Speaker diagnostic question

I have a 1957 Wurlitzer model 2150. I had the amp rebuilt and converted to accept a stereo cartridge; although the amp is mono. My issue is that the speakers come in and out. If I wiggle the plug that goes into the amp, it will usually kick back on, so I assume the issue is with the plug. I have taken the plug apart, cleaned it and validated it has a good circuit. Similarly, I checked the socket on the amp and, again, appear to have all good connection. I've checked the end point of the speaker wire (there are three daisy chained speakers connected) and, again, appear to have a good circuit. My test is simply using a Digital multimeter set to test resistance. I assume there is a better way to localize the issue. While I am guessing it is at the plug (since I can wiggle/adjust the plug to get it to cut back on), perhaps it is somewhere else, or perhaps there are multiple issues and the plug is simply the straw that breaks the camel's back. Thoughts?
Thanks
Brooks

Hi Brooks,
It's possible that "it is the straw---"-but I would suspect the plug, or socket first--
On SOME sockets, you can "insert" a probe into each pin, and "re-form it", however, I would first try cleaning it with a pipe cleaner saturated with Deoxit 5. Also make sure the plug/socket have no "cold solder joints"---
BTW-- A "digital" meter, especially a self adjusting type, will not confirm a "good" connection. It can only be used if the connection(s) are known good--an analog meter usually will check the connection. Ron Rich

Thanks. Yes, as I understand it a DMM will confirm that I have some degree of connectivity, but not the quality of the connection. Anyhow, I'll give those suggestions a shot
Brooks

Brooks, as you probably figured out, the speaker connection pins on the plug are 5 & 6. The three speakers are each 16ohm and the total load is approx 6 ohms facing the amp. On a DC resistance meter this will show as a little over 4 ohms.

While one can test for that impedance and thus check for any broken-erratic wires from the male plug to speakers, it is not practical to test from under the chassis socket as the output transformer will load the meter and make an accurate reading impossible.

As Ron mentioned, is is possible to -slightly- tighten the clips inside the chassis female to make better contacts (if that is the problem). Use a tiny screwdriver or sometimes the probe tip from your meter will work to carefully squeeze together the contacts a --little bit--. Set the amp up where you have good light and can really see what you are doing. Too much force will move the clips too close and they will double-over and break when you try to re-insert the plug.

Check/reflow the solder connections behind the socket.

As for general reliability...well...these old E-M machines CAN be reliable IF they have been gone over properly. But, understand that like your E-M pins, they have a lot of moving parts and contacts. At this point the oldest machines I have on location are Seeburg from the 1950's and one LPC along with a bunch of vintage wallboxes. The Tormat era Seeburgs I use are quite reliable and some are enduring 1000+ play/wk with less than one service per year on some machines. However even with the Tormat eliminating a lot of mechanical pins and coils, contacts still need to be cleaned regularly to ensure reliability and prevent pitting. For home use, just about any machine can be made adequately reliable and after a 'boilout" period you'll have very little problem IF the proper restoration has been done.

BTW: Did you thoroughly oil the mech?

Rob/NYC

Thanks for the info.
I believe I have everything well oiled, which is not to suggest it is a 'well-oiled' machine (at least not yet). Are there any areas that are especially problematic that I should recheck/regularly inspect?.

I will definitely try to clean and tighten up the clips a bit since it feels like there is a bit of play. I also fear that my wiggling may exacerbate the issue by further loosing up the fit. I find some of the layout/design to be suboptimal for service. The position of the speaker plug on the amp makes a 'straight shot darn near impossible, so I can see how things would loosen up over time if people had to play with that plug much.

What's the old joke, that hell for engineers is to have to maintain the products they design and hell for those who write instructions for toys is to have to put each others toys together following the instructions.

As the holiday season is upon us, I wish the best of luck to those who have small children and have purchased toys with the dreaded "Some Assembly Required" sticker on the front of the box. (Align part A so that the tab from part B is positioned to the side of the opening in part C to allow the pin in part D to have adequate clearance. Verify all seven posts are facing up toward the chip. When translated into English becomes. "Part A is in a line on the side of part B in the position of part C. Clear part D adequately. Have a seven up and chips."

Hi Brooks,
The"oil point" most often "missed" on a WurliTzer, is the one in the "center of the carrousel"--It takes a LOT of oil in that oil hole to fill the large wick. One thing about it is they colored the wick red (in most cases), so that when it needs oil, it turns from brown to red--
As for "some assembly required"--I have more problems "assembling" things that have only "picture instructions"(no "words")--I hate them !!
Ron Rich

Arghhh
I have used deoxit on plug and socket, reflowed solder. Heck even removed and resoldered one of the wires. Tried to tighten the clips in the socket. There was some play in the clips on the socket, so I put the plug in and gently pushed on the clips from underneath to make sure it was well seated. Plugged it in and it actually was worse, no sound at all. It appears the best connection is when the plug is barely in, so my attempt to seat the clips probably did more harm than good. I would guess, based on the symptoms, that the ends of the pins are larger diameter than the base of the pins due to wear. The solution may be to 'tighten' up the clips in the socket as deep as possible but I really can't seem to do that since I am flying blind. Just sticking the tip of a very small screwdriver no idea what I should be doing. Is there some trick to it? I'm almost to the point of cutting the wires and soldering it to the socket contacts!
So where is the err of my ways?
Thanks

(also the wiring is a puzzle to me. On the plug you have a jumper from pin 1-3 while, as you noted, 5 is black and 6 is red. Then on the socket, you have 1 to 5 to ground with 3 to the transformer and 6 to the speaker selector dial. So, in essence you have 1, 3 and 5 all to ground and the transformer. Seems like you could have accomplished this with 2 pins.)

Hi OldGoat,
You gotta anna "icepick" --seems that anyone named "Old Goat" should have ! Use it on the socket, or replace that socket---
Reason for the "jumper system" is to shut down B+, if the speaker(s) are un-plugged. Ron Rich

I gave up and hard-wired the speakers to the socket. Much to my chagrin, NO SOUND. It makes me wonder about that jumper on the plug. I went ahead and wired across the two on the socket. Should I have simply soldered to 5 and 6 and left the rest alone?

If not, any other ideas on why I have no sound?

Thanks
Brooks

OG,
I would need to look at the schematic( which I do not have) to answer that--
Ron Rich

I have the schematic, but I ain't bright enough to figure out what it means. I do have a question after fiddling with it some more. As noted earlier, the black wire (pin 5) goes into socket 5, which is connected to socket 1, which is wired to ground., so obviously, when I check resistance with my DMM it indicates a complete circuit with the black speaker wire and ground. The red wire is on pin 6 which goes to what I am guessing is the speaker selection dial. When I check resistance with pin 6 to ground it also indicates a complete circuit. So, I have both 5 and 6 going to ground. Because of this, when I test the speaker wire and put one probe on the red wire and one on the black, I get the beep that means the circuit is connected. Mind you this is testing the wires in the socket, so there is no speaker connected. I would think any signal sent to the speaker on 6 would simply go to ground rather than through the speaker and then to ground on pin 5. Maybe that is not the case. Is it reasonable that both red and black go to ground.
Thanks
Brooks

Goat, connect as follows:

Pin 3 to chassis ground. That is the center tap of the B+ (Hi-V). If this pin"s connection is not connected to chassis; no high voltage-no sound.

One speaker wire to chassis ground.

The other speaker wire to Pin 6. Doesn't matter whether you use the Red or Black speaker wires at this point. Note thta Pin 6 in the socket is the audio output from the amp and chassis ground is the negative-return from that audio.

I do suggest that you wire-in a plug of some sort (RCA, etc) for the speakers to allow you to easily remove the amp in the future.

Rob/NYC

I'm looking at a terrible print of a 532 amplifier, but it looks like Pin 6 is the output for the speakers and the return is on Pin 5. When you measure across those two pins with no speakers hooked up, the resistance you're seeing should be that of the output transformer. If you actually show zero resistance, something's amiss. I believe it should be a low resistance, but not zero. You do not want to short those two pins together with the amplifier powered up.

Pin 3 is the B+ enable. That needs to go to ground if you don't have the speaker plugged in via the correct connector. Without any B+, you won't get any sound.

This diagram also shows a fader switch. Have you cleaned that switch to make sure all the connections are good as well?

-Jim

Ha ha. Rob beat me to the punch, but it looks like we're on the same page.

I am totally ignorant on the electronic side of things, other than it is a bad idea to stick a paperclip into an outlet. Don't ask me how I know that.

I'll definitely get some mono RCA plugs and the Shack tomorrow. Fortunately I am three time zones later than you, so I'll be popping a nice malt beverage in a bit and tackle it tomorrow

Jimmler wrote:This diagram also shows a fader switch. Have you cleaned that switch to make sure all the connections are good as well?

-Jim
.

Interestingly, when I take a screwdriver and turn the fader switch, I could hear the speakers pop. So, I discovered that if I position the fader switch between settings, I get sound. Now the sound is maybe 10% with a good bit of hum, but definitely sound coming through. I assume the issue must be with ground and since the speaker plug/socket is wired to the fader switch, I'm guessing that may be the source of my problem and wiggling the plug simply resulted in my making ground some other way. Does that make any sense to you experts? I'll try cleaning the fader switch tomorrow and see what happens

Thanks
Brooks