Siglent SPD3303X-E Binding Post Issues - Solved

[Gandalf_Sr]

My SPD3303X-E had the binding post issue - the banana plugs would not grip firmly in the binding posts and, despite Siglent sending me new binding posts, the problem persisted - regular banana plugs would fall out of the binding posts at the slightest touch.  Today I did some research and figured out what was wrong.  In the diagram below, you're looking at a cutaway of the end of the binding posts; the banana plug needs to go 6.64 mm into the post before it even gets to the actual 4mm ID connection (this is a much greater distance than most binding posts) and the internal diameter of the hole (where the colored inserts are = shaded area)) is only 4.5 mm which means that many banana plugs won't fully insert because they have flared flanges that take the actual plug into the insulated support.  The solution was simple, just drill out the end of the colored insert so that it's at least 5.5 mm ID, I found a stepped drill bit that was perfect to achieve this with minimal fuss.

I'll follow up with pictures of the whole process

[Gandalf_Sr]

Here we go withe the pictures.  In the first set, the top (black) post has been modified but the bottom (green) one hasn't, note that the plug doesn't go all the way into the bottom one.
Then we see the step drill - I got this from harbour freight and tool and the step marked with a dot is 7/32 5.56 mm) and the smaller steps work as a guide - you carefully drill into the end but don't push too far.
The final set show the actual PSU modified, in the before picture you can again see that the plug doesn't go all the way in, after the mod is does - it's only a difference of about 1 mm but it makes the plugs stay in well.

[tautech]

Thanks, very interesting !

When I look at the banana plugs you've been having problems with it seems from the center of the 'lantern' spring to the shoulder of the plug the distance looks quite short, in that the lantern in not engaged past it's midway point.
Then of course they'd just fall out !

I've looked at this issue for members here and myself when I bought the first of these models in when reportably the binding post issue had been fixed.
With any of the banana leads I have I found no issues with loose plugs and have posted several times to that effect.


So I've just measured some stackable leads that have retractable shrouds and the total pin length was 16.25mm and the 'lantern' spring center measures 10mm from the pin shoulder/base.
That would place the center of the 'lantern' ~3.5mm past the step without modification of the binding post.
This style works perfectly with these Siglent PSU's.

Yours don't look that long, can you measure them please ?
And for Siglents benefit (emailed) please list their manufacturer and Pt # ?

[Gandalf_Sr]

Tautech, I have about 6 different styles of banana plugs, only 1 type works with no issues in the SPD3303X-E binding posts.  All the other equipment that I have with binding posts, including cheap Chinese bench PSUs do not have this issue with any of my banana plugs.

The point of my post was not to get into a long list of which plugs work with the SPD3303X-E and which don't, it was to point out that there is a problem with the particular binding posts Siglent chose to fit on the SPD3303X-E - I identified why they were problematic and I described a simple way to fix it.

If Siglent want to change the design then good for them. If users want to buy multiple plugs until they find ones that work, they can do that; or they can try my simple modification.

[tautech]

Tautech, I have about 6 different styles of banana plugs, only 1 type works with no issues in the SPD3303X-E binding posts.  All the other equipment that I have with binding posts, including cheap Chinese bench PSUs do not have this issue with any of my banana plugs.

The point of my post was not to get into a long list of which plugs work with the SPD3303X-E and which don't, it was to point out that there is a problem with the particular binding posts Siglent chose to fit on the SPD3303X-E - I identified why they were problematic and I described a simple way to fix it.

If Siglent want to change the design then good for them. If users want to buy multiple plugs until they find ones that work, they can do that; or they can try my simple modification.

Sure.
A measurement to the center of the lantern of the 5 types you have and have trouble with will help others select what WILL work and give Siglent some info of different shoulder to lantern lengths that they maybe don't encounter in their part of the globe.
I know 10mm to shoulder works, what length are the problem ones you have ?

If we know that, then we can select banana plugs by measurement and not have to buy a selection rather than as you put it: 'buy multiple plugs until they find ones that work.'

[Gandalf_Sr]

I will take measurements of my banana plugs and post.  I will also take measurements of the binding posts on my gear.  This issue is simply one of a slack standard - no pun intended (unless someone can point me to the ISBP (International Standards for Binding Posts) document).

It's clear to me that, if Siglent made the following changes to their binding posts:
a. Reducing the 6.64 mm depth to 2 or 3 mm
b. Increasing the 4.5 mm aperture to 5.7 mm or greater

They would probably have far fewer complaints about loose banana plugs.

[Gandalf_Sr]

A few more observations:

1. The step drill can be bought from Harbor Freight https://www.harborfreight.com/titanium-high-speed-steel-step-bit-set-3-pc-60379.html
2. When using the step drill, DO NOT PUSH IT INTO the end of the binding post too hard, if it goes in too far, it starts to remove metal from the actual 4 mm sleeve that makes the contact
3. If the binding post also has a spade connector fitted, then the 6.4 mm depth number is increased by the thickness of the spade terminal, in my case this makes it so that some banana plugs don't work at all.

[Performa01]

My SPD3303X-E had the binding post issue - the banana plugs would not grip firmly in the binding posts and, despite Siglent sending me new binding posts, the problem persisted - regular banana plugs would fall out of the binding posts at the slightest touch.

Now that raises the question: what is the difference between the original binding posts and the new ones sent by Siglent?

[Gandalf_Sr]

Now that raises the question: what is the difference between the original binding posts and the new ones sent by Siglent?

When I contacted Siglent America, they thought that my Ser# should have the new binding posts but sent me replacements anyway - the replacements were the same as the ones fitted.

[DaJMasta]

For what it's worth, I could find four styles of banana plugs in my drawer and I tried all of them with my SPD3033X-E and they fit fine... considering I haven't really seen complaints about it, I don't know how widespread the issue is.

Maybe your banana jacks are a bit short and the extra depth from getting that back ridge in the post itself is giving them the depth they need to grip firmly?  Though one of the styles I had and tested was fairly short and felt like a firm connection.


Also I think the binding post issues reported with Dave's review were fixed quite quickly, as in, maybe with the first or second batch of production units, so if there is an issue with them now, I don't think it's the same one as that even if the symptoms are similar.

[BillB]

I also have a late model SPD3033X-E and haven't run into any "inadequate" length issues, yet...  With the banana plugs, I mean.

[Gandalf_Sr]

I haven't had many complaints about inadequate length, the occasional moan but no complaints.

[tautech]

I haven't had many complaints about inadequate length, the occasional moan but no complaints.

Then let's make this the first one !

Without measurements we don't know if you're inadequate or not ! 

From your OP we know we need 7+mm from the shoulder/base of the plug to the center if the 'lantern' spring for the plug to be retained firmly in the binding post.

I've heard squat back from Siglent as yet so I guess this issue is being discussed at length and they're maybe investigating alternative binding post suppliers to address your inadequate length issues Gandalf_Sr. 

[bsudbrink]

I have an early SPD3303X, ordered right before Dave's video, and it has the binding post issue.  I've tried it with a number of different leads, including real Pomonas and none work.  I was not aware that they would provide new binding posts.  I just tried to create a user account on the Siglent web site, but that doesn't seem to be working at the moment.  Is there an email address for someone at Siglent that you could provide?  Thanks.

[Performa01]

As you're in the US, you could complete the form here:

https://www.siglentamerica.com/contact-us/

I've just tried it and it seems to work okay.

Alternatively, there's also an email address: info@siglent.com

[Gandalf_Sr]

I have an early SPD3303X, ordered right before Dave's video, and it has the binding post issue.  I've tried it with a number of different leads, including real Pomonas and none work.  I was not aware that they would provide new binding posts.  I just tried to create a user account on the Siglent web site, but that doesn't seem to be working at the moment.  Is there an email address for someone at Siglent that you could provide?  Thanks.

If you want, PM me with your address and I'll mail you the replacements that Siglent America sent me, I didn't fit them as they were the same as the ones that came with my power supply.  I'll also pre-drill them out for you.

[Gandalf_Sr]

So I took some measurements (all mm) on other power supplies I own, the Korad KA3305P and the Mastech HY3003.  Here's the depth (distance from front edge of binding post to start of metal tube) and aperture (ID across inside of the binding post at front).

	Depth	Aperture
Korad	6.13	6.85
Mastech	5.32	5

Both have smaller depth and larger aperture numbers than the SPD3303X-E, both have no issues with any of my binding plugs (see next post)

[Gandalf_Sr]

and now for my motley collection of banana plugs, all bought on eBay or Amazon.  I'll number them 1 - 8 from the left (bottom row).
1. (Red) Good quality binding posts from Amazon - fit with no issues, the plastic shield screws in from the front (no holes) reccd
2. (Green) Poor quality bought from eBay - these are a problem, not just in their poor fit in the binding posts of the Siglent BPs but the metal cage is loose (spins around) and this gives a poor (high resistance) connection with any binding post  - not recommended
3. (Red) Same as 2 but gold-plated - not recommended
4. (Black) Good quality bought from eBay - OK connection on Siglent BPs but much better after BP mod - recommended
5. (Yellow) Good quality piggy-back style plug - problems before Siglent BP Mod, not after - recommended
6. (Brown) same as 5 above - recommended
7. (Silver) These are great BPs from Amazon but the outer sheath is metal, if they were available with insulated sheaths they would be excellent - not recommended
8. (Red) Straight BP - unknown origin - these work well in all BPs - don't know if they are still available

All these banana plugs fit securely on my other power supplies but the loose cage style (2 & 3) are not recommended

The picture also shows 4 BPs / sockets, I'll number them 1 - 4 top row from left
1. These were bought on eBay and look similar to number 4 (the replacement Siglent BPs), they suffer from the same issue and can be modified in the same way.
2. These BPs are ubiquitous, they come with many breadboard kits, the depth is less than 2 mm (front to metal) and they are cheap - recommended
3. Obviously not a BP but included in my picture - work well - recommended
4. Siglent replacement BPs sent to me by Siglent America - better after my Mod IMHO

[Ducttape]

Does anyone have a link to a specification drawing for banana plugs? I expected it to be an easy Google search but came up dry. Or is there just a verbal record that gets passed on during casual campfire talks through the years?

[Gandalf_Sr]

Apparently GE invented the banana plug, there are 2 different sizes I think but the most common is 4 mm shaft size.  If you can find a definition that would be good.

[rf-loop]

Apparently GE invented the banana plug, there are 2 different sizes I think but the most common is 4 mm shaft size.  If you can find a definition that would be good.

Banana plugs dimensios are total mess. Reason is that it is not at all standardized. There is only practice.
There is history also. But then we can also ask who's history. Different area in world have different trumpth of history. As also in many science there is "The Political Science of...this and that. GE launched it.   If I tell Hirschmann launched it after then whos history more right. Here rumors tell that it was Hirschmann. Who have more money his history is more right or who have biggest gun his history is most right - or then not.

There is so many dimensions and not only main dimensions but also so many details dimensions. And if want more mess, after then we add tolerances to this soup.  I have seen from around 1mm to around 8mm plugs in my life but highly very common is 4 and then 2mm.
But also whole big mess is also coming partially from fact that different part of world have been with differeent units. We live here with metric system but some others live with foots and fingers and inches. Then some kind of more or less accurate rounding between these.

Even if we take as called as "4mm" banana plug, there is lot of with different detailed dimensions. Who can show what are accepted tolerances - I do not mean opinions, I mean facts. Where is definition.
Even if diameter is around 4mm +/- some but then length is huge mess. But in america, I think,  more common is short and in europe is long.  Most common lenghts are around 15mm (around 14 - 16mm)  then other very common is around 20mm (something between 19 - 20.5mm) and then there is also sopme times these 11-12mm. (and then some amount  all between 10 - 25mm).

I have used these in lab mostly and these always work without any problems. There is also other models. Also Pomona do some good.
Robust and simple models are:
Hirschmann BSB 20 K
Hirschmann BUELA30K

(And also with these, "looks like" copy products are (mostly) total crap shit - example these contact springs loose force or is originally wrong due to wrong manufacturing and wrong materials. One copycat example about crap but cheap )

With tens of years experience in professional use I have never meet problems with genuine Hirschmann banana plugs (or high quality compatibles). But also some experience with cheap "looks like" copy shits - sometimes learning has also become expensive.

If I recommend some banana plugs for example Siglent SPD3303 series it is just these genuine Hirschmann with "standard" ~20mm length.  Kind of "industrial" references. More different more bad.
Also Siglent.Eu show these. (but are they genuine - I doubt because price)

Pity that Rosenberger, Lemo or Suhner do not make good industrial-military quality banana plugs.

Then what is idea for need big aperture in binding post. 4.5mm is well enough if banana plug is well made. I can not at all understand why they do these fat neck banana plugs. For what? Oh, perhaps audiophiles think they look more cool... who in industry ands professional work in lab or industry use these. Perhaps in  some rural poor area where they do not have money for buy tools. If I type banana plug to google... omg what kind of mess and shit there can see if select show images. OMG.

[Gandalf_Sr]

rf-loop, thanks for your detailed input.

The plugs I find most useful are the stackable ones (like the yellow plug in my earlier picture), I have them on many of my leads because I'm always finding the need to add another connection to the same point e.g. plug a voltmeter in parallel to check actual voltage coming from the supply - the plugs that have a 4 mm hole through them serve the same purpose but they are messy in that they leave exposed metal that can short to adjacent connections.

Maybe I could get rich and retire early by designing the perfect stackable banana plug?

[rf-loop]

rf-loop, thanks for your detailed input.

The plugs I find most useful are the stackable ones (like the yellow plug in my earlier picture), I have them on many of my leads because I'm always finding the need to add another connection to the same point e.g. plug a voltmeter in parallel to check actual voltage coming from the supply - the plugs that have a 4 mm hole through them serve the same purpose but they are messy in that they leave exposed metal that can short to adjacent connections.

Maybe I could get rich and retire early by designing the perfect stackable banana plug?

Hirschmann BSB 20 K is stackable so that they do not leave metal parts exposed.

[BillB]

I expected it to be an easy Google search but came up dry. Or is there just a verbal record that gets passed on during casual campfire talks through the years?

With a not so careful google search, or perhaps campfire lore, you might end up with one of these...


Seriously, I'm kinda partial to the overmolded or solder only ones that are stackable, I don't like using solderless "speaker" plugs - I have an irrational fear of touching that little exposed set screw.

 

[geekGee]

I just received an SPD3303X yesterday from Saelig which I ordered after confirming with them that their units in stock have the newer posts.

I have played with it using a couple flavours of Pomona leads and they fit snugly.  I tried a set of Cal Test leads and they did not insert well at all but work fine with my Rigol DP832A.

I guess the current posts are usable but fussy.