So here's a new episode in my troubleshooting adventures. While following one of the diagrams (troubleshooting diagram number 3, the non-storage portion), I encountered a note recommending that I disable the storage section of the scope. It took me a while but I eventually found directions on how to do this. But these are kind of crude and I am not sure I did everything correctly:
1. Disconnect P3008 from the A12 Trigger Generator Sweep Logic board (see Figure 8-17)
2. Disconnect P483 from the A23 circuit board and connect a jumper between the two square-pin connectors on the board. I found this to be a bit confusing: is it asking to short the two pins of conector P483 with a jumper (which I did by soldering a piece of wire) or should I short more than one connector, and if so which one?
3. Move P307 (at the rear of A14 Vertical Mode Switch board) to the Test Mode position (see figure 8-15). But what is this Test Mode position? I am sure it is referenced somewhere in the 600 pages but after a couple hours of skimming through both volumes I can't seem to find it. There's no mention of a test mode connector on A14's schematic. The only thing I could see is this other connector, P206, that is sitting on top of P307. I switched 307 with 206 it but the scope wouldn't display anything and the fan was not turning anymore.
So I must have gone wrong somewhere and If anyone knows how to disable the storage unit, any guidance would be greatly appreciated. Thanks for your patience with my lack of experience, I'm really enjoying this repair so far!
Jerome.
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--- In TekScopes@..., "jeromequelin" <jerome.quelin@...> wrote:
Thanks for your suggestions jtjewell83. Sadly I was not able to trigger on a line signal (either picking it up from my finger or from a 24V AC signal). I have checked the trigger level pot and there doesn't appear to be any short or open circuit. The only thing that "works" about this pot seems to be the slope switch, which enables me to trigger on a signal for a fleeting moment in NORM trig mode, as I have described in a previous post (I have just now noticed that when I exercise this switch from + to - and vice versa in AUTO trig mode, the trace drifts ever so slightly faster for a fleeting instant. It doesn't briefly trigger as it does in NORM though). I am going to have to make a little video to give you all a better picture of what is going on. I might be doing something completely stupid! I am also in the process of reading the "Theory of Operation" section from the service manual and looking at the block diagrams and troubleshooting charts. There could be something wrong with the signal picked up from the CH1 preamp board that prevents the trigger circuitry to generate a trigger signal (if that makes any sense whatsoever!)
I'll keep you posted this weekend, and thanks again for the support. I am learning so much already, I do not regret an instant my purchasing this scope. Now if only I could buy another functional one to troubleshoot the Tek :)
Cheers,
Jerome.
--- In TekScopes@..., "jtjewell83" <jtjewell83@> wrote:
Another suggestion: Set the SOURCE switch to LINE triggering, and with the vertical sensitivity cranked up pretty high (i.e., like 100 mV) on the channel that your probe's connected to, touch the probe tip to your finger. You should see a triggered 60 Hz signal (assuming your house current is 60 Hz), assuming that your body is not grounded. Alternately, use an old AC adapter ("wall wart") that has an AC output, but turn the channel's vertical sensitivity down (i.e., like 5V).
--- In TekScopes@..., "jeromequelin" <jerome.quelin@> wrote:
Alright I realized I could couple the cal. signal into the ext. trigger
bnc with my second scope probe... silly me! Unfortunately it didn't
change anything, meaning that I still have my untriggered signal no
matter how much I turn that trigger level knob. I have been patiently
browsing the service manual (though I have not read it religiously cover
to cover quite yet) and I haven't found a good chart for troubleshooting
the triggering section yet. For all I know the problem could be more
general and not be caused by faulty circuitry on the trigger board at
all!
Thanks a lot Tom for your input.
Jerome.
--- In TekScopes@..., "jeromequelin" <jerome.quelin@>
wrote:
It looks like I'm going to need some more coax for this :(
But if I go into "A Trig View" mode, change source to ext. and press
the beam finder button, a straight but slightly distorted trace appears
beneath the signal and here again adjusting the trigger level doesn't
change anything.
Next thing on my to-buy list : bnc to bnc coax and a T adapter.
--- In TekScopes@..., "Tom Miller" tmiller11147@ wrote:
Feed the test signal into the Ch1 and the Ext trigger input. Select
Ext on the trigger source. What happens?
Tom
