Similarity of 11000-series interface and 7000-series interface
Questions to John Addis:
- To what extent do 7A-series plug-ins work in 11000-series mainframes?
- To what extent do 11A-series plug-ins work in 7000-series mainframes?
Answers from John:
The short answers to your two questions are:
- Simple mechanical modification of most 7000 series plugins is required
- None, really
The reasons for this are many.
Neither plug-in can be physically fully inserted into the other series’ mainframe. The reason for this is that there are different projections at the top of the plugin connectors that prevent full mechanical insertion of the wrong series plugin into either mainframe. The 7000 series plugins have a short, wide and thick projection with four holes and the 11000 series has a long, narrow and thin projection.
Neither projection performs any electrical function and it is possible to mechanically remove the part which extends beyond the base and above the connector guides of the 7000 series connector without harming the plugin or mainframe.
The 7000 series projection contains four atavistic holes which were once going to hold SMB connectors for the signal and trigger paths. They were designed into the interface at an early date. Roy Hayes (3A3, 3A8 and 7A12 designer) then suggested that an edge connector could be made with adequate HF response and that the connectors and cables would be an unnecessary expense. The SMB connectors were never used.
The projections can be easily removed with a Dremel tool, allowing a 7000 series plugin to be inserted into an 11000 series mainframe, and vice versa.
The 7000 series fixed and flexible extenders can also be modified using a Dremel so that 11000 series plug-ins can be partially trouble-shot in 11000 series mainframes. I have done this to a flexible extender. However, you cannot calibrate the 11000 series plug-ins in the 11000 series mainframes when using the 7000 series flexible extender as there are several wires not present in the extender which the 11000 series plug-ins need. This is probably true for the 7000 series fixed extender also. An 11000 series flexible extender is useful for all 11000 series plugin problems except for very high frequency problems.
The rear connectors contain 38 contacts on each side of the board in both 7000 and 11000 series instruments. The top contact on the left side (seen from the front panel) is A38. The bottom contact on the left is A1. On the right side, the contacts are B38 at the top down to B1 at the bottom. Not all of the contacts of either series were ever used. A few were used on both mainframes but for different functions.
The contacts for power supplies and signals are the same with the exception that the 11000 series has extra plug-in “aux trigger out” contacts, one pair for each of up to 4 channels. In the 7000 series, these connectors were used for the on screen readout.
- A38 is ground and B38 is + CH1 aux trigger out.
- A37 is ground and B37 is − CH1 aux trigger out.
- Etc
- A31 is − CH4 aux trigger out B31 is ground.
A37-A30 and B37-B29 are used for the display of plug-in readout information in the 7000 series
A20 and B20 are differential trigger inputs to the plug-in in 7000 series (not sure these were ever used).
In 11000 series, A20 is a serial data interface for mainframe to plug-in information. B20 is an “11000 series detector” tied to +5 V through 10 kΩ in 11000 series.
A21 in 11000 series is serial data clock, B21 is plug-in to mainframe serial data interface while these appear to be unused in the 7000 series.
There are other differences in the interface connector.
Aside from that, the 11000 series plug-ins have no front panel controls except for a single On/Off push button, labeled "CH1", for example). Without a serial data interface you cannot control 11000 plug-in functions (V/div, Coupling, Offset, Bandwidth) in a 7000 series mainframe. This makes 11000 series plugins essentially useless in 7000 series mainframes.
However, the 7000 series plug-ins have front panel controls that can be used in 11000 series mainframes. You have to find a way to turn the Left, Center, or Right 11000 series digitizers on so they will display the 7000 series plug-in signals. This is done by touching "DefWfm" on the 11000 series mainframe's screen. ("DefWfm" stands for "Define Waveform".) From the resulting pop-up menu you can turn on the Left, Center, or Right plugin hole containing the 7000 series plugin. The 11000 series mainframe then acts as a calibrated 7000 series scope. One significant advantage of the 11000 series mainframe now available is the ability to average waveforms from a 7000 series plugin.
The 11000 series plug-ins can be neither controlled nor calibrated in 7000 series mainframes, making this a useless configuration.
FYI, the way self calibration works in 11000 series is that the mainframe tells the plug-in when it needs to be calibrated due to either temperature change or time since turnon. The plug-in then sends requests for a series of accurate voltages and the measured results are returned to the plugin by the mainframe. The requested voltages are frequently signals that run over a limited range of the mainframe’s digitizer in a small sawtooth (to provide an accurate average signal). A large number of these signals and measurements constitute the information which the plug-in uses to create calibration constants. The calibration constants set calculated voltages in the plug-in ACVS (Analog Control Voltage System) which make the plug-in calibrated. The plug-in also corrects for the mainframe’s imbalance in the calculation. It can do this because the plug-in puts out a reliable differential zero volts to the mainframe when the channels are all “OFF”.
The entire calibration routine comes from the brilliant mind of Brian Rhodefer.
These calibration constants (“cal constants”) are stored in the plug-in’s NVRAM along with other data such as any probe serial number, and probe cal constants (if any) and the plug-in’s serial number. The latter so that the mainframe knows whether that plug-in was there when last calibrated. Lifetime of the battery-operated NVRAM, specified as working for 10 years minimum, is typically over 25 years. When it fails, the plug-in must be calibrated every time the instrument is turned on, and it does not come on in the same state as it was when it was turned off. To restore proper operation, the Dallas Semiconductor NVRAM chip (typically the tallest IC on the plugin's circuit board, and labeled DALLAS 1220Y-200) must be replaced. Instructions for this are elsewhere on the Tekwiki website you are now visiting.)
Using a 7000 series plugin in an 11000 series mainframe can be useful. An 11000 series plugin is essentially useless in a 7000 series mainframe.
John Addis