What banana plug size does HP's old power supply use?

[yugu]

Hi there. I have an HP 6237B power supply. I quite like it except that its power terminals are pretty big. The standard 4mm banana plugs are too small to fit! The spade connectors don't fit either    I know I know it's not a blocking issue. But I have to say it's quite annoying to deal with these nonstardard size connectors.

It seems the biggest size of banana plugs is 4mm. Was HP following old standard of plug size? Are they still in the market? What's your solution? 

[mzzj]

Never seen such a thing. Can you measure the hole diameter?
One possibility is that someone with (chinese) over-size plugs has drilled the holes to bigger diameter...

IF the holes are 3/16" then you might be able to fix them with brass sleeves cut from 3/16" brass tubing available from RC hobby shops( good match for banana connectors, 0.160" =4.06mm nominal internal diameter)

[Shock]

Back of drill bits make nice hole gauges. 

[Zero999]

Back of drill bits make nice hole gauges.

Probably a bit off topic but beware that a drill will always cut slightly larger holes than its shaft diameter.

[Shock]

Back of drill bits make nice hole gauges.

Probably a bit off topic but beware that a drill will always cut slightly larger holes than its shaft diameter.

Better than buying a set of small hole gauges if your micrometer doesn't fit.

[timb]

I've got an HP supply from the mid-70's and it uses standard banana jacks that look just like those. In fact, pretty much all HP gear used the same jacks through the 70's, 80's and 90's.

What do you mean when you say it doesn't fit? Is it too loose or too short?

I've found a lot of older equipment used banana jacks that seem too short for modern banana plugs (that is, when a lead is plugged in it doesn't go all the way and there's generally some of the metal plug exposed).

I tend to just replace these types of jacks with new ones. For supplies with rear screw terminal access, I'll use the non-binding post style jacks (because they don't extend the leads out as much and the plug is more secure, which is important when you stack cables like I often do).

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[yugu]

The same banana plug and spade connect fit perfectly with my BNC-to-banana adapter. But when I connect them to the power supply, the banana plug is too loose and the spade connector is too small to fit. please check the attached photos.

@mzzj, since both the inner and outer diameter are larger, it's unlikely that someone enlarged them by drilling ;-)

They look original too. The only explanation that makes sense to me is these connectors were larger in the good old days (1977).

If you happen to have the same 6237B power supply, could you please verify the size of those plugs?

I will replace them with modern ones, when I find good quality replacements.

[mzzj]

The same banana plug and spade connect fit perfectly with my BNC-to-banana adapter. But when I connect them to the power supply, the banana plug is too loose and the spade connector is too small to fit. please check the attached photos.

@mzzj, since both the inner and outer diameter are larger, it's unlikely that someone enlarged them by drilling ;-)

They look original too. The only explanation that makes sense to me is these connectors were larger in the good old days (1977).

If you happen to have the same 6237B power supply, could you please verify the size of those plugs?

I will replace them with modern ones, when I find good quality replacements.

There is no standard size for spade connectors so no mystery there. The banana connector hole diameter is a open question and mystery still.

[yakitoo]

I recall coming across these many years ago when I was working in the HP ISD division.

We were sent them to fill a bench PSU requirement because they were 'available' and had a 'low budgetary impact'. Apparently they were originally built for a customer who had specified non-standard connectors. Never did find out if the specification was real or simply an accident in the design office. I don’t think many were made and I've certainly not seen any outside HP.

It was a real pain as we had to keep the leads separate from the standard ones and make sure they went out with the units when they were needed offsite.

[Shock]

www.ebay.com/itm/Agilent-HP-1510-0529-BINDING-POST-GRAY-W-BLACK-/300925352229

[edavid]

The springy part of a classic banana plug like Pomona or HH Smith is 4.2-4.5mm in diameter, and fits fine in the HP binding posts.

[timb]

Yeah, that's true. A lot of older banana plugs had wide "springy" sides so they fit very tightly into jacks. Modern ones don't seem to do that.

Like I said though, I've got a 6235A from 1978 that fits everything from cheap Chinese to Pomona plugs just fine. Must be your specific unit.


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[yugu]

I measured the plug sizes today

                              Inner            Outer
6237B-Banana     4.2mm           6.1mm     (@yakitoo, are these sizes close to those in your story?)
BNC-2-Banana     4.0mm           5.7mm

The sizes of my banana plugs varies from 4.0 to 4.1x. I could just expand a pair of them and use them only on this power supply.  Not a big deal.

@edavid, yeah you are right. Plugs with 4.2-4.5mm in diameter will fit these binding posts.

@timb, how springy are your cheap plugs? is the diameter larger than 4.2mm?