DOD - 585 A Analog Delay [schematic]

Chappy · Post by **Chappy** » 26 Jun 2009, 15:08

Anyone here have a schematic for the DOD 585-A Analog Delay pedal or some gutshots?

I'm trying to fix one and I am finding differences between the board and the 585 schematic that I have. As well I'm not sure if some of the wire jumpers and changes were factory made in the A revision, or if the changes are the result of someone modifying the pedal.

Any help greatly appreciated

Chappy

Dirk_Hendrik · Post by **Dirk_Hendrik** » 26 Jun 2009, 15:23

Ere you are

dod585_delay_analog.pdf: (147.03 KiB) Downloaded 553 times

Chappy · Post by **Chappy** » 26 Jun 2009, 16:20

Dirk

I already have that schematic which is for the 585 model. My 585-A seems to be quite different in places. From what I have traced so far the last opamp is a unity gain buffer with the inverting input and output tied together. As well there is an extra 100K trimpot which I think is applying a DC bias voltage to the input of the 3005 chip. The board has extra jumpers, and traces that are not being used. It is quite confusing to follow. I was hoping that someone had a 585-A schematic so I can determine what are factory connections, and what may be someones mods.

Maybe you could help with a troubleshooting question.

Is it a common occurence for either the MN3101 or MN3005 chips to go bad in analog delay pedals? So far from the troubleshooting I've done it doesn't seem to be a faulty opamp that is screwing up the signal.

Chappy

Dirk_Hendrik · Post by **Dirk_Hendrik** » 26 Jun 2009, 16:54

No.
In my personal experience the BBD's are usually the last to go, contrary to the far more common assumption that when a delay goes bad the first component expected is the BBD.

Do you have a scope?

Step1 is to determine if the BBD and it's clock driver are correctly powered.
Step2 is to determine for sure how the BBD bias is supplied
A scope will tell you if there's a 2 phase clock going to the BBD.

When the BBD does have an input signal as well on pin 13 (7) one should be able to get a chopped up signal on the output as well, perhaps by adjusting the BBD bias. If not either the bias is out of range/does not adjust correctly (I've been there) (measure with a DMM) or the BBD is dead indeed.

pls post your findings

Chappy · Post by **Chappy** » 26 Jun 2009, 17:05

Good news. It works.

I'm not sure exactly what may have been the problem, but I suspect a loose connection between the clock chip and its socket. Further to that it works with another 3005 chip I pulled from an broken Ampeg analog delay pedal. Hopefully I can get that one working too, now that I know its not the 3101 or 3005 chip that is the problem. If not I have a vintage 3005 for an Aqua Puss build!

Thanks for the comments Dirk. I do have a scope and I'll have a look at what you are pointing out to better my understanding of the 3101 and 3005. I will use your suggestions to help troubleshoot the Ampeg pedal when I get a chance.

Cheers
Chappy

Dirk_Hendrik · Post by **Dirk_Hendrik** » 26 Jun 2009, 17:16

Way to go!

but, bear in mind,
Make sure that you're working ESD safe when swapping BBD's. They're easily blown.

Chappy · Post by **Chappy** » 26 Jun 2009, 17:21

Dirk_Hendrik wrote:
Way to go!

but, bear in mind,
Make sure that you're working ESD safe when swapping BBD's. They're easily blown.

Thanks for the tip. I did not know that. Should I store the spare chips on the black electrostatic foam like I do with my CMOS chips?

Dirk_Hendrik · Post by **Dirk_Hendrik** » 26 Jun 2009, 18:59

Yep! Very advisable.

mikeC · Post by **mikeC** » 17 Jan 2014, 14:18

hello friends,

hope it's cool to dredge up this old post to get a Q answered re- my DOD-585a ...

using Mix control to dial in blend i require: at a certain point, instead of wet signal diminishing it just turns off. i've compared two units side by side and both behave the same. i've douched pot as well w/ no luck.

can anyone suggest a work a round? i love how delay sounds i just find it too "wet" for some generic music scenarios.

a million thanks in advance and happy new year,
mike

Chappy · Post by **Chappy** » 16 May 2014, 01:34

mikeC wrote:hello friends,

hope it's cool to dredge up this old post to get a Q answered re- my DOD-585a ...

using Mix control to dial in blend i require: at a certain point, instead of wet signal diminishing it just turns off. i've compared two units side by side and both behave the same. i've douched pot as well w/ no luck.

can anyone suggest a work a round? i love how delay sounds i just find it too "wet" for some generic music scenarios.

a million thanks in advance and happy new year,
mike

Mike,
I just dug my 585-A out of storage again. I remember that I had to change two pots on my unit to get it to work. My Mix pot works albeit it is very subtle. It seems that the useable range from a balanced wet/dry signal to a drier signal with a little delay is very minimal before it is a fully dry signal. Just a hunch but I'm guessing that your Mix pot is probably shot. I remember that when I fixed mine the original pots seemed very cheaply made to me and two of them had dead spots.

You could also try substituting a different valued pot and you might get more control over the mix. You could try a 50K or a 500K instead of the stock 100K. I'm not sure which one would be better unfortunately.

You are right too. The delay sounds really nice. I am comparing it to my DM2 and I like it just as much.

Chappy

tele twister · Post by **tele twister** » 29 Mar 2016, 02:50

Hello everyone!
I recently acquired a DOD 585-B, and immediately took to fixing the slider switch. I really don't know a whole heck of a lot about circuits, but I got lucky figuring out that the slider switch was open, This prevented the pedal from changing to the delay 1 mode, where the LED goes of and on. At first I thought the pedal was stuck on, or the FT SW was broke. I autopsied the slider and sure enough, the contacts were broke. I found a source for the original MSL33 switch and it's on it's way.
My question, is my MN3101 chip in backwards? I thought the scallop end of the chip was supposed to be at the same end as the socket scallop.

armdnrdy1 · Post by **armdnrdy1** » 29 Mar 2016, 04:13

Nope...
It looks like the socket is.
https://www.google.com/search?q=DOD+585 ... bZtR4WM%3A

tele twister · Post by **tele twister** » 02 Apr 2016, 03:28

I replaced the slider switch on my DOD 585-B and she is up and running and sounding just like an analog delay should. I found the exact switch at Mouser, which I thought was lucky because this pedal is about 33 years old.
As for being a dual delay, to clarify, it only toggles between two separate, user set delay times and therefore is not capable of ping pong type echo. IMHO, the switch should be labelled 1or2, not "1&2".
When in position "1", the FT SW activates delay 1 and lights the LED.
In position "1&2", the LED lights, and the FT SW toggles between delay 1 and delay 2.
And, she does not self oscillate, which is cool with me.
Both delay times are in the 10 to 300ms range, using my calibrated ear and my watch, which revealed about three repeats per second.
Here's some shots;