Scared newbie about ribbon cables

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robotbror
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Scared newbie about ribbon cables

Post by robotbror » Fri Jul 31, 2020 5:33 pm

I just got my first modules and I’m really scared I’m gonna blow this shit up. How do I double check that a ribbon cable is made correctly?
I’ve checked that the red stripe matches the little arrow on both connectors of every cable and put that in the -12v on both the bus board and the module is that 100% all I need to do or is there anything else I can also check?

I saw Mylars video on this and he started talking about some notch? I might just be stupid but I really don’t get what notch he’s talking about, there are like 3 little notches.

I’m just trying to fool proof this to the extreme because I can’t afford to lose any modules! Thanks!

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Re: Scared newbie about ribbon cables

Post by forrest » Fri Jul 31, 2020 5:54 pm

Most modules wont blow up.. Red goes to -12v, typically represented by a white line.. Or they will have sockets that can only go in the right way because of that notch..

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ranix
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Re: Scared newbie about ribbon cables

Post by ranix » Fri Jul 31, 2020 5:57 pm

inspect your modules, on the rear of the module near the power connector a pin "1" should be clearly indicated with screen-print on the PCB if you have a module that has no notch mating connector. The stripe goes toward pin 1

if you have a module with neither a notch connector or a pin 1 clearly indicated, please post a picture of the power connector here so we can all point and laugh at the manufacturer
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e-grad
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Re: Scared newbie about ribbon cables

Post by e-grad » Fri Jul 31, 2020 5:58 pm

robotbror wrote:
Fri Jul 31, 2020 5:33 pm
he started talking about some notch?
I am out of Euro for while but I think it's Analogue Solution who were using power sockets with a notch. Doepfer do not any orientation which way to connect the module to the bus board other than the red stripe goes to -12V. Nor any other manufacturer I am aware of uses any other orientation but the red stripe.
A100_bus.gif
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Re: Scared newbie about ribbon cables

Post by dBVelocity » Fri Jul 31, 2020 6:15 pm

The notch being referred is that of a keyed header. Some bus boards have these. Many modules do not so there is room for error there. You are on track and there's not much more to it unless you want to get a multimeter and verify the bus board is outputting the correct voltage polarities i.e wired up correctly. Unless you did it yourself, and you have doubts, it's very likely correct and not worth the time.

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Re: Scared newbie about ribbon cables

Post by kwaidan » Fri Jul 31, 2020 6:29 pm

With notched headers, it is important to make sure that the same wire—typically red—is correctly connected at both the modular and the enclosure power strip. Rarely, you may find a cable that is incorrectly keyed at one end. If so, you can sand off a key, but you need to make sure that you have the negative 12 V rail correctly identified.

At the modular end, some manufacturers use a thick line, sometimes white, to indicate -12 V.

Occasionally, you may buy a module with the ribbon cable incorrectly connected to the module, so check if before racking it.

Here are some pictures of notched headers and notched power cables:

Keyed header at back of module
5BDD1972-A247-418A-A6E4-70DCFD407E8D.jpeg
Keyed flying bus power strip
ACE32056-23B6-4E93-B762-8D883D571A64.jpeg
Keyed power cable
CB2BBA8F-4908-496B-A7D9-7C4B412D6331.jpeg
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dubonaire
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Re: Scared newbie about ribbon cables

Post by dubonaire » Fri Jul 31, 2020 8:47 pm

forrest wrote:
Fri Jul 31, 2020 5:54 pm
Most modules wont blow up.. Red goes to -12v, typically represented by a white line.. Or they will have sockets that can only go in the right way because of that notch..
Many will. You only have to do a search on this forum to see how frequently it happens.

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Re: Scared newbie about ribbon cables

Post by forrest » Sat Aug 01, 2020 7:13 am

Yeah its pretty rare and usually with DIY, reverse protection diodes/rectifiers are $0.20 to add to a design, it’s fairly unlikely with most new modules, pretty standard design thing..

In my time hooking up modules I've connected them backwards (in case and on module) at least 100 times and never had one blow up that way.. I realize it happens, but it's not necessary to be "afraid" to plug in your modules, just take your time and do it right if you're worried about it, you have all the info you need now 8-)
Last edited by forrest on Sat Aug 01, 2020 7:34 am, edited 1 time in total.

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Re: Scared newbie about ribbon cables

Post by 3hands » Sat Aug 01, 2020 7:23 am

I always remember the analogy of “red stripe down”. Until of course I bought a case that had the bottom power strip mounted upside down and it was red stripe up. I still get the heeby jeebies mounting new modules in it!
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Re: Scared newbie about ribbon cables

Post by EATyourGUITAR » Sat Aug 01, 2020 7:32 am

forrest wrote:
Sat Aug 01, 2020 7:13 am
Yeah its pretty rare and usually with DIY, reverse protection diodes/rectifiers are 0.20 to add to a design, it’s fairly unlikely with most new modules, pretty standard design thing..
no it is not standard. modulargrid shows 7960 modules produced between 1996 and 2020. doepfer still had no protection on 2020 on new production modules and new designs. the power headers are not keyed on the modules. and some of the doepfer modules are NOT red stripe down. we should advise people to look and see before plugging away hard earned cash. telling people to do something that puts them at risk is generally not prudent advice. if you restrict yourself to a few manufacturers known to use polarity protection then this is true. if you consider that doepfer IS the eurorack, doepfer is the largest company producing in 2020. then I think that is definitive proof that polarity protection on modules and keyed headers are not a eurorack standard. not yet. cwejman is not a super small obscure brand either, they are mainstream with an alternate keyed header orientation.
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Re: Scared newbie about ribbon cables

Post by sierraoskar » Sat Aug 01, 2020 9:36 am

This may be useful:

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Re: Scared newbie about ribbon cables

Post by Tonefloat01 » Sat Aug 01, 2020 9:41 am

When in doubt contact the manufacturer if their documentation is missing and/or not so straightforward.
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Re: Scared newbie about ribbon cables

Post by pugix » Sun Aug 02, 2020 11:12 am

The main thing to know is that pin 1 from the power distribution header must go to pin 1 on the module power header.

I always check cables to make sure that pin 1 (small triangle indicator) goes to pin 1 on the other end. Typically pin 1 matches to a red stripe on the cable, but only if the cable was assembled properly. I make sure all of my cables are like this. Then I only need to make sure that the red stripe goes to pin 1 on both ends.

And check that any shrouded headers with the keyed notch go the correct way on the PC board. I have a couple of Super Synthesis PH01 modules that have the keyed header soldered on the wrong way. :doh: The cables that came with them are also backwards, so they work. But if a proper cable were connected to one of these modules, it would be backwards.
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Re: Scared newbie about ribbon cables

Post by flipper16 » Sun Aug 02, 2020 11:32 am

What pugix said...

1. Always check cables.
2. Always check connectors.
3. Red stripe is not necessarily -12v.
Power Ribbon.jpg
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Re: Scared newbie about ribbon cables

Post by Pelsea » Sun Aug 02, 2020 12:39 pm

I use a spot of paint or nail polish to mark any boards that are unclear. I would also replace any header that I found installed backwards. I throw away any strangely wired cables.

How to find pin one on the header.
  • Find an 8 pin IC anywhere on the board.
  • Google its identifying part number-- it's probably an op amp, maybe dual. TL072 is very common, for instance.
  • Verify the negative terminal of the ic is pin 4 (Your Google will find this too.)
  • Use a continuity tester to verify the ic pin 4 is connected to pin 1 and 2 of the header. If it connected to header pins 3-8 find another 8 pin ic to test.
This may seem daunting, but it gets easy with practice. The hard part is figuring out which numbers printed on the case are the part number. It usually has two letters and 3 or 4 digits, like LM741 or TL061, perhaps with more letters following. Just Google the whole thing. Once you have identified the part, the pinout will show how it hooks up:
LM741.png
The -12 pin will be labeled V- or occasionally, Vee.
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Re: Scared newbie about ribbon cables

Post by EATyourGUITAR » Sun Aug 02, 2020 12:47 pm

Ironically this test is unreliable if the module has polarity protection. Your meter is in continuity mode with some unknown polarity then you test continuity of a diode maybe. You would need to do this in both directions for each rail with enough voltage from the meter to forward bias the diodes. Then you need to interpret those results. Even if you forward bias the diode, the impedance is not zero. Will it beep? Maybe.
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Re: Scared newbie about ribbon cables

Post by noisewreck » Mon Aug 03, 2020 3:38 pm

Just want to add one more consideration as the notch thing and orientation have been covered pretty well above...

Connect one module at a time. Connect module, power up system, check things are OK. Then move on to the next module. Repeat.

This way, if something goes wrong, it will be easy to ID which module cause the issue.

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Re: Scared newbie about ribbon cables

Post by prephylve » Mon Aug 03, 2020 6:24 pm

I've reversed power and "blown up" modules a lot lol. Thankfully I'm handy with repairs and the stuff that did blow up was diode protected. That said, after so many silly completely avoidable power reversals, I've decided to bring my live sound engineer logic to it and make everything "stupid" proof.

I asked my wife for red nail polish and I grabbed a contrasting paint marker. I painted the following:
  • A red dot somewhere close to the -12v pin on the module (keyed or unkeyed)
    Red dot on the -12v of each header on the ribbon cable
    Different color on the +12v of each header on the ribbon cable
    Red dot next to the -12v on the bus board
I've still managed to reverse the ribbon cables but haven't blown a module up since.
I should probably use a brighter color for the +12v. Maybe white?

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Re: Scared newbie about ribbon cables

Post by thetwlo » Mon Aug 03, 2020 6:43 pm

the NOTCH is only reliable with the cable it shipped with.
Get yourself a red PAINT Sharpie https://www.officedepot.com/a/products/ ... Point-Red/ or similar and mark the -12v PCB and/or header with it! Then a few months later, when you're moving things around it's very clear.

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Re: Scared newbie about ribbon cables

Post by EATyourGUITAR » Mon Aug 03, 2020 10:20 pm

thetwlo wrote:
Mon Aug 03, 2020 6:43 pm
the NOTCH is only reliable with the cable it shipped with.
cwejman cables come with cwejman modules but they don't come with cwejman power supplies

:cwejman:
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Re: Scared newbie about ribbon cables

Post by thetwlo » Mon Aug 03, 2020 11:18 pm

EATyourGUITAR wrote:
Mon Aug 03, 2020 10:20 pm
thetwlo wrote:
Mon Aug 03, 2020 6:43 pm
the NOTCH is only reliable with the cable it shipped with.
cwejman cables come with cwejman modules but they don't come with cwejman power supplies

:cwejman:
:doh: but we at least should know the orientation of the -12v (red line) on the distro board/pSU/

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Re: Scared newbie about ribbon cables

Post by acidbob » Tue Aug 04, 2020 3:31 am

Module -12 goes to busboard -12. Always. Not matter what. Follow that rule and you are good.

No matter the ribbon cable, notch and color.

Yes, I went euro when it was the wild west :)

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Re: Scared newbie about ribbon cables

Post by omega8870 » Tue Aug 04, 2020 5:05 am

As a sDIY guy myself, I've literally built my entire eurorack system, including power system. And I still get worried about plugging in power cables in wrong. Especially since I literally cut them and crimp them self. I've commited to using keyed headers, but mistakes can always happen!

All worries are quickly settled by my trusty multi-meter. Test plug cable into distribution, check voltages/continuity, then plug into module.

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Re: Scared newbie about ribbon cables

Post by Pelsea » Tue Aug 04, 2020 11:57 am

EATyourGUITAR wrote:
Sun Aug 02, 2020 12:47 pm
Ironically this test is unreliable if the module has polarity protection. Your meter is in continuity mode with some unknown polarity then you test continuity of a diode maybe. You would need to do this in both directions for each rail with enough voltage from the meter to forward bias the diodes. Then you need to interpret those results. Even if you forward bias the diode, the impedance is not zero. Will it beep? Maybe.
True that...

But diodes identify pin 1 better than an op amp. A diode is a little cylinder or box with a single stripe at one end:
Diodes.jpeg
There will be two diodes close to the header. Pin 1 will be attached to one of them at the end with a stripe. (Test with the meter-- connections are not always visible.)

Frankly, any module that is not clearly labeled deserves to be blown up, then sent back to the maker with a demand for replacement and reimbursement for shipping costs.
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Re: Scared newbie about ribbon cables

Post by FraMauro » Tue Aug 04, 2020 2:33 pm

Dieter Doepfer, who invented Eurorack, said the one thing he regretted was not making the power cables single sided

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