Question about MA Audio Hard Kore HK-898 Car Audio Amplifier

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Heat at some transistors and resistors in suv800x

Cracking sound both ch. if turn more than half volume is ok.and sound nomal all volume position.i found burning colour at pcb. and heat some transistors power supply circuits 60v. to 17.8 v and 12v.

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  • Master
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Most likely you have played your with either spk bad or bad wiring i have the same exact amp played it hard for more than two year and still have it sitting right now just bench test it last week still drive hard i think you make bad connection some for that to burn like that

Posted on Jun 26, 2009

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Posted on Jan 02, 2017

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Why does amplifier sound die after a short period of use?


There is a heat sensor on the heatsink (to cooling IC / transistor) which decides current / voltage, in case of overheating. This is indeed to secure IC / transistor power of destruction.
The cause of the excessive heat, the impedance mismatch between the amp to the speakers. It is also possible that parts already exist within the amplifier that is almost / half broken, for example, changing the resistor value, electrolytic capacitors are bulging or dried, isolation transformer windings were charred, solder joint cracking etc. Should be checked, before the fatal damage.

Heatsink on the amplifier (the picture is owned Connelectronic):


25850288-l1qpqmriditabltrjczr2eku-4-0.jpg

Sep 05, 2015 | Laney Music

1 Answer

No pic no sound no a/v only vol. & ch. display


pls. check the resistor in series with the crt heater.

Jul 04, 2013 | Sharp 25R-S100 25" TV

1 Answer

Denon AVR2106 One output channel shorted and blown. 2 power transistors shorted, emitter resistors and base resistors blown Have replaced all, including bias transistor I think bias is still wrong (no...


I would also replace 2sa992 (2pcs) and 2sc1845 on preamp board- sometimes they look ok when you test them by regular meter. Check 1.2 kOm and 4.7ohm resistors at preamp pcb. Check diodes on output pcb (could be smd type, connected from base of output transistors to emitter i think)

Sep 07, 2011 | Denon Audio Players & Recorders

1 Answer

My sr 870 (marantz is probably about 7 - 8 years old, and have noticed that this issue with loud sounds is getting worse over the years, I have upgradedmy cabling , to the speakers, have upgradedall the...


Something is tripping the safety in the unit.
I'd be checking the output transistors or hybrid chip, and take a good look at the electrolytic capacitors and make sure none of them are leaking or bulging at the top.
Look for signs of heat wear on resistors especially near the output stages.
You may simply have to take it in for service if you aren't electronics savvy.

Mar 01, 2011 | Audio Players & Recorders

1 Answer

TEAC A-H300 Amp no output


If you still have the following voltages (0.3,44,0) and (-.1,-44,0) then the final stage is not turned on and you will only get low level sound. The driver +/or bias circuits are defective. Disconnect the center lead from each of the transistors and measure the 2 outer leads to ground,. Check the driver transistors for either an open or shorted condition and replace as necessary. Once the driver and bias circuits are working, the 2 outer leads should read +/- 0.5 and 0.

That should resolve the problem. Look for low valued resistors that are open.

Keep us posted.

Dan

Feb 28, 2010 | Teac A-H300 Amplifier

2 Answers

Technics amp su-vx800 goes in to protection mode after approx. 10 to 15 mins of play depending on the volume level.switch it off for 2 mins and it operates again.Could this be a faulty muting ic AN7073, a...


yes it can, it sounds like its over heating, make sure that your product is able to get fresh circulated / cooler air
if it already is, then it probably is a faulty product.

Nov 22, 2008 | MA Audio Hard Kore HK-898 Car Audio...

1 Answer

Screen goes black,with sound


No picture sound ok
Note 1 a Raster is the name for a screen made of lines of brightness
Note 2, A Blank raster has no snow or picture, its just a lit up screen

Sound ok but no raster.
First increase tube's first anode voltage (knob on the loptx) to see if the screen is just too dark.
if after you have turned up the bottom knob on the loptx, there is still no brightness,check, for crt heaters, and EHT 25kv and focus voltage (2kv) and A1's/Screen/G2 voltage is 300-600v.
and check for field timebase (height), the next thing to check is the sandcastle pulse.
If it's present, colour decoder chip is probably faulty or lacks supply from the LT regulators.

NO LINE DRIVE If it's absent,check the line driver, locate the loptr(big and usually has heat sink).
follow the print from the base back to the driver stage , where you will usually find a tiny transformer with 4/5 pins
resolder it, even if it looks good,then with power on, check for voltage on all its pins, 2 should have LT(12v to 32v) or HT (90v to 150v), if not there follow the print back and look for either a transistor(linedrivetr), or the feed voltage line (maybe regulated),
If the voltage is ok on two of the driver transformer(drvtx) legs, the look from the base of the driver transistor to locate the timebase chip
and check round its pins for a 12v supply line, if there ,replace the timebase generator chip

Method of testing line drive, remove line output transistor, and connect a normal red led, across the B/E (longest leg to base), and when you power up the led should lite up.


Trace the pcb back from the BASE leg to find the line driver stage,
Its usually a very small transformer (4/5 legs) and a transistor connected to it,
The driver transformer legs(pins) will be two with voltage and two without
The two with power will either be about HT level (110v=145v) or about LT level(25v)
If not then trace back and look for a biggish 3w resistor.
linedrv.jpg
If the voltages are correct the look for line pulses from the Timebase oscillator chip to the base (some overvolts protection circuits remove pulses if ht is too high).
If the voltage is low and the feed resistor is getting hot then check the base of the driver transistor if its HI over 0.5V then its being turned on by the timebase oscillator chip (protection ?)
If the voltage is zero check the feed resistor
If all seems normal check that 12v is getting to the timebase oscillator chip (IC) (12v regulator?)
Method of testing line drive, remove line output transistor, and connect a normal red led, across the B/E (longest leg to base), and when you power up the led should lite up.

Hope it may help you;
Regards,
VOTIT

Oct 10, 2008 | Philips 42FD9954 42 in. Plasma HDTV

1 Answer

Problem with volume dials in an electric guitar.


If you can't clean the pots or if you just want to try replacing them, try using
500k pots again, in case one or both of the pots is worn or dirty or
defective. If that doesn't work, and cleaning or replacing the
switches doesn't work, then the problem is probably elsewhere.
You could put a 500k resistor (with a sufficiently-high power rating of at least half the power rating (Watts) of the pot) in parallel with the pot, or, to cover all bases, put a 500k resistor from each of the two outer lugs of the pot to the middle lug. That should change it into the equivalent of a 250k pot. You could even just temporarily clip the resistors on, with alligator-clip leads, if you're very careful, just to test it.

Good luck,

The dude.

Aug 07, 2008 | Dean Dimeblade Tribute Electric Guitar

1 Answer

MISTUBISHI VS-50501A - top 3/4 of screen displays ok, rest does not


Check the vertcle yoke pins for solder cracks. Check verticle output circuitry resistors and transistors. And also check for Coolant leaks from the CRTs this happens alot. Check capacitors for any signs of sweeling or heat as well.

Sep 15, 2007 | Mitsubishi VS-50501 50" Rear Projection...

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