finally write the repair more 'complex and fascinating that I'm finding to do.
This is a popular brand of amplifier Linn Majik model, unfortunately struck by lightning. The owner has explored various ways to repair, but the poor amplifier and 'finished in the tray (more' than anything else attic) of oblivion, awaiting further developments.
The diagnosis of a patient and it was rather shabby so 'that ends' in my room, where I also gave him hope for him .. I had intended to retrieve a few connectors and components are healthy, or at best exploit the mobile good as the original house for a new amp .. But in my heart I hoped ..
Just brought home, I immediately opened, and the show was not the best, since almost all the chips showed signs of an explosion, and various printed circuit tracks were merged or stopped. When switched on, needless to say, no sign of life. Just the voltage of + and - 45V at the capacitor to filter the feed section. Well, better than nothing, I thought, I can always take advantage of the nice toroid for the amplifier without house we were talking about before. I have provided accurate
dismantling electronics, and are left with the bare board, which itself 'integrates everything. A hand is' only the LED panel and a small card with the buttons and 7-segment display, which also appeared in good condition.
Removed damaged organs I immediately noticed the abundance of voltage regulators LM317, LM337, there are 5, and I know their qualities of strength .. Have hope that something was still alive, even if already imagined 'desolder all of the desoldering iron, and cannibalize their own skin.
was so 'long observed that the card, the ski routes, the chip broke, and I do not know how, I decided that maybe something could be groped.
Dissaldai TDA1514A then the four burned with unusual care, noting the high quality 'of the PCB, who survived torture each heat. When removing the heatsink (very small also) amps, the two power transistors 2SC3519 and 2SA1386, I later discovered to be used as a linear regulator to power, I have remained virtually in hand, and were then crumbled in the operations of dismantling of what remained. The lightning must have them just crossed her going ..
The digital section is very compact, consisting of a PIC16XT54 a '74HC373, all obviously SMD, appeared intact. Stood a rack jumper, complete with a legend and I 'is useful.
I decided then, instinctively, to give power back to the body, with the intention of measuring something, because the components were burned now removed, and the risk of any short circuit due to the same had been deleted.
We try to energize Then connect the torus, I link the ticket with buttons and display, and do 'tension. Shot of current transformer and then silence. Some key components: cold, some lukewarm, just the voltage regulators. I take
meter: 45 volt dual ok, there are, we knew it.
measured downstream of the first LM317-337 I see: +15 and -15 volts. Something works!
Measure 317 all alone in the middle of the card: 5 volts. Clearly, and 'he who gave power to the logic section! Ah yes, look at the display: off, silent, does not react to any button. Discomfort. I turn off everything, I try to calm the trembling of the hands and speak.
The tensions are all there, and must be the right ones. Carelessly touch with the index of the SMD chip in the input section, the one crossed by the discharge in full: e 'HOT! I almost scot!
seem quite dead ... Evidently those SMD chip in the letters are rendered indecipherable. Double depression. Practically the only semiconductor voltage regulators are healthy!?! Triple discomfort.
course of wiring or manual will not speak of the Linn Majik seems unknown to the web .. We hope that with this blog it is a little 'less ..
In the meantime I decided to place a pair of NPN and PNP power instead of the 2SA1386 and 2SC3519, hoping to get something more '. The voltages of +26 and-25V are now governed by the new transistor (for the first proa I put a TIP127 and TIP122) are flanked by 317 and 337.
Santa patience, I said to myself, I know the PIC are quite robust, if the line operates at 5 volts means that there is something healthy '!
Look again at the rack for the jumpers, and I read "link to disable Poweramps 1 + 2".
Want to see who notices that the chip is completely missing the final and goes into "protection"?
I have not even thought about it, I took a jumper from the PC, and I joined the bridges 1 and 2.
solution ...!
Power ..
magically appears on the display says "CD". The shout of joy I think he felt up to Pluto.
The keys respond, changing the writing, "You, T1, T2, Au, Cd digital volume ...", replied" 30, 31, 32 ... 31, 30, 29 ...".
control electronics and 'GOOD!
The discouragement of experience, and 'was blown away, I can really think to return the amplifier to its former glory!
Taken by the heat, unsolder the chips melted the input stage, after being photographed and marked so as to reconstruct the exact location.
note well: if the input 'and' consists of four integrated DG508ADY signed, which the datasheet
appear to be eight times the analog switch controlled by 3 bits of address.
Well, in fact, the amplifier has 7 inputs .. But why '4 Octal switch? After careful analysis of the slopes, I discovered that two of these chips (one per channel) were devoted to the actual input selection to send to the final, while the other two were dedicated to the input selection to be sent to TAPE OUT. Well, at least we know something more '. Together with the mob of spiders
time, an integrated desoldering also signed DG411DY, also analog switch (see datasheet
).
And now? Problem: Where can I find replacement parts for little-known chip?
Obviously, no one supplier network held a catalog of objects so 'unusual, nor MDS. At best, I found some DG408DY, Distrelec from the catalog, but I was not very confident about their performance. If you chose DG508ADY Linn, DG508ADY should be. Taken
despair (we are now the fourth ration I think), I started to wander around the sites of large houses (Philips, Fairchild, ST ...), looking for a possible equivalent (pure utopia).
When suddenly enlightened.
Salvation: www.maxim.it Site Maxim.
Free Sample.
could not believe it. That evening I ordered
DG508ADY 10, and 5 DG411DY (for replacement double, can 'happen to burn something). I write the address and sending the order.
honestly do not believe it, I was definitely not very confident.
After a week, I write to Maxim to see if the service works, if you ever see 'those chips or whether I just deluded.
The answer:
"Being Your order is processed from the Philippines, it will take about two weeks to be shipped."
Incredible, I see the light.
Works! Twenty days after the postman comes at my house with a bag signed MAXIM. Inside, three boxes with the infamous DG508ADY, DG411ADY, and a letter that thanked me for choosing MAXIM. Two or three pinches
later, I started to pay off the gift came from heaven.
SMD soldering, as mentioned, and 'was a pleasure to see the new lodge working chips on plots of their predecessors, and the pond flowing ..
As already 'mentioned, the quality' of the PCB and 'nothing short of amazing, chips are soldered with ease', considering that I had virtually never soldered SMD before.
Let ... arrive at power. Do 'tension. + And - 15 volts. Chip cold. This 'already' a small success!
must now check if everything works, or if the chip switch properly.
It 's also the time to find out if all those components in SMD (FET seem very delicate .. ..) work, or if I have to finally abandon the idea ..
then I connect to the parking spaces that would end in the non-inverting pin of the TDA1514 a shielded cable, the entrance to the T-AMP built the first month (yes, I took a couple of kits from the site www.41hz.com, sensational! But I will tell you 'once more calmly).
Food T-Amp.
amplifier supplies the card: slight bump at the exit, a good sign.
signals to the sockets, RCA initialed CD .. output changes. But
', maybe I'll' selected the wrong entry! Change with the buttons beside the display, but nothing.
It 'nice to see the display to respond, but at the same time and' deeply disturbing silence on exit. Just a little 'hiss with the volume to maximum. At least the volume control seems to work.
Nothing, everything is' dumb.
I follow the signal path on the slopes, check continuity ', it seems all right. I did not want to resign myself to the idea that the FET preamplifiers were gone, could not be true, after the PIC so I had 'delusional ..
Evidently someone missing (cast components) control signals with the tester to the address pins of DG508: all at +5 volts. Checking in datasheet: Code "111" - Input / Output "8". In Linn the I / O number of DG508 and 8 'grounded. It means that everything comes back. But the chips do not commute.
I follow the tracks of the address signal, and arrives at the notorious '74HC373. It seems healthy, and 'next to the PIC .. It must be healthy!
But the same control for the sake: tester connected to a pin of address and power: 5 volts, it was reasonable to expect. 5.01, 4.99, 5 short.
Input Change, select "T1" and remains 4.99 to 5.02. In short, always cursed 5 volts!
Exchange, select CD. I read 4.90 volts. Back to T1, read 5.02.
Want to see the 373's has been cast out, and the "logic zero" and 'to 4.9 volts? Absurd, ridiculous.
But try not cost anything. Indeed, unsolder and solder a SMD chip starts to like a while! I take a '74LS373 (not HC, but such was the despair that anything would have been fine, but to read a logical "family"), I had at home, unsolder from a computer knows' that in time, and substitute.
turn on, place the tester, and read: T1: 5.01 V. CD Input: 0.05 Volts! It works! Finally, the logic analyzer senses!
was just the 373. I turn on the MP3 player that I connected to, the food T-Amp, and part of the melody. A unique emotion, feel the amplifier rise gradually from the ashes. Input Change, and the volume fades to pass another piece to the line (input''You''). Input Change, and again repeat the magic.
I can say with certainty to have completely fixed the input stage amplifier, and have limited the problem to end. Satisfaction.
Considerations I enjoy the music for a few minutes (actually 'buffer, as the signal passes through a FET preamplifier and still, only now I realize that they are miraculously healthy!), And watch the card.
I am aware of some tension.
+26 Volt and -25 Volt would feed the TDA1514A. The eye falls on two LM317 and LM337 in the area. Are their own to provide these voltages. They key, I'm pretty hot. Strange, there's' no load connected ..
Measures for the sake of the input voltage regulators for +15 and -15 V: +26 and -25.
Unbelievable, only now I discover that the 45 volt dual are first set to +26 and -25 from this pair of 317-337, these tensions are passed to another pair like that generates the +15 and -15 for the inputs, and +15 from the last 317 draws the 5 Volt! What a bizarre choice .. But if Linn has done so, 'why was all right. Perhaps in this way, the power dissipation is distributed better, and our thoughts turn to the powerful 2SC3519 and 2SA1386, still missing in the power supply stage of the heat sink and cooled by the same Finished (
datasheet 2SC3519 2SA1386 ).
Well, we try to replace the dead with some replacement transistors more 'powerful TIP122 and 127 that I put it temporarily. This is still a common NPN and PNP power.
Instead of the square a nice
2SC3519 BD249C (bipolar standard), and instead of 2SA1386 are forced to put a TIP145 darlington type
(guess' where he came from?).
Do 'live again, the display ready to respond and start to do some testing on the power section, simulating the load with some resistance from a few tens of ohms. All regular, tensions remain fixed and regulated, even under stress (2-3 A). The transistors as heat duty, apart from the TIP145, which causes an abnormal warming dell'LM317 that commands it.
thinking a bit 'is also obvious: it is a Darlington, and the voltage Vbe' about twice that of a standard bipolar transistor, and recalling the pattern of the 317 coupled to PNP power, and 'clear that the Vbe resulting in reality 'from the current absorbed by 317. The 317 was dissipating twice the power compared to that for which he had been nominated. Not bad, when I find 'a PNP standard will provide' on the exchange and verify 'my guess.
is meanwhile a bit 'of photos of the main board of the amplifier after the replacement of the components mentioned above:
Overview of the sheet
Detail section final (missing) and a power supply:
back of the card in the end zone, some bridges have been made to reconstruct the tracks evaporated:
Half the job is done! remain to be precisely the power transistors, and the notorious TDA1514. But the entrance works, and I can always make up an alternate ending, without having to resort to the TDA1514. I'll think, 'I said, for now the joy and' too large.
