Seeburg AY/AQ 100/160 Jukeboxes

Symptom:  After about 15-20 minutes, the mechanism no longer stops at selected records.

I’ve come across a couple of Seeburg jukeboxes of this vintage that have had this problem.  It has been a difficult problem to diagnose in the field, but I was fortunate that an owner allowed me to take the Tormat Selector Unit (TSU) back to my home office where I could bench-test it and really dig down to find out what the problem is.

The first thing I had to do was replace R513 (2.2 Meg) because the -7 volt test signal wasn’t working.  This test voltage is present on TP-C.  Momentarily feeding this voltage into the RCA jack where the Tormat plugs in (J510) will test the pulse amplifier.  The Tormat Pulse Amplifier (TPA) is the gold colored box mounted to the TSU, with a 12AX7 tube on it.

Tormat Pulse Amplifier (TPA)

Tormat Pulse Amplifier (TPA)

Fairly quickly, I was able to determine the problem was in the pulse amplifier.  I hooked my oscilloscope to the output at Pin 4 of the TPA socket (J509), accessible from the rear of the TSU.

I connected a jumper lead from TP-C to the shaft of a small Phillips screwdriver that would fit into the RCA jack.  Moving the screw driver in and out would send pulses through the amp.

Output of pulse amplifier when working correctly.  Pulse is about 75 milliseconds.

Output of pulse amplifier when working correctly. Pulse is about 75 milliseconds.  Note ground is at top of pulse and the output normally sits at about -76V.

When everything was cool, the pulse output was 75 milliseconds long.  As the TPA and TSU warmed up, the pulse got shorter and shorter until it was gone.

Output of pulse amplifier after it warmed up.

Output of pulse amplifier after it warmed up.  Pulse is now way too short to trip the mechanism solenoid.

After trying a new 12AX7 tube, I opened the TPA box and checked the resistors.  Some were marginally out of tolerance (all to the high side), but this was minor.  Using hot air, I heated the amp and measured the resistors again and there wasn’t a significant change.

I measured the capacitance of C506 (0.05uF, 400V), which is partially responsible for stretching the pulse to 75 milliseconds.  It was 40% higher than it’s rated value.  As I heated it up, it’s value more than doubled from it’s already high value.  This was the culprit.

The closest capacitor I had on-hand was 0.05uF at half the rated voltage.  Since I wasn’t seeing more than 195V in the circuit, I tried a 200 volt cap as a temporary fix.  And it worked!  The pulse output remained at 75 milliseconds throughout the hour I tested it.  I have ordered the 400V version of the cap as a permanent replacement.

New capacitor installed.

New capacitor installed.

I’m glad to have finally solved this mystery.



Wurlitzer Model 3300 (1969)

Location: Henderson, CO
Symptoms: Both record lifting arms jammed into the record carousel.  The carousel was unable to rotate.  Trip switch not working.

I spent a good half-hour trying to unjam the record arms from the carousel and realized there was no hope without total dis-assembly.  Both tips were bent over facing the rear of the jukebox.  I’m not sure how they got that way, possibly when the jukebox was moved to the basement.  I’m surprised the plastic tips hadn’t broke.  The only option was remove to the record playing mechanism from above the carousel, then remove the carousel.  I advised the owner that this was going to take several hours.  I got the go-ahead.

Once everything was disassembled, I noticed the three rollers that support the carousel were frozen.  A generous dousing of WD-40 didn’t solve the problem.  I finally took a pair of pliers and rocked the rollers back and forth sideways to break whatever corrosion or gunk kept them from turning.  That worked.  Then another dousing of WD-40.  I followed up with regular oil and all three rollers were spinning freely again.

The tips on the record lift arms needed to rebuilt after being jammed.  They are spring loaded and should open up as the arm rises into the carousel.  I disassembled each tip, cleaned, readjusted, and lubricated with silicone.

I put the mechanism back together and did a couple of trial runs with no records installed.  Everything seemed to be working great.

Once again, another bad trip switch.  I encounter these a lot on later model Wurlitzers.  As I have described here in this log before, I broke open the cover and flushed with contact cleaner.  It’s pretty much all one can do, as you really can’t get to the contacts themselves with any kind of abrasive. I reassembled the trip switch, adjusted it, and played several records.  Seemed to work okay after that.  On the jukeboxes I have done this, they are still working after nearly two years.  But still, it would be nice to find a replacement switch.

Amplifiers, Amplifiers, Amplifiers!

In an odd quirk of fate, I’ve had a rash of jukebox amplifiers to work on, as well as some Seeburg control centers.  The amplifiers are a Wurlitzer 532, Seeburg TSA1, Seeburg SHP3, and an amp from a Rockola 424.  The 532 is the oldest and the SHP3 is the newest.

Testing a Wurlitzer 532 amplifier.

Wurlitzer 532

At the customer’s house, the 532 was exhibiting all kinds of problems.  The sound was popping, cutting in and out, and most of the time was severely distorted.  One of the items that was causing all of the popping was a bad connection in the octal socket between the mechanism and the amplifier.  The power to the amp runs out, and back in, through the connector (except for the tube heaters which are on all of the time).  Also the amp has a rectifier on it which supplies power to the mechanism.

Each female pin on the octal socket is shaped like a “U”.  Over the years with the plug being unplugged and replugged, the top part of the “U” spreads apart and doesn’t make a good connection with pin. I took a sharp ice pick and poked it down into the edges of each hole and bent each arm of the “U” so they would be closer together.  That solved that problem.

However, there was still a lot of distortion.  I opted to bring the amp back for a bench test.  With a bench test, I can inject a known signal and trace it through the circuit with an oscilloscope to see where the signal breaks down. In this case, it was bad at the output of the first tube in the chain.  It wasn’t a bad tube, but a bad electrolytic capacitor connected to the cathode of the tube.  The amplifier will be getting re-capped (replacement of all electrolytic capacitors).  It’s overdue.

Seeburg TSA1

At the customer’s house the amp was distorted especially in the lower frequencies.  Changing the volume had no effect.  It seemed to be in both channels.  There wasn’t good stereo separation.

I brought the amp back for bench testing.  There is a coil in the amp that connects the left and right channels together.  I’ve seen this in other jukebox amps of the late 1960’s, and it doesn’t make sense.  After I disconnected it, I discovered the distortion was only in a single channel.  And it took me a while to discover it as I had to drive the input fairly hard for it to show up.  And it was more prevalent at bass frequencies.  It looked like someone was taking a bite out of the lower side of the sine wave (it wasn’t at the peak).  After checking the bias and the caps around the preamp stage where the problem was, I concluded it had to be the transistor.  I replaced it, and the problems cleared up.  I chalk that one up to weird transistor failure.

Rockola 424 amplifier

The service manual calls this a 40276A.  The amplifier itself has 40218 labeled on it.  Regardless, one channel was completely dead.  The mono switch didn’t have any effect, so the problem was in the output stage.

I brought it back for bench testing. I quickly discovered the 1200uF capacitor used in the feedback circuit had a broken lead.  This amp had been previously worked on by somebody else and they had replaced the capacitor without securing it well.  The vibration of moving the jukebox to Colorado from the east coast probably caused it to break. Since the lead was broken right at the capacitor, it needed to be replaced.

While checking out the amp, I noticed some electrolytic capacitors where leaking.

Electrolyte leaking from capacitors.

Those 100uF capacitors got replaced, as well as the main filter capacitor (2940uF was replaced with a 4700uF).  After cleaning the preamp wirewound pots (not easy or effective), the amp is working well.

The Seeburg SHP3 amplifier will be covered in a future post about a Frankenstein jukebox.

Wurlitzer 2104 jukebox (1957)

Location: Lakewood, CO
Symptoms: Needle not contacting record, plays wrong selections.

We selected a record and the needle hovered about 1/8 inch above it.  I moved the tone arm and felt it binding.  I put some silicone lubricant on the tone arm pivots.  I also noticed the tone arm audio cable seemed to be a little tight which added to the binding.  I loosened the cable clamps and gave it another 1/4 inch of slack.

Usually when a Wurlitzer is not making the correct selections, the problem is either dirty switch contacts in the keyboard, or a lubrication issue with the pre-selection arm or disk at the bottom of the mechanism. Since this was probably the cleanest unrestored jukebox I’ve come across, I didn’t suspect dirty switch contacts.

On the ’04 models the pre-selection disk (I don’t know what Wurlitzer calls it) is used to differentiate the letter selections.  I call it pre-selection because this disk the first thing that begins moving when making a selection.  The disk rotates into position determined by a couple of solenoids, then fires one of the numbered solenoids visible around the edge of the mechanism. This disk rides on 3 nylon wheels, which often stop turning with age. I lubricated the nylon wheels and got them turning again.  The jukebox now made the correct selections.

One additional item was that I cleaned the volume control with potentiometer cleaner.

Seeburg M100C Jukebox

Location: Centennial, Colorado.
Symptom: Visible smoke coming from jukebox.

The owner said the smoke was visible at the front of the jukebox.  This could have been the mechanism or the selector switches, or even something from down below.  I visually checked the latch solenoid, but I didn’t notice anything wrong.

I checked the fuses and none were blown.  I carefully powered up the jukebox.  The jukebox was in the middle of playing a record when it was shut down, so it continued playing the record when I powered it up.  All seemed normal.

After a while, smoke did appear and it was coming from the latch solenoid behind the selector switches.

This is a common problem.  The solenoid isn’t designed for continuous use.  Under normal circumstances, a person deposits coins, the solenoid energizes, the person makes selections until their credits are used up, then the solenoid is de-energized.  That process probably takes no more than 30 seconds.

In this case, the jukebox had a small pushbutton switch on the rear that gave three credits every time it was pressed.  It was being used at a party and someone probably pushed the button a number of times establishing the maximum number of credits, then the person didn’t follow through and use all of the credits.  Eventually the latch solenoid overheated and shorted.

Victory Glass sells a solenoid protector that is plugged in between the Wired Selection Receiver and the selector keyboard. It has a small switch on it that selects between coin operation and free play.  The advantage to this solenoid protector over the solutions provided from various internet sites (where the latch solenoid is wired to the hold relay), is that if a letter is selected without a number or vice versa, the solenoid eventually times out and releases after about 30 seconds.  This is great if you have small kids around who might be randomly pressing buttons and then walking away.




Rockola 460 Jukebox

Location: Castle Pines, Colorado
Symptom: At the end of record play, the gripper arm would start to return the record to the magazine without actually gripping the record.

This one stumped me for a while.  If I turned off the gripper motor and turned it by hand, the gripper arm worked just fine.  But if I energized the motor and ran it at normal speed, the gripper arm would miss the record, leaving it on the turntable.

It turned out to be a lubrication issue.  The old oil/grease was just gummy enough work fine at hand speed, but not work at normal speed.  There are two gears, side by side, with one gear mounted on the shaft of the other.  See 12 and 13 below.  Oiling between the two gears and getting some oil down on the shaft fixed the problem.

The cooler temperatures of winter seem to cause a lot of problems with both jukeboxes and pinball machines.  Although pinball machines don’t use as much lube as jukeboxes, in both cases old gummy lubrication gets more gummy in cooler temperatures.


Gripper Arm Assembly. Click for larger.


Cadette (CMM4), AMI/Rowe Jukebox (1970)

Location: Denver, Colorado
Symptoms: Wouldn’t make correct selections, if any.  Right channel sound was fuzzy.

I wasn’t able to obtain a service manual for the CMM4.  The closest thing available was a CMM1 manual, which ended up being of no help.  There were quite a few electrical differences in the mechanism, like different cam switches (CMM1 has 8 cam switches, CMM4 has 5 cam switches).  Also, the CMM4 has a tube amp and the CMM1 has a solid state amp.

The “write” side of the selector plate was working well.  The “read” side scanner would usually jump right over the selector pin, unless it was actuated by a pin on the outer ring. The pin reset solenoid wasn’t actuating.  Long story short, it turned out to be a bad stop switch.  The switch was reading many thousands of ohms when it should have been zero.  I drilled a hole into the side of the microswitch to try chemically cleaning it.  It helped bring the resistance down to about 180 ohms, but that’s was not good enough.  I found a compatible switch in my pinball parts and replaced it.  The jukebox made the correct selections after that.

The amplifier had a tube that looked bad.  Looking at it more closely, it had a crack in the glass at the base.  It was a 12AX7.  We used the tube from the left channel and the right channel started working.  The owner had a spare 12AX7 from a guitar amp that we used to get the amp fully working.

I also looked at the owner’s AMI G-120. It had a few minor problems that I was able to fix with some cleaning, adjustment and lubrication.

Wurlitzer “One More Time” 1015-CD jukebox

Location: Soda Fountain, Lyons, CO

Symptom: Arm that holds CD on spindle wouldn’t release properly causing CD to fling against the back of the cabinet.

I don’t normally work on CD jukeboxes, but I made an exception because Lyon’s Classic Pinball is located across the street and that would give me an excuse to go over and play some of Kevin’s 35 pinball machines from the 1960’s through present day.

Sometime after Wurlitzer stopped making jukeboxes in 1974, the remaining Wurlitzer company in Germany began making some nostalgic jukeboxes with modern CD players. In the past I’ve worked on the original 1015 from 1946 that plays 78 RPM records, so this was interesting.

I spent some time familiarizing myself with the mechanism.  I looked at the lever that actuates the lift rod. Someone in the past had placed some rubber pieces at the bottom of the lift rod.  Not having a service manual for this jukebox, I didn’t know how it was originally designed.  It didn’t make sense how it was assembled.  So I disassembled the bottom section of the lift rod and reassembled it.  The lift rod and spindle arm worked correctly after that.

Examining the cam that actuates the lever, it appeared mushroomed in various places, which would have reduced the height of the lift rod, which probably prompted someone to put additional rubber pieces under the lifting rod. That cam will need to be replaced someday.

This post would make a lot more sense with either photos or some drawings.  Maybe in the future I will update it.


Wurlitzer 2600 Jukebox (1961-1962)

Location: Boulder, CO

Symptoms: Some selections not played, record arm jamming.

When I first arrived the mechanism motor wasn’t working.  This was due to the Service Switch being off.  This is used to turn off the motor when making adjustments to the mechanism.  The normal operating position for the switch is on.

Once we got the mechanism running, the record lift arms were occasionally jamming against the sides of the record carousel.  Both right and left record arms are designed to raise at the same time.  If the carousel is aligned properly, one will glide into the record slot, while the other will stop against the record divider on the opposite side of the carousel.  Some of the record dividers were bent which caused one of the arms to get caught and then free itself, launching the record across the room.  Once I straightened the dividers, we didn’t see that problem again.

The jukebox played most records without problems, but some selections didn’t seem to work.  I tested each letter and each number selection to make sure the solenoids and switches were working.  There was no correlation between the non-working selections (i.e. there was letter group or number group that was not working).  I had the owner make selections while I watched the selector mechanism.  The rocker arms that release the selector pins were working but the pins were stuck.  After some cleaning and light lubrication, the problems started going away.  The owner is going to finish the cleaning and lubing on his own and will call back if he has any problems.



Wurlitzer 3500 “Zodiac” Jukebox

Location: Longmont, CO

Symptoms:  Would not return after playing record.  Sound playing out of only one speaker (out of 4 speakers total).

As with other Wurlitzers of this era, the trip switch fails intermittently. I haven’t found a source for replacement switches, yet.  But with past experience, opening the switch and spraying contact cleaner inside seems to solve the problem.  The switch is glued together and to open it requires breaking it open.  This is done by inserting an X-acto knife under the edge of the top cover at the opposite end from where the trip wire attaches.  Usually about a half inch of the cover breaks away cleanly, allowing it to be re-glued or taped together again.  The contacts are directly underneath where the cover is removed.  I spray the contact cleaner on the contacts and cycle the switch dozens of times.

When playing records, I noticed the pair of top speakers (tweeters) were not working, and one woofer in the bottom was not working, leaving only one speaker that was working. No wonder it didn’t sound very good.  Wurlitzer, instead of referring to the right and left channels, refers to them as “A” and “B”. I swapped the speaker leads and determined that channel “A” of the amplifier wasn’t working. At the same time, when moving the “A” speakers to the “B” channel, the tweeter of channel “A” worked fine.  So there were two problems with the sound, channel “A” of the amp wasn’t working and the tweeter of channel “B” wasn’t working.

I decided to tackle the amp first.  I swapped the input cables from the tonearm to make sure the problem was not the cartridge or the tonearm wiring.  With my oscilloscope, I traced the signal from the input to the output of channel “A”.  The signal was fine until it got to Q6 and Q8.  Beyond that point, it was dead.  I checked the bias voltage between the base and emitter of each transistor. Q8 was 0.05 volts, which is way below the 0.6V needed.  Q6 was 1.2V, which was double the 0.6V that it should be.

At this point, since I knew I had a bad transistor and that it would have to cross-referenced and a replacement ordered, I decided to take the amp back to my shop for final repair.

Before I removed the amp from the jukebox, I wanted to find out what was wrong with the tweeter on channel “B”.  After checking continuity of the speaker connections with the ohmmeter, and checking the coil resistance of the speaker, the only thing left was the 8 uF capacitor in series with speaker connection.  I bypassed the capacitor with a jumper wire and it started working.  The capacitor is used to block the bass frequencies from coming out of the tweeter.  Somehow the capacitor had failed in an open condition. I added this to the list of parts to order.

With the amplifier at my home shop, I unsoldered both Q6 and Q8 from the printed circuit board to isolate them so I could test them individually.  I checked the base-emitter junctions with the multimeter in “diode” mode.  The junctions on silicon transistors should look like a diode, 0.6V one way, open circuit the other way.  In the case of Q6, it was open both ways.  Definitely bad.  Q8 checked OK and didn’t have any shorts between any pins.

As usual, with Wurlitzer, it is difficult to cross reference transistors because they used their own part numbers on them.  According to the service manual, Q6 is a 130537-5. Sometimes the first place I’ll go looking for a replacement semiconductor is NTE.  In this case, I typed in the part number 130537-5 and got NTE289A.  The basic specs seemed applicable to the circuit, so I was confident it was a good cross reference.  Another source I’ll use sometimes is this page that shows some of the cross references for Wurlitzer transistors.

As I was working on this amp, I noticed some leakage on two of the capacitors.

Capacitors (C19) on both channels are leaking electrolyte.  Click for larger.

A lot of people advocate replacing all of the electrolytic capacitors in a solid state amp of this vintage.  While electrolytic caps do have limited life, I prefer to wait until there are visible or audible symptoms.   The gray caps in the center of the above photo look burnt, but that is just residue from burning dust on some power resistors not shown in the photo.  Also, jukeboxes have spent most of their lives in establishments that had a lot of cigarette smoke, which leaves a residue.

The two leaky capacitors were replaced.  Since the new caps were much smaller with shorter leads, I soldered them directly to the back of the circuit board.  With the transistor replaced, the amp works fine.