Exactly It the main reason I love to restore old test gear especially and make it useful again as no better feeling to see something that would have been trash otherwise come back to life and be of a good use and love to see others do it as well as hate the now throw away culture we live in currently.
Good thing to see a old piece of gear to get back into fully working order that was would have been scrapped and was already scavenged for parts already otherwise. Good save, now you have a decent dual timebase analog oscilloscope to add to the bench, what I planning on doing with mines as used one for 10 plus years at a shop I use to work for and reason decided to get one myself as like that scope and very familiar with it. Thankfully found the issue with the vector board on mines and even manage to finally get the readout to work correctly temporary as hack in a few transistor in temporary as all I had, same as you pretty much, but unfortunately for me found the digital board definitely has bad ram which have to narrow down but now have the row it in as ran the advance diagnostic as readout works now and hopefully assuming goes as plan will have mines going in a couple weeks once parts start to arrive to finish it up and do a update video of course on it and hopefully be on bench to finish reel to reel decks I have to restore but using the 2235 for now.
Nice find. Exactly what I’d do, go along the signal path until I find a change. Nice you had the horizontal channel right below to make cpmparasons to, but that difference between 1.98v and 7v would have been enough for me. Usually when I measure transistors on “diode test” I would do the base-emitter junctions too, but it is more likely that the base-collector junction be damaged. Sometimes you can get a “Good” 600mV on both base-emitter AND base-collector, but the device can be shorted collector-emitter, not common but worth making a mental note of. You know, you could have matched the differential paor of descretes…a good chance to use your curve tracer “in anger” ! I would have put in a “turned pin” Dil-14 socket and poked the transistors into that to “save” the board and make it easier and quicker to install the CA3046 when you get it. I had a CA3046 fail in the +5v regulator of my 7623. I did not have any other CA3046’s, but I did have a CA3086, jts pin out and arrangment of transistors inside looked the same, so I tried it snd it fixed the fault. Personally I’d just leave those transistors in there…why fix it “again” if it works? So nice to see you persevering with “real” faults, most of what I’ve been doing is prophplactically replacing tantalum capacitors in 7000 series CRO’s…definitely not worth filming for you tube! Do have a cloud of smoke two days ago as a decoupling resistor upwind of a shorted tant got a bet “red in the face”…the missus was NOT impressed with the smell and had to open all the windows and air the room out. Oh, and looking st the circuit…and nice to see you got the actual paper manual…shipping costs here to Tasmania are prohibitive so you only buy what you absolutely HAVE to…but you did not need to install that fifth transistor…the one that was “parked” with all its collector, base and emitter to the negative rail. Good designers do things like that…say half of that 4053 mux was not needed..a good designer “parks” all the unused inputs to ground or negative rail…a bad designer leaves high impedance inputs, (and MOSFET gates come to mond here) ..completely floating to accrue charge and float up into the linear region and get really hot. But, yes it is a sign of a really good designer to “park” even relatively low impedance BJT’s in a CA array! Those sample and hold integrators…and I see the feedback integrator cap is actually inside that he chip too…remond me of my upcoming battle with to such, much older and less integrated (sp’scuse the pun) S+H’s in that damn 7L5!
Thank you as always Globe Collector! I do enjoy the more interesting faults! Thats one of the reasons I purchased this 2230 in the first place - I saw the calibration sqaures stuck on the CRT in the advertisement for it and thought: "that must be an interesting one to troubleshoot!" I would leave those transistors in, but due to the pinout of the CA3046, it required some of the legs to be twisted around a bit. I already ordered the CA3046s and they arrived the other day. Thank you for the clarification on that 5th transistor not really being needed. I was wondering why emitter, base, and collector were all tied together like that! Speaking of the 576, I had mentioned this display issue in the Groups.io Tek group and someone had said that the CA3046 gives some weird curves when tested on a 576. So I tested the new ones on it - didn't notice anything strange. All the transistors looked normal providing hFE ~150.
Oh, and PLEASE, clean that smutty sticker off the left bottom of the tube bezel….now it works, make it look nice and “loved”…it needs a bit of TLC after years of neglect by previous owners!
It's an awesome feeling when you do something like this and arrive there by thinking it through, this is why we do what we do !....cheers.
Exactly
It the main reason I love to restore old test gear especially and make it useful again as no better feeling to see something that would have been trash otherwise come back to life and be of a good use and love to see others do it as well as hate the now throw away culture we live in currently.
Agreed! It's one of the main reasons I love repairing and troubleshooting!
Good thing to see a old piece of gear to get back into fully working order that was would have been scrapped and was already scavenged for parts already otherwise. Good save, now you have a decent dual timebase analog oscilloscope to add to the bench, what I planning on doing with mines as used one for 10 plus years at a shop I use to work for and reason decided to get one myself as like that scope and very familiar with it. Thankfully found the issue with the vector board on mines and even manage to finally get the readout to work correctly temporary as hack in a few transistor in temporary as all I had, same as you pretty much, but unfortunately for me found the digital board definitely has bad ram which have to narrow down but now have the row it in as ran the advance diagnostic as readout works now and hopefully assuming goes as plan will have mines going in a couple weeks once parts start to arrive to finish it up and do a update video of course on it and hopefully be on bench to finish reel to reel decks I have to restore but using the 2235 for now.
Nice find. Exactly what I’d do, go along the signal path until I find a change. Nice you had the horizontal channel right below to make cpmparasons to, but that difference between 1.98v and 7v would have been enough for me. Usually when I measure transistors on “diode test” I would do the base-emitter junctions too, but it is more likely that the base-collector junction be damaged. Sometimes you can get a “Good” 600mV on both base-emitter AND base-collector, but the device can be shorted collector-emitter, not common but worth making a mental note of.
You know, you could have matched the differential paor of descretes…a good chance to use your curve tracer “in anger” ! I would have put in a “turned pin” Dil-14 socket and poked the transistors into that to “save” the board and make it easier and quicker to install the CA3046 when you get it.
I had a CA3046 fail in the +5v regulator of my 7623. I did not have any other CA3046’s, but I did have a CA3086, jts pin out and arrangment of transistors inside looked the same, so I tried it snd it fixed the fault. Personally I’d just leave those transistors in there…why fix it “again” if it works? So nice to see you persevering with “real” faults, most of what I’ve been doing is prophplactically replacing tantalum capacitors in 7000 series CRO’s…definitely not worth filming for you tube! Do have a cloud of smoke two days ago as a decoupling resistor upwind of a shorted tant got a bet “red in the face”…the missus was NOT impressed with the smell and had to open all the windows and air the room out.
Oh, and looking st the circuit…and nice to see you got the actual paper manual…shipping costs here to Tasmania are prohibitive so you only buy what you absolutely HAVE to…but you did not need to install that fifth transistor…the one that was “parked” with all its collector, base and emitter to the negative rail. Good designers do things like that…say half of that 4053 mux was not needed..a good designer “parks” all the unused inputs to ground or negative rail…a bad designer leaves high impedance inputs, (and MOSFET gates come to mond here) ..completely floating to accrue charge and float up into the linear region and get really hot. But, yes it is a sign of a really good designer to “park” even relatively low impedance BJT’s in a CA array!
Those sample and hold integrators…and I see the feedback integrator cap is actually inside that he chip too…remond me of my upcoming battle with to such, much older and less integrated (sp’scuse the pun) S+H’s in that damn 7L5!
Thank you as always Globe Collector! I do enjoy the more interesting faults! Thats one of the reasons I purchased this 2230 in the first place - I saw the calibration sqaures stuck on the CRT in the advertisement for it and thought: "that must be an interesting one to troubleshoot!" I would leave those transistors in, but due to the pinout of the CA3046, it required some of the legs to be twisted around a bit. I already ordered the CA3046s and they arrived the other day. Thank you for the clarification on that 5th transistor not really being needed. I was wondering why emitter, base, and collector were all tied together like that! Speaking of the 576, I had mentioned this display issue in the Groups.io Tek group and someone had said that the CA3046 gives some weird curves when tested on a 576. So I tested the new ones on it - didn't notice anything strange. All the transistors looked normal providing hFE ~150.
Nice work!
Thanks!
Oh, and PLEASE, clean that smutty sticker off the left bottom of the tube bezel….now it works, make it look nice and “loved”…it needs a bit of TLC after years of neglect by previous owners!