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MB-6582 BOM questions


jaytee
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Making a big Mouser order for the MB-6582 parts I couldn't source from Tayda. I have a few questions about the BOM.

- Is there anywhere to source the necessary rocker-style power switches? All I can find is a couple references to Wilba selling them from a larger batch. I used the photo on the old group buy wiki page to figure out what part it was, but can't find any place to purchase it. Is there another suitable part? Does anyone on the board have these? Should I just go with some other (probably panel-mount) switch and adjust the rear panel design as needed? I think I'm going to do that with the power jack anyway, since I'm gonna run it from a single 12V supply and want to use a standard jack instead of the 7-pin DIN jack.

EDIT: I seem to have found a switch that matches. First of all, it looks like the switch that Wilba was supplying is the R8011L from Salem (caveat, this is my best guess based on the image on the group buy wiki page). As far as I can tell, this switch (E201J1AV2BE2 from C&K) seems to be a close match. Only difference I can find is that the rocker sticks out an extra fraction of a millimeter. Not cheap, unfortunately. I'll probably buy one and give it a shot unless anyone points out that I've missed some crucial detail that makes it incompatible. I'll report back whether it works or not. Hopefully this is a help to anyone else looking for this rare part. Actually, upon closer inspection, I think the switch that Wilba supplied was the R8017L from Salecom. Ever so slightly different. C&K lists a matching part in their datasheet (E201J1V5BE2 ), but it doesn't seem to be for sale anywhere. Back to the drawing board.

- The feedback pots aren't on the BOM. I think they're supposed to be 500k dual-gang pots, right? Log or linear taper (I think log, right)? Can anyone suggest a matching pot/knob combo? I know that the pots probably aren't hard to find, but I feel totally inept at match knobs to pot shafts. 

- Speaking of the feedback pots, how useful do folks find them? I'm considering leaving them out entirely. Despite seeing successful installs from other folks, I worry about noise coming in on the audio-in pin, and about eventually blowing the SID filters, which I've heard the audio-in can do. I'm using 8580/6582 SIDs, if it makes any difference.

- There's nothing in the BOM about securing the base PCB to the Pac-Tec case. Are the screws included with the PT-10 sufficient or are those only to close the case? I can't really tell from the PT-10 data sheet.

- Can anyone give me a quick primer on crimp pins/female connectors for the headers on the base PCB? I promise I've googled this, but I must not be searching for the right things. It seems like a lot of DIY stuff assumes knowledge on what pieces and parts one needs to buy to assemble female connectors for headers, but this will be my first time not just soldering wires directly to the board in lieu of headers altogether (trying to do this right!).

- Speaking of connectors, can anyone offer Mouser part numbers for the correct LCD connector. I have a better idea how to assemble this piece at least, thanks to the guide to MIDIbox display cables, but I just want to be sure I'm getting the right part; again, first time working with these types of connectors.

-Any other parts that aren't on the BOM that I should pick up? Even just basic stuff that most folks would already have in their workshop. Only things I've come up with are shunts and a few machine-pin female headers (for SID capacitors and LED resistors).

 

Sorry, I know this is a ton of questions about stuff that most folks here (and elsewhere in the DIY world) take for granted as simple matters. Just looking for a little guidance before I drop a bunch of money on parts. Better to ask these questions now than after parts arrive and I get the wrong stuff.

 

As a post-script, let me just say that I do not recommend buying IC sockets from Tayda, or at the very least, not the 28-pin wide sockets (i.e. SID sockets). On two separate sockets, a pin came loose while placing it into the PCB and the wipers slid upward. Really poor quality.

Edited by jaytee
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Hi,

- I do not know how you are planning  to organize cooling inside yours MB-6582 case. When you are using  a single 12V power supply you will get a lot of heat from a +5V linear stabilizer ic inside the SID synth case.

- Some about feedback pots from one of Hawkeye messages:

"1. 100kohm work fine, 500kohm will also work... the value just specifies the max feedback "dampening" which is at maximum for 100kohms already.

2. you need four "stereo" feedback potentiometers for four stereo pairs of SIDs, no matter what type of sids."

or otherwise you don't forget to grounded an analog inputs.

Regards,

Janis

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Thanks @Janis1279.

I will be using a Recom switching regulator to get 5V. It comes well-recommended by other members of the forum, and those that have installed it report no heat issues or switching noise. I am not worried about this aspect of the build at all.

Re: feedback pots. Thank you for confirming the necessary resistance. Do you know if log or linear is better? Can you recommend a specific pot/knob combination? Have you noticed any noise issues with the feedback pots as opposed to tying the inputs to ground?

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9 hours ago, jaytee said:

- The feedback pots aren't on the BOM. I think they're supposed to be 500k dual-gang pots, right? Log or linear taper (I think log, right)? Can anyone suggest a matching pot/knob combo? I know that the pots probably aren't hard to find, but I feel totally inept at match knobs to pot shafts. 

- Speaking of the feedback pots, how useful do folks find them? I'm considering leaving them out entirely. Despite seeing successful installs from other folks, I worry about noise coming in on the audio-in pin, and about eventually blowing the SID filters, which I've heard the audio-in can do. I'm using 8580/6582 SIDs, if it makes any difference.

I have them, but I've never really used them. Mine are log. I haven't noticed any noise problems.

With pot shafts and knobs I think you've got knurled shafts, round smooth shafts and D-shaped shafts. Knurled shafts don't have tightening screws on them, but smooth ones do. Of D-shaft ones I'm not sure, I think they tend to use push-on knobs, so no screw. Note also that the diameter of length of the shafts may vary; e.g. diameter can be 6.0mm or 6.3mm, and while you can fit a 6.3mm knob (with a screw) on a 6mm shaft, it won't be completely centered. Knurled shafts tend to be split (to facilitate a push-on knob), but smooth ones are always solid (as far as I can tell) and need a knob with a tightening screw.

I have knurled shaft pots with push-on knobs.

 

Quote

- There's nothing in the BOM about securing the base PCB to the Pac-Tec case. Are the screws included with the PT-10 sufficient or are those only to close the case? I can't really tell from the PT-10 data sheet.

It was years ago when I built my MB6582, but I think the screws came with the PacTec case.

 

Quote

- Can anyone give me a quick primer on crimp pins/female connectors for the headers on the base PCB? I promise I've googled this, but I must not be searching for the right things. It seems like a lot of DIY stuff assumes knowledge on what pieces and parts one needs to buy to assemble female connectors for headers, but this will be my first time not just soldering wires directly to the board in lieu of headers altogether (trying to do this right!).

I used JST connectors, but only because I have them (and the crimp tool) available at work. The biggest threshold for JST is probably the insane price of the crimpi tool itself, at least the JST original. I wasn't able to find a knock-off that would have crimped them adequately. I tried two cheaper models but neither of them worked properly on JST, so I'm using Dupont connectors nowadays for my projects. The advantage of JST though is that it's about 50% more shallow than Dupont, and I'm not sure if Duponts would fit in the space available in the PacTec case.

 

Edited by jjonas
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Thanks @jjonas! This is very helpful.

With the knobs, I always just worry that I'm misinterpreting a measurement, like that the diameter is the inside of the knurls instead of the outside, or that they won't cover the threaded section of the pot... I think I need to just bite the bullet and buy some, and if they fit, they fit, and if they don't, I learned something.

As for the connectors.... Hmm. At the very least, it's encouraging to know that they come in "kits." Previously I was trying to look up the right parts on Mouser/Digikey and I couldn't make heads or tails of what bitsies went with which bobbinses. Hopefully someone else can chime in about whether the cheaper-but-taller connectors fit in the Pac-Tec....

Or I could just skip the Pac-Tec altogether. I know someone who makes sheet metal + wood cheeked enclosures that look really nice. They've made MB-6582 cases in the past I know. I haven't inquired about price (I'm sure it ain't cheap) but the Pac-Tec seems like a little bit of a pain in many ways (space mostly). I only figured I'd go with it because I found a source of cheap panels.

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I opened my MB6582 to check whether Dupont connectors might fit. There's two images below, they show the way I've connected the two boards: I've used JST connectors for both ends of the connection. It would seem that Duponts won't fit on the base PCB end, but for the CS PCB it's different (see the lower image with an empty Dupont connector at the 8-pin connection closest to the bottom of the image). For the CS PCB you'll have to use angled pin headers if you want to use any kind of connector, and that way there's more space, so it seems Duponts would fit there.

One way you could get away with just Duponts is that you solder wires straight into the base PCB and make a detachable connection at the CS PCB end only, with Dupont connectors. Probably ribbon connector is not the most durable material here, so if I was to do my connections properly some point, I'd use individual pieces of wire instead of ribbon cable.

A few more words about the JST crimp tool. The originals cost over 200 euros (or was is GBP), so I bought a cheap "JST crimp tool" on eBay, but it didn't do the job. Then I went to a local shop where I asked to try out various cheap (less than 50 euros) crimp tools, and none of them worked for the JST crimps that I had. But they did work on the Duponts, so I bought a crimp tool for around 30 euros and switched to Dupont. So I'm not saying there's no good cheap JST crimp tools out there; I just didn't feel like buying several candidates on eBay just to try them out. But I would still prefer JSTs because they are so much smaller and thus handier than the Duponts.

medium.mb6582-connectors1.jpg.b833f4e2ba

large.mb6582-connectors2.jpg.065a6efc74f

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Ah, I see what you're talking about. I actually hadn't even considered the board-to-board connections yet; I was still stuck on the headers for the panel-mount stuff on the back (mix out, expansion port, etc). But it is good to know that the CS board will fit them, if barely.

Probably going to order more parts tomorrow!

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I'm looking for a rocker switch as well. You can find some at eBay from time to time (search for c64 switch, I think they will fit but I'm not 100% sure). Currently a seller in Germany has some of them, but 9 Euro for a used part...

Have you seen Hawkeye's great Building the MB-6582 Control Surface - Photo Tutorial ? It's very helpful and contains part numbers.

BTW: For the base to cs connections I would recommend to just follow Wilba's instructions and use the stiffy flat flex cable. It's more than sufficient. Once you are done you will open the case maybe 5 times. A detachable solution is always nice but not worth the effort.

Edited by verpeiler
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On November 17, 2016 at 5:39 PM, verpeiler said:

I'm looking for a rocker switch as well. You can find some at eBay from time to time (search for c64 switch, I think they will fit but I'm not 100% sure). Currently a seller in Germany has some of them, but 9 Euro for a used part...

Have you seen Hawkeye's great Building the MB-6582 Control Surface - Photo Tutorial ? It's very helpful and contains part numbers.

BTW: For the base to cs connections I would recommend to just follow Wilba's instructions and use the stiffy flat flex cable. It's more than sufficient. Once you are done you will open the case maybe 5 times. A detachable solution is always nice but not worth the effort.

I have Hawkeye's tutorial on a permanent tab on my computer browser ;)

I can't seem to find anyone in North America selling those switches, unfortunately. I would honestly pay $10 or so for the right switch (fuck it!) but $10 plus international shipping is getting ridiculous. Unless someone has a spare or a suitable replacement is found, I'm probably gonna find something to panel mount, as much as I hate it.

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  • 2 weeks later...
On December 4, 2016 at 3:29 PM, ilmenator said:

Why is everybody so obsessed with these rocker switches? There are many panel mount / snap in alternatives out there. Panel mount means no stress on the PCB...

I ask a couple questions about a part and now I'm "obsessed." :rolleyes:

Getting the part intended by the designer, in this case, saves me from doing extra work: shopping through digikey's enormous selection of switches, checking datasheets to make sure it's a good fit for the available space, re-jiggering the back panel cutout. It's all minor stuff, but not as minor as spending two minutes to ask around a forum for spare parts (which paid off, I might add, as a friendly member sent me the part for only the cost of shipping).

In other cases, the effort to use the intended part might *not* be worth it. For instance, I won't be using the C64-style DIN7 plug for power. I'll have to re-jigger the back panel to fit my panel-mount choice, but it saves me from having to assemble a power supply with a DIN plug.

Do these tiny calculations of worthwhile effort make me obsessed? Perhaps. But I'm building myself a synthesizer; why shouldn't I make it to my very own specifications?

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You can obviously build to whatever spec you like, and if that switch is an integral part of your building satisfaction, then you should definitely go for it :happy:.

It's still kind of interesting, because if I remember correctly, then originally the idea was to recycle a part that everybody who had salvaged the SID chip from a C64 was supposed to have anyways. So, no offense meant, rather a friendly "shaking of head in disbelief"...

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