Boss DD3

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Boss DD3

Postby Bernardduur » 07 Feb 2016, 12:12

Nice page on all the versions

So, I got this DD3 in that I could not recognise from the insides. I have seen a lot of different versions over the years (Big IC, IC on the 'other' side of the board, SMD units, etc) but this one is different.

I got this in for a trails mod, a mod I've done a lot on the older models. But this unit lacks the common points I use to perform the mod. There is no 570 IC in this unit and the signal path is different. It also sounds not like my own DD3...... more clean-ish and the repeats don't drown that nice with the feedback cranked.....
I call it version 4
Boss - DD3 v4 1.JPG
Boss - DD3 v4 2.jpg
Boss - DD3 v4 3.jpg


DD3 v4.JPG
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Re: Boss DD3

Postby ranjam » 07 Feb 2016, 20:38

I have the same DD3 that isn't working. I haven't found a suitable schematic, so it just sits in the 'one day I'll give up and toss it' pile. :cry:
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Re: Boss DD3

Postby Bernardduur » 08 Feb 2016, 22:07

Service notes for the 1st and 3rd version

DD-3A_SERVICE_NOTES.pdf
DD-3T_SERVICE_NOTES[1].pdf
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Re: Boss DD3

Postby floris » 13 Feb 2018, 18:16

A question about the Boss DD3-A:
DD-3A_SERVICE_NOTES.pdf
download/file.php?id=27741

Mine has only clean signal but no delay signal.

I see that the AD conversion is done by a "Successive approximation ADC" with the micro-controller IC7, the resistor ladder RA1, Sample&Hold circuit with 4066 IC3c with cap C017, and comparator IC5.
Because of the "Successive approximation ADC", I see that output of the resistor ladder RA1 and buffer opamp IC8b, is fed back into the comparator IC5 pin 2, as expected. So I expect this to be the approximated input signal.

I'm confused about the delayed signal output, coming from the micro controller IC7.
It looks like this also comes from resistor ladder RA1 and opamp output IC8b, and then goes to Sample&Hold circuit 4066 IC3b with cap C033, and from there to Q006.

Is it so that the DA output of the resistor ladder and opamp 8b, is switched between the "delayed signal" and the "approximated input signal"?
And that the S&H circuit of IC3b makes sure that only the "delayed signal" goes to Q006?
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Re: Boss DD3

Postby Dirk_Hendrik » 14 Feb 2018, 09:14

I'd say your analysis is correct.
Sorry. Plain out of planes.

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Re: Boss DD3

Postby microbailey » 16 Feb 2018, 01:07

floris wrote:A question about the Boss DD3-A:
DD-3A_SERVICE_NOTES.pdf
http://www.freestompboxes.org/download/ ... p?id=27741

Mine has only clean signal but no delay signal.

I see that the AD conversion is done by a "Successive approximation ADC" with the micro-controller IC7, the resistor ladder RA1, Sample&Hold circuit with 4066 IC3c with cap C017, and comparator IC5.
Because of the "Successive approximation ADC", I see that output of the resistor ladder RA1 and buffer opamp IC8b, is fed back into the comparator IC5 pin 2, as expected. So I expect this to be the approximated input signal.

I'm confused about the delayed signal output, coming from the micro controller IC7.
It looks like this also comes from resistor ladder RA1 and opamp output IC8b, and then goes to Sample&Hold circuit 4066 IC3b with cap C033, and from there to Q006.

Is it so that the DA output of the resistor ladder and opamp 8b, is switched between the "delayed signal" and the "approximated input signal"?
And that the S&H circuit of IC3b makes sure that only the "delayed signal" goes to Q006?


Yes. The DAC (which is formed form RA1 + 8b) is doing both the functions. It will work like this, in time order:
1. IC7 pin 28 pulses (once very audio sample) and will sample the audio input waveform voltage on C017, and the delayed output audio waveform voltage on C033. This will be a narrow pulse.
2. IC5 compares the sampled input voltage to the voltage on 8b pin 7 and the ADC conversion starts working. IC5 pin 7 is binary (either low or high voltage) feeding a string of fast pulses into IC7 pin 30
3. Over the next 12 pulses (probably the clock on pin 84) IC7 will update the binary values driving RA-1 and respond to the high/low on pin 30 (the binary values on pin 30 are "shifted" into IC7 pin 30 on each clock pulse)
4. When the A-to-D conversion is finished (all 12 bits are done) and held inside IC7, IC7 switches to outputing the delayed digital sample value (which it has retrieved from IC6) on RA-1 and so 8b now has the delayed signal waveform voltage
5. IC7 pin 28 pulses again and this delay sample is 'pushed' onto C033. Simultaneously the input signal is sampled again (see #1) above and the loop starts over again

So in summary, 8b pin 7 is providing both the delayed sample (on C033) and playing its part in the successive approximation ADC conversion of the analog value on C017. It swicthes between these functions very quickly.

I hope that all makes sense :scratch:

You should be able to measure (if you have a scope) the voltage on C033 or better on Q006 source and see your delayed audio as a waveform.
If nothing there, try 8b output - this will be jumping around but at least you should see it change when there's audio coming in.
If that's all dead check the basics - is there a square wave clock on IC7 pin 84, are RAS and CAS lines on IC6 toggling?

If you don't have a scope it'll be tough fault finding a digital circuit like this.

Hope that helps a bit :D
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Re: Boss DD3

Postby floris » 16 Feb 2018, 11:21

Thanks for the detailed explanation, it confirms what I was thinking and makes it all very clear.
Yes I have a scope, so I'll probe some more to see what is failing. Currently I suspect the Sample & Hold circuit IC3b 4066.
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Re: Boss DD3

Postby microbailey » 17 Feb 2018, 23:00

floris wrote:Thanks for the detailed explanation, it confirms what I was thinking and makes it all very clear.
Yes I have a scope, so I'll probe some more to see what is failing. Currently I suspect the Sample & Hold circuit IC3b 4066.

Good luck. Those 4066 chips can get easily blown by static discharge if I remember well so could be damaged.
Look for dry joint on the board too - many old boards have dry joints which are PITA to find :x
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