Rocktek BBD Delay. No Power. Please, I need Troubleshooting Help. Hi Def Photos.

[jgoldkamp]

My trusty 80s Rocktek BBD Delay died. I have soldering skills luckily, and a little experience troubleshooting electronics, but only the easy stuff like blown caps/diodes/burns/shorts. I have a great multimeter that does everything, oscilloscope, soldering iron, and adjustable power supply that will display watts being used.

I tried multiple 9V center negative power supplies that work with others, then I tried a battery, no luck. When I plug it all up and I kick it on/off (I can't tell when it is on or off because no LEDs turning on) via the footswitch, there's no sound either way.

I know what a burned cap smells like and I don't smell that. None of the diodes looked blown/burnt up to me either. I also don't see any burn marks on the blank side. This pedal was working just a little tiny while ago, and it was just sitting in my unused pedal box temporarily since xmas.

Here are a bunch of photos of the board. I'm still trying to find a schematic:

https://imgur.com/a/FeIktre

[ElectricDruid]

If it's not turning on or off, you might be in luck (relatively speaking) and the problem might well be in the FET switching. Start by checking the actual pushbutton switch itself.
There's a 4027 flip-flop which is probably controlling the FETs. Checking whether anything is happening on the output pins of that would be a good idea.

https://www.ti.com/lit/ds/symlink/cd4027b.pdf

[jgoldkamp]

Thank you, I'm going to try and take a look now!

[jgoldkamp]

The switch is momentary, which was a surprise. I replaced it anyway, but it accomplished nothing. I'm not sure how to test the flip flop? I have an oscilloscope and hooked up to where the clock should be and I just saw straight 9v, no very fast square wave.

D3=.725V
D2=.610V
Oh, it's D1!

I'm going to replace and let you all know

[jgoldkamp]

Oh and does anyone have a schmatic for this? Or know what D1 is supposed to be?

[Kevin Mitchell]

The switch is momentary, which was a surprise.

In a latching system it will be momentary - similar to Boss and Ibanez stuff.

The datasheet of the flipflop is helpful, which Druid had provided. It's dual channel and has two outputs on each channel, one normal and one inverted. The photos you've provided show that only channel 2 is being used, while channel 1 is disabled by being pulled to 0v.

Monitor pins 1, 2 & 3. Since the inputs are held high, the idea is that when the clock pin cycles (per the switch) the outputs flip.
So check on pin 3, see that the signal from the switch shows here and then monitor pins 1 & 2 to see if they flip & latch.
If the button shows on pin 3 but nothing happens on pins 1 & 2, you've got a bad 4027.

[ElectricDruid]

Oh, it's D1!

What did D1 do that made you think that?

Oh and does anyone have a schematic for this? Or know what D1 is supposed to be?

I wouldn't take D1 out unless (a) I was certain it was faulty and (b) I had a replacement I was certain was going to work. Anything else is introducing more variables into a debugging process (Did I get the right diode? Did I solder it correctly? Did I damage something else with heat? etc etc).

A schematic would certainly help, but I've had no luck either.

[Rob Strand]

You should start by checking power is getting to any of the IC's - by measuring the DC voltage with your multimeter.   It could be something simple like bad contact in one of the jacks.

Schematic at top of this thread, missing footswitch,
https://www.ultimate-guitar.com/forum/showthread.php?t=1059724

There's a few chorus schems showing the footswitch,
https://manualmachine.com/rocktek/chorus/5142324-schematic/

[jgoldkamp]

It is def D1. I found it when checking the diodes with a multimeter. Nothing at D1 so I take a closer look and the lower half has cracked off. The top looked fine though, which is how i missed it. I removed it already and just need to know what to replace it with.

Oh, it's D1!

What did D1 do that made you think that?

Oh and does anyone have a schematic for this? Or know what D1 is supposed to be?

I wouldn't take D1 out unless (a) I was certain it was faulty and (b) I had a replacement I was certain was going to work. Anything else is introducing more variables into a debugging process (Did I get the right diode? Did I solder it correctly? Did I damage something else with heat? etc etc).

A schematic would certainly help, but I've had no luck either.

[jgoldkamp]

Ok, so I can't find the schematic for this pedal, but their chorus ONLY uses 4148 diodes, so I went with that. Soldered it in and.... nothing.

[jgoldkamp]

Found the schematic!

[PRR]

That is missing something in the power supply. There's a jack, and a batt, but no way to turn-off the batt. You expect switch or, more often, an extra contact on an audio jack, but I don't see it. Vbatt magically turns into Vcc? It's not all there. (Also probably not a factory plan.)

[ElectricDruid]

+1 what Paul said. That schematic looks like a trace, so watch out for errors. Also it doesn't include any of the switching logic which is a bit of a giveaway. The only diode I can spot is the one connected to the FET gate. Still, it's much better than nothing.

So, where are we at? You found a cracked diode and replaced it. So far, so good.

What are the symptoms? This is the order I'd approach it:

Do we have power to the board?
Do we have power to the chips?
Do we have a momentary switch that works?
Do we have a signal to the flip-flop input when we press the switch?
Does the flip-flop output toggle when the switch is pressed?

That gets us reasonably far for starters.