I suggest you add a replacement battery to your parts ordering form. You will need to maintain voltage with a lab power supply while unsoldering and replacing the battery (using a non-grounded soldering iron.)
> >
> > Good luck,
> >
> > Patrick Wong AK6C
> >
> > --- In TekScopes@..., "machineguy59" <machineguy59@> wrote:
> > >
> > > ...That parts list is for a 2365B but it looks to me that it will also work for a 2465. Does anyone know if there are differences?
> > >
> > > Then, with the heat sink on U800 and the knowledge the glue is cleaned out, I will resume the quest to find why the gain is messed up on Ch 1 and Ch 2. This gain on Ch ! and Ch 2 is my only serious concer for the scope.
> >
>
