Any ideas to replace the speaker terminals on a 400?

John Henry

Still driving, man.
Since I don't ever plan to sell it, I want to make a small modernization to my 400. I'd like to replace those screw-down wire posts on the back. Two of them are broken (they screw down only so tight then suddenly loosen). And they're very close together. I'd be happier with something more solid and convenient back there.

I've been looking for the right parts to do it, possibly something like a group of these: Link
260-302_L.jpg


So I thought I'd see if anyone here has seen or used something good for this. (I tried searching, but didn't do very well... probably poor word choice on my part.) Any ideas or advice appreciated.

Thanks!
 
So I'd need to tap or re-thread the screw holes currently on the back of my 400 for those to screw in?
 
More than likely. IIRC the screws are 6/32. With them worn out the 6/32 banana plugs would do the same as your screws. Best to drill to the next size up for 8/32 and tap for 8/32. The njust screw the banana post in.

Or you can get involved and fabricate a masonite plate with 5 way binding posts, and a terminal for the oHms Tap. Kinda Tight tho. Even Ratshacks smallest Binding post with a nut on the back (bag pack loose, no plate) is too large for the existing plate opening.

Make an adapter using a solder binding post, a piece of speaker wire, Heatshrink and spade lugs. Solder the wire to the Binding post, and the spade lugs. Heatshrink both ends. Then solder the spade lugs to the terminal strip while screwed down as much as you can get. Gonna take more heat than a 30w ron can do tho. Not pretty but it works.

Last option but it probably wouldn't work on yours seeing that the terminals are stripped. Binding posts for terminal strips on Ebay. Kind of expensive for 8. Supposedly gold plated.

Larry
 
Five way binding posts are nice, but they tend to be large. That's why I've settled on the Pomonas. They're not cheap (coming in below $4 a pop plus shipping), but they're small, non-intrusive, color coded, and can be placed close to each other. They're 10/32.

Now, I'm not advocating for these for any reason other than convenience or the fact that i've got a bag of them. I'm open to alternatives at any time. I just haven't found a reliable source for small, non-intrusive binding posts.

Jim McShane sells replacement binding posts.
 
Thanks for all the advice, guys. It seems to me that the Pomonas may be best simply because space back there is so limited. I'm a little worried about tapping for new threads though. I've tried that before with limited success. And if I damage the existing panel, I'll need to fabricate a new one.

So still open to new ideas. Thanks again!
 
I worried about tapping also. Tapping with 10/32 is not 100% successful. I suggest tapping slightly smaller and buying some washers to extend out the Pomonas 1/16 of an inch or so.
Why?
The thread ends before the end of the shaft and you can try and tighten them down into unthreaded territory and the stock at that point is thinner than the thread. Look at the picture on the link again and what I just wrote will make sense.
 
Heck, that thing has a left-hand thread in the Mouser picture. That can't be right.

It's correct. It's a right handed thread. No Lefty in their right mind would put a threaded part picture up incorrectly. Right?
 
I have 5-way binding posts with 6-32 thread that I use on these terminal strips. If some are stripped, you could use a nut on the inside...
 
I have 5-way binding posts with 6-32 thread that I use on these terminal strips. If some are stripped, you could use a nut on the inside...
Those sound perfect. Do you happen to remember where you got them? I've spent a lot of time on Mouser, but have not gotten that good at searching yet.

Also, can anyone shed a little light on how those OEM screws work, ie can you damage the threads in the socket when you unscrew them past the stopping point?
 
Also, can anyone shed a little light on how those OEM screws work, ie can you damage the threads in the socket when you unscrew them past the stopping point?
For any people reading this in the future, the OEM screws come straight out. There is a little extra resistance towards the end, but not enough to cause any damage.

I picked up some screw in banana sockets at Fry's today, screwed them in and everything looks and sounds fine. They're a bit larger than I'd like, but I'm happy.
 
For any people reading this in the future, the OEM screws come straight out. There is a little extra resistance towards the end, but not enough to cause any damage.
I picked up some screw in banana sockets at Fry's today, screwed them in and everything looks and sounds fine. They're a bit larger than I'd like, but I'm happy.
Thanks for this topic, John. The future is here and I'm looking for a similar solution.
I found recently a good deal on restored vintage Fisher X-202-C amp. I'd like to be able to switch between spade and colored banana adapters for its old style screw terminals.
I found on ebay 2 types of colored adapters with 2.7mm and 3mm threads - ebay links are below. I suspect they could be the same and if not which one should I order to match the screw thread on those old amp terminals?
I don't want to drill to the next size as all of my screws are not worn out. I see in the discussion above that original Fisher screw thread should be 6-32 and there is some confusion with conversion to metric size. For ex. according to this doc http://www.engineeredpartsinc.com/pdf/metric-conversions.pdf
6 - 32 corresponds to M3.5 x .06
The next smaller size M3 x .05 corresponds to 4 - 40 inch equivalent and there is no such size as M2.7

Here is what I found on ebay: Black-Plastic-Shell-2-7mm-Male-Threaded-Diameter-Banana-Binding-Post:
https://www.ebay.com/itm/10-Pcs-Bla...ed-Diameter-Banana-Binding-Post-/310943791008
Black-Plastic-Shell-Metal-Body-3mm-Dia-Thread-Banana-Binding-Post:
https://www.ebay.com/itm/20-Pcs-Bla...m-Dia-Thread-Banana-Binding-Post/310803031905

In my understanding I should try with 3mm connectors. Can somebody please clarify this?
Thanks a lot,
Bob
 
Here are my new findings today. I checked the original Fisher speaker terminal screw in the local Lowe's and can confirm it's 6-32 thread.
M4 - 0.7 bolt is a bit large for 6-32 nut and M3 - 0.5 bolt goes through 6-32 nut without screwing.
So I see both 3mm and 2.7mm banana adapters may be used with those old terminals without any drilling and I will need to use their nuts to secure them from inside.
 
I use those on several things, they're great. Just don't hang cables from them or you may break the phenolic board. Support your cables and its fine.
 
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