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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to comp.arch.embedded,rec.radio.amateur.homebrew,sci.electronics.repair
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Tektronix 7603 scope behavior when readout board is missing
Greetings:
I just acquired a Tek 7603 scope with 7A18 dual-trace vert. and 7B53A timebase plugins but upon internal inspection and cleaning discovered that the readout board (when facing the front of the instrument it is found on the upper right side midway along the length) is missing, as are all interconnecting cables it uses. The display is very corrupted: odd blanking and sawtooth displays appear with no vertical input and horizontal sweep width changes with timebase selection in a drastic way. A vertical input signal modulates the strange displays in a fashion that suggests the vertical section is functional and the vertical position controls do work. The plugins are supposed to be in operating condition. The internal logic timeshares the display between readout and waveforms and is rather complex and implemented in Tek custom hybrid ICs and a mix of TTL and CMOS. I would really appreciate a report of the behavior on a working 7600 series scope when the readout board is disconnected; the service manual describes various voltage measurements with the board removed so it is permissible to do so and power the instrument (but no mention is made of the scope's behavior with the board removed). Many thanks to anyone willing to do this. Regards, Michael |
#2
Posted to comp.arch.embedded,rec.radio.amateur.homebrew,sci.electronics.repair
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Tektronix 7603 scope behavior when readout board is missing
On Sat, 05 May 2007 22:14:57 -0500, msg wrote:
Greetings: I just acquired a Tek 7603 scope with 7A18 dual-trace vert. and 7B53A timebase plugins but upon internal inspection and cleaning discovered that the readout board (when facing the front of the instrument it is found on the upper right side midway along the length) is missing, as are all interconnecting cables it uses. The display is very corrupted: odd blanking and sawtooth displays appear with no vertical input and horizontal sweep width changes with timebase selection in a drastic way. A vertical input signal modulates the strange displays in a fashion that suggests the vertical section is functional and the vertical position controls do work. The plugins are supposed to be in operating condition. The internal logic timeshares the display between readout and waveforms and is rather complex and implemented in Tek custom hybrid ICs and a mix of TTL and CMOS. I would really appreciate a report of the behavior on a working 7600 series scope when the readout board is disconnected; the service manual describes various voltage measurements with the board removed so it is permissible to do so and power the instrument (but no mention is made of the scope's behavior with the board removed). Many thanks to anyone willing to do this. Regards, Michael Post what options were sold as part of this scope. Some were sold without readouts, the fact there are no connectors indicates that possibly the readout option was deleted. IMHO, (and this is just a WAG) the problem you are reporting is not related to the readout... |
#3
Posted to comp.arch.embedded,rec.radio.amateur.homebrew,sci.electronics.repair
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Tektronix 7603 scope behavior when readout board is missing
PeterD wrote:
On Sat, 05 May 2007 22:14:57 -0500, msg wrote: snip I would really appreciate a report of the behavior on a working 7600 series scope when the readout board is disconnected; the service manual describes various voltage measurements with the board removed so it is permissible to do so and power the instrument (but no mention is made of the scope's behavior with the board removed). snip Post what options were sold as part of this scope. Some were sold without readouts, the fact there are no connectors indicates that possibly the readout option was deleted. Digging through Internet archives this morning I noticed a few posts from folks seeking the readout board for 760x scopes with a mention that 'Option 01' was a cost-reduced version sans this board so evidently the scope should work without it (if properly optioned?). I was not sure if any cable modifications would be needed if the board were removed from a scope not-so-optioned. And indeed I now discover an "Option 1" label on the bottom of the left bay so this scope never had the board. Its problems are elsewhere. Thanks, Michael |
#5
Posted to sci.electronics.repair
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Tektronix 7603 scope behavior when readout board is missing
msg wrote in
: PeterD wrote: On Sat, 05 May 2007 22:14:57 -0500, msg wrote: snip I would really appreciate a report of the behavior on a working 7600 series scope when the readout board is disconnected; the service manual describes various voltage measurements with the board removed so it is permissible to do so and power the instrument (but no mention is made of the scope's behavior with the board removed). snip Post what options were sold as part of this scope. Some were sold without readouts, the fact there are no connectors indicates that possibly the readout option was deleted. Digging through Internet archives this morning I noticed a few posts from folks seeking the readout board for 760x scopes with a mention that 'Option 01' was a cost-reduced version sans this board so evidently the scope should work without it (if properly optioned?). I was not sure if any cable modifications would be needed if the board were removed from a scope not-so-optioned. And indeed I now discover an "Option 1" label on the bottom of the left bay so this scope never had the board. Its problems are elsewhere. Thanks, Michael #1 check power supplies. the LV regulator board at the top rear of the scope had problems with the TO-3 connections to the PCB;the solder joints would crack and cause intermittents,also the DIP socket was removed and the IC soldered direct to the PCB. The cap-rectifier board had electrolytics go bad and cause voltage problems. I used to dismantle the LV reg assy,unsolder all the 6-32 studs for the TO- 3 xstr connections,file off the chrome plating down to the brass,and resolder,and they would be much more reliable. also,there's 4 electrolytic caps on the interface board that can cause Ps problems. Then there's the "gold-dot ribbon cables" that were a cause of intermittents;the TEK-mod was to replace all the ribbon cables with new ones that did not have the "gold-dot" connectors. G-D connectors are a paler color than the good gold-plated connectors. Since you cannot get new ones anymore,you would have to rework or build new ribbon cables.( a real project!) -- Jim Yanik jyanik at kua.net |
#6
Posted to comp.arch.embedded,rec.radio.amateur.homebrew,sci.electronics.repair
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Tektronix 7603 scope behavior when readout board is missing
msg wrote:
Greetings: I just acquired a Tek 7603 scope with 7A18 dual-trace vert. and 7B53A timebase plugins... snip The display is very corrupted: odd blanking and sawtooth displays appear with no vertical input and horizontal sweep width changes with timebase selection in a drastic way. A vertical input signal modulates the strange displays in a fashion that suggests the vertical section is functional and the vertical position controls do work. The problem was a defective C811 (14000 uf / 25v), the -18V filter capacitor for the -15V supply. Scope works well now. Regards, Michael |
#7
Posted to comp.arch.embedded,rec.radio.amateur.homebrew,sci.electronics.repair
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Tektronix 7603 scope behavior when readout board is missing
On 7 Mai, 04:12, msg wrote:
msg wrote: Greetings: I just acquired a Tek 7603 scope with 7A18 dual-trace vert. and 7B53A timebase plugins... snip The display is very corrupted: odd blanking and sawtooth displays appear with no vertical input and horizontal sweep width changes with timebase selection in a drastic way. A vertical input signal modulates the strange displays in a fashion that suggests the vertical section is functional and the vertical position controls do work. The problem was a defective C811 (14000 uf / 25v), the -18V filter capacitor for the -15V supply. Scope works well now. Regards, Michael Sounds good to my repair eperience. Due to own experience bad/dried filter caps in the LV pwr supply of Tek 76xx is often a problem. I had more than 50 of these for repair, and most of these due to cap problems. Good luck with your fresh repaired scope, it is a nice instrument (with and without readout option). hth, Andreas |
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