BBD Tester Help

[armdnrdy]

I'm working on a tester for the M3XXX series BBDs. I'm very close with the design but I have a few questions about the signal entering the BBD.

I need to input a 7 volt signal into the BBD under test, have that signal exit the BBD outputs to stop a counter IC and hold an LED display.

I understand that a guitar signal is AC and that a BBD has a DC bias at the input.

What I was thinking to do is incorporate a simple sine wave generator to input into the BBD and rectify the voltage that exits the BBD to use to control the counter/LED driver IC (CD4011BE).

Does this sound correct?

[scratch]

you might want to check out this thread ...

http://www.diystompboxes.com/smfforum/index.php?topic=98770.0

[armdnrdy]

Hey Scratch,

Thanks for the heads up but.......I started that thread!!

I've been working on a universal BBD tester design in which I'm very close to finishing. I've been graced with the knowledge of RO TIREE and Mark Hammer which have led me in the right direction to work out a few issues.

After I build a working prototype, I'll post a project.

[scratch]

well duh ... That's what I get for posting too quick ...

[newperson]

neat idea.  just adding myself to see the updates.

[R O Tiree]

armdnrdy - All that a BBD does is to pass voltages from one end to the other. When the clock signals at pins 2 and 6 (for a 3208 or 3205) flip, whatever the instantaneous voltage is at the input gets fed to the input stage. While the clock signals flop, the input voltage will vary. Meanwhile, that voltage level in stage 1 gets passed on to stage 2. Once they flip again, it injects the new instantaneous voltage into stage 1. Next flop, the first one we sampled goes on to stage 3, the second one goes into stage 2... and so on, 2048 or 4096 times (for those 2 chips). It doesn't matter at all to the BBD whether ALL the samples are the same. I used 7V because that is just about the minimum you can use as a logic high when running CD4XXX chips at 9V. Remember, we're looking for logic high out of the BBD at the same time as we get logic high out of the end of the counter, so we can flip the SR latch and turn on the LED. If you feed that tester we talked about off-thread a sine wave input, then who knows whether the sine wave output level would be low, high or somewhere in between when the counter gets to the required number?

[scratch]

a pulse is the best way to go, as you for sure know when it has hit the output of the BBD ... with a continuous signal, once it starts coming out the BBD, it is impossible to distinguish from the input ... at least that is what happens when I scope it ...

could always use a comparator on the output, such that as soon at the output starts to rise, you can have it trigger ... and use it to stop the 'counter' ...

[armdnrdy]

This is the simplified version of how the design works.

Push a momentary button, it sends a DC signal through the BBD and the clock signal to the decade counter/display ICs which start the counters. When the DC signal exits the BBD, it shuts off the timer and "holds" the display.

The number on the display is equal to the time it takes for the BBD to pass the DC signal from input to output. Different stage BBDs will display a different number.

When the test is completed, You push a reset button which resets the display and the test.

A chart will be compiled by me displaying the proper BBD number range from verified BBDs. A decal of the chart can be attached to the side of the tester enclosure.

This tester should be able to be built for under $20.00 and will save time troubleshooting and finally give a final answer to the question, is this BBD real or counterfeit?

[Fender3D]

This is the simplified version of how the design works.

Push a momentary button, it sends a DC signal through the BBD and the clock signal to the decade counter/display ICs which start the counters. When the DC signal exits the BBD, it shuts off the timer and "holds" the display.

Look for 555 pulse generator 

The number on the display is equal to the time it takes for the BBD to pass the DC signal from input to output. Different stage BBDs will display a different number.

The number displayed will be the stages number.
You'll want a fairly slow clock ie 10KHz or similar freq.

[armdnrdy]

Hey Federico,

I was going to use a pulse generator (astable oscillator) but since the counters are turned off (channel A of CD4053 goes high and sends signal to CD40110 which stops counter) when the BBD signal reaches them, it doesn't matter whether the signal is a single pulse or constant.

You'll want a fairly slow clock ie 10KHz or similar freq.

That's where I planned to set the frequency. I set up the BBD/clock section on a bread board and was able to pass the DC voltage through the BBD. I've got a few small issues to get past and then I'm ready to build the prototype.

[aballen]

sorry for resurrecting a very old thread, but were you able to get this working?  Is there a circuit diagram somewhere? 

I think I saw your youtube vid with the M320x tester, I'm looking for an MN300x tester.

These things are getting increasingly hard to find, It would be great to test one without building a pedal for it first.