looking for some vintage audio geek help

69.5CUDA

Blah Blah Blah
soooo lets start here
i picked up a wurlitzer 3700 from a wrecking yard along with a car not far from it...spent tim eworking on it which led to..a SECOND 3700...you know how things seem to multiply..

anyway some time later ive managed to solve both rigs issues save for 1 which is a cam bearing follower problem which prevents the record from fully coming down on the turn table..and ive not had time to rip out the transmission and see if i can source a suitable bearing replacement...

BTW both rigs are stereo and sound soo warm and nice thus why id love to get a lil creative with external inputs, the working unit is packed full of random "test" 45s i got for free..about half of the 100 records(200 selections) are stuff id keep....but ive also got a HUGE stash of mom n dads old stuff to load..so 2 machines in different local's makes sense

wife randomly comes in drops a quarter in and just pushes random number/letter not caring what comes on..so yeah she loves it

rig #2 came with bar "mike" hookup as well as "bar" controled volume and "record cancel", which is quite cool cause you can basicly"corded" remotely control some things....im on a hunt for a "well loved" but cheep PTT desktop/intercom mike(yes wurlitzer has it all as silkscreened mike not mic)

anyway to the question, the plug on the mic hookup seems to be a 91-mc4f, requiring a mc4m, mind you ive found some but they aint cheep...thing is i cant seem to figure out the pinout or find the info on the pinout wiring for the plug

what i want to do is setup a small project box that plugs into said mc4 plug that has both a 3.5 jack and a bluetooth, so i can setup a laptop with music that i dont have in the box, but also be able to just "stream" music from my phone...cheepo tiny car BT adaptors are cheep enough in the 3.5 , and obviously id need a switch to turn on the PTT.
the issue is 91-mc4 is such an old format i cant find much info, let alone how id like to use it..or if thats even possible
 
Sounds like a fun project, good luck with it.
ive been having FAR too much fun with both of them...and i forgot how good records sound, ESPECIALY out of a good juke!!!!!!

sadly as much work as ive done, ive little else i can actualy do with either of them, short of taking them down to the bone to clean n paint....and the 1 machine i REFUSE, 73000 plays of patina, scratches in the glass, general wear, but its still in amazing condition overall..even my wife said i wasnt allowed to do anything more than clean and repair..as its got too much character

this is machine 1 the auto wrecking yard "office/misc showroom piece"
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and this is rig #2, thats got 10k plays on it and is neerly new on the inside..however..it was SEVERELY mistreated and abused, so the "casing" is broken in a few spots, all said this one ill have to do major repairs on and..since my wife REALLY wants a 3800 AKA the purple people eater(as dubbed by the juke community) ill likely re-paint and mod it into said 3800...
the change between 3700-3800 is the keyboard and chrome housing, 2 inlay changes and the broken side rails painted purple...ive allready found the keys and trim, and 1 inlay

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second machines twice as pretty for sure. even if abused and busted up

buying the second machine i got scolded for sure!!!!!
but
it allowed me to troubleshoot every last fault out of the first machine as machine 2 simply had a WRONG powersupply in it which came down to flip flopping 3 wires on the transformer..but it allowed me a "working" rig to test components from rig1..so it went from months of head scratching to suddenly a week later both were done..which made wife VERY happy..

since they both have rca outs as well as speaker outs, she wants some outdoor speakers for the deck...yeah she loves it just that much
 
This gives me anxiety
yeah me too initialy, thats machine #2 which has 2 extra "options" which makes it select and play the "top10" and top 10 most played..so its got a whole mess extra over machine#1...
but..whats REALLY cool is its all oldschool as ehll, its barely a step out of transformers, the manual has full schematics
those 3 orange things are next to the triacs..i replaced those, as well as most of the caps on both rigs...but seriously its scary lookin but SUPER easy to work on

that blown cap..i exploded 10 of them before i managed to isolate the issue..didnt even spot the "wrong" powersupply till i started swapping parts between the units and made note of an odd part number on it after blowing that same cap on the OTHER control box ..come to find out the powersupply was from 3 gens earlier visualy identical, and the wiring neerly identical thus the amp functioned as it should..hell put a big enough cap on and you could get the whole rig to work fine for about 1 min before it would blow(12v replaced with 50v)..had to swap a couple diodes and 2 wires and ground a leg off the transformer to make it match the correct unit...that was fun to understand and figure out
 
whats REALLY cool is its all oldschool as ehll, its barely a step out of transformers, the manual has full schematics
I've got a buddy who taught himself to repair pinball machines and talked about them the same way.

I need to point him to this thread, although I doubt he'd be interested because music is just so damned convenient these day, you know? Now a pinball machine, you can play with that for a while, maybe a long while, before the excitement wears off.
 
DO NOT attempt to connect anything but an unpowered microphone to that Amphenol connector. Microphone and line-level inputs are very different things. That is an amplified input, so connecting something at line level (1/8" or RCA) will be extremely loud and horribly distorted for the short time until it damages the jukebox. If you've ever tried to plug a CD player or cassette deck into the "PHONO" input on a 1960s-'70s receiver/amplifier, you've probably already experienced something similar, just not as extreme.

Old turntables require a "phono preamp" to be connected to a modern receiver/amp without a phono input. Old receivers with a dedicated phono input have a built-in preamp. Pro-sound microphones (the type intended for that jukebox) require "phantom power" which is a similar, but different, circuit when used outside their normal application, like connecting it to a PC. Those parts "pre-amplify" their respective device's output signal up to line level, which is then fed to the amplifier (stereo and pro sound microphone inputs always have a built-in preamp).

Regardless, since that Amphenol is a mono input you'd only get one channel, left or right, depending on how you wired it. You cannot simply wire the left and right signals together. At best, it'll sound like absolute hell. At worst--and far more likely--you'll damage whatever's plugged into it.

If you want an auxiliary input, the first thing I'd try is removing the cables from the "PHONO INPUT" jacks and connecting them to the CD/tape/video inputs of a home-stereo amplifier using RCA extension cables. DO NOT connect anything to the jacks in the jukebox! Fire up the Wurly and check the volume.
  • If it's just as loud (or very close to it) as a tape deck or DVD/CD player would be, you're golden. Install Y-connectors there and connect your auxiliary equipment as you see fit.
  • If it's noticeably faint by comparison then you'll have to keep reading.
If it's faint you need to trace wiring from the back of the "PHONO INPUT" RCA jacks through their first amplification stage (the preamp). That's where you'd want to tie auxiliary inputs into the wiring--after the preamp circuit and before the main speaker amp. I believe you'll find that the "AUX AMP OUTPUT" RCAs are tied into the post-preamp circuit somewhere. That does not mean those can be used as inputs, although it is possible.

The other trick might be switching the amplifier, unless the speakers are always making some kind of noise. I would guess that the amplifier is off when the jukebox is powered but not playing a record. Newer jukes are like that, but I can't say on the relics. Play one song, and put your head next to the speaker as the song ends. Listen to see if you hear the amp shut off, or if the speaker continues making a very-faint hum. If it's the latter, no problem. If it's the former, well, you'll need some kind of override.

If you really want to know how good that old jukebox sounds, replace the speakers with modern equivalents. The magnets in those old speakers (with the square frame around them) often lose power over time. The dash speaker out of the '74 Challenger parts car wouldn't hold a 1/4" socket; the one out of the Valiant wouldn't hold a paper clip (seriously). They both still worked, just not well. There wasn't a good shot of the speakers so I've no idea of size or impedance, but replacing them will new, even inexpensive, full-range drivers will almost certainly improve the sound dramatically. Parts Express, Madisound, and even Digi-Key have good selections of replacements.

Want to get truly silly? Run a pair of RCAs off the "AUX AMP OUTPUT" to a powered subwoofer.

If you want to know how to actually connect a microphone to that external control box, I have the required pinouts to convert to the now-standard XLR connector.
 
I've got a buddy who taught himself to repair pinball machines and talked about them the same way.

I need to point him to this thread, although I doubt he'd be interested because music is just so damned convenient these day, you know? Now a pinball machine, you can play with that for a while, maybe a long while, before the excitement wears off.
they are very akin to pinball machines with the fact its mostly switches levers and relays, with some electro mag pulled pins to triger switches as well
 
DO NOT attempt to connect anything but an unpowered microphone to that Amphenol connector. Microphone and line-level inputs are very different things. That is an amplified input, so connecting something at line level (1/8" or RCA) will be extremely loud and horribly distorted for the short time until it damages the jukebox. If you've ever tried to plug a CD player or cassette deck into the "PHONO" input on a 1960s-'70s receiver/amplifier, you've probably already experienced something similar, just not as extreme.

Old turntables require a "phono preamp" to be connected to a modern receiver/amp without a phono input. Old receivers with a dedicated phono input have a built-in preamp. Pro-sound microphones (the type intended for that jukebox) require "phantom power" which is a similar, but different, circuit when used outside their normal application, like connecting it to a PC. Those parts "pre-amplify" their respective device's output signal up to line level, which is then fed to the amplifier (stereo and pro sound microphone inputs always have a built-in preamp).

Regardless, since that Amphenol is a mono input you'd only get one channel, left or right, depending on how you wired it. You cannot simply wire the left and right signals together. At best, it'll sound like absolute hell. At worst--and far more likely--you'll damage whatever's plugged into it.

If you want an auxiliary input, the first thing I'd try is removing the cables from the "PHONO INPUT" jacks and connecting them to the CD/tape/video inputs of a home-stereo amplifier using RCA extension cables. DO NOT connect anything to the jacks in the jukebox! Fire up the Wurly and check the volume.
  • If it's just as loud (or very close to it) as a tape deck or DVD/CD player would be, you're golden. Install Y-connectors there and connect your auxiliary equipment as you see fit.
  • If it's noticeably faint by comparison then you'll have to keep reading.
If it's faint you need to trace wiring from the back of the "PHONO INPUT" RCA jacks through their first amplification stage (the preamp). That's where you'd want to tie auxiliary inputs into the wiring--after the preamp circuit and before the main speaker amp. I believe you'll find that the "AUX AMP OUTPUT" RCAs are tied into the post-preamp circuit somewhere. That does not mean those can be used as inputs, although it is possible.

The other trick might be switching the amplifier, unless the speakers are always making some kind of noise. I would guess that the amplifier is off when the jukebox is powered but not playing a record. Newer jukes are like that, but I can't say on the relics. Play one song, and put your head next to the speaker as the song ends. Listen to see if you hear the amp shut off, or if the speaker continues making a very-faint hum. If it's the latter, no problem. If it's the former, well, you'll need some kind of override.

If you really want to know how good that old jukebox sounds, replace the speakers with modern equivalents. The magnets in those old speakers (with the square frame around them) often lose power over time. The dash speaker out of the '74 Challenger parts car wouldn't hold a 1/4" socket; the one out of the Valiant wouldn't hold a paper clip (seriously). They both still worked, just not well. There wasn't a good shot of the speakers so I've no idea of size or impedance, but replacing them will new, even inexpensive, full-range drivers will almost certainly improve the sound dramatically. Parts Express, Madisound, and even Digi-Key have good selections of replacements.

Want to get truly silly? Run a pair of RCAs off the "AUX AMP OUTPUT" to a powered subwoofer.

If you want to know how to actually connect a microphone to that external control box, I have the required pinouts to convert to the now-standard XLR connector.
amp is always on..touch the needle lol..it NEVER shuts off, ive considered adding a trip for the amp to turn on/off with the needle arm swing switch...would be simple enough

now i was under the impression i could run an atenuator to bring the line level down to mic level?..but that just left me with more questions than answers...as again they dont seem to adress the PTT...and i "think" the 4wire plug is specificly for PTT units?...IE like a bartop intercom mic or a mash mike?..but then i also came across info that the 4pin was a setup for both high/low impedance...so...i figured it best to just find info

i know better than to try pluggin shit in lol...good way to break stuff

im not 100% that it even has aux amp outputs aside from speakers, but ive not dug much into the amps

as for the speakers id never considered mag degridation..but let me ask this.."if" i were to replace the speakers would it lose the warmth? ...the bottom units are uhh 12s? i think pretty sure they are not 15s, the uppers are 6s i think and need replaced as someone tossed car speakers into it
on the other side of speaker talk..would the 10k plays unti have the same de-magnitization as the 70k plays?..ive never considered how speaker mags age

all said if i cant use the mic in..i may get a vintage correct mic for it just for shits n giggles

at the end of the day..i want it to work as intended as much as possible, as nicely as possible...i had to bypass the BO/AC unit(bonus acumulator IE the coint cointer and credit unit) and ran a trip off the coin mech switches so that ANY coin triggers a play....just to make it "feel" like its working right as in you have to pay to play

the ONLY reason id like to aux in somehow(tho idealy thru the mic box)..is just to be able to use it more..which is why i tracked down the factory mic box as well as the remote volume control..the more the unit can stay closed the more real it feels..ya dig?..but being able to adjust the volume externaly is really nice..but its also got a button on it to reject a song on the spot...so if it skippping or just buggin ya or you picked the wrong one..1 click and it puts it back
 
amp is always on..touch the needle lol..it NEVER shuts off, ive considered adding a trip for the amp to turn on/off with the needle arm swing switch...would be simple enough
Well, if you're going to wire in an auxiliary input of some kind, the amp being always-on is actually to your benefit. Otherwise you'd have to figure out how to make the amp come on with the aux. Not impossible, but a bit time-consuming. It's just something about which you don't have to worry.

now i was under the impression i could run an atenuator to bring the line level down to mic level?..but that just left me with more questions than answers...as again they dont seem to adress the PTT...and i "think" the 4wire plug is specificly for PTT units?
Attenuators bring speaker-level signal down to line level. I've never seen one that goes below line level. Line level is much too hot (high voltage) for that input.

They don't address the push-to-talk because it's unrelated to the plug. Push-to-talk is built into the microphone--totally self-contained--and has no bearing on anything outside the mic, including the plug or wiring. Shure Electro-Voice microphones have a high/low impedance switch on them, used to adapt the microphones to different types of PA/amplifier inputs. There are four pins: Shield, "High Z", "Low Z" and audio negative.

And, as I mentioned previously, at best you'll only have one channel of whatever signal source you use on your auxiliary input.

im not 100% that it even has aux amp outputs aside from speakers, but ive not dug much into the amps
Peek-a-boo! Lower RH corner:

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as for the speakers id never considered mag degridation..but let me ask this.."if" i were to replace the speakers would it lose the warmth? ...the bottom units are uhh 12s? i think pretty sure they are not 15s, the uppers are 6s i think and need replaced as someone tossed car speakers into it
on the other side of speaker talk..would the 10k plays unti have the same de-magnitization as the 70k plays?..ive never considered how speaker mags age
I guess it depends on if by "warmth" you mean muted highs. Let's be honest here: You're never going to get 20KHz highs out of a 6" single-cone driver, never mind a 12". Much of the "warmth" of vinyl has to do with the stylus against the record, and you won't lose that regardless. There are a lot of turntables out there connected to multiple $40,000 Nelson Pass monoblock amps and $60,000 Vimberg speakers... clear as a bell, but still "warm" to the ear. You also have the "FULL/MED/CUT" switches for treble, so if new speakers sound a bit bright you could back those down a step or two if desired.

The amount of use on the speakers has little bearing on magnet strength. Magnets degrade over time, whether they're in use or not. They're always pullin' no matter what.

all said if i cant use the mic in..i may get a vintage correct mic for it just for shits n giggles
I can't say I wouldn't. It's like the New-York-City mandated "CITY/COUNTRY" horn switch in 1974-model cars (yes, it was a law). My Challenger didn't have it, but I found an NOS setup so I could add it.

It's a useless curiosity--cool to have, but doubtful I'll ever use it. 😁

the ONLY reason id like to aux in somehow(tho idealy thru the mic box)..is just to be able to use it more..which is why i tracked down the factory mic box as well as the remote volume control..the more the unit can stay closed the more real it feels..ya dig?..but being able to adjust the volume externaly is really nice..but its also got a button on it to reject a song on the spot...so if it skippping or just buggin ya or you picked the wrong one..1 click and it puts it back
Y'know, I wonder if you couldn't tap the auxiliary into the wiring feeding the volume control. I would guess you've got at least four wires, maybe six, at the potentiometer (at least L & R line-level, possibly with shared audio negative but not likely). That would make it rather simple: Piggyback onto the pot on the feed side, and you could replace the existing microphone plug (reuse the opening) with your 1/8" jack. If you need an audio ground for your auxiliary, you could use one of the existing MC4 wires. At the jukebox end, just disconnect it and follow the audio feed leads to their source. There'll be an audio negative connection there.

Of course, that eliminates the possibility of using a microphone, but it should all be easily reversible.
 
hmmmmm
so the volume contol is actualy pretty wild..its a momentary switch, that drives a worm drive motor onto a clutched big gear, with slipper control coupled to the pot with an aluminum sleeve with 2 small wires in it, simple but effective

im diggin the idea of tapping at the pot for an input, and i could still come out the mic plate wiring as well, with the same 4 wire OE wiring as ive got 300ft of it

i shot a vid earlier today ill try and get uploaded as i took the time to make up selection cards and stocked the box...mind you its just the crap ive gotten for free .....and not my mom n dads gems that ive got stashed..as im not sure where they are stashed atm

on the atenuator some digging had pointed me at the shure a15
 
hey doc if i poped up the schematic for the amp would you be intrested in looking it over for said mods?
 
If you've got the schematic for the volume potentiometer, sure. As far as the amp itself goes, I'll take a look but I'm not sure what I'll find. Those schematics can be nightmarish, but I might be able to figure out where you can tap for an auxiliary.
 
If you've got the schematic for the volume potentiometer, sure. As far as the amp itself goes, I'll take a look but I'm not sure what I'll find. Those schematics can be nightmarish, but I might be able to figure out where you can tap for an auxiliary.
ko will do i have the whole manual as a pdf, will see if i can nip out just that page of the pdf..either way its on the benchtop machine..so tommaro
 
I didn't forget about you, man. I've been a bit under the weather but trying to decipher that wiring diagram regardless. I'm starting to wonder if their techs didn't go to Wurlitzer School because the labeling is fairly awful for the uninitiated. I think I know what's happening there but I don't want to guess and have you let any smoke escape.
 
I didn't forget about you, man. I've been a bit under the weather but trying to decipher that wiring diagram regardless. I'm starting to wonder if their techs didn't go to Wurlitzer School because the labeling is fairly awful for the uninitiated. I think I know what's happening there but I don't want to guess and have you let any smoke escape.
lol dude i am NOT in any kind of hurry
my "spare" time is light gaming that i barely have time for, the "other" free time i have is cataloging 500ish 45s..i found mom n dads stash

on top of that im TRYING to get a roof on the house SOLO before winter..did i mention im changing the pitch for solar panels too.......ive managed to score some INSANITY level deals tho..and have everything on hand save for wrap and shingles

on top of all else i had a nice job fall in my lap with ZERO prep time and a simple..if i turn it down its going up for sale..so i took the work..it will basicly recover the roof materials PLUS some...and the guy was far too nice to turn down

ive been in and out of wrecking yards like MAD...yesterday was 6 hours in the same yard on the same car..cutting out a firewall(its actualy glued in like a windshield) in a yard that allows no cutting tools of any kind....never mind the 3 hours down 3 hours back drive

i have something else that may..add some clues? i dunno..there was a tech update on upgrading the amp via some minor changes...lemmy see if i can find the "service slant" as they called it


i can also pop the amp out and take a picture of it if you want..since they were made to be worked on they hinge out for service..and everythings exposed
 

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