BBD tester

[armdnrdy]

I woke up this morning....once again....and was pondering what I'm going to work on today.
I'm waiting on parts orders for a few new projects but....I have boxes of parts for projects that I've worked out previously.

One such project is a BBD tester.

I think it's time that I build this thing to get it out of the way....and make room for more project parts boxes. 

The tester consists of three stacked circuit boards. A Ziff socket board, a display board, and a main board. (switching/clock/power)

Here's the whole schematic:



Here is the description of operation:

When tester is powered up, the green LED (D2 positioned by the start button) is lighted and all functions are ready for test.

You will notice that there is a BBD bias control and a ten bar graph display. When the bias control is adjusted, the display LEDs will light, providing a visual indication of the bias voltage.

I am confident that future testing of different BBD models will produce a "ballpark" (within a couple of bars) parameter of bias adjustment.

Pushing the start button brings base of Q1 low, sends a high pulse to the base of Q3 which sends pin 9 of the NOR gate (IC1C) low, causing the latch circuit (IC1A, IC1B) to change states, activating the red LED, (D1 positioned by the reset button) and activating channel A, B, and C of IC2.

Pressing the start button also sends a high signal to latch circuit (IC5A, IC5B) causing it to output a low signal to the toggle enable pins of the counters which allows counters and display to function.

Going back to when channel A, B, and C of IC2 are activated:
When B is activated it sends a 20kHz clock signal to the counters. (IC 7-10) When A is activated it sends the counter reset pins (pins 5) low allowing the counters to function. When channel C is activated it allows signal from sine wave generator (IC3) to be sent through BBD.

When the sine wave exits the BBD, the delayed signal is sent through a mixing node, (R24-27) through C9, (removes any transient clock DC) and finally through a half wave rectifier (D5, R29) and smoothing cap. The "new" DC signal sends the base of Q6 high which sends pin 9 of the NOR gate (IC5C) low which brings the output of the latch circuit (IC5A, IC5B) high to stop and hold the display.

At the BBD clock frequency of 10kHz, the LED display will show the BBD stage number.
S = T*2F
Example: 1024 = 51.2ms*(2*10,000)

After the test is concluded, the reset button is pushed. The green LED is activated; IC2 channel A, B, and C will return to their normal states and the counters will be reset to zero.
The reset button also sends a high signal to the latch circuit (IC5A, IC5B) which causes the output to go low, sending a low signal to the counter toggle enable pins (pins 4) making the counters ready for the next test.

[Mich P]

Wow ! really impressive !!
Congrats,
Mich P.

[Dave W]

wow! nice work.    i would love to see it in action. any chance of a video?

[armdnrdy]

Thanks guys,

Today I'm going to build the display board and breadboard the rest of circuit to confirm the circuit and work out any bugs.
I've breadboarded sections of this circuit...but not the whole thing.

When I'm finished there will be a video and build document.

[newperson]

..neato..

[armdnrdy]

I made some headway this weekend after hitting a few brick walls. I was working from a schematic that I had revised previously. 

I worked this project out about a year ago...and then set it aside for builds that go whoosh!

Yesterday, I bread boarded a good portion of the circuit with good results.

Later this afternoon I'll finish bread boarding and testing the main body of the circuit.

Within a few days, the display board will be built, connected to the main circuit and tested.

I've got my fingers crossed!   

[scratch]

looking forward to the finished product ... need to figure out what to change to be able to test the pairs of SAD1024 and SAD4096 that I have.

[armdnrdy]

I'm working out a few issues with the sine wave generator and the voltage after the output of the BBD.
I have the BBD passing the sine wave, and I'm working on the tail end.

It's very close!

This tester will test SAD1024s.

The other day I had the thought to design a few daughter boards that will "plug" into the ziff sockets to test the more uncommon BBDs.

I'll put the SAD4096 on the list.

[pinkjimiphoton]

wow, larry, you've outdone yourself!! nice!!

[armdnrdy]

Well.....

After some trials and tribulations with the BBD output signal, I finally got it set up correctly.
I had it set up for a flanger or a delay...which turned out to be not so good for the switching of the tester.

I built the display board and.......I'll be damned......it works!

I'm currently using a MN3207 for the BBD under test and the display reads 1025 for the 1024 stage device.
I'll take a .01% deviation from the actual stage number. 

I have to work out placement of a few pull down resistors (the counter doesn't reset to 0000 because there is 900mv on the 4053 pin (when grounded) that is connected to the reset pin of the counter/display driver IC.

Almost there!! 

[mth5044]

That's incredible. You are a very smart individual.

[armdnrdy]

I think the correct word to describe me would be stubborn? maybe determined? 

[Govmnt_Lacky]

Soooo many questions... 

[pinkjimiphoton]

WELL DONE!!!!

[armdnrdy]

Thanks Jimi.

I solved the reset issue with a 100K pull down.

The tester seems to display either 1024 or 1025 when reset, then start button is pushed.

I'll test different stage BBDs to check the results.

I'll update the above schematic for review.

[Scruffie]

Wicked Awesome...

[Govmnt_Lacky]

Larry.... if you dont mind my asking 

- What will the tester do if you were to insert a BAD chip?
- Concerning the SAD1024.... what if the unit under test has only 1 good side? Will it only display 512 stages? I ask because the SAD1024 is unique in that it has (2) seperate sides as opposed to the likes of the MN series BBDs that are all-in-one.
- Will this tester require different adapter boards for testing DIP-8, DIP-16, and the 4-pin DIP 16 chips like the MN3005 and MN3008?

Sorry for the questions but I have been thinking about these since you started this thread 

[armdnrdy]

Hey Greg,

If a bad BBD is tested, the counter display will keep running since there is no output to switch it off at the proper stage. (ms of delay from when the signal enters the BBD, until is exits)

I have the SAD1024 ziff socket connected in the series configuration which will display 1024 stages.

In that configuration, it uses both outputs. If one output doesn't pass the signal, then the IC will show as bad and will need further testing (oscilloscope) to check if one side is good.

A note on a SAD1024 IC with one good side:
I am not aware of an existing design that uses only one side of a SAD1024. (If one exists...please correct me)
1024s are used in series for 1024 stages or parallel for a lower noise 512 stage device.
Both configurations use the A & B outputs.
Now this is not to say that a 1024 with one good side can't be used for a design. One would have to work up a build that would accommodate both sides and add jumpers for the good side....either A or B of any given IC.

The tester I'm currently working on is a "positive" voltage tester.
There will be three Ziff sockets located on the top of the enclosure.
One socket will accommodate the DIL8 MN32XX series. (MN3204, 06, 07, 09) the second socket will accommodate the long DIL8 package (MN3208, 05) and the third socket is for the SAD1024.

The next tester on the list will be for the negative voltage BBDs.
I was working on a CMOS switching arrangement to switch socket pins to various places so that the positive and negative ICs could be tested with one tester but.....it turned out to be a bit too much for what it was worth....so I went with two separate tester designs.

The negative voltage tester will accommodate MN3004, 07, 09.....MN3005, 08 and TDA1022.
I was going to include MN3001 and MN3002 but they have a different pin out, and aren't that commonly used or found.
I plan to design daughter boards for some of the more obscure BBDs that will "plug" into one of the testers ziff sockets.

[armdnrdy]

I just plopped in a MN3209 that I purchased some time ago.

The IC looked a bit suspicious to me. There is a white film residue on the seam where the pins exit the ICs body, and the printing is very light.

But....it checks out good!

It passes signal and reads 256 and 257 on the display for the 256 stage device.

It's a good day!  

Edit: Checked MN3204.......512 and 513 for the 512 stage BBD.

[Govmnt_Lacky]

Sweet deal Larry...

Now maybe you could sell these to some of those Chinese fellas on eBay!