Chris,
U1094 is held in contact by a frame and some sort of elastomeric pad. There are instructions starting at page 4-30 in the service manual (070-2314-00) on how to deal with this "HYPCON" connection.
I suspect that the pin 3 connection has gone open, removing the main ground path to the chip. With luck, this connection break is not inside the hybrid but at the accessible HYPCON contacts. Following the manual directions, carefully remove the hybrid, clean the contacts with isopropyl alcohol (91% or more), dry, and reassemble.
--John Gord
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--- In TekScopes@..., "chrismh_somenumber" wrote:
Another Update:
I've worked my way down the horizontal amplifier board, checking all voltages and waveform test points. Everything was looking good until I reached U1082. The voltages at many of the pins were high.
Suspecting a problem with the readout, I removed Q1052 and Q1072, connecting the pads from emitter to collector with a wire. (This is recommended in the service manual, page 3-57, to remove the feedback path).
More of the voltages around U1082 were OK after that change (15, 17, 18, 19 were still high), but TP1038 and TP1078 were still high. I lifted the collectors of Q1028 and Q1034 to remove the readout positioning, but that did not change TP1038 and TP1039.
The voltages around U1094 are all wrong. Most read .5 to 1 volt high. Pins 13 and 14 read 4.5V high, and pin 3 reads 0V (it should be 4.2V). The output waveform going into the CRT (test points 5 and 6) is a flat line.
I checked component values around U1094 and they seemed OK. The
Is it likely that U1094 is bad? The U1014 OpAmp appears to be op-amping, and its supply voltage is OK. The voltages in that bit of circuitry utilizing U1094 are running a little high, but could that cause U1094 to not produce any output at all?
Thanks,
Chris
--- In TekScopes@..., "chrismh_somenumber" wrote:
My recently acquired 7104 has a problem, which I assume is something to do with the horizontal amplifier (please feel free to correct me...).
When the scope starts up, I get a normal trace for about 3-5 minutes, then it changes to a compressed vertical line. It appears that the vertical is working since I can make the vertical line grow and shrink (vertically) by varying the v/div or by varying the input signal. However, the entire trace, and the readout, is compressed to a single vertical line.
Thoughts?
Thanks,
Chris
