I love and hate these models. In terms of repair, I would rather mess with an unknown 8640B than this. It has its own disappointing set of issues. But at least the most common problems like plastic gears, sliders, and couplings are an easy and obtainable fix. Love them cause they're HP and a good function gen when working. Hate them cause of these ICs and the transistors of the output amplifier section. Now for advice/spoilers: Seems like R1 cracked due to the VCO IC being a short internally at some point. May have to check that gray box of the fan for any issues also. As per schematics on K04BB, the fan unit runs in series with R1 but is parallel to both the unreg 5+ and -5.2 rails. Which partly explains why it wouldn't turn on as the downstream regulation circuitry expects that fan load. All these parts can also fail in spectacular fashion. You'll definitely need to check if everything is clean and properly cooled overall. Cooling is key here and probably why the IC failed to short internallly. Extra but worth looking into: For me, I had 5/13 of these output amplifier transistors fail as shorts on me. Which blew the -24V rail fuse and gave me ERR 42. 4 were screwed onto the small and large heatsinks. 1 had no heatsink.
Thanks for your comment and all the info! I was under the impression that R1 was to limit current draw of the fan. R1 at 47ohms provides ~220mA current which is exactly what the fan pulls when I tested it out of circuit when I was cleaning it up. I thought that since the fan was very loud/noisy it was drawing max current to keep at its regular speed, which eventually caused the resistor to degrade due to thermal stress. The burn marks on the pads where the resistor is soldered seem to indicate a degradation that occurred slowly over time. I can understand why you have a love/hate relationship with these units! Seems the ASICs are a weak point which is a real pain. But I do like this unit's ease of use, that it can provide waveforms up to 50MHz, and it has a pretty fast transistion time at
Still want to see a “debrief” on the Tek 2230 when you get the replacement switch rack…you can’t play a piece of music and leave the last bar off! I have been busy too, a friend gave me a Rockland 7530 FFT Spec An, (a third party plug on for a Tek 7000 that turns it into a 0-100KHz A.F. spec an) and a HP 3456 volt-ohm meter that seems to work but is a bit out on the AC ranges, so I will be looking at the true RMS converter sometime soon. Also acquired a second 7L5, (from fleabay) that I can use as a board level swapper sort of like what you are doing here. As for the HP “fanboys” vs Tektronix “fanboys…I see you tend to lean HP whilst I tend to lean Tektronix, however, there is ONE THING that “killed” both of their high end test gear offerings with s lot of guys out there….and that eas ehen they decided NOT to include circuit diagrams in their manuals! I have this really swanky HP oscilloscope here, a 1980B, take a look online, a FEW people have made videos about it, but not many. The reason this device is not popular is because the manual does not include the circuit. As the gear of both companies got more and more software controlled a mentality seemed to pervade both companies that software and self-analyis routines could be a panecea for ALL faults and thus later manuals focused heavily on software and “ckompletely forgot” the underlying foundation in the OSI model, the HARDWARE it is all built on. As you would know, no amount of software self-analysis routines are of any value if the power supply, (or EHT in a device with a CRT) goes fut! Again, I was “playing along” in my other wn locally downloaded copy of the manual, however the first manual I found, like the bloody 1980B under my bench…had no circuit, but I dug deeper and found the same manual you have there and thus I could play along with you. Had I not been able to locate a manual with a circuit, I would reccommend you just “pack it in” and move on to something you DO have the circuit for…but luckily for this unit…and unlike that “brick” under my bench..there is a circuit! Now I know what you are dealing with here, I hsve two other HP generators that work on the same principle, the 3311A and the 3312A, the latter of which goes up to 13MHz, but inside is largely descrete and no large “ASIC’s” inside. So the way this type of generator works “synthetic”, it literally sinthesizes the output waveform from DC! The “VCO”…and I reccommend you download the 3312 A circuit so yiu can see it done descretely outside a chip..basically is just two voltage controlled constant current source/sink, their current sink/viurce control voltage comes from the frequency control on the front pannel…or a DAC I assume, in this thing. Between the current source/sink(s) is a “bridge” of four fast switching diodes, this acts as a switch that switches berween the current source and current sink…I’ll explaon wast switches it later, but the output of this switch goes to a capacitor, (or a whole switched bank of them). Imagine it starts with the current source connected to the capacitor, then the voltage in the capacitor ramps up…that is the up-slope of your triangle wave. Once the voltage gets to a certain limit, it trips a comparator that has its input connected to the capacitor, this comparator has very wide hysteresis ..but once it trips, its output goes back to the “bridge” of four switching diodes and flips the capacitor over to be connected to the current sink, so the voltage on it now slopes down…the downslope of the triangle wave…once this gets right down to the other end of the hysteresis range of the comparator, it trips again and the upslope recommences for the second cycle…so off the capacitor you have a triangle output, your buffer it of course to get a noce low impedance for the next stage. The square wave cones off the output of the comparator and is st quadrature phase to the triangle wave. If you change and track the two source-suink control voltages, you sewwp the frequency, if you change the capacitors, yiu change the frequency ranges! If yiu put different voltages onto the source and sink, you get sawtooth waves that slope either one way or the other…AND you automatically alter the mark -space ratio of your square wave. So this is what that VCO ASIC does, it probably has the diode switch in there, the comparator too and possibly the source and sink as well. The main reason they integrated it was to make it FAST, 50MHz fast! The shaper ASIC, is also pretty simple, leadt the first bit of it prior to the AM, FM, PWM bit. This is what turns the triangle wave into a sine wave and how it does it is really simple. The triangle comes in through a resistor that forms half of a potential devider. The other half of the potential devider consists of half a dozen or so resistors in parallel and each in series with a zener. As the triangle ramps up, the zeners start turning on in sequence, adding more resistors as they do and causing the devider to devide by more with each step, so the output slope gets leass and less and approximates a reasonably good sine wave…least to our ear…doesn’t fool a spectrum analyser! In reality, the diodes are not zeners, but ordinary diodes, but each is connected to a sucessively higher voltage at the far end. A whole second rack of resistors, diodes and voltage sources of the opposite polarity do the other half cycle of the triangle…and that’s the guts if it in a nutshell! That us whybthese type of generators always have trisngle, square and sine. So that diode clipper was the first stage in that second ASIC. Note how your “faulty” waveform at TP 4…which is the output..was, top half, triangle and, bottom half, sine….sort of like the sine clipper was working on just the nehative half cycle…and the inputs on pins 14 and 15 looked a little rounded on the top….I bet there was a DC bias in those inputs that should not be there, and that is why the sine shaper was being activated one side only. There was signal inversion happening bwrween the input and TP 4. Would love to see the waveforms from this up on the 2230…I must say, I never warmed to the raster display of the 54600!
Happy New Year Globe Collector! Hope you enjoyed your holidays! Thank you as always for watching and the comment of great info; I always look forward to it! I have not forgotten about the 2230! I was waiting on some parts/materials to come in to finish the repair and do the final step of performance checks/cal adjustments. The repair is pretty much done. I just felt like I was dragging things out a bit too much with all the videos so I wanted to wrap it all up in one last video where I do the performance checks. Speaking of which, I grabbed a nice bit of kit for that: a Tek CG 5011! I am waiting for it to come in and the seller really didn't know what condition it was in, so this will likely spark another video on inspecting and possibly repairing it! Also grabbed a TM5003 to power it from the same seller - they say this one works, but we'll see. The 8116A was meant to do some of the performance checks, but now I have an actual oscilloscope calibrator to do them! So it might be some time until I do a final video of the Tek 2230. But it should be worth the wait! Yes I guess you could say I am more of an HP fanboy. This started well before I became interested in electronics. I started out with a degree in chemistry and worked as a chemist for years. And I did a lot of HPLC/GC work. My favorite HPLCs/GCs were made by HP/Agilent. They were the easiest to service and had the best software. So considering that experience, I gravitated quickly towards HP electronics. I still think they are the best as far as servicability and being user-friendly. But Tektronix is starting to grow on me. And yes I agree it is a real shame that both companies stopped including schematics in their service manuals. The service manual for the HP54600 I use is a sorry excuse for a manual, with barely any troubleshooting guides and no schematics. Which is crazy to think because that scope is only a few years older than this 8116A - what the hell happened in that amount of time!? Anyway, I could go on forever about right to repair... Wow as always a wealth of info - thanks for explaining the ASICs! I'll admit some of that went over my head lol. But I will definitely have a look at 3312A circuit to see how its done. It seems these ASICs are a pain point in these units which is a real shame. I'll be in touch!
Thanks for the new year salutation, we had a quiet one this year…went to bed early like roight little party poopers! Heard the booms of the fireworks st midnight though. I will wish you snd your partner not only a happy new year, but a safe new year too! Yep the circuit of the 3312A will mske its function clear…read my description again whilst looking st it. oh, ahnother thing…to save you time scrolling through the manual pdf on film, just open a second instance of the same pdf in another tab and have it set at the other part of the manual. Some manuals I’m using here, I have had four or five instances open in different tabs, one on the circuit, another in the component list and a third in the description or instructions section…often the description will ask you to refer to a psrt of the circuit, so with this method you can rapidly switch tabs back and fourth without loosing either place in the manual! Odd you should say you were/are a chemist…same here, was right into transition metal ligand complexes! Used GC/MS at Uni on organic unknowns, never used HPLC though, but I have seen it set up in a lab…miles of stainless tubeing and high pressure fittings. Years ago s GC csme up st auction snd I bought it…for forty bucks without the cylinders, but with the ingection port and a column and pre column in the oven. Days later the chemist that had been using it in a government lab cane looking for it, the bean-counters had simply swiped it out of his lab without prior consultation…and the column in it was all set up with his reference measurements and half his data measurements…needless to say, he wanted it back. He offered 1500 for it, do I tooke the offer and ysed the doosh to finance a trip to Viet Nam! Funny how calibration routines call for things like marker generators with, say 1us “pickets”, I just use my RF signal generator…could reference its master oscillator to GPS if I eanted to be really pernikety…and just dial up a 1 : 1 square wave at 1MHz and simply line up the rising and falling edges with the graticule. Often you have to be inventive in the absence if vert specific gear you can’t afford or well never find or own. Talking about HP vs Tek…sort of like pertol -head hoons here with their Ford vs Holden…if you ever see an Australian BWD brand oscilloscope…one of their later models like the 845, see if you can acquire it and work on it…they are an absolute breeze to work on, both electronically and mechanically…the guy who designed them wasn’t even a “qualified” engineer! Take a look here… 7fTC_UM_4Fo, an old engineer who worked st BWD reminices!
Yes I remember now that you had mentioned somewhere you had a chemistry background! Metal Ligand Complexes - thats where things start to get complex (no pun intended) Takes me back to the horrors of inorganic chemistry in school getting my degree. I dealt mostly with organic. Worked with GCMS and LCMS, too! But I'm starting to loose all that now as its been a few years since working in that field. I've considered picking up some analytical chem equipment to repair as well! GC would be difficult to swing though - they are big, bulky, and require a gas source like He, H2, or N2. Sounds like you made out well on that deal 😂 I do the exact same thing with keeping several different tabs open of the same manual! It definitely makes it easier. I just looked up BWD scopes and found an old brochure for them. They look really neat! They have this offering called the 880 Powerscope that can measure 660V rms signals without external HV probes. A real beast! I'll keep an eye out for one! @@thanhhuynh272
If you watched the video I mention above, you’ll….or should I say, Y’all…will see a powerscope 880 behind Charlie Pandolfo, the engineer who worked at BWD. He mentions that John Beasely…the “B” in BWD…designed it when he saw some power engineers with a Tek 7603 connected to a three phase pannel and “adjusting” it with a wooden broomstick. If you search the internet with the trem, “Siemens Oscillar D1020” you might find an image of an oscilloscope with a black front pannel and green seven segment display with the EXACT same layout as the BWD 881A….so which came first, the chicken or the egg? As an Australian it would give me a warm fuzzy feeling that Germans clobed something we designed!
Sorry I completely glossed over that link you added for the video. I just watched it - neat stuff! Probably pretty cool place to work from what he describes. I love that they made an in-house calibrator for validating their scopes (seemed like a time marker). And he did mention how easy they are to service. I'll keep an eye out for em!@@thanhhuynh272
I love and hate these models. In terms of repair, I would rather mess with an unknown 8640B than this. It has its own disappointing set of issues. But at least the most common problems like plastic gears, sliders, and couplings are an easy and obtainable fix. Love them cause they're HP and a good function gen when working. Hate them cause of these ICs and the transistors of the output amplifier section.
Now for advice/spoilers:
Seems like R1 cracked due to the VCO IC being a short internally at some point. May have to check that gray box of the fan for any issues also. As per schematics on K04BB, the fan unit runs in series with R1 but is parallel to both the unreg 5+ and -5.2 rails. Which partly explains why it wouldn't turn on as the downstream regulation circuitry expects that fan load. All these parts can also fail in spectacular fashion. You'll definitely need to check if everything is clean and properly cooled overall. Cooling is key here and probably why the IC failed to short internallly.
Extra but worth looking into:
For me, I had 5/13 of these output amplifier transistors fail as shorts on me. Which blew the -24V rail fuse and gave me ERR 42. 4 were screwed onto the small and large heatsinks. 1 had no heatsink.
Thanks for your comment and all the info! I was under the impression that R1 was to limit current draw of the fan. R1 at 47ohms provides ~220mA current which is exactly what the fan pulls when I tested it out of circuit when I was cleaning it up. I thought that since the fan was very loud/noisy it was drawing max current to keep at its regular speed, which eventually caused the resistor to degrade due to thermal stress. The burn marks on the pads where the resistor is soldered seem to indicate a degradation that occurred slowly over time.
I can understand why you have a love/hate relationship with these units! Seems the ASICs are a weak point which is a real pain. But I do like this unit's ease of use, that it can provide waveforms up to 50MHz, and it has a pretty fast transistion time at
Still want to see a “debrief” on the Tek 2230 when you get the replacement switch rack…you can’t play a piece of music and leave the last bar off!
I have been busy too, a friend gave me a Rockland 7530 FFT Spec An, (a third party plug on for a Tek 7000 that turns it into a 0-100KHz A.F. spec an) and a HP 3456 volt-ohm meter that seems to work but is a bit out on the AC ranges, so I will be looking at the true RMS converter sometime soon. Also acquired a second 7L5, (from fleabay) that I can use as a board level swapper sort of like what you are doing here.
As for the HP “fanboys” vs Tektronix “fanboys…I see you tend to lean HP whilst I tend to lean Tektronix, however, there is ONE THING that “killed” both of their high end test gear offerings with s lot of guys out there….and that eas ehen they decided NOT to include circuit diagrams in their manuals! I have this really swanky HP oscilloscope here, a 1980B, take a look online, a FEW people have made videos about it, but not many. The reason this device is not popular is because the manual does not include the circuit. As the gear of both companies got more and more software controlled a mentality seemed to pervade both companies that software and self-analyis routines could be a panecea for ALL faults and thus later manuals focused heavily on software and “ckompletely forgot” the underlying foundation in the OSI model, the HARDWARE it is all built on. As you would know, no amount of software self-analysis routines are of any value if the power supply, (or EHT in a device with a CRT) goes fut!
Again, I was “playing along” in my other wn locally downloaded copy of the manual, however the first manual I found, like the bloody 1980B under my bench…had no circuit, but I dug deeper and found the same manual you have there and thus I could play along with you. Had I not been able to locate a manual with a circuit, I would reccommend you just “pack it in” and move on to something you DO have the circuit for…but luckily for this unit…and unlike that “brick” under my bench..there is a circuit!
Now I know what you are dealing with here, I hsve two other HP generators that work on the same principle, the 3311A and the 3312A, the latter of which goes up to 13MHz, but inside is largely descrete and no large “ASIC’s” inside. So the way this type of generator works “synthetic”, it literally sinthesizes the output waveform from DC!
The “VCO”…and I reccommend you download the 3312 A circuit so yiu can see it done descretely outside a chip..basically is just two voltage controlled constant current source/sink, their current sink/viurce control voltage comes from the frequency control on the front pannel…or a DAC I assume, in this thing. Between the current source/sink(s) is a “bridge” of four fast switching diodes, this acts as a switch that switches berween the current source and current sink…I’ll explaon wast switches it later, but the output of this switch goes to a capacitor, (or a whole switched bank of them). Imagine it starts with the current source connected to the capacitor, then the voltage in the capacitor ramps up…that is the up-slope of your triangle wave. Once the voltage gets to a certain limit, it trips a comparator that has its input connected to the capacitor, this comparator has very wide hysteresis ..but once it trips, its output goes back to the “bridge” of four switching diodes and flips the capacitor over to be connected to the current sink, so the voltage on it now slopes down…the downslope of the triangle wave…once this gets right down to the other end of the hysteresis range of the comparator, it trips again and the upslope recommences for the second cycle…so off the capacitor you have a triangle output, your buffer it of course to get a noce low impedance for the next stage. The square wave cones off the output of the comparator and is st quadrature phase to the triangle wave. If you change and track the two source-suink control voltages, you sewwp the frequency, if you change the capacitors, yiu change the frequency ranges! If yiu put different voltages onto the source and sink, you get sawtooth waves that slope either one way or the other…AND you automatically alter the mark -space ratio of your square wave. So this is what that VCO ASIC does, it probably has the diode switch in there, the comparator too and possibly the source and sink as well. The main reason they integrated it was to make it FAST, 50MHz fast!
The shaper ASIC, is also pretty simple, leadt the first bit of it prior to the AM, FM, PWM bit. This is what turns the triangle wave into a sine wave and how it does it is really simple. The triangle comes in through a resistor that forms half of a potential devider. The other half of the potential devider consists of half a dozen or so resistors in parallel and each in series with a zener. As the triangle ramps up, the zeners start turning on in sequence, adding more resistors as they do and causing the devider to devide by more with each step, so the output slope gets leass and less and approximates a reasonably good sine wave…least to our ear…doesn’t fool a spectrum analyser!
In reality, the diodes are not zeners, but ordinary diodes, but each is connected to a sucessively higher voltage at the far end. A whole second rack of resistors, diodes and voltage sources of the opposite polarity do the other half cycle of the triangle…and that’s the guts if it in a nutshell! That us whybthese type of generators always have trisngle, square and sine. So that diode clipper was the first stage in that second ASIC. Note how your “faulty” waveform at TP 4…which is the output..was, top half, triangle and, bottom half, sine….sort of like the sine clipper was working on just the nehative half cycle…and the inputs on pins 14 and 15 looked a little rounded on the top….I bet there was a DC bias in those inputs that should not be there, and that is why the sine shaper was being activated one side only. There was signal inversion happening bwrween the input and TP 4.
Would love to see the waveforms from this up on the 2230…I must say, I never warmed to the raster display of the 54600!
Happy New Year Globe Collector! Hope you enjoyed your holidays! Thank you as always for watching and the comment of great info; I always look forward to it! I have not forgotten about the 2230! I was waiting on some parts/materials to come in to finish the repair and do the final step of performance checks/cal adjustments. The repair is pretty much done. I just felt like I was dragging things out a bit too much with all the videos so I wanted to wrap it all up in one last video where I do the performance checks. Speaking of which, I grabbed a nice bit of kit for that: a Tek CG 5011! I am waiting for it to come in and the seller really didn't know what condition it was in, so this will likely spark another video on inspecting and possibly repairing it! Also grabbed a TM5003 to power it from the same seller - they say this one works, but we'll see. The 8116A was meant to do some of the performance checks, but now I have an actual oscilloscope calibrator to do them! So it might be some time until I do a final video of the Tek 2230. But it should be worth the wait!
Yes I guess you could say I am more of an HP fanboy. This started well before I became interested in electronics. I started out with a degree in chemistry and worked as a chemist for years. And I did a lot of HPLC/GC work. My favorite HPLCs/GCs were made by HP/Agilent. They were the easiest to service and had the best software. So considering that experience, I gravitated quickly towards HP electronics. I still think they are the best as far as servicability and being user-friendly. But Tektronix is starting to grow on me. And yes I agree it is a real shame that both companies stopped including schematics in their service manuals. The service manual for the HP54600 I use is a sorry excuse for a manual, with barely any troubleshooting guides and no schematics. Which is crazy to think because that scope is only a few years older than this 8116A - what the hell happened in that amount of time!? Anyway, I could go on forever about right to repair...
Wow as always a wealth of info - thanks for explaining the ASICs! I'll admit some of that went over my head lol. But I will definitely have a look at 3312A circuit to see how its done. It seems these ASICs are a pain point in these units which is a real shame.
I'll be in touch!
Thanks for the new year salutation, we had a quiet one this year…went to bed early like roight little party poopers! Heard the booms of the fireworks st midnight though. I will wish you snd your partner not only a happy new year, but a safe new year too!
Yep the circuit of the 3312A will mske its function clear…read my description again whilst looking st it. oh, ahnother thing…to save you time scrolling through the manual pdf on film, just open a second instance of the same pdf in another tab and have it set at the other part of the manual. Some manuals I’m using here, I have had four or five instances open in different tabs, one on the circuit, another in the component list and a third in the description or instructions section…often the description will ask you to refer to a psrt of the circuit, so with this method you can rapidly switch tabs back and fourth without loosing either place in the manual!
Odd you should say you were/are a chemist…same here, was right into transition metal ligand complexes! Used GC/MS at Uni on organic unknowns, never used HPLC though, but I have seen it set up in a lab…miles of stainless tubeing and high pressure fittings. Years ago s GC csme up st auction snd I bought it…for forty bucks without the cylinders, but with the ingection port and a column and pre column in the oven. Days later the chemist that had been using it in a government lab cane looking for it, the bean-counters had simply swiped it out of his lab without prior consultation…and the column in it was all set up with his reference measurements and half his data measurements…needless to say, he wanted it back. He offered 1500 for it, do I tooke the offer and ysed the doosh to finance a trip to Viet Nam!
Funny how calibration routines call for things like marker generators with, say 1us “pickets”, I just use my RF signal generator…could reference its master oscillator to GPS if I eanted to be really pernikety…and just dial up a 1 : 1 square wave at 1MHz and simply line up the rising and falling edges with the graticule. Often you have to be inventive in the absence if vert specific gear you can’t afford or well never find or own.
Talking about HP vs Tek…sort of like pertol -head hoons here with their Ford vs Holden…if you ever see an Australian BWD brand oscilloscope…one of their later models like the 845, see if you can acquire it and work on it…they are an absolute breeze to work on, both electronically and mechanically…the guy who designed them wasn’t even a “qualified” engineer!
Take a look here… 7fTC_UM_4Fo, an old engineer who worked st BWD reminices!
Yes I remember now that you had mentioned somewhere you had a chemistry background! Metal Ligand Complexes - thats where things start to get complex (no pun intended) Takes me back to the horrors of inorganic chemistry in school getting my degree. I dealt mostly with organic. Worked with GCMS and LCMS, too! But I'm starting to loose all that now as its been a few years since working in that field.
I've considered picking up some analytical chem equipment to repair as well! GC would be difficult to swing though - they are big, bulky, and require a gas source like He, H2, or N2. Sounds like you made out well on that deal 😂
I do the exact same thing with keeping several different tabs open of the same manual! It definitely makes it easier.
I just looked up BWD scopes and found an old brochure for them. They look really neat! They have this offering called the 880 Powerscope that can measure 660V rms signals without external HV probes. A real beast! I'll keep an eye out for one! @@thanhhuynh272
If you watched the video I mention above, you’ll….or should I say, Y’all…will see a powerscope 880 behind Charlie Pandolfo, the engineer who worked at BWD. He mentions that John Beasely…the “B” in BWD…designed it when he saw some power engineers with a Tek 7603 connected to a three phase pannel and “adjusting” it with a wooden broomstick. If you search the internet with the trem, “Siemens Oscillar D1020” you might find an image of an oscilloscope with a black front pannel and green seven segment display with the EXACT same layout as the BWD 881A….so which came first, the chicken or the egg?
As an Australian it would give me a warm fuzzy feeling that Germans clobed something we designed!
Sorry I completely glossed over that link you added for the video. I just watched it - neat stuff! Probably pretty cool place to work from what he describes. I love that they made an in-house calibrator for validating their scopes (seemed like a time marker). And he did mention how easy they are to service. I'll keep an eye out for em!@@thanhhuynh272