And another Tektronix repair saga begins - Page 1
Forum section: electronics / repair

author: slburris
author_rank: Frequent Contributor
timestamp: December 24, 2012, 05:14:49 am
content: Sigh, I'm a sucker for deals on old analog Tektronix oscilloscopes.Recently a 2465 came up on eBay and I snagged it for $140US. I got itprimarily as a source of parts for my working 2465 but now that it's inmy hands I'm tempted to repair it.It was advertised as "powers on". Well, it does do that. I can see theon screen readouts although they aren't focused well. And I can see sometraces that don't appear to be sweeping.Time to crack it open and start with the power supply :-)I'll post some pics as I find anything interesting.Scott

author: SeanB
author_rank: Super Contributor
timestamp: December 24, 2012, 06:20:37 am
content: Sucker for punishment aren't you.......... good luck, at worst you will have spares or an idea of what goes wrong, at best a second scope.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 24, 2012, 02:26:18 pm
content: Quote from: SeanB on December 24, 2012, 06:20:37 amFor some reason I doubt it will be a 'second' scope

author: SeanB
author_rank: Super Contributor
timestamp: December 24, 2012, 02:37:31 pm
content: Second of the type..........

author: PaulAm
author_rank: Frequent Contributor
timestamp: December 24, 2012, 03:57:19 pm
content: Unless a parts scope is missing major pieces I generally can't stop myself from fixing it.Which generally means I need to get another parts scope ...

author: slburris
author_rank: Frequent Contributor
timestamp: December 25, 2012, 12:43:35 am
content: Now that I've looked at it a little more carefully, I'm convinced there'snothing seriously wrong with it.It seems the time base was stuck in X mode. It appears that somethingis broken with the clear plastic back switch on the timebase switch(if that makes sense). As you turn the timebase switch, the clearplastic (which marks the timebase) will turn counterclockwise, but itdoesn't turn clockwise. It's possible to manually turn it and thesweep starts and runs.I've checked all four channels with the front panel calibration signaland can get a nice square wave on all of them. I can fiddle with the readoutfocus and get either the top readouts or the bottom readouts in focus, butnot both at the same time. The trace focus seems to be OK.So I definitely have a mechanical problem with the switch, and I'm hopingthe focus problem is a capacitor problem in the power supply. I don't thinkthe non-A and non-B versions have the A5 board with leaky SMD tantalums,but I won't know for sure until I take this apart.My biggest fear when buying the 2XXX series scopes is having abroken Tek hybrid, but so far I've been lucky. I know otherswho collect the 4XX series instead because they have more obtainable parts(other than the models with tunnel diodes!!).Scott

author: slburris
author_rank: Frequent Contributor
timestamp: December 31, 2012, 02:00:07 am
content: Well, so much for the hope that this would be a simple power supply thing.I measured all the power supply test points in the service manual, and allare within spec, including ripple.Still having problems with not being able to get the top readout and bottomreadout in focus at the same time. Guess I'll have to study the service manualin more detail.And...I've found a new problem. Once of the cursor lines stops being adjustableabout 1/3 of the way from the left hand side of the screen. The readout changesas the knob is adjusted, but the line stops moving to the right. The other cursorline can be moved anywhere. More studying of the service manual.Scott

author: BravoV
author_rank: Super Contributor
timestamp: December 31, 2012, 02:33:49 am
content: Had problem with the cursors at my 2465B before, though not similar to yours, the position of the vert cursors were shifted down abit as pic below, while it should be at the correct location as pointed by the red line.Lucky me, the problem was solved just by unplugging all connectors to A5 board and plugged all back again, probably loose connections.