It sounds like you are off to a good start. However, as stated in previous posts, all electrolytic caps on the main power board should be removed. Caps are rather inexpensive and can be obtained from Digi-Key.com. For the ones you were looking for 470 uf 200v, they will likely be Snap-In type and will set into the holes, lock in and solder easily into the space provided as long as the dimensions of the cap are correct. Digi-key part number P11613 mfgr part EETED2D471BA fits perfectly, or the Rubycon I suggested will work as well.

Caps are relatively inexpensive and replacing them will eliminate present and future problems.

Extreme care should be observed when removing and installing components, especially the caps with the feed through connections. I have found that a 30 watt solder iron with a pencil tip works best. Also to ensure the components are removed quickly and cleanly, I got a can of "duster" which is essentially bottled air under pressure, from Radio Shack or Walmart. Using the plastic tip provided with the can or a longer one of your own be used to concentrate the air pressure to the solder tip area to blow out the solder at the same time as the component is removed to ensure a clean removal without damage to the pads or holes. You will have to be careful that the solder does not spray all over the boards by placing a cloth beneath the board you are working on. Of course copper braid works fine if you are careful to not drag the pad off the board.

Bare copper can be covered by using a non conductive acrylic to prevent corrosion. I can help with getting those caps you need if you want.

Removing the glue should be done by carefully scraping/pushing off the glue without scratching the board and green coating. It takes patience and time, but may be the difference in saving the unit. I have found some dental tools helpful and they also have rounded edges which do not damage the board.

Good luck and hope I can help.

The short might have occurred because of some glue left on the board or a defective connection after replacing the cap. That is only a possibility and could have been something else, however you will have to clean up the area with special care, removing all trace of glue and other deposits while keeping the solder hole intact. Make sure the heat sink is not shorting to the caps. Then you will have to replace the electrolytic cap as well as the one next to it. I believe they are C62 and C7. U2 next to the C7 and D26 zener diode should be checked as well. You may want to replace the electrolytic that got zapped with a high temp ceramic as I believe Lex suggested, and may have been the cause of the problem because it is so clse to the heat sink.

MG Chemicals acrylic conformal coating for pcb catalog 419c 55ml clear is suitable to protect bare copper on pcb.

This post has been edited by dlduscg: Feb 1 2015, 10:03 PM

Lex seem MIA for sometimes...

i just would like some part info like what is the t2 replacement and what are the Q1 Q2Q3Q$ HELP PLEASE

The T2 info should be on the transformer itself. The Q1,Q2,Q3s are IRF740 MOSFET transistors, 10A 400V TO-220 type case, and generally cost as low as 5.00 dols depending where you buy them.

So, I know what C62 is as that's one of the capacitors I had to replace before, but I have no clue what to look for with C7, U2 or D26. Can you help me out there?

If I recall correctly, the capacitor he suggested replacing with a high temp ceramic was actually C63 (and I did replace that one with a ceramic) but could do the same with this one if that's likely to be the issue.

help me pls

Unless there is obvious evidence that other components nearby may be the cause, I would assume a faulty connection when C62 replacement or glue remnants caused the short, and clean up the area very carefully while checking for a possible defect on the board. If there is evidence of being burnt or damage to other components, then I would consider replacing them as well. D26 is a 24V Zener diode but if a simple front to back resistance check looks good I would not replace it. Likewise if the C7 blue capacitor is intact and does not show a short I would also leave it alone for now. C7 is 470p 250V ac safety cap. It is not possible to know whether or not heat was a factor, I rather doubt it.

This post has been edited by dlduscg: Feb 4 2015, 11:55 AM

Sorry, I do not know of your problem and Lex has not been on for quite a while. If you want to give me some info, I can see if I can be of help.

This post has been edited by dlduscg: Feb 4 2015, 11:48 AM

Hi, thank you for this information. I am using a pencil tip soldering iron. I dont have bottled air but i have a sucker which pulls the soldier up, away from the board when heating the area. It seems to work alright that way. Is the non conductive arylic some sort of spray paint? i have not got around to taking any photos yet , sorry for this and i need to carefully read what all the electrolytic caps means. such as if it includes the blue, black and brownish smaller components or not. at the moment i have just removed all the cylindrical components, small and big which i thought were capacitors. i am worrying that my board will go rusty now as it has exposed areas. i feel all of this work is very difficult, even though the price of caps are cheap, the time and effort seems high. i also have a multimeter if this helps but i am scared to test stuff with it. So when i have some more time i will show you what i have and also look at the caps you sugguest. i would appreciate the help in selecting the caps. i live in the UK, if you could just list website links , then i can just make an order quick.

You seem to be doing fine with the solder which is also a good way to remove solder safely. I think you need to go back to the beginning of this topic, all the way back to page 1 and read through it to understand and gain a thorough knowledge of this project. The bare copper areas you mention, and I hope there are few, can be coated after you have completed work in those areas. I found MG Chemicals Acrylic Conformal Coating item 419C-55ml available on Amazon to be a good product to seal those areas and prevent corrosion and future problems. It is a clear liquid in a small 55ml size bottle with a small brush applicator.

You should also obtain the schematics for the power supply, you can find them at the following link: http://www.tgahinfo.homecall.co.uk/S750%20...y%20Schematics/

Then read all the comments concerning removing the degraded glue.

In addition, you will find other types of capacitors on this board as well as many other components which are not caps. You will find out more information when you get the schematics and understand how to locate the various devices on the board. The small brown discs and the blue ones are ceramic type capacitors. There are also resistors, diode rectifiers, transformers, coils, inductors, etc., which you will be able to identify later when you get the schematic. The only ones of these you need to replace are the ones which you see damaged or have been suspected of being faulty.

The following is a list of all the electrolytic capacitors on the PSU board that should be replaced because they are of inferior quality and may be the cause of your present problem or future problems:

- 4x 470uF 200V 105C, high ripple handling type (for inverter and/or ballast operation)
- 2x 330uF 100V 105C, low impedance and/or low ESR type (for SMPS operation)
- 5x 220uF 35V 105C, low impedance and/or low ESR type (for SMPS operation)
- 5x 100uF 35V 105C, low impedance and/or low ESR type (for SMPS operation)
- 1x 68uF 450V 105C, high ripple handling type (for inverter and/or ballast operation)
- 2x 47uF 25V 105C, low impedance and/or low ESR type (for SMPS operation)
- 1x 0.1uF 50V 105C, high temperature type prefered (such as ceramic) as its very close to the heat sink.

You should have not removed any other caps or components at this time.


You can probably get all of these at www.digi-key.com. I will give you the exact digi-key order number if you want.

In addition, I hope you will learn how to use your multi meter correctly and safely before attempting to use it. Your meter can be seriously damaged if you attempt to measure voltage with the selector in the range for resistance, and if the range is too low for the current or voltage you are measuring. Please be careful.

I will check back from time to time to see how you are doing, and if you need help. Good luck.

Before we go any further, you should not attempt to work on this project without having a thorough understanding of electricity and the extremely dangerous hazard to your life if you do not observe the proper safety precautions to protect yourself at all times. I know this should have been established a the very beginning of our discussion, and therefore I will need your assurance; that you are capable of handling this complex technical project, and will seek help locally if you venture into uncharted waters. Take care.

I've fixed the power supplier part but when I connect all of it, the speakers don't work, the most curious thing is that if I connect the headphones to the speakers volume control it work. The speakers turn on but they dont make a noise.

Hi,

Thank you for the reply. Could you list the exact digi key order number for me for the above list please. i will double check what i have removed but this seems the same amount. i did have a read a while ago from page one but maybe i must read this again as i have obviously missed important parts and get back to you. :-). i have not attempted to use my multimeter and feel i would only do so if really necessary.

Hi thank you for your concern. I will be very careful when dealing with electricity. i have not attempted to use my multimeter as of yet and have an understanding of how dangerous electricity can be. I do agree this should be an important statement at the beginning of the discussion. I will try my best to seek help if it comes down to this. I am a technical person, have done some simple circuitry in the past but not in extensive detail.

This post has been edited by LordNubus2: Feb 6 2015, 06:26 AM

Are you using the audio control to turn on the power?

Thanks for your understanding. Of course you will use your meter to check for resistance, shorts, connections, etc., it is only when you go on a live circuit will you be exposed to dangerous conditions that even the most experienced must be extremely careful and I know now from your email that you are experienced, that was my main concern. Ok, here is the list of digi-key part numbers for the 20 capacitors you should replace. All except for the last one are electrolytic radial can type capacitors; the last one is the ceramic that is near the heat sink and is recommended to use instead of the electrolytic can you removed. If there are any (end of life) that you are unable to get, I can help you with a substitution.

(4) 470uf 200V snap type Panasonic P11613-ND

(2) 330uf 100V Rubycon 1189-1042-ND

(5) 220uf 35V Nichicon 493-1579-ND

(5) 100uf 50V Nichicon 493-11570-1-ND

(1) 68uf 450V Nichicon 493-13090-ND

(2) 47uf 25V Nichicon 493-1547-ND

(1) .1uf 50V Nichicon 478-5096-ND

That should do it for now. Let me know if you have problems.

This post has been edited by dlduscg: Feb 6 2015, 11:20 AM

yes

I assume your fix worked because you have it in the phones. Make sure all of the connectors inside the box are properly seated and did not get twisted or pulled out when you close the box. Make sure that the green led is on and stays on when you apply power. Carefully plug in your inputs inputs and outputs and recheck the input source, DVD player, PC, or whatever you are using is on and running. Inspect the audio control plugs for damage, bent pins etc, and are plugged in and seated correctly. Does the red led on the audio control stay lit and when you press the power on the audio control are all the led lighted?

Then let me know what is happening please.

all that is on the trans is TWI 885239 0350