Checking voltages on the source side is more complex since its all floating except when the grounding is engaged. Then the ground swings at 1/2 the output voltage. I would put either PCB on an extender float the outputs and measure from local ground to pins on an IC to check voltages.
I have not seen issues on the supplies. Boonton recommends replacing the main supply caps because they cook back in the supply housing which makes sense. A quick check for excessive ripple will show that.
With care the analyzer can get down to .0006% with only minor upgrades. Setting the notch adjustments and the input common mode adjustments will be the most important after the input opamps and all the others in the pre-notch and notch chain. There are some non-inverting opamps in the chain and those will need to be opamps with low input C modulation. I'm currently using LME49710's for the input and AD797 for the diff amp stage. There is a mod that eliminates the fet opamps which can be done since the LME's have much better DC stability. Mike's mod for the notch board seems to work well but my gen 1 with only some opamp upgrades performs as well at .0006% midband. (FWIW I have a Shibasoku that is similarly limited at .0006% right now. I think its the 5534 in its notch filter circuit as well.
The source side will be a bigger challenge. The FETs on the first gen were a problem with too much RDSon. Yours should both have J108 fets. get a supply of those anyway since they are now obsolete. Then optimum tweaking of the analog multipliers becomes the next limitation.
I have not seen issues on the supplies. Boonton recommends replacing the main supply caps because they cook back in the supply housing which makes sense. A quick check for excessive ripple will show that.
With care the analyzer can get down to .0006% with only minor upgrades. Setting the notch adjustments and the input common mode adjustments will be the most important after the input opamps and all the others in the pre-notch and notch chain. There are some non-inverting opamps in the chain and those will need to be opamps with low input C modulation. I'm currently using LME49710's for the input and AD797 for the diff amp stage. There is a mod that eliminates the fet opamps which can be done since the LME's have much better DC stability. Mike's mod for the notch board seems to work well but my gen 1 with only some opamp upgrades performs as well at .0006% midband. (FWIW I have a Shibasoku that is similarly limited at .0006% right now. I think its the 5534 in its notch filter circuit as well.
The source side will be a bigger challenge. The FETs on the first gen were a problem with too much RDSon. Yours should both have J108 fets. get a supply of those anyway since they are now obsolete. Then optimum tweaking of the analog multipliers becomes the next limitation.
Here's my interesting question... Since the sets are mostly the same, if I put all 8 of the 1121 boards into the working 1120 set... Should that set then become an 1121 ? If the Errors 34,33,32,31,30 -> Error 31 doesn't follow the set of boards, then I have isolated the problem to either the PS or main motherboard. If the Error 34,33,32,31,30, etc. follows the boards, I should be able to go one board at a time to isolate the problem board.
I also note that the 1121 was property of Boonton's parent Telecom company due to an 'asset tag'. The unit ROM has a plain white unprinted label, so maybe it is an experimental part that did not work??? What do you think?
Steven
If you swap the source board and the 1121 works OK its just a source board problem. if not and the source board works OK in the 1120 then its an opto problem. Figuring out which opto is really hard. They are socketed. Get 8 (10? I don't remember) and swap them all. Otherwise you will be looking at a bunch of bursty signals that are a real PITA to sort out. Or make a tester and check them.
I have never swapped CPU's. Not sure what would happen. Its really unlikely that you have an odd firmware issue. I think during boot you can see which firmware is in it.
I have never swapped CPU's. Not sure what would happen. Its really unlikely that you have an odd firmware issue. I think during boot you can see which firmware is in it.
Demian:
Yes, perfectly understandable.
Thanks, no need to send the info because I don't have a Boonton. However, it has been interesting to read and follow in the schematics. I have always liked studying well designed test equipment, so it was really a treat getting info direct from the original designer!
mlloyd1
Yes, perfectly understandable.
Thanks, no need to send the info because I don't have a Boonton. However, it has been interesting to read and follow in the schematics. I have always liked studying well designed test equipment, so it was really a treat getting info direct from the original designer!
mlloyd1
Different firmware numbers do come up at boot time. Since the number of readout LEDs in the 1120 and the 1121 is the same, I guess it is firmware that gives the 1121 the extra right hand digit in the Analyzer on fractions of 1% distortion.
I wonder if switching the ROM's on the A5 board would give the 1120 the 1121's extra digit capability?
Actually I just looked again, and I was wrong about the A5 ROM with the blank label, it is in the 1120, the working unit.
I will try the known working (A6) Source board in the 1121, after I compare voltages on the five big caps to check for any anomaly's between the sets.
There are 14 of those HCPL2601 8 pin dips on the motherboard situated between the A5 and A6 boards, is that all of the Opto's in this set?
Steven
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Ongoing Errors
In the interim, while waiting for the new dozen opto couplers to arrive, I pulled one opto out of the 1120, the working unit, and swapped it for the first opto in line, in the 1121, then tested for the Boot Errors. The same sequence of boot Errors showed up.
I then replaced each of the next 13 Optocouplers in succession with the prior piece in line, again testing for the Boot Errors each time. Theoretically, if only one opto piece is bad, at some point, it should be out of the set, and replaced with a working opto.
After all of these changes, I got the same series of Boot Errors 14 times, meaning either multiple opto's with different date codes went bad, or something else (stuck relay, open coupling cap, defective solder connection, dead op amp, shorted power line, etc. is the actual problem that the signal is getting lost between the Source and the Analyzer).
I am getting the idea maybe it is something else. I called Boonton in N.J. over a week ago, and asked if they had any 'Service Notes' or info on known failure modes for these 1120 and 1121 sets. I spoke to one tech who transfered me to the voicemail of 'Jim', the Head of their Service Dept. I left a detailed message included both my phone and email, but I never received any reply. I guess their support for their units is primarily for the military, or anyone spending half a million dollars... I did gather that they will still sell parts for the 1121, but probably at above my pay grade amounts.
At this point, I just wish any of the Boonton Manuals had some photos of both the signals and/or the voltages that should be present at all those test points (TP1, TP2, TP3, etc.) on the main board, and likewise on the plug-in boards. It will be comparing like points between the two units, (when they exist, not all the boards are equivalent) which is a time consuming job and a half.
- Steven
In the interim, while waiting for the new dozen opto couplers to arrive, I pulled one opto out of the 1120, the working unit, and swapped it for the first opto in line, in the 1121, then tested for the Boot Errors. The same sequence of boot Errors showed up.
I then replaced each of the next 13 Optocouplers in succession with the prior piece in line, again testing for the Boot Errors each time. Theoretically, if only one opto piece is bad, at some point, it should be out of the set, and replaced with a working opto.
After all of these changes, I got the same series of Boot Errors 14 times, meaning either multiple opto's with different date codes went bad, or something else (stuck relay, open coupling cap, defective solder connection, dead op amp, shorted power line, etc. is the actual problem that the signal is getting lost between the Source and the Analyzer).
I am getting the idea maybe it is something else. I called Boonton in N.J. over a week ago, and asked if they had any 'Service Notes' or info on known failure modes for these 1120 and 1121 sets. I spoke to one tech who transfered me to the voicemail of 'Jim', the Head of their Service Dept. I left a detailed message included both my phone and email, but I never received any reply. I guess their support for their units is primarily for the military, or anyone spending half a million dollars... I did gather that they will still sell parts for the 1121, but probably at above my pay grade amounts.
At this point, I just wish any of the Boonton Manuals had some photos of both the signals and/or the voltages that should be present at all those test points (TP1, TP2, TP3, etc.) on the main board, and likewise on the plug-in boards. It will be comparing like points between the two units, (when they exist, not all the boards are equivalent) which is a time consuming job and a half.
- Steven
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That's why I shotgunned all the opto's. However I would bet that its more likely a dead jfet on the oscillator board. You should have an extender board (they all were shipped with them) so you can put the source (oscillator) on an extender.
Then watch TP3 with ground on TP2 with a scope. Set the unit to floating output. On the boot sequence the unit goes through 4 sequential frequencies and confirms they are on target. if not you get the errors. Even with the errors you can manually input a frequency.
1) It should show oscillation on TP 2. If not the oscillator circuit has a problem that should be pretty fundamental. Look at the opamp outputs for something that's not right.
2) If its not on the frequency selected most likely one of the FET's is dead. The CPU will tune up or down to get it on frequency if a little out.
3) Check TP8 to see that frequency info is going out. You can follow that over to the frequency counter (pin 30)
4) The CPU has a fine tune input to the card that comed from the output card. An ADC fine tunes the outout to better than 5 digits.
The source function on the Boonton is exceptionally precise with the tuning of a synthesizer and level accuracy of a calibrator. Still needs lower distortion, a TBD.
Let me know what test points you need some input on. Most should be pretty obvious. The controls are all parallel and latched which makes it all even more challenging to troubleshoot at that level. On one unit two lines were shorted, a real PITA to sort out. Swapping board between those inits should just work. I would move first source board and then output board from the bad unit to the good one. Those and the counter are the only boards involved with those errors.
Then watch TP3 with ground on TP2 with a scope. Set the unit to floating output. On the boot sequence the unit goes through 4 sequential frequencies and confirms they are on target. if not you get the errors. Even with the errors you can manually input a frequency.
1) It should show oscillation on TP 2. If not the oscillator circuit has a problem that should be pretty fundamental. Look at the opamp outputs for something that's not right.
2) If its not on the frequency selected most likely one of the FET's is dead. The CPU will tune up or down to get it on frequency if a little out.
3) Check TP8 to see that frequency info is going out. You can follow that over to the frequency counter (pin 30)
4) The CPU has a fine tune input to the card that comed from the output card. An ADC fine tunes the outout to better than 5 digits.
The source function on the Boonton is exceptionally precise with the tuning of a synthesizer and level accuracy of a calibrator. Still needs lower distortion, a TBD.
Let me know what test points you need some input on. Most should be pretty obvious. The controls are all parallel and latched which makes it all even more challenging to troubleshoot at that level. On one unit two lines were shorted, a real PITA to sort out. Swapping board between those inits should just work. I would move first source board and then output board from the bad unit to the good one. Those and the counter are the only boards involved with those errors.
Some adventures in JFets for the switching here: Low-distortion Audio-range Oscillator Low-distortion Audio-range Oscillator Low-distortion Audio-range Oscillator
Unfortunately, neither of my Boonton's still had it's extender board under the hood. I did order one a few weeks back, but it's coming in from the Middle East, so I just hope I live long enough to see it arrive...�� At least in the Boontons, all the plug-in boards have/use the same 72 pin? extender! Then I will be able to more easily test various test points with my scope, to find out the "Failure Mode" of my 1121, and also replace the tantalum caps in the signal path with bipolar electrolytics, and also swap in some more modern LME49710's, LME49720's, OPA2604A's, OPA1611A's, OPA1612A's, OPA1641A's, and OPA1642A's, so (hopefully, none of my parts are counterfeits, or sub-par parts) and I can get to see some lower-end resolution improvements in both the 1120 and 1121 sets.
Beyond that, I believe the HP 8903A/B/E use three different extender cards, a combination of either two 44 pin parts, and/or one 44 pin and one 30 pin, or all three, on various different cards. I have not pulled any boards from my 8903B, but I noticed several 8903A/B boards for sale on eBay, and the photos reflected the need for at least three different extenders needed for the boards, that I saw offered. Maybe four... Does the 8903 PS or Output Board require yet another card extender?
I have also ordered three HP card extenders, but of the first two HP 44 pin cards to arrive, they are of slightly different heights, so I may have to cut / Dremel / resolder lots of pins to get a working set. The HP 30 pin card has yet to arrive, and may be an even more problematic height, as it looks like it cannot be shortened due to its design, and if it doesn't match the shorter 44 pin card, it may prove to be unusable...
Like I need more projects to do !!!
Steven
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This guy's extenders have worked out fine for me. I got a pair for the ShibaSoku. Boonton 82AD Modulation Meter Extender Board in KIT FORM Riser | eBay The board linked is the same for the 1120, 1110, 1130 etc. I think they all share sheet metal.
No- the guy specializes in making extenders. He has a CNC and routes extenderds from copper clad PCB material. They are well worth the really modest cost.
The AM70A and the 725D use the same connectors except the AM70A needs 2. These are the same as a Sony VTR which he had so he adjusted the length by 1/2" for me. They work fine. I'll post more on my AM70A project in that thread.
Back to Boonton here.
The AM70A and the 725D use the same connectors except the AM70A needs 2. These are the same as a Sony VTR which he had so he adjusted the length by 1/2" for me. They work fine. I'll post more on my AM70A project in that thread.
Back to Boonton here.
Getting back to the Boontons, since the original Jfets used in the 1120 were replaced with the J108 parts in later units, and also in the 1121, and now J108 Jfets are both obsolete, and not easily obtained, has anyone either experimented with, or found an improved substitute for J108 Jfets, which being more modern - is even more Linear, and has an even lower RDSon? 2N5462 maybe, or ???
Steven
The FETs are obsolete mostly due to the package. Variations are available in SMT. I bought 100 on eBay recently and they test way better than the ones in the older unit I have. Now that I have a Metcal desoldering tool I'm almost ready to swap out 30 FETs. But not quite. . .
I'm looking at ways to sort that are not too difficult. So far what works well is to mount a socket with gate shorted to source through a 5K resistor and then apply 5V AC through 600 Ohms across source-drain and measure the voltage there. Lower is better and use the lowest in series with the lowest value resistors (5K) in the attenuator networks.
I'm looking at ways to sort that are not too difficult. So far what works well is to mount a socket with gate shorted to source through a 5K resistor and then apply 5V AC through 600 Ohms across source-drain and measure the voltage there. Lower is better and use the lowest in series with the lowest value resistors (5K) in the attenuator networks.
I bought 10 of these 10ea: J108 NATIONAL JFET N Ch Transistor TO-92 NOS 10 PCS | eBay I may buy another batch while I still can.
Demian,
Thanks for the link! I searched for "J108" a dozen times on eBay since I got the first Boonton unit, and that link NEVER came up. D***!
Also I have seen the J108 come up as P Channel, and as N Channel, in various places and on various datasheets, for instance, on the Toshiba Datasheet it says it is: P Channel. I always thought a 2SJxxx was P-Channel, and a 2SKxxx was N-Channel, for either Jfets or Mosfets, etc. Either that doesn't hold or most places get it wrong?
Steven