28 July 2010, 14:39 | #21 |
hastala vista winny vista
|
do you have audio output from paula ?
solder a couple of wires to paula left and right output and see if you have sound. it will be very high, distorted because you're by passing the filter. but it will save you from changing paula if nothings wrong with it. personally I think you should supply +12v directly to op amp. |
28 July 2010, 14:43 | #22 |
Registered User
Join Date: Jul 2010
Location: .
Posts: 34
|
Unfortunately I don't have the tools. Otherwise I would already have desoldered and cleaned under LF347.
But I don't think Paula or LF347 are faulty. It's what arrives to LF347 that is wrong. All the capacitors I changed had leaked a little, but I haven't seen broken vias. The point is: R301 has +12v. From the schematics (audio decoupling) it should go directly to LF347 pin 4. It doesn't. From what I can see, from C303 the via goes under LF347. What happens if I connect a wire from C303+ to LF347 pin 4? Does anyone know where I can find a picture of the board with LF347 removed? |
28 July 2010, 14:46 | #23 | ||
Registered User
Join Date: Jul 2010
Location: .
Posts: 34
|
Quote:
Should I solder a wire from pins 33 & 34 and feed it to the TV directly? Quote:
|
||
28 July 2010, 14:47 | #24 |
hastala vista winny vista
|
|
28 July 2010, 15:14 | #25 |
Registered User
Join Date: Jul 2010
Location: .
Posts: 34
|
Ok, thanks. I have to go to work now, I'll report back later.
|
28 July 2010, 17:03 | #26 |
Precious & fragile things
Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
|
Any leakage can be enough to chew tracks away the outside view of LF347 can be all rosy, but underneath it's rotten track hell.
|
28 July 2010, 20:32 | #27 |
Registered User
Join Date: Jul 2010
Location: .
Posts: 34
|
We're almost there! Connecting pin4 to R301 or C303 restored almost all the sound.
BUT it looks like one of the channels has problems. I tested it with "into the wonderful", and some sounds are missing now and then. It doesn't look like a frequency problem, as only some samples are missing. But the defects are always the same ones, so it's not random. I'll have another go trying to desolder lf347, but I only have a soldering iron, no hot air. In the meantime, suggestions regarding how to fix defective audio channels are more than welcome! |
28 July 2010, 22:30 | #28 |
Registered User
Join Date: Jul 2010
Location: .
Posts: 34
|
No success with LF347. I don't have the proper tools for smd.
Could the sound defect be caused by it? I tried connecting the audio output directly from paula, but the audio is very low and I can't understand if it's working properly. What would be the best course of action now? |
28 July 2010, 23:26 | #29 | |
Registered User
Join Date: Sep 2006
Location: Thunder Bay, Canada
Posts: 4,323
|
Quote:
If youre in Canada and want to send it to me i can replace paula and the lf347 |
|
28 July 2010, 23:39 | #30 |
Registered User
Join Date: Jul 2010
Location: .
Posts: 34
|
Thanks for the offer kipper2k, but I am Europe. Shipping would cost more than a full A1200 setup :/
|
29 July 2010, 06:24 | #31 |
Precious & fragile things
Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
|
Hassle Zetr0, he's in UK, I'd do it but I know what it would cost to send it to Australia.
|
29 July 2010, 06:36 | #32 |
Registered User
Join Date: Feb 2007
Location: Melbourne, Australia
Age: 41
Posts: 3,773
|
Simply cut the legs of the op amp with a knife and remove the chip, then remove the legs with your iron.
Soldering the chip will be very easy if flux is used. |
29 July 2010, 11:59 | #33 |
Registered User
Join Date: Jun 2010
Location: PL?
Posts: 2,888
|
Also serial port translator 1488/1489 are responsible for strange things - at least one person made ale replacement for this - not so long ago - check history
IMHO replace them for something decent and more modern like MAX232 or similar - usually faster and simpler application circuit. |
29 July 2010, 12:34 | #34 | |
Precious & fragile things
Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
|
Quote:
|
|
29 July 2010, 12:37 | #35 | |
Precious & fragile things
Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
|
Quote:
Clip the leg leads with sidecutters then desolder the leg stubs from there. but be warned, use very fine sidecutters as they limit the amount of stress placed on the pads, always cut from directly above not from the side. |
|
29 July 2010, 13:15 | #36 |
Registered User
Join Date: Feb 2007
Location: Melbourne, Australia
Age: 41
Posts: 3,773
|
Think you're more likely to do damage with a pair of sidecutters to be honest. Never slipped once with my little craft knife.
I don't really appreciate being called a butcher, I take a lot of pride in my work and have never damaged a board in my life. |
29 July 2010, 13:42 | #37 |
Registered User
Join Date: Sep 2006
Location: Thunder Bay, Canada
Posts: 4,323
|
To remove SMD's you MUST use a hot air rework station especially if the chips are 4 sided, you can remove the chips quickly and prevent damage and bending of the legs.
here is a link for same model i use... http://cgi.ebay.ca/SMD-Rework-Solder...item43a0af3e52 Set the temp at 350 deg and use the smallest nozzle, i actually took the small round nozzle, and squished it flat to elongate the nozzle to give more control. Practice removing components on an old board, you do not need a lot of air flow (especially on a densely packed board). You would be surprised how much heat these chips can actually take, saying that, make sure you direct the air flow to the legs only, constantly moving back and forth and side to side, do not heat the chip up directly. it would take about 10 seconds to remove the LF347 for example, with no stress on the pads It is not hard, a bit of practice and you will be impressed with yourself. |
29 July 2010, 14:38 | #38 |
Registered User
Join Date: Jun 2010
Location: PL?
Posts: 2,888
|
It can be removed (by normal solder iron) by putting very thin steel (or similar not very well solder-able material) between legs and pads on PCB - for example blunt razor blade or event better one of thin feeler gauge sheets.
If You use hot air it is better to cover surrounding areas by some thermal insulator - like glass fiber mate - easily available due of frequent use for repairing composite structures (cars, yachts...) - can be easily cut by scissors. More expensive (but slightly better) is kapton tape - yes it is used in industry for thermal protecting many sensitive devices. |
29 July 2010, 15:45 | #39 | |
Precious & fragile things
Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
|
Quote:
|
|
29 July 2010, 15:59 | #40 | |
Precious & fragile things
Join Date: Feb 2009
Location: Victoria, Australia
Posts: 1,946
|
Quote:
The point you missed in this thread is that the owner of the board is an amateur, craft knife expertise in removing chips isn't recommended for amateurs, more to the point SMD isn't recommended for amateurs but if people are adament that they want to try advanced techniques on a board to save a few dollars on a repair that could be done by someone competent and run the risk of destroying their boards that's fair enough, I just try to offer advice based on sound techniques that I know work and that are easy. I would personally use hot air to take the chip off, if I didn't have that a fine iron and a dental pick, even the latter can't be done without having some practise prior and as a last resort the sidecutter technique mentioned earlier. By the way, if you use very fine sidecutters from directly above you cause minimal disturbance to the pads, but if they're not fine then you run the risk of clipping a second leg at the same time and putting a sideways shear on one or both pads. |
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
Thread Tools | |
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
audio device in use problem | Hungry Horace | project.WHDLoad | 14 | 28 January 2019 11:41 |
A1200 - Audio noise | NovaCoder | support.Hardware | 6 | 11 March 2012 23:57 |
Re CD32 Audio noises problem | calibra | support.Hardware | 4 | 03 March 2012 22:02 |
E-uae audio problem | lomdav | support.OtherUAE | 0 | 27 August 2010 10:01 |
a1200 audio sound problem | ITGuy | support.Hardware | 9 | 11 April 2009 16:26 |
|
|