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Power on but no click sound. found some transistors and resistors burn in a small board located at down side of the amp, need scematic circuit diagram to repair it. Please send.

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If you have burnt the transistors that are located on the circuit board, then you wont be able to repair it I dont think because in the circuit board there are probibly mulitple layers of electrical wires the are extremely small and fine that would make it impossible to connect the transistor to the right layer. Try contacting the manufacturer though

Posted on Oct 08, 2009

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1 Answer

Where can I get the scematic for the Veco 21 STC voltage control circuit board?


try mailing the manufacturer

hot transistors are usually shorted out, or driving a short!!

a multimeter across the 3 transistor legs (TO-3 transistors have 2 legs & the case which is the 3rd leg) will reveal if they're dead (remove the transistors first as the circuit may give a false reading) - if you get a zero ohms reading between any of the legs it's dead - don't forget to check the smaller driver transistors too,, as a dead main transistor will kill its smaller driver transistor

speakers are marked,, usually 4 ohms or 8, though sometimes 16 ohms - use a multimeter to ensure you have something very close to these values according to the label on the speaker box & measure from the wires at the point where they connect to the amp

power the unit without any speakers or speaker wires connected,, if the transistors still get hot, you're very likely looking at bad transistors

Feb 21, 2015 | Audio Players & Recorders

1 Answer

I have a second hand Mackie m1400 power amplifier. From startup the hot light remains on and there is no sound from the amplifier in any mode. Many thanks.


Replace transistor Q91 with a 2SD1264A transistor.
Replace resistor R205 with a 10 ohm 1/4 watt resistor.

These will be located on the small board that the fan plugs into.

This is a fairly common problem with this amp. Parts can be found on the net for a few bucks. The shipping is usually more than the parts.

Jun 27, 2011 | Bob Mackie MACKIE M1400/M1400i Car Audio...

2 Answers

I received a PV1500 amp that had only one channel working. i decided to open the amps to check the other channel being that i usually repairs amps. up on analyzing the damage circuit board of that channel,...


It seems there's another component (a capacitor, a diode, etc) causing a short circuit to triac and transistor, or there's an over voltage on this stage, please check if the voltage is according to the one feeding the good channel.

Mar 01, 2011 | Peavey Music

1 Answer

I have a MTX Thunder 81001 car amp in my repair shop. It has power but no sound, what can i do to repair this amp?


You can open it up and smell for any burned components. Once you identify the burned resistor, transistor, capacitor try to replace it with the same value in RADIO SHACK. Also check for burned out tracers on the circuit board. Thats when the copper etching on the board has literally melted away. You reconnect it by soldering small wires and bridge the connections back together. Need solder and soldering Pen. The soldering gun is too strong and may do more damage to the circuit board if used to long.

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1 Answer

Pmp3000 problem power supply.ic circuit problem.number series ic circiut..


I have a PMP5000 that I had to resurect. I had to trace out the power supply to repair it.

I can give you hint: First, a small supply runs directely from the line and generates some of the small voltages. While this starts, the main power caps are charged through limiting resistors. The main switcher is brought online and if the power amps acheive balance, then a relay connects the speakers and shorts the limiting resistors.

This is what is in the 5000 and I suspect the 3000 is similar.

In my 5000, there was arcing at one side of the power amps. The board was burned and three power fets fried. Cancer of burned board had to be carved out and traces replaced by hardwiring.
In addition, the limiting resistors were blown open, both main switching transistors were blown and 4 small driver transistors (surface mounted) and several diodes AND a switching regulator chip (surface mounted).all fried/

Hint: When restarting the unit, put a 150 watt light in series with one of side of the power input to limit the current in case you did not get all the dead bodies out.

This is a class "D" amp which drives PCM waves into a filter which is then the audio output. It is much more efficient thaan a linear amp.

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1 Answer

Marantz SR19 no sound?


When replacing output transistors on amplifiers it is generally a good practice to replace the output capacitors as well as the biasing resistors. Just because one transistor is bad does not mean that that is the whole problem. Look for what caused the problem. Bad speakers,bad wires,defective traces on circuit board,poor soldering. Also when mounting the transistor make sure it is insulated and grease it with a dab of silicone heat sink compound. Whenever I service a board I examine all components for tolerance as well. A resistor marked at 1% tolerance,example 1k ohm + or - 1% should read no less than 990 ohms and no more than 1010 ohms. Anything else your asking for trouble. Another point is that some amplifiers use matching pairs. Pairs complement each other in an output stage and must be replaced in pairs. I repaired a Sansui Amplifier a while back and it looked as if a power output resistor was burned. Comparing the two channels I figured the matching value from the other side and replaced all of them and the system has worked flawlessly for years now. I am a retired electrical engineer and have worked in a few areas of electronics for over 35 years. Hope this information helps you.   

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2 Answers

A chip on the circuit board started smoking


The component sounds like a resistor, and the fact that it was attached to a heat sink means its a power handling resistor. You said it was burning, so this means that whatever it is attached to is drawing too much current. From what you are saying a component on a board is drawing too much current and is causing another component (the 1 ohm resistor) to burn. My question is what board is this (I am suspecting the deflection or the HV power supply). Please post a picture of the board in question. That way I have a visual guide as to the board and if I can find the schematic, or if you can supply the schematic I'll be able to at least give a better diagnosis of this problem.

Thank you,

Shuttle83

http://www.electron-age-technologies-llc.com

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1 Answer

Audiobahn car amplifier


Sounds like you have fried your output transistors. They can be replaced if u have the patience and know-how. Also check the resistors near the transistors. Some of them may need to b replaced too. I fu replace the transistors and the resisitors are still fried, u run the chance of burning up the new transistors again. I usually just replace both items since it's not that expensive and I'm doing the labor. What have you got 2 lose?

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1 Answer

No Picture Has a bright horizontal line with off white & gray vertical bars


The Problem Philips 27TS54 c101 27B800-7562 White horizontal line in the center of the screen. Color is present in the first half inch of the leftist corner of the horizontal line.
Audio is present and controllable. The green power led from a cold non plugged in state remains solid until CRT goes to ignite. A click is heard then the green power LED blinks.
I found service manual diagram of repair part or parts and install instructions
HTTP://WWW.servicemanuals.net/results.aspx?type=SM&brand=100&model=27ts54
I request any info or tips you might have pertaining to this problem
Thank-you
Sincerely
Gmyers@sbcglobal.net
2/20/2008
P.S. 25”-27” CRT board APT187

Possible Answer Posted by PEE_WEE 4/28/2005
On the CRT circuit board(picture tube), you will find R3340, which is a 10 ohm 1/3w resistor. The location of the resistor is printed on the bottom of the ckt board. It is burned open, replace with a 10 ohm 1/2w resistor. This will solve your problem. The original resistor was sized too small, should have been a 1/2 watt. This resistor is mounted standing up on ends. Mount the replacement resistor the same way. Be careful and don't get the circuit trace too hot and damage the circuit trace. (it's very small) The resistor is located on the crt(cathode ray tube), pcb(printed circuit board) socket. The resistor supplies apx +200v to the collectors of the r, g, b, video driver transistors. If this voltage is low, it causes excess brightness(excess beam current), causing the set to "shut-down". If the shut-down is too quick, you will NOT see the excess brightness, because the picture tube has not warmed-up enough to display anything on the picture tube. To see if the set displays "excess brightness", you will need to turn the set "on" about 5 to 10 times. This will heat the picture tube enough to display "excess brightness", IF that is the PROBLEM. Of course, there are OTHER defects that will cause a tv to shut down. There are built in safety circuits, that will "activate" if excess voltage/current or heat is detected anywhere in the set.

NOTE
My resistors are not numbered the same on my crt board APT187. GSM 02/20/2008

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