Re: Tek 7603 Followed Me Home

bobh@joba.com
 

So far no plugins and the light isn't lit.  I'll check it.

Bob.

On 9/8/2018 7:43 PM, Robert Hay wrote:
I have seen this Tek 7603 scope sitting on the table at the Tek Country store for at least three years.  I have tried to power it up and twist some knobs several times over the years with no response.  They have been asking $35 for it and I noticed today there are about 5-6 price stickers stacked up under the current one.

I have been thinking a 7603 would fit into my ensemble if I clear space for it by giving another scope to the Tek Museum.   So, I asked if they would take $25 for it and they did.  So, here it sits with the covers off and the power supply hanging out the back.  It doesn't do nut-tin when powered up.

The main fuse, the fuse on the regulator board and the one on the power supply board above the caps are good. I checked the power supply voltages on the regulator board with the following results:

Volt        VDC      VAC
130       114          11
50            44           5
5            4.396       0.25
15           13.2        1.4
-15         -13.17      1.3
-50          -44          4.8

Unregulated Voltages

50           66            0.16
-50        -52              13
15           24              0.04
-15       -24               0.1
5           12.4             0.05

Seems to be discrepancies between the ripple on the corresponding regulated and unregulated supplies which I don't understand.

The 130 volt supply is partly made up from the 50 volt supply and the voltage on the emitter of Q850 should add about 40 volts but I measure 10.8 volts DC there.  Maybe I see it now, if the 50v supply is at 44 volts there is no way the emitter of Q850 can get to 40 v.

I appreciate any ideas from folks especially those who have been thru a 7603 before.  Haven't had a chance to research the archive but will do that before doing more troubleshooting.  I can't take another scope to the Tek Museum until I know we can bring this one back to service.

Bob.





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