BOSS DD-2 only output dry Signal

[tone5]

Hi,
my DD2 only output dry Signal,no problem with power(+9v and +5v),LED light,switch to Hold on function LED will turn light,
but no delay Signal form mono or stereo.

After trace signal IC7(main controller) pin31 signal in but no output from pin46

Any Idea where can go next? Thanks

[Slowpoke101]

Welcome to the forum and hopefully we can help with your problem.

Digital pedals can be a bit difficult to repair but I think that your DD-2 won't be too hard.
You found an audio signal going to pin 31 of IC7. Good. But the signal you found on pin 46 is not audio. It is data and will not sound anything like your initial audio input.
The delayed audio output from IC7 is found on pin 14 of the R73 resistor network. R73 is a R2R resistor network which converts the digital data from IC7 to an analog (audio) signal. If you use an audio probe you should be able to hear the delayed audio on pin 6 of IC6 assuming that IC7 is working. It is most likely fine and the problem will be elsewhere.

Old pedals can suffer from dried out electrolytic capacitors. The BOSS digital pedals are prone to this problem due to internal heat buildup. The pedal works for years and then suddenly stops working.
On the schematic, look at IC2 (NE570 compander) and the electrolytic capacitors connected to it (the symbol for these capacitors have a + symbol next to the capacitor). Using an audio probe check for audio on pin 7 of IC2 (this is audio going to IC7) - You probably have audio here anyway as you have some signal on pin 31 of IC7. Then check for delayed audio on pins 14 & 15 of IC2. Most likely you will not have delayed audio available. C39 and C34 are notorious for causing the problem that you have described.
Good luck and let us know what you find.

[ElectricDruid]

+1 agree with Slowpoke.

Pin 46 is not audio. you'd be better checking for audio on pin 14 of R73 or on pin 6 pf the following 5534 op-amp.

No delayed audio could be caused by all sorts of things. Those 4066 switches might not be working, for instance. Or it could be something in the Compressor/Expander stages, as Slowpoke suggested. Or it could be a dead transistor in one of the output filters. Or a dead FET (Q8?) further along.

So long as the micro controller is working, none of them are super-difficult to fix. It's just a question of working through the circuit logically until you get to the point where the signal disappears.

HTH,
Tom

[tone5]

This is a very helpful information.
i will follow this step trace signal.Thank you

Welcome to the forum and hopefully we can help with your problem.

Digital pedals can be a bit difficult to repair but I think that your DD-2 won't be too hard.
You found an audio signal going to pin 31 of IC7. Good. But the signal you found on pin 46 is not audio. It is data and will not sound anything like your initial audio input.
The delayed audio output from IC7 is found on pin 14 of the R73 resistor network. R73 is a R2R resistor network which converts the digital data from IC7 to an analog (audio) signal. If you use an audio probe you should be able to hear the delayed audio on pin 6 of IC6 assuming that IC7 is working. It is most likely fine and the problem will be elsewhere.

Old pedals can suffer from dried out electrolytic capacitors. The BOSS digital pedals are prone to this problem due to internal heat buildup. The pedal works for years and then suddenly stops working.
On the schematic, look at IC2 (NE570 compander) and the electrolytic capacitors connected to it (the symbol for these capacitors have a + symbol next to the capacitor). Using an audio probe check for audio on pin 7 of IC2 (this is audio going to IC7) - You probably have audio here anyway as you have some signal on pin 31 of IC7. Then check for delayed audio on pins 14 & 15 of IC2. Most likely you will not have delayed audio available. C39 and C34 are notorious for causing the problem that you have described.
Good luck and let us know what you find.

[tone5]

Thanks so much,i will keep trace this week.

+1 agree with Slowpoke.

Pin 46 is not audio. you'd be better checking for audio on pin 14 of R73 or on pin 6 pf the following 5534 op-amp.

No delayed audio could be caused by all sorts of things. Those 4066 switches might not be working, for instance. Or it could be something in the Compressor/Expander stages, as Slowpoke suggested. Or it could be a dead transistor in one of the output filters. Or a dead FET (Q8?) further along.

So long as the micro controller is working, none of them are super-difficult to fix. It's just a question of working through the circuit logically until you get to the point where the signal disappears.

HTH,
Tom

[tone5]

Hi Slowpoke101 and ElectricDruid,
my trace report:
IC7  pin31                 signal  yes

R73 pin14                 signal  no

IC 6 5534 pin6          signal  no

IC 5 pin2 pin7           signal  yes
IC 5 pin3                  signal  no

IC 2 NE570 pin7        signal  yes
IC 2 NE570 pin14 15  signal  no

C34 C39                    signal  no

looks not a good sign 

[ElectricDruid]

Ok, so you've got signal at the compressor, but you've got nothing coming out of the processor. We need to be sure there's a good signal going in.

Is there a signal at pin 7 of 3b, the 5218 on the way into the processor?

If not, it might be those switches ahead of it (4a, 4b). If there is a signal going in, then it looks like the processor isn't happy for some reason.

[tone5]

I use signal generation input 1KHz Square wave

yes,has signal at pin 6,7 of 3b and go to pin 2 of IC5 .

Ok, so you've got signal at the compressor, but you've got nothing coming out of the processor. We need to be sure there's a good signal going in.

Is there a signal at pin 7 of 3b, the 5218 on the way into the processor?

If not, it might be those switches ahead of it (4a, 4b). If there is a signal going in, then it looks like the processor isn't happy for some reason.

[Slowpoke101]

From your results it seems that the microprocessor is not working. The next step (or steps) is to find out why.
Locate IC10 (78L05 +5V regulator) and measure the voltages on its pins. You should have +9V on the IN pin, 0V on the G pin (ground) and +5V on the OUT pin. If you find that you have nearly 0V on the OUT pin and the regulator is hot, then something is causing an overload.
Now if you find that you do have +5V you then need to confirm that it is available on IC7 pin 64 and IC8 (74HC00) pin 14.
If these are OK then now is when things get more complicated.
Do you have access to an Oscilloscope or Frequency Counter. If you do, check the signal on IC7 pin 63. It should be a nice clean square wave that can be varied by the D-TIME control. The frequency range should be between 1.28MHz to 5.12MHz.
If you don't have access to either piece of test equipment, just measure the voltage on IC7 pin 63 with the D-TIME at minimum and then remeasure with D-TIME at maximum.
Let us know what you find.

[tone5]

Thanks for your reply. This is what i find,

IC10  78L05
+9V on the IN pin  ✓
0V   on the G pin   ✓
+5V on the OUT pin ✓

IC7 pin 64  5v ✓
IC8 pin 14  5v ✓

i don't have Oscilloscope so i measure the voltage
IC7 pin 63
D-TIME 
minimum 0.612V
maximum 0.146v

PCB point 8 voltage
D-TIME
minimum 5V
maximum 2.19

IC8 voltage on each pin
1. 2.27v
2. 2.27v
3. 4.85v
4. 4.85v
5. 4.85v
6. 0.14v
7. 0v
8. 0v
9. 0.14v
10. 0.14v
11. 0v
12. 5v
13. 5v
14. 5v

[Slowpoke101]

From your measurements on IC8 it looks that it isn't oscillating. Although just measuring the voltages on this type of oscillator can be a bit misleading it really looks as if it is not working. Make sure that the voltages on IC8 pins 1 and 2 vary when D-TIME is adjusted. If it does not vary check the diode D8.
Check diode D10. This diode does go open circuit but rarely.
The most likely problem is that IC8 has gone faulty or C46 (33pF) is bad.
IC8 is a 74HC00 Quad 2 Input NAND Gate. A very common IC and not expensive. Try to find a replacement and see if that solves your problem.
Let us know how you go.

[ElectricDruid]

Do the two clock trims allow the unit to be pushed to the point at which it stops oscillating? Might they have got knocked out of whack?

Could one of the trims have gone open-circuit? That would stop the oscillator too.

HTH,
Tom

[tone5]

Hi,
i measure the D-TIME voltage of IC8 area,and already order some 74HC00 on the way.