REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Monday 4 February 2019

JBL S120PII POWERED SUBWOOFER SCHEMATIC - STUDIO™ SERIES - 400WATTS RMS

JBL S120PII Powered Subwoofer schematic - Studio™ Series - 400Watts RMS

JBL powered Sub-woofer S120PII - Schematic - Exploded view - Test procedure and specs; 400Watts RMS output - Studio Series
The S120PII is equipped with both a master power switch and an auto turn-off switch.  In order to function, the sub woofer must be plugged into an active electrical outlet [but not an accessories outlet on another component of your audio system, such as a receiver], and the master power switch must be turned ON.
Distortion When Coming Out Of Standby
  In the event you receive an S120PII sub-woofer with the complaint “There is a brief chirping sound or short oscillation that occurs when the unit is in the AUTO mode, in Standby, when it’s triggered ON with a music signal”, follow the procedure below to correct this condition:
Synopsis: Replace D60 (RLS4148 diode) with a 3.6V Zener Diode; add new Resistor.
1) Remove the amplifier assembly from the sub-woofer cabinet (12 Phillips screws).
2) Remove the Plastic Amp Cover from the face-plate (4 Phillips screws).
3) The area of concern is on the Class D Driver PCB (Small Upright PCB on the MAIN AMP PCB). A long, thin, soldering iron tip is recommended. Care must be taken not to damage surrounding components, like large inductor pair L8.
4) Locate, remove D60 (RLS4148 diode); replace with a 3.6V zener diode, JBL Part# ZMM5227BCT-ND.  When replacing D60 the polarity of the new (zener) diode should be reversed.
5) Add new 27KΩ resistor, JBL Part# 299-27K, to the indicated connections. (This component, electrically, will be in parallel with R37, reducing its value to <22KΩ). Assure the leads do not come into contact with any other connections; insulate the leads if necessary.
6) Replace amp cover and return amplifier assembly to cabinet.
7) Test the sub-woofer to assure the distortion is no longer present.
Circuit diagram [Click on the pictures to magnify]
Exploded view
JBL S120PII SPECIFICATIONS
Amplifier Power (RMS): 400 Watts
Driver: 12" PolyPlas™ (polymer-coated cellulose fiber) (4.4 ohms DCR)
Inputs: Line Level (switchable to LFE), BassQ™ and Speaker Level
Outputs: BassQ and Speaker Level (High-Pass)
Low-Pass Frequency: Continuously variable from 50Hz – 150Hz
High-Pass Frequency: 150Hz when using speaker-level outputs
Frequency Response: 22Hz – Low-pass crossover setting
Dimensions (H x W x D): 17-3/16" x 16-3/16" x 18" (19" with grille) (with feet, without spikes) 437 x 411 x 457mm (483mm with grille)
Weight: 56 lb/25.5kg
SYSTEM AURAL SWEEP TEST
Equipment needed:
* Function/signal generator/sweep generator
* Integrated Amplifier
* Multimeter
* Speaker cables
* RCA phono cables (pair)
General Unit Function (UUT = Unit Under Test)
Switches/knobs on the amplifier faceplate:
Crossover Frequency Adjust full CW (150Hz)
Phase switch – either position
Normal/LFE switch – Normal
Auto On/Off - either position
1. From the signal generator, Connect both right and left line level inputs (RCA jacks) – to signal generator and UUT. Use Y-cable if necessary from mono source.
2. On the amplifier, turn the LEVEL control full Counterclockwise (Min).
3. Turn on generator, adjust to 100mV, 50 Hz.
4. Plug in UUT; turn the power switch ON. Turn LEVEL control full Clockwise (Max).
5. LED’s (top of UUT) should now be Green; immediate bass response should be heard and felt from port tube opening.
6. Turn LEVEL control full Counterclockwise (Min). Turn power switch OFF.
7. Connect one pair of speaker cables to one set (either R or L) of the Speaker Input terminals on UUT. Cables should be connected to an integrated amplifier fed by the signal generator.
8. Turn on signal generator and adjust so that speaker level output at the amplifier is 2.5V, 50 Hz.
9. Turn power switch ON; turn LEVEL control full Clockwise (Max).
10. Bass response should be heard and felt from port tube opening.
Sweep Function
1. Follow steps 1-5 above, using a sweep generator as a signal source.
2. Sweep generator from 20Hz to 1kHz. Listen to the cabinet and drivers for any rattles, clicks, buzzes or any other noises. If any unusual noises are heard, remove woofer and test.
Driver Function (Woofer)
1. Remove woofer from cabinet; detach + and - wire clips.
2. Check DC resistance of woofer; it should be 4.4 ohms±10%.
3. Connect a pair of speaker cables to driver terminals. Cables should be connected to an integrated
amplifier fed by a signal generator. Turn on generator and adjust so that speaker level output is 5.0V.
4. Sweep generator from 20Hz to 1kHz. Listen to driver for any rubbing, buzzing, or other unusual noises.
Posted By: FRANK at 06:44
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