Home Theater-Stereo

Home theater questions? Ask a technician for answers ASAP

Ask an Expert,
Get an Answer ASAP!

This answer was rated:

I can wait. I have an amp and one of the channels has a

ForCustomeronly. I can wait. I...
ForCustomeronly. I can wait. I have an amp and one of the channels has a fault. Please provide a list of culprits and necessary steps. Whats the best way to clean off corrosion on the board. I have removed the board with the transistors. Whats the best way to test them?
Show More
Show Less
Ask Your Own Home Theater-Stereo Question
Answered in 10 minutes by:
11/17/2017
Louie
Louie, Technician
Category: Home Theater-Stereo
Satisfied Customers: 13,430
Experience: Have been in the business 25+ yrs., down to component level.
Verified

Hi again and welcome back to JustAnswer.

Ask Your Own Home Theater-Stereo Question

Initially, let's try check and review the basics. Proposed preliminary considerations and tries (if have not been done):

  • • since the other channel is still working, then that particular good channel can be used as a reference/template in locating the suspect components in the faulty board with the use of a multi-meter;
  • • use alligator clips with wires similar to the items shown HERE to connect the 2 boards and form a common ground between these 2 boards;
  • • connect the black probe of a multi-meter to this common ground;
  • • set the multi-meter to low range Ω mode;
  • • select a test point (any) in the good board;
  • • get a reading using the red probe;
  • • locate the same spot/test point in the faulty board;
  • • get a reading using the red probe;
  • • compare readings;
  • • repeat using mid range;
  • • if (nearly) identical Ω value, then the parts on/near that selected test point is presumably good;
  • • any deviation, then that part/test point is highly suspect;
  • • once suspect part identified/located, de-solder and test out-of-circuit;
  • • please click HERE for a video tutorial on how to test a transistor;
  • • and HERE for testing output/power MOSFETs;
  • • after a soldering job and/or to clean corrosion, use an old toothbrush and plastic safe / non-staining CRC 2-26, DeoxIT DN5 or LPS 03116 Contact Cleaner or equivalent.
Ask Your Own Home Theater-Stereo Question
Customer reply replied 8 months ago
Is it a good idea to remove channel 2's output section and connect with a dc power supply and test?

No harm in that but since the suspect(s) are removed, then tests would not be conclusive.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 8 months ago
How is this?https://www.homedepot.com/p/CRC-11-oz-QD-Electronic-Cleaner-05103/205021975

For some reasons, access denied. Perhaps a regional restriction.

Still, if it is an electrical contact cleaner, then it would also serve the purpose.

Ask Your Own Home Theater-Stereo Question

Yes, would serve our need for cleaning + an old toothbrush.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 8 months ago
Louie one of the output boards is bad. It produces low output and distortion. I swapped it out with a good output section and the power supply side is fine. I measured the transistors and they all seem fine. What else can it be?Also, there appears to be corrosion on the board? What can cause this? If the amps are left in a garage with the hot and cold weather would this affect it?Certain traces had to be jumped as they were corroded. What can I safely use to stick the jumper wires on the pcb? The wires I used are from at cat5 cable solid strand copper lines with insulation.
Customer reply replied 8 months ago
Also how is this?https://www.ebay.com/itm/1000-WATT-8-ohm-test-DUMMY-LOAD-non-inductive-for-audio-amplifier/292215401541?hash=item4409652c45:g:SG4AAOSwo4pYfUf-

If the output transistors are good, then:

  • capacitor and/or resistors (least likely);
  • smaller drive transistors (likely);
  • cold solder / connection issues (most likely).

Yes, dampness and humidity can cause corrosion particularly if the capacitors hold residual charge; almost like electrolysis.

The bridging wires may be held to the board with silicon sealant. I use RTV sealant for high temp automotive gasket. Please click HERE.

And yes, these dummy load would serve the purpose. I particularly like the idea of soaking them in transformer oil for heat dissipation.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Can you recommend a sealant from homedepot? So this sealant will not destroy the insulation of the jumper wires, be conductive or destroy the pcb?

Unfortunately, access denied again to https://www.homedepot.com/

Ask Your Own Home Theater-Stereo Question

Thanks.

Any and all would do the job. All are electrically inert; i.e. non-conductive at any state/temp/condition.

Louie
Louie, Technician
Category: Home Theater-Stereo
Satisfied Customers: 13,430
Experience: Have been in the business 25+ yrs., down to component level.
Verified
Louie and 87 other Home Theater-Stereo Specialists are ready to help you
Ask your own question now
Customer reply replied 7 months ago
Would these be a better solution than hot glue?
Customer reply replied 7 months ago
Homedepot does have them in stock? How about the below link?https://www.harborfreight.com/3-oz-rtv-silicone-red-90026.html

Yes too. as any silicone based sealant (gasket) is inert; i.e. electrical neutral hence provides very high electrical insulation.

And appreciate again the rating.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Ok thanks.How do these compare to hot glue gun?How much time do these gasket sealers require to set?

The typical cure time (drying time) for silicone caulk; about a 3/16" bead "normally" completely cures in 24 hours. The cure time could vary depending on the moisture in the air. Lack of humidity will make the curing process slower.

Glue gun would also do the job in a fashion but as its name implies would require a heated applicator whereas the silicone sealant is ready to apply from the tube. Perhaps more importantly, the silicone can withstand high temp while the glue would soften/melt at the presence of heat.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
I'm still getting distortion and about 50 percent power level loss from one of the output board. The output transistors dont show any short or are not open. Whats the best way to isolate the output transistors.

Please post back with clear pictures of the board and the output transistors op & bottom

Thanks

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
check email
Customer reply replied 7 months ago
Louie, it looks like U543, Q504, Q533, L500, Q511, R518 need to be replaced. Something accidentaly shoted and blew these components. Can you send me links from digikey for replacements please.

Sorry to hear of this.

For some reason, Digikey appears not to have these parts:

  • U543 - could it be U503? If yes, LM6364N HERE from Mouser;
  • Q504 - 2SC2336BR;
  • Q533 - MPS8097 from Mouser;
  • L500 - 470uH;
  • Q511 - MJL3281A from Mouser;
  • R518 - 100Ω from Mouser.
Ask Your Own Home Theater-Stereo Question
Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Would this be a good replacemetn for L500?https://www.mouser.com/ProductDetail/EPCOS-TDK/B78108S1474J/?qs=sGAEpiMZZMsg%252by3WlYCkUwkmiFJnoZ0dGmfCpRG0Y60%3d

Yes; should work since the same 470uH

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Are all the other values the same?

The schematics only provide this particular value; 470uH.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Is that the most important value? If the other values differ a bit will be detrimental?
Customer reply replied 7 months ago
Ok also the LS Bias pot is bad can you find a replacement

Yes; the inductance is the critical value. The physical size would determine its current carrying capacity and in this instance negligibly low thus the size would just be for circuit board hole fitting.

Low Side Bias is 500Ω. Please click HERE.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
I desoldered one of the legs of the output transistors like Q519 and it tested fine no short not open. Is this test sufficient to say the output transistors are %100 functional? I didn't apply any load to it.Also, I was thinking about using 2-4 water heater elements like the picture and put it in a 50 gallon bucket of water as dummy loads. What do you think?

Would depend on the DC resistance of the heater element and how good is the insulation preventing direct water contact with the element(s). Water of course is a conductor of electricity and therefore would have its own electrical resistance.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
I believe they are 8ohms load
Customer reply replied 7 months ago
I desoldered one of the legs of the output transistors like Q519 and it tested fine no short not open. Is this test sufficient to say the output transistors are %100 functional? I didn't apply any load to it.

IF all the output transistors showed nearly identical readings and the same with a known to be good output transistor, THEN yes; these output transistors are good too.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
I need replacement parts for R505, R556, R568, R566, Q534, Q531, D523, D524, D506

For:

  • R505 - High Side Bias is 500Ω. Please click HERE same as R556;
  • R556 - see above;
  • R568 - 100K HERE;
  • R566 - 10K HERE;
  • Q534 - 2N4123 HERE;
  • Q531 - MPSW92 HERE; might as well replace Q532 too same value
  • D523 - 1SS143 no source / no substitute;
  • D524 - 1N4148 HERE;
  • D506 - MR822 HERE.
Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Also C520, C512, C506, C500, C504

For:

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
They dont have c500 in stock. Will this be a good replacement?https://www.digikey.com/products/en?keywords=490-9412-ND

Yes; it is also rated 47pF @ 250V

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Would this be a good replacement for Q531? Not available at mouserhttp://www.newark.com/diodes-inc/ztx757/transistor-pnp-300v-500ma-1w-e/dp/98K4087?rpsku=rel3%3AMPSW92

Yes.

As earlier posted two (2) would be needed. Considering the cost, order some more for stock/spares.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Happy Thanksgiving Louie.

...and Happy Thanksgiving too.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Louie I'm still having problems with one of the output boards. I removed the opamp with a good one same low output and distortion. I also removed all the out transistors with another board and still same problem. Have narrowed it down to the board with the opamp. What can it be?Also, when testing an amp with a signal generator and a dummy load is it a good idea to test for 30 minutes to make sure the amp is good? Will this damage the amp in any way?Also, looking at all 3 amps do they share the same output transistors, opamps and other major components?

On:

  • narrowed it down to the board with the opamp - Part Number please of these OP-Amps
  • good idea to test for 30 minutes - as long as there is a dummy load, then it would/should be safe. Amp damage can only happen if there is still a weak/failing part.
  • 3 amps do they share...major components - to m,y understanding and based on the schematics, yes.
Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Louie I confirmed it wasn't the op amp and its not the output transistors. Whats else could it be. I hear music but when I start to increase the gain I hear distortion and it only goes but so much higher in levels.
  • narrowed it down to the board with the opamp - Part Number please of these OP-Amps

The above was meant to determine the circuitry and components likely to be causing the distortion near these OP-Amps.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
The part number for the opamp is LM6364N

Please measure carefully the voltage between pin 15 and pin 13 of P500 of the suspect board.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Its very hard to measure voltage because the boards are connected together and slide into the rear of the chassis and are not accessible. Any way I can test p500 without powering up the board?Also, what does this chip do?

These are module connectors.

Use a known to be good board similar to the board in question. Join together these 2 boards to have a common ground using alligator clips with wires.

Using the Ω function of a multi-meter, test compare the readings of the various pins of P500.

...do the same for U503.

...and even Q531 and Q532. These two transistors form a differential pair and critical in the LOW SIDE BIAS configuration.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
OK I will do that soon. Can you find a replacement at digikey or mouser?

LM6364N - not available from either Mouser, Digi-Key. Please inquire HERE and HERE.

MPSW92 - from Digi-Key HERE.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Louie I found a break in the line on pin 6 on u503 to be bad. I will fix. Would this be the culprit?

Yes, definitely; as pin 6 is the output of U503 and directly affect the LOW SIDE BIAS.

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
Ok I'll let you know soon.

Nice find!

Ask Your Own Home Theater-Stereo Question
Customer reply replied 7 months ago
u503 is the opamp for all output transistors?What specifically is its role in the circuit?

U503 indeed is an OP-Amp but in this particular application, it is used as an sensor amp for the dynamic and static balance of the output. Any deviation from normal operation and U503 magnifies it causing auto-protect to kick in.

Ask Your Own Home Theater-Stereo Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a technicianLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Louie Your Own Question
Louie
Louie
Louie, Technician
Category: Home Theater-Stereo
Satisfied Customers: 13,430
13,430 Satisfied Customers
Experience: Have been in the business 25+ yrs., down to component level.

Louie is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Louie

Louie

Technician

13,430 satisfied customers

Have been in the business 25+ yrs., down to component level.

LOAJ3256

LOAJ3256

Technician

497 satisfied customers

35 years in Home Theater and Systems Integrator, Senior

Federico

Federico

Licenciate

44 satisfied customers

Home Theater and Automation systems integrator.

HomeTheatreGuru

HomeTheatreGuru

Engineer

31 satisfied customers

Home Theatre, home automation and related wiring, commercial A/V systems

Rod

Rod

Engineer

27 satisfied customers

40+ Years of Electronic Repair and Installations.

Neil

Neil

Engineer

23 satisfied customers

Electronics engineer with 25 years of experience.

glenemoore

glenemoore

Customer Service

19 satisfied customers

Experienced in audio/video systems and design

< Previous | Next >

Related Home Theater-Stereo Questions
Sorry I took so to get back so I'm posting the same question
ForCustomeronly. Sorry I took so long to get back so I'm posting the same question as before.Louie I have 2 exact PCBs one being good and the other being bad. I need assistant in finding the culprit. … read more
Louie
Louie
Technician
13,430 satisfied customers
Louie I have 2 exact PCBs one being good and the other being
ForCustomeronly. Louie I have 2 exact PCBs one being good and the other being bad. I need assistant in finding the culprit. Please advise.Also, what are the different methods to find a bad component o… read more
Louie
Louie
Technician
13,430 satisfied customers
Louie I have an amp which is having problems on both
ForCustomeronly. Louie I have an amp which is having problems on both channels. The output does not get to full power and after a 1 minute or so it goes into fault. Check email.… read more
Louie
Louie
Technician
13,430 satisfied customers
I have an amp with 2 channels. Channel 1 is bad and channel
ForCustomeronly. I have an amp with 2 channels. Channel 1 is bad and channel 2 is good. I would like to use channel 2 as a reference with the power on. I need instructions on what checkpoints to compa… read more
Louie
Louie
Technician
13,430 satisfied customers
Louie I have an amp that is old. I would like to do
For Benimur only. Louie I have an amp that is old. I would like to do maintenance to it. What are the necessary steps that I should take?… read more
Louie
Louie
Technician
13,430 satisfied customers
This question is foronly. Louie I have an amp which appears
This question is forCustomeronly. Louie I have an amp which appears to have a severe short. The fuse is blown and is dark on the inside. Please advise.… read more
Louie
Louie
Technician
13,430 satisfied customers
Louie I have an amp which as 3 premap boards. The amp wasn't
ForCustomeronly. Louie I have an amp which as 3 premap boards. The amp wasn't producing any output. Below are my questions.Are the small board considered preamp boards?Am I correct in thinking that th… read more
Louie
Louie
Technician
13,430 satisfied customers
Louie, I purchased an Onkyo TX-SR806 that was stuck in
Hi Louie, I purchased an Onkyo TX-SR806 that was stuck in protect mode. I opened the receiver and replaced the bad output transistors, and then noticed when cold it would make a horrible amount of sta… read more
Louie
Louie
Technician
13,430 satisfied customers
31 July 2015 11:35 Louie only please.Louie only. , I am
31 July 2015 11:35 Louie only please.Louie only. Hi, I am again working on one of my Kenwood Eleven receivers. ( same as 1100G ) Some time back one channel became all distorted. Using the rear panel M… read more
Louie
Louie
Technician
13,430 satisfied customers
ForCustomeronly. Louie I have a cd player which has a pair
ForCustomeronly. Louie I have a cd player which has a pair of rca output jacks and only one of them is working the other isnt. Please advise.… read more
Louie
Louie
Technician
13,430 satisfied customers
Hi,I have an Onkyo TX-SR806 receiver that goes immediately
Hi, I have an Onkyo TX-SR806 receiver that goes immediately into standby mode whenever I try to power it on. If I press the "Zone 2" button, the display says "Zone 2: Off?" and after 10 secs or so it … read more
Louie
Louie
Technician
13,430 satisfied customers
Hi, I have Harman Kardon HK3380 and has no output at all. No
Hi, I have Harman Kardon HK3380 and has no output at all. No error codes just no sound. What should I check?… read more
Louie
Louie
Technician
13,430 satisfied customers
I have a Sansui BA2000 Amp that was working fine until I stupidly
I have a Sansui BA2000 Amp that was working fine until I stupidly disconnected the speakers to change the style speaker while the power was on and volume was full output. I ended up losing sound out o… read more
Louie
Louie
Technician
13,430 satisfied customers
New question forCustomer Not a duplicate. Have purchased another
New question forCustomer Not a duplicate. Have purchased another 949 receiver. It is the one that protector at times shuts it off, but otherwise works fine. Its likely easier for me to repair this uni… read more
Louie
Louie
Technician
13,430 satisfied customers
Question forCustomerregarding 5 units of same make and model
Question forCustomerregarding 5 units of same make and model and which is likely the easiest to repair. I have done some testing and looking over each unit and what appears involved in repairs to each… read more
Louie
Louie
Technician
13,430 satisfied customers
Ongoing question Im working with Benimur on. Submitted as
Ongoing question I'm working with Benimur on. Submitted as new due to previous question being closed for no known reason. I was not able to find exact match for the 5 watt resistor. It calls for 5W 0.… read more
Louie
Louie
Technician
13,430 satisfied customers
Hello agin, I have the replacment Teac ordered. The seller
Hello agin, I have the replacment Teac ordered. The seller of the first one is asking if I would be interested in keeping it at a reduced price. He says do not worry about insulting him with a low off… read more
Louie
Louie
Technician
13,430 satisfied customers
I have a vintage Sansui G9000 made in 1978 and have the service
I have a vintage Sansui G9000 made in 1978 and have the service manual. My issue is the protector light is flashing red and no output to speakers. For a brief time it turned green and things powered o… read more
Louie
Louie
Technician
13,430 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x