ARP 1601 clone Build Thread

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Re: ARP 1601 clone Build Thread

Post by elmegil » Thu Sep 17, 2020 12:33 am

Are the other q outputs off z25 ok? Probably if the stairstep is good.... Any chance that pin is shorted to ground?

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Re: ARP 1601 clone Build Thread

Post by KSS » Thu Sep 17, 2020 5:52 am

Sorry, can't see linked imgur pics. If you want us to see them don't link, upload. That also preserves them here for future readers.

Yes, TP18 is the staircase.
-----------
Work backwards from the outputs.
Look at pin 9 and 10 of Z30. those are the inputs to the S/H's. Do they look the same as the outputs? If yes, you've eliminated the S/H's as problems.

You've got something happening semi-randomly/cyclic and seems to be related to pot mid position. that's why I keyed on the staircase. The staircase sets the available quantized voltages. If it's all over the place, or missing steps, then the rest of the circuit can be working exactly right and you'd still have the weird outputs. Since the staircase is made by switching in the precision resistors using 4051's, from counter Z25 -under the influence of Z24d, clocked by Z31abc and using Z27d to inhibit alternating 4051's, these become suspect. The semitone current shift would be included but as I said before, that would be a more rapid fault than what you've described. Which again will show up in the staircase anyways. The staircase should have nice even uninterrupted steps. Z27d would screw up around half the staircase. That missing or corrupted "half" may relate to your shared 50% slider problem.

There's no magic in the clock speed and you could slow it down to help your troubleshooting. But you should have a clean clk or everything else suffers.

Once the CLK and staircase are confirmed, with the S/H elimintaed, we come to the alternating inputs. It's simple enough to bypass Z30ab going direct in -through a 10K R- to Z26b,pin5. I always socket Z30 so its removal is easy, and when it's gone, then the output selectors composed of its c,d portions is also easily bypassed. And you don't need an extra 10K R, since tyou can jumper the socket pins.
Z30,pin 8 and 11 have the staircase, and pins 6 and 12 are the S/H control AKA "sample/hold" bits. Since we've already eliminated the early days Hi-Z input CKT and the OPAs of the S/H as having problems -along with their output mixing- we can look at how the control bits for them are working.

With a slow clock -even replacing it with a debounced pushbutton- you can step through the stairs and see when the comparator changes and if its signal gets though the Z24 and Z28 logic to the removed Z30 anaSW.

You asked about the comparator Z23. With Z30 removed, its pins 2 and 3 give entry to the Z26b buffer and you can read the output at TP19. You can get even more 'granular' by lifting the legs of R186 and R187 to feed it -Z23- directly and again look at TP19 to see if it's doing what it should. If I got this far, I'd probably already have confirmed OPA Z26b and wouldn't need to raise a leg on R187. Same with the staircase and R186. Already chk'd.

At his point, the CV inputs are checked and eliminated, the staircase, S/H and output buffers are checked and eliminated. The CLK is checked and eliminated. the 4016 is ck'd and eliminated. all that's left is the Z24,27,and 28 logic. Well, except for the semitone curent shift. But that would've shown up in the staircase. So it's eliminated too. Check D23 and 24 are correctly oriented. <--AKA "CR" but re-using that term at this point is just dumb. Ck that C27 and 28 are correct and OK.

Keep us posted. Will be nice to see what it ends up being.

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Re: ARP 1601 clone Build Thread

Post by synthcube » Thu Sep 17, 2020 3:47 pm

People always ask us what's so dang special about the synth DIY community and it's examples like this that we like to point to.
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Re: ARP 1601 clone Build Thread

Post by Kipling » Fri Sep 18, 2020 10:03 am

Assuming that you have socketed the ICs, I would remove all components (there are only four ICs) that connect to TP17 on net 0454; Z25, Z21, Z24 and Z27 and check that TP17 is not held high or low by a short to +15V or Ground, it should be totally floating.

Check the sockets are OK from above (no gold contact inserts missing - it has been known) and that all pins of these four ICs are correctly soldered with no bridges or dry joints. Check also that you have continuity between Z25 pin 5, Z21 pin 6, Z27 pins 12 & 13, and Z24 pin 1 by testing from the top side of the sockets.

If all is well, test each of these four ICs (noting that you have already replaced Z25 twice) if you have the facility to do so, or replace with known good new ones. Check all pins are inserted correctly with none bent over.

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Re: ARP 1601 clone Build Thread

Post by KSS » Fri Sep 18, 2020 11:04 am

While I don't subscribe to 'fixing' and troubleshooting by the scattershot chip replacement suggested above, I do agree that checking for bent pins, and good solder joints should be high on the early list of things to do when things go wrong.

Sticking in new IC's until it works seems to be the preferred method used in these DIY projects, based on build threads here and elsewhere online. But the ICs are rarely the problem when compared to simpler -and far more often the culprit- things like wrong resistors, bad soldering and bent pins.

You don't learn anything about the real problem when you do the whole IC swap thing. You might 'fix' it and it later comes back. Because the problem wasn't the IC, the blown IC was a result of whatever the underlying problem is-was.

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Re: ARP 1601 clone Build Thread

Post by elmegil » Fri Sep 18, 2020 11:29 am

KSS wrote:
Fri Sep 18, 2020 11:04 am
While I don't subscribe to 'fixing' and troubleshooting by the scattershot chip replacement suggested above
I don't see any scattershot replacement suggested though.

Kipling suggested removing the chips to make measurements. Chips selected specifically because they are in the vicinity of the problem.

Yes, uwe has been doing "just replace the most obvious thing" but they don't have your level of experience. Talking down to folks who are struggling isn't much help either, much less appearing to be taking potshots at the guy who's probably helped fix more of these than any of the rest of us.

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Re: ARP 1601 clone Build Thread

Post by KSS » Fri Sep 18, 2020 12:13 pm

Fair enough. Thanks for the feedback.

No potshot intended. If I didn't respect Kiplings work and efforts I wouldn't be in this thread at all.

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Re: ARP 1601 clone Build Thread

Post by elmegil » Fri Sep 18, 2020 12:23 pm

KSS wrote:
Fri Sep 18, 2020 12:13 pm
Fair enough. Thanks for the feedback.

No potshot intended. If I didn't respect Kiplings work and efforts I wouldn't be in this thread at all.

Fair enough back at you :) I apologize for seeing things that weren't intended.

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Re: ARP 1601 clone Build Thread

Post by KSS » Fri Sep 18, 2020 12:44 pm

No, you made a good call. I didn't read and fully grasp what he'd written before feeling the hairs go up on words like "remove all components" in the first line and then "replace with known good new ones" at the end. But the middle words I'd glosse over in haste make all the difference.

I needed to be called out. When you did, and I read the post more care-fully, then I could see why you'd written what you did. And what I'd glossed over before posting my reply. So thank you.

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Re: ARP 1601 clone Build Thread

Post by Kipling » Fri Sep 18, 2020 2:06 pm

Glad we can all get along here for the benefit of those who run into difficulties. :tu:

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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Tue Sep 22, 2020 4:06 am

I built the REV 1 of this lovely sequencer and have always found it to be brilliant. After a period of external upheaval I am now hoping to incorporate it into my system again and it needs a little bit of tlc. The main thing I want to do is:

- Install a new power supply. I've been using a diy Frequency Central that's not properly fixed in the case. Can I use the one listed in the latest BOM's and are the starred items in the latest revision still good for REV1?

- Troubleshoot some clock issues - it tends to run very fast when switched on and the minimum speed stays quite fast. It does accept external clocking though. I will try my hand at this with the service manual and a scope.

- Nice end cheeks. Are there any templates circulating?

I'd be very grateful for any other tips that I may have missed in scanning the threads - it's been a long time.

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Re: ARP 1601 clone Build Thread

Post by synthcube » Tue Sep 22, 2020 8:10 am

finnurbjarna wrote:
Tue Sep 22, 2020 4:06 am
I built the REV 1 of this lovely sequencer and have always found it to be brilliant. After a period of external upheaval I am now hoping to incorporate it into my system again and it needs a little bit of tlc. The main thing I want to do is:

- Install a new power supply. I've been using a diy Frequency Central that's not properly fixed in the case. Can I use the one listed in the latest BOM's and are the starred items in the latest revision still good for REV1?

- Troubleshoot some clock issues - it tends to run very fast when switched on and the minimum speed stays quite fast. It does accept external clocking though. I will try my hand at this with the service manual and a scope.

- Nice end cheeks. Are there any templates circulating?

I'd be very grateful for any other tips that I may have missed in scanning the threads - it's been a long time.
does your chassis have sloped sides? If so we have a couple of spare (obsolete) side cheek sets we can share for the cost of postage.. michigan synth works did the template, we had a couple made...
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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Tue Sep 22, 2020 8:39 am

synthcube wrote:
Tue Sep 22, 2020 8:10 am

does your chassis have sloped sides? If so we have a couple of spare (obsolete) side cheek sets we can share for the cost of postage.. michigan synth works did the template, we had a couple made...

That's very kind of you - thank you! :woah:

I'm guessing my case is obsolete - it looks like this:
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Re: ARP 1601 clone Build Thread

Post by synthcube » Tue Sep 22, 2020 8:48 am

yes, that's the older version of the case, but we do have a couple sets of laser cut cheeks that will fit nicely-- if you like we can send photos and calculate the shipping cost, just send us an email-- it will be nice for them to have a good home ....
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Re: ARP 1601 clone Build Thread

Post by 3hands » Tue Sep 22, 2020 9:01 am

I want to buy a kit just to be able to interact with everyone in this thread. This reminds me of old Muffs...

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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Tue Sep 22, 2020 9:13 am

synthcube wrote:
Tue Sep 22, 2020 8:48 am
yes, that's the older version of the case, but we do have a couple sets of laser cut cheeks that will fit nicely-- if you like we can send photos and calculate the shipping cost, just send us an email-- it will be nice for them to have a good home ....
Marvellous - you are a star! :yay:

I will email you.

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Re: ARP 1601 clone Build Thread

Post by nickbtx » Tue Sep 22, 2020 9:14 am

Hi Gang,
I ordered a 1601 v6 this past weekend and wondered if there any bugs that I should be aware of? I scanned through this thread and the only errors I found appear to have been corrected with v6, e.g. though-hole spacing. This is going to be the largest project I've attempted without the benefit of a build guide and I'm a little apprehensive. Makes me appreciate Fuzzbass' TTSH build guide all the more. ;)

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Re: ARP 1601 clone Build Thread

Post by elmegil » Tue Sep 22, 2020 11:27 am

finnurbjarna wrote:
Tue Sep 22, 2020 4:06 am
- Troubleshoot some clock issues - it tends to run very fast when switched on and the minimum speed stays quite fast. It does accept external clocking though. I will try my hand at this with the service manual and a scope.
There's a frequency calibration step in the service manual, the very first part of the calibration. That should resolve this.

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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Tue Sep 22, 2020 2:18 pm

elmegil wrote:
Tue Sep 22, 2020 11:27 am

There's a frequency calibration step in the service manual, the very first part of the calibration. That should resolve this.
Great, thanks - that will be my first port of call then.

I think my questions regarding updated parts and compatibility are mostly answered at the front of the thread - I had another look :hihi:

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Re: ARP 1601 clone Build Thread

Post by Kipling » Tue Sep 22, 2020 4:56 pm

finnurbjarna wrote:
Tue Sep 22, 2020 2:18 pm
I think my questions regarding updated parts and compatibility are mostly answered at the front of the thread - I had another look :hihi:
You’ll need the original style dc/dc converter with the 1” x 2” footprint similar to the early TTSH. There are a few cheaper options other than the one I originally specified.

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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Wed Sep 23, 2020 11:12 am

Kipling wrote:
Tue Sep 22, 2020 4:56 pm

You’ll need the original style dc/dc converter with the 1” x 2” footprint similar to the early TTSH. There are a few cheaper options other than the one I originally specified.
I looked up the Rev 1 Mouser BOM on LED Man's page and it looks like that part is still the same, i.e. AEE00CC18-LS. Am I getting something mixed up?

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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Wed Sep 23, 2020 11:18 am

nickbtx wrote:
Tue Sep 22, 2020 9:14 am
Hi Gang,
I ordered a 1601 v6 this past weekend and wondered if there any bugs that I should be aware of? I scanned through this thread and the only errors I found appear to have been corrected with v6, e.g. though-hole spacing. This is going to be the largest project I've attempted without the benefit of a build guide and I'm a little apprehensive. Makes me appreciate Fuzzbass' TTSH build guide all the more. ;)
It's a very fun build if a bit unusual because of the hugeness of the board - I'm sure you will enjoy it. No reason not to make use of the build guide, though. It's there in the first post of the thread.

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Re: ARP 1601 clone Build Thread

Post by nickbtx » Wed Sep 23, 2020 11:36 am

finnurbjarna wrote:
Wed Sep 23, 2020 11:18 am
No reason not to make use of the build guide, though. It's there in the first post of the thread.
DOH!! Don't know how I missed that. Thanks!

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Re: ARP 1601 clone Build Thread

Post by Kipling » Wed Sep 23, 2020 5:00 pm

finnurbjarna wrote:
Wed Sep 23, 2020 11:12 am
Kipling wrote:
Tue Sep 22, 2020 4:56 pm

You’ll need the original style dc/dc converter with the 1” x 2” footprint similar to the early TTSH. There are a few cheaper options other than the one I originally specified.
I looked up the Rev 1 Mouser BOM on LED Man's page and it looks like that part is still the same, i.e. AEE00CC18-LS. Am I getting something mixed up?
The Meanwell DKE10A-15 is a much cheaper option than the Artesyn part. Currently £15.06 at Mouser.

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Re: ARP 1601 clone Build Thread

Post by finnurbjarna » Thu Sep 24, 2020 1:54 am

Kipling wrote:
Wed Sep 23, 2020 5:00 pm

The Meanwell DKE10A-15 is a much cheaper option than the Artesyn part. Currently £15.06 at Mouser.
Can't argue with that. I've opened the sequencer up now and my board is actually the REV 2 from May 2nd 2015.Can I still use that converter?

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