Question about Velodyne DLS-3500 Subwoofer

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Output stage bad

The output stage appears to be blown, several hi-power transistors are open. I need a schematic to complete debug before ordering parts. Also having trouble finding a substitute for the UTC D669A and UTC B649A transistors.

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  • fredjones May 11, 2010

    May not find the schematic for this other than with Velodyne.



    You may have to contact velodyne for the info or have them fix it.

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Only place for parts and service is Velodyne.

Posted on Dec 20, 2009

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Samson SX1200 - Protect light on. No blown output transistors.


Have you checked the power supply section? Also look out for any IC's in the amp stages. They can go causing that kind of fault.

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AM 35 Amplifier problem Dear Fixya I ma using two technics turntables into Vestax PMC 25 powered by Akai AM 35 amp. The amp Balance switch between left and right is not working. Also the amp...


From your description, I would guess that the output stage of the amp is not working properly. Rather than the outputs being shorted (the most common failure), the output transistors appear to be open. This basically means that you are attempting to drive the speakers with a "pre-amp" section. This could be a power supply problem or defective transistors. An examination of the last stage of the amp is needed here. If the outputs are open, the parts cost will be in the $40-$60 range. Power supply repairs will likely be in the $20-$40 range for parts.

Hope this helps a bit.

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Aug 20, 2011 | Audio Players & Recorders

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When powering up all i get is a red screen with black lines across. Sound is still there and can change channels and ocationaly after several attempts it will give a picture albeit rather green.


Hello
Your TVs video output transistor [Red] has got shorted. Usually a transistors are used in most of the colour telivisions in video output stage.. If it is a transistorised video output stage, replacing red output transistor will solve the problem. In some modern sets there are so many types of Integrated Circuts [ICs] are used. If your TV uses Ic as video output, replace the Ic.

Oct 16, 2010 | Loewe Aconda ACO9303 30" TV

1 Answer

Attenuated output


Since you are able to view the output i'm assuming you are using an oscilloscope and only the positive or negative half of the sine wave is displayed. The output stage will be using a complimentry pair of output transistors, one amplifies the positve half cycle the other the negative. These are driven by a driver stage (phase splitter). One side is not amplifying. First measure the pos' and neg' LT supply rails. If ok check
ouput transistors with analog Ohm meter for base / emitter / collector continuity. If the amp uses an output IC and LT supplies are ok then use scope to view input signal, if input ok but output bad then IC is suspect. Since both channels are affected your problem is most likely a missing LT supply rail.

Mar 29, 2010 | Adcom GFA-5400 2-Channel Amplifier

1 Answer

Output stage scheme for pioneer vsx-d1 channel floating negative.


It should be a push pull. The fact that you have negative voltage almost certainly means push pull. One side will be constructed using NPN transistors ran off the positive DC rail and the other side will be constructed using PNP transistors ran off the negative rail. I don't know the age of your amp but I know pioneer now uses integrated amp modules instead of discrete transistors.

http://pdf1.alldatasheet.com/datasheet-pdf/view/82968/SANYO/STK412-020.html

example of integrated amp module (sorry for the chinese)

Feb 11, 2010 | Audio Players & Recorders

1 Answer

Behringer PMP5000. The Powered Output B dead


Make sure the three position slide switch is set correctly for the stereo usage, that is NOT the bridged OR the Mon mode.

MAKE SURE the pan pots are set to middle as they control the spit of the audio to the two channels.

This is a class "D" amplifier (switching) and there really isn't any fuse for a single channel.

MAKE SURE your speakon connections are good by swapping your speaker cables.

I repaired my unit and had to do that without schematics... Behringer will not give them out. Mine had a severe arc-over on one side power amp taking out about ten transistors and diodes and one swithcing regulator chip. Had to cut out the "cancer" of the burned board.

This unit uses a complementary output stage that is made up of one transistor on one side and a pair in parallel on the other. This drives the inductor/capacitor filter... I think the switching frequency is between 100KHz and 1 MHz as I recall. All those transistors were gonzo. It also fried the main power switching transistors in the power supply, several smaller transistors, diodes, and the switching regulator chip.
Also two 10 ohm power resistors were fried. They soft start this unit by charging the main caps via two resistors that limit the inrush current.
A small switching supply has to come up first before the main supply which sends the DC to the amp section.

Nov 23, 2009 | Behringer Music

1 Answer

Noisy left hand power output stage. Noisy transistor? No circuit diagram.


If the speaker is not blown, there must be an output capacitor. If no output capacitor, and you have a blown transistor the speaker will blow from DC current. You can further check the transistors with a multimeter. A transistor looks like 2 diodes and you should be abobe to test with a mulimenter like a diode test.

May 12, 2009 | Audio Players & Recorders

1 Answer

Amp turns on just fine but no sound comes out


Amp Failure:
There are many different ways that an amp can fail but the two most common failures are shorted output transistors and blown power supply transistors (< those are not blown). There are several types of protection circuits in amplifiers. The most common are over-current and thermal. The over-current protection is supposed to protect the output transistors. Sometimes it doesn't work well enough to prevent the failure of the output transistors but it will work well enough to shut the supply down before the power supply FETs are destroyed. If the amp remains in protect mode, goes into protect mode or blows the fuse as soon as the remote voltage is applied, shorted output transistors are almost certainly the cause. If the fuse protecting the amp is too large, if the protection circuit doesn't respond quickly enough or if the power supply is poorly designed, the power supply transistors may fail. If you see a lot of black soot on the power supply transistors (near the power transformer), the power supply transistors have failed. Soot on the board doesn't necessarily mean the transistors have failed. Sometimes, technicians don't clean up the mess from a previous failure. Transistor Failure/Checking Transistors:
In general, when a transistor fails, it will either short (common for output AND power supply transistors) or open (common for power supply transistors). Transistors act like valves. They control the current flowing through a circuit. A shorted transistor acts like a valve that's stuck open (passing too much current). In the case of an output transistor, the shorted transistors tries to deliver the full rail voltage to the speaker output terminal. If you've ever seen a damaged amp that pushed or pulled the speaker cone to its limits when the amp powered up (common on some Rockford amplifiers), that was almost certainly due to a shorted output transistor. When checking transistors, you most commonly look for shorted connections inside the transistor. You do this by using a multimeter to look for low resistance connections between the transistor's terminals.

Seems as you have blown an output. Seek repairs.

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3 Answers

Kenwood KR-4010 (late 70's vintage) with signal to IF amp but no output


Don't bypass the relay contacts. They serve to disconnect the amp stages from the speaker if a DC condition is present, and in doing that, save your speakers form damage. Check for a DC offset condition on the junction of the emmitter stabilizer resistors to the STK0040 on each channel. They will be 0.47 ohm power resistors(2 per STK) connected to pins 3 and 8 of the STK. Anything substantially greater that 100mv here generally indicates a blown STK. Don't bother to change both, but just the one that is faulty. Another common problem for this age of amp. The high silver content in the legs of the transistors allows for "growth" between legs and internal connections of the transistor. Check for "black death" on the legs of transistors driving the STK. . . I tend to replace them if in doubt. If you need expert advice, comment me back. I am an audio specialist.

Feb 03, 2008 | Audio Players & Recorders

1 Answer

Channel short


Hi there, sounds like you may have a short to ground on the output transistors. Does it have transistors or an IC output. It is most likely that you have not replaced a mica washer or insulator. Check to ground with a meter from the case of the output devices.

Aug 24, 2007 | NAD S300 Amplifier

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