AIO-8 DB-25 Connector Screw Locks

[Dreamsequence]

Does anyone know for a fact what the thread size and pitch is on the AIO-8 connectors? I have several cards where previous owners have tried to install the cables with an impact wrench, shearing the threads off when removing the snakes. I called Hosa to see how the DB-25 to TRS fanouts are shipped from the factory, because they send both 4-40 US and 3mm screw posts with the new snakes. Technical Support assumes the 4-40's are pre-installed for US distribution. But I just went through 15 AIO cards, and only one had 4-40 female threads. I double-checked them with several snakes, none of which had 4-40 screw posts. The internal threads inside the connector are definitely 4-40. Searching around, I did find a listing for a screw lock (the nut portion) with a 4-40 external male thread, and a 3mm internal thread.

[Bruce Graham]

Hey;

I have had this trouble as well. Some are 4-40, and some are 3mm.

What I did was changed all my snake cables and card threads to the same standard which was 4-40, NOW....

The other issue, for me anyway, is the thread length on the bolt of the cable. I have not yet established what is the proper length, more specifically, between the bottom of the nut on the card and the length of the bolt. this bolt should pull the connector tight enough so there is no movement. The down side has been they are too long and thus do not "pull" the db25 cable in tight. This has caused loss of audio as the connection is lose. I have put additional #40 washers between the shell of the connector and the screw head (in an attempted to shorten the length), but it has not always work! This has always been at a gig (I move my console around). I haven't been able to find the time to fix this.

I know it doesn't specifically answer you questions but may lead to other expressing what they have found!

Cheers for now
Bruce

[Dreamsequence]

Thanks Bruce.

I have some more checking to do, but I'm relatively certain the female thread is 3mm x .35 pitch. This is the metric fine pitch. I tried 3mm x .50, listed as metric standard pitch. I can't prove it because my usual mega-source hardware store doesn't carry metric fine pitch hardware.

I absolutely agree that these screw locks (studs) must not only be installed the correct height, the length of the hex portion & depth of the threads affects how well the connectors draw together. I will take some measurements and try to find a source for these. No idea why the AIO cards would have metric hardware, as my experience is the Mackie snakes do bolt up without changing the screw posts. The last time I did this, I connected an SDR to a Presonus digital board via direct outs. The DB-25's fit at both ends without a struggle, yet the Hosa technical data sheet says the posts are 4-40 UNC. They include the other threaded posts, but I never swapped them out.

I have another SDR; I'll see which posts fit those connectors.

[Dreamsequence]

I discovered an answer in the HDR Technical Reference Manual on page 214. It states that Mackie uses standoffs with metric threads. This can be verified because the jack post (screw) will only install approximately 1-1/2 turns before seizing. It continues by saying the user can change them out for 4-40 US threads, and Mackie can supply them. My issue with this is it requires the user to have 4-40 screw locks and jack posts on hand. If you should happen to purchase a card that has the US threads, and your cables have the original Mackie metric jack posts, you'll need to change something to get them to bolt up tight. I'm 99% certain that Hosa cables ship with the metric jack posts installed, at least for the DB-25 to TRS cables, aand the DB-25 to DB-25 direct out cables.

I am making an inquiry into getting a few samples from a manufacturer that has a close match in inventory, but they are in Germany. The screw locks are also bagged 1,000 pieces per. Yikes!

[Bruce Graham]

Good find.

I will check what I have on my cables (I purchased AES/EBU Cables from HOSA) and see what I have.

I did get my hands of 4-40 standoffs and short screws for same, but that doesn't help on my cables.

Thanks for tip.

Bagged in 1,000 pieces! Let me see, that's you, me, Crash (just because) and ......

Cheers
Bruce

[Dreamsequence]

I finally figured it out, and there's good news, and bad news if you are running Hosa cables with the original thumbscrews in the DB-25 connectors:

Newark Element 14 has the exact replacement screw locks (the female part). Their SKU # is 16M3374. This is 12.77mm long, with a 2.6mm female thread, and a 4-40 US male thread. They are $0.73 each, so you can buy as many as you need. They will bag you $5.00 for shipping, so it is tough to justify one at a time. They do not include the 4-40 split lockwasher, but you can reuse your old ones, or try a hardware store or hobby shop.

You are correct that the connectors won't quite bottom as tightly as you would like. I removed the lockwasher, and you can gain about .6mm, so it is better. However, unless you use a drop of Loctite ThreadLocker on them, it's tough to remove the connector from the screw locks w/o the lockwashers. They tend to spin out unless the screw locks are really tight. Plus, you run the chance of scratching up the paint on the plates (unless you don't care). According to my testing, the screw locks should not extend beyond the flush face of the card connector. They are just enough too long to work well. The other choice is to use a 4-40 flatwasher instead of the split washer. That should gain .4 to .5mm.

Oh, yeah- the bad news: I could not locate anyone who manufactures the jack post in 2.6mm. Bummer. Hosa does not offer them separately, and in fact do not have a Parts Department. When they need them to solve a customer's problem, they rob them from returned merchandise. The only thing I can think of doing, is buy some closeout cables as cheap as possible and remove the screws. They end up costing about $4.00 each if you buy the DBD models you get (4) at a time.

This only matters if you have lots of Hosa cables with the standard 2.6mm posts. If you are only concerned about your use, it would be far easier to replace both pieces on your I/O cards and your snakes. Pro Audio houses only use 4-40 hardware, so they would recommend replacing all. Make sure the screw locks do not extend beyond the face of the card connector. They can kit something up. Try: http://www.proaudiola.com