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Having restored my R7623A Storage Oscilloscope to operational status, though there's still some issues on the Output Signals PCB tucked away inside the Power Supply Rectifier/Filter assembly, VERY inaccessible, so I capped off the connector that normally plugs onto the Trigger Select PCB assy to yield a Vertical Output Signal on the rear panel...that board was the fault in not having Internal Trigger on that scope. Then today, I found the CRT Graticule Lamp PCB assy not working, where not only were all three 6.3V/200mA Incandescant lamps all burned out, but there isn't any Voltage coming to the PCB now, it's origin at the back end of the Storage PCB assy where a forest of ribbon cables pass thru, so the other end of that 2-wire cable connector is buried and basically inaccessible. So, until I get really adventuresome, there won't be graticule lights on that scope now in service.
I extracted this 7633 Storage Scope from the right side of my Test Bench equipment stack, and opened it up yesterday. This scope is a good 15 years older than the R7623A that I just restored to service, which also served as an exercise in digging into these beautifully crafted 7000 series modular scopes in Tektronix product line from the early 70's. When Aerospace and Military Industries scrapped the 7000 series for the next generation 11,000 series scopes and later technology in the mid-90's, I bought into the 7000 series scopes. Several 100MHz mainframes, loads of Vertical Amp plug-ins, Time Base Plug-ins, and some other functions plug-ins that made use of their CRT Readout functions, it made it very affordable to have spare parts to keep these extremely well-built scopes running. The R7623A I just restored to service was built in mid-1984, while this 7633 scope I just pulled from service to the Check-out bench was built in early 1970 or late 1969. I see date codes in the late 60's in it.
This morning, having found the 2A FAST Fuse that feeds the HF Oscillator for the CRT Hi Voltage Circuit was open, I did find all of the Low Voltage Regulator circuits were up and running. So, that's a relief, not having to pull that regulator board out to trouble-shoot it, as I had to do on the R7623A.
But, the HV CRT Power Supply PCB assy is NOT readily accessible on this instrument.
As I have all of the Service Documentation on these scopes and their Vertical and Horizontal Plug-ins, which are interchangeable between instruments, the plan to begin the 'education' on digging into the mainframe of the R7623A proved to be a good idea. Not only did it yield a working replacement scope for the test bench, but I'm now more acclimated to working on these scopes to hopefully solve this CRT Circuit failure. I'm going to have to take a trip to my storage lockers in Gardena, and find my Simpson High Voltage probe (1000:1 10kV) along with the Triplett 630NS VOM that I had forgotten I had purchased at a TRW Radio Amateurs Technical Swap Meet in the late 90's.
I also have a spare 7633 Scope Mainframe there. I don't recall what it's status is, but, it might become handy if I have serious HV problems on this mainframe. Not sure if that 630NS VOM works (nor where in what box I packed it away into), or if it had the 4100VDC range on it, which comes in handy on the moderately high voltages in the CRT circuits. I have a feeling that if it worked, I would have kept it with me and not tucked away in storage. I never worked on Televisions in my early electronics career. My Electronics indulgence was all Rock n' Roll based gear, being the bass player in my band and the guy who could cobble larger PA rigs from our band and other band's gear at gigs where there were more than one act.
So, this adventure begins.
I did find the Low Voltage Regulator supplies ALL WORK and in spec: -50VDC Ref Regulator Ckt, +50VDC, +15VDC, -15VDC, +5VDC and an moderately regulated +130VDC supply. That's the PCB assembly on the rear panel, sitting underneath a vented cover which I've removed. I replaced the 2A fuse F814, after checking to see if there was any short on Q1195, it being the TO3 Power Xstr that drives the Primary of the HF Switching Xfmr T1199 on the A10 High Voltage PCB Assembly. I didn't measure any short there, so tried it with a fresh 2A FAST fuse installed. Fuse didn't blow, found 20VDC on the collector of Q1195, but, no CRT came up either. No idea what caused the 2A fuse to blow, so this will be an education.
I've also posted this adventure on TekScopes@groups.io where I had some good help and assistance in troubleshooting the R7623A to success.
I extracted this 7633 Storage Scope from the right side of my Test Bench equipment stack, and opened it up yesterday. This scope is a good 15 years older than the R7623A that I just restored to service, which also served as an exercise in digging into these beautifully crafted 7000 series modular scopes in Tektronix product line from the early 70's. When Aerospace and Military Industries scrapped the 7000 series for the next generation 11,000 series scopes and later technology in the mid-90's, I bought into the 7000 series scopes. Several 100MHz mainframes, loads of Vertical Amp plug-ins, Time Base Plug-ins, and some other functions plug-ins that made use of their CRT Readout functions, it made it very affordable to have spare parts to keep these extremely well-built scopes running. The R7623A I just restored to service was built in mid-1984, while this 7633 scope I just pulled from service to the Check-out bench was built in early 1970 or late 1969. I see date codes in the late 60's in it.
This morning, having found the 2A FAST Fuse that feeds the HF Oscillator for the CRT Hi Voltage Circuit was open, I did find all of the Low Voltage Regulator circuits were up and running. So, that's a relief, not having to pull that regulator board out to trouble-shoot it, as I had to do on the R7623A.
But, the HV CRT Power Supply PCB assy is NOT readily accessible on this instrument.
As I have all of the Service Documentation on these scopes and their Vertical and Horizontal Plug-ins, which are interchangeable between instruments, the plan to begin the 'education' on digging into the mainframe of the R7623A proved to be a good idea. Not only did it yield a working replacement scope for the test bench, but I'm now more acclimated to working on these scopes to hopefully solve this CRT Circuit failure. I'm going to have to take a trip to my storage lockers in Gardena, and find my Simpson High Voltage probe (1000:1 10kV) along with the Triplett 630NS VOM that I had forgotten I had purchased at a TRW Radio Amateurs Technical Swap Meet in the late 90's.
I also have a spare 7633 Scope Mainframe there. I don't recall what it's status is, but, it might become handy if I have serious HV problems on this mainframe. Not sure if that 630NS VOM works (nor where in what box I packed it away into), or if it had the 4100VDC range on it, which comes in handy on the moderately high voltages in the CRT circuits. I have a feeling that if it worked, I would have kept it with me and not tucked away in storage. I never worked on Televisions in my early electronics career. My Electronics indulgence was all Rock n' Roll based gear, being the bass player in my band and the guy who could cobble larger PA rigs from our band and other band's gear at gigs where there were more than one act.
So, this adventure begins.
I did find the Low Voltage Regulator supplies ALL WORK and in spec: -50VDC Ref Regulator Ckt, +50VDC, +15VDC, -15VDC, +5VDC and an moderately regulated +130VDC supply. That's the PCB assembly on the rear panel, sitting underneath a vented cover which I've removed. I replaced the 2A fuse F814, after checking to see if there was any short on Q1195, it being the TO3 Power Xstr that drives the Primary of the HF Switching Xfmr T1199 on the A10 High Voltage PCB Assembly. I didn't measure any short there, so tried it with a fresh 2A FAST fuse installed. Fuse didn't blow, found 20VDC on the collector of Q1195, but, no CRT came up either. No idea what caused the 2A fuse to blow, so this will be an education.
I've also posted this adventure on TekScopes@groups.io where I had some good help and assistance in troubleshooting the R7623A to success.
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