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Tek 7a13 mechanical to LED display conversion ? / 7ct1n user notes ?
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This may be two (2) silly questions:
a) Is there a way to convert the 7a13 mechanical ( "veeder root" type ) display to the LED display ? Did Tektronix provide any field Tech notes for doing such ? Does someone have the schematic & parts list for the LED module ? ( does anyone have that module from a dead 7a13) Could it be transplanted into a 7a13 that has the older mechanical module ? b) I am trying to understand how to use the 7ct1n Curve Tracer in a 7704 with the 7a13. Does anyone have a set of simple notes written up for this ? The 7ct1n manual seems a tad confusing ... thank you, rick |
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Yes, silly question for part " a) "
... according to the &A13 TekWiki: " In the newer version, the zener-derived reference voltage is always positive. A 10-turn pot for coarse selection combines with a single-turn pot for fine control. The resultant voltage is displayed on a 4-digit simplified DVM built around a Fairchild 3814 4? digit DVM controller. For negative values of VC, an opamp polarity inverter circuit is switched in." A field 'mod' does not make sense at this stage of the game ! { esp. when an older-newer 7a13 unit can be had on eBay for ~ $40, with LED's ! } ... a1) question: " ... The plug-in can still be used when the counter fails, by using an external voltmeter to monitor the comparison voltage, Vc." - So, on the old version, where is Vc to 'tap' into , ... & has anyone done that ? ! |
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Rick,
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Download the 7D13 mechanical version manual and the 7D13 digital version manual and look at the very first section of the manuals where there is a detailed photograph with callouts that show where everything is located on the front panel. Aside from the mechanical readout and it's knob everything else is exactly the same and in the same place. Vc Out is in the same place on both versions also. Then read the section on First time use to learn how to set the 7A13 up. The only thing you might want to change is to set the + input to DC, ground the - input, Set the bandwidth to 5MHz, set the Volts/Div knob to 50mV/Div and un-calibrate the vertical Volts/Div. Last thing is to connect the 7CT1N wire to the + input of the 7A13. That is all you need except to read how to setup the 7CT1N for the particular transistor or FET you will be testing. To test a FET you must reverse the Drain and Gate leads as the plugin clearly shows under the banana jacks. Dennis Tillman W7PF -----Original Message----- <snip> " ... The plug-in can still be used when the counter fails, by using -- Dennis Tillman W7PF TekScopes Moderator |
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On Sat, 09 Jun 2018 19:11:48 -0700, you wrote:
This may be two (2) silly questions:I've never heard of that, but I suspect that it's much too much of a job, never had a mechanical 7A13, went for the digital ones. OK, the 7CT1N can be used in either the vertical or horizontal slot. It requires a horizontal plugin (you could use a vertical plugin in a horizontal slot, I think) that has an external input. If used in a horizontal plugin slot, you can plug it into a vertical slot. It does not have any readouts (N suffix). Harvey
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Hi Rick,
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The brilliant designers of the 7000 series made sure all of the slots were "generic". In other words the slot doesn't care whether you put a horizontal or vertical type plugin in it. There is nothing in the backplane that distinguishes a horizontal slot from a vertical slot and there is nothing that informs a plugin what kind of slot it is in. By design the signals coming from the two vertical slots will go to the vertical amplifier and result in a vertical (Y axis) deflection on the CRT. The one (in a 3 wide mainframe) or two (in a four wide mainframe) horizontal slot(s) will go to the horizontal amplifier and result in a horizontal (X axis) deflection on the CRT. In the case of the 7CT1N you can put it in any slot as long as you tell the plugin whether it was a horizontal or vertical slot that you put it in. Which type of slot (Vertical or Horizontal) you put it in requires an AMPLIFIER to go in the opposite type of slot (Horizontal or Vertical) to create the deflection on the other axis. The gain of this amplifier should be set to 50mV/Div. There are a few timebases that have an amplifier input (7B50, 7B50A, 7B53A, 7B70, 7B80 Option 2) but the gain is not variable over a very wide range so you would be better using the 7A13 in the horizontal slot (set to 50mV/Div) and have the 7CT1N in a vertical slot. Dennis Tillman W7PF -----Original Message----- -- Dennis Tillman W7PF TekScopes Moderator |
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On Sat, 09 Jun 2018 19:11:48 -0700, you wrote:
a) Is there a way to convert the 7a13 mechanical ( "veeder root" type ) display to the LED display ?Tektronix never did this but I think someone on the list may have done it so a search through the archives may reveal something. I know we discussed various options for the ADC and display because I was part of that. The biggest problem is finding a small enough LED display. One of those tiny OLED graphic displays could work but would be more complex to drive. b) I am trying to understand how to use the 7ct1n Curve Tracer in a 7704 with the 7a13.The 7CT1N works with the 7A13 like it does with any vertical amplifier set to 100mV/div. |
David Hess
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