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ftwizard
Copper Member
United Kingdom
22 Posts |
 Posted - 02/17/2007 : 20:20:09
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Hi everyone.
I have a DD-3 (DD-2 type) that doesn't work. The LED works as it should, but all I get is the basic sound, no delay effect.
Anyone have any idea what could be the problem.
Cheers.
Wayne. |
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 02/19/2007 : 10:28:02
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Not working at all? Does it kick in after a few minutes, almost like it has to warm up. Slow to kick in usual for old dd3's.
Does it look like it was modded previously, or have any visibly burnt comps or damage to the pcb like blistering?
Could be as easy as a few comps, or alot of trouble shooting. Maybe someone else who had a similar prob could share their experiences.
The dd3 is a popular topic for rework/modding
good luck
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ftwizard
Copper Member
United Kingdom
22 Posts |
Posted - 02/19/2007 : 21:40:34
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Hi. Yes it does work, but only the uneffected sound comes out. It doesn't matter if the pedal is on or off, the sound is the same.
I haven't tried leaving it on for a few minutes, I'll give it a go.
Cheers.
Wayne. |
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guirat
Silver Member
United Kingdom
186 Posts |
Posted - 02/22/2007 : 05:02:03
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Your post motivated me to have another look at my non-working dd-3. It has the same problem as yours, the light is on but no effect sound.
I'd given mine up for dead, but tonight it worked!.. briefly.
I tried wiggling the input cable, having it half-in etc, and I got the effect. My previous fears of a fried chip might have been unfounded, I'm going to have a close look at the input jack tomorrow.
It could also be the main stomp switch, I had a problem with the one on my TW-1 too. I don't know if this is good practice, but I jumpered the switch with a paperclip to turn the pedal off/on, and in so doing narrowed down the fault to the switch. I'll be checking this switch on the dd-3 tomorrow too (but seeing as how the light goes on and off with the switch it is probably fine). When I say it worked briefly, it just stopped working for no apparent reason, maybe a slight movement of a cable in a jack, or maybe a component is overheating? A short circuit somewhere? Hopefully the first option is true. |
Edited by - guirat on 02/22/2007 05:06:55 |
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Basstyra
Gold Member
France
523 Posts |
Posted - 02/22/2007 : 09:57:17
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| Could be a dead FET. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 02/22/2007 : 15:55:18
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quote:
Originally posted by Basstyra
Could be a dead FET.
Hi Basstyra & guys
I'm pretty sure Basstrya means a switching FET.
in the flip flop circuit.
Regards Dr. Bob  |
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ftwizard
Copper Member
United Kingdom
22 Posts |
Posted - 02/22/2007 : 20:29:38
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Would the LED still work if there was a dead FET in the switching circuit?
I'm not sure the input would cause the problem, as the uneffected sound passes through no problem.
Wayne. |
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 02/22/2007 : 21:02:03
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| The LED would work but you wouldn't be able to turn it off. If you can turn the LED on and off, the flipflop (and FETs) is not the problem. |
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Basstyra
Gold Member
France
523 Posts |
Posted - 02/23/2007 : 16:54:30
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You're wrong, guys... You mix up the flip-flop circuit and what's beside.
The flip-flop in itself is only 2 bipolar transistors, and some caps and resistors. It rarely breaks down, I never found one broken. Bipolar transistors are quite tough, and even a bad,partially damaged transitor, could continue to work ok in the flip-flop. It's not a circuit where sound goes. It's not critical.
Then, it controls several things : the led, and the switching FETs.
So the led can work perfectly, On, Off, with the switch, which means the flip-flop is ok, but a switching fet could still be out of order.
In this case, the FETs only switches On and Off the delayed signal. It doesn't affect the dry signal. So it could be a dead FET.  |
Edited by - Basstyra on 02/23/2007 16:56:42 |
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bossarea
Forum Admin
United Kingdom
3652 Posts |
Posted - 02/23/2007 : 17:16:33
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Yes, you're right.
I was thinking about what would happen if one of the transistors in the flipflop broke. I haven't seen that happen but I've seen a capacitor in the flipflop brake with the same effect.
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ftwizard
Copper Member
United Kingdom
22 Posts |
Posted - 02/23/2007 : 20:37:48
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quote:
Originally posted by Basstyra
You're wrong, guys... You mix up the flip-flop circuit and what's beside.
The flip-flop in itself is only 2 bipolar transistors, and some caps and resistors. It rarely breaks down, I never found one broken. Bipolar transistors are quite tough, and even a bad,partially damaged transitor, could continue to work ok in the flip-flop. It's not a circuit where sound goes. It's not critical.
Then, it controls several things : the led, and the switching FETs.
So the led can work perfectly, On, Off, with the switch, which means the flip-flop is ok, but a switching fet could still be out of order.
In this case, the FETs only switches On and Off the delayed signal. It doesn't affect the dry signal. So it could be a dead FET.
Thanks for such a detailed answer. I can only see two FETs in the circuit, I'll check them both.
Cheers.
Wayne. |
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Basstyra
Gold Member
France
523 Posts |
Posted - 02/23/2007 : 21:02:01
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On the DD-2/DD-3 schematic, one FET switches the delayed signal On or Off, the other switches the dry signal out of the main output, throught the second ("Direct") output. So only one, named Q8, should be to check.
Do you have an oscilloscope, or a AC DMM, to check if there's a signal somewhere in the circuit ? |
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ftwizard
Copper Member
United Kingdom
22 Posts |
Posted - 02/24/2007 : 18:09:21
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quote:
Originally posted by Basstyra
On the DD-2/DD-3 schematic, one FET switches the delayed signal On or Off, the other switches the dry signal out of the main output, throught the second ("Direct") output. So only one, named Q8, should be to check.
Do you have an oscilloscope, or a AC DMM, to check if there's a signal somewhere in the circuit ?
Now, that's what I thought, but Q8 was fine. I then checked Q5, and my Peak analyser said it was faulty.
Now I won't know if that is the problem until I can get hold of a replacement FET.
Any ideas which FETs would be suitable?
Wayne. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 02/25/2007 : 03:59:30
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Hi ftwizard
The Peak Semiconductor Analyser is a great bit of equipment.
I have one as well, have had it for a while now.
Just be careful with some of the readings, the version that I have, will not analyze a J201 FET correctly, it says it's a Bipolar something.
There is a later version of the Rom code, that corrects this.
If you contact them, I believe they will upgrade the PIC-ROM for the cost of the return postage.
I have an old contact there.
We also have about 10 or 12 of these where I work.
Just to double check, take a similar FET from a pedal that you don't use a lot, & replace it for now.
I believe that it's a general purpose FET.
Regards Dr. Bob
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Basstyra
Gold Member
France
523 Posts |
Posted - 02/25/2007 : 12:06:02
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| The switching FETs are not critical. I think every N-channel FET will switch correctly. |
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Topic |
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DD-3 Not Working...Ideas?
