OK, the amplifier is fixed. It indeed was the differential stage.
However, there were some problems. Out of 4 replacement transistors I got, only 2 worked. I was therefore unable to match any. They both had significantly different Hfe values (290 and 220), and consequenty. the DC offset is quite high (114 mV, as opposed to 50 mV of the other channel). It's not really going to be a problem I think, but I informed the owner of the amp of the situation, and he said he may order some new ones in the future, and select a better matched pair.
It was good luck I tested the transistors before I installed them (per the suggestion to match them). I have never done that before. If I hadn't now, more serious malfunction could have been caused, as one of the faulty transistors was shorted.
That freeze spray works very nicely to detect errors BTW. It may even help to get a drink cold fast 🙂
However, there were some problems. Out of 4 replacement transistors I got, only 2 worked. I was therefore unable to match any. They both had significantly different Hfe values (290 and 220), and consequenty. the DC offset is quite high (114 mV, as opposed to 50 mV of the other channel). It's not really going to be a problem I think, but I informed the owner of the amp of the situation, and he said he may order some new ones in the future, and select a better matched pair.
It was good luck I tested the transistors before I installed them (per the suggestion to match them). I have never done that before. If I hadn't now, more serious malfunction could have been caused, as one of the faulty transistors was shorted.
That freeze spray works very nicely to detect errors BTW. It may even help to get a drink cold fast 🙂
Hi halfgaar,
For the low cost of these transistors, and the high cost of shipping I normally order 10 or 20 at a time. Sometimes more.
Nothing like being able to do a great job! You will find in many cases the same transistors being used over and over. And they may sub for each other once you look them up.
Glad you found the fault though!
-Chris
For the low cost of these transistors, and the high cost of shipping I normally order 10 or 20 at a time. Sometimes more.
Nothing like being able to do a great job! You will find in many cases the same transistors being used over and over. And they may sub for each other once you look them up.
Glad you found the fault though!
-Chris
There were no shipping costs. I've been told that in America, it's normal to pay for shipping, even when ordering at a store (instead of post order), but that's not usual here. But, I guess the parts themselves are more expensive to compensate 🙂
Anyway, there is indeed nothing like being able to do a great job. Luckily you guys here have enough repair experience to suggest the right place to look 🙂 Repairing is quite different from building from scratch...
Anyway, there is indeed nothing like being able to do a great job. Luckily you guys here have enough repair experience to suggest the right place to look 🙂 Repairing is quite different from building from scratch...
Hi halfgaar,
What part numbers did you order, and how much did they cost?
-Chris
The assumption in service is that the item worked at some point in time. This is not always true. Very amusing when the device has a QC sticker and is in a state where it very obviously never worked.
What part numbers did you order, and how much did they cost?
-Chris
I ordered 3x: "2SA 1123" (I got 4), and they cost € 0.95 (USD 1.22151 and 1.35111221 Canadian dollar according to google currency conversion) each.
They usually have some quantum discount, sometimes starting at 5, and sometimes at 10. I don't know how much this particular type would have cost when I had ordered enough for a discount.
Hi halfgaar,
One thing to keep in mind is that you can always use extras for DIY. Just keep that in the back of your mind when ordering parts. Some may open up ideas for you.
-Chris
One thing to keep in mind is that you can always use extras for DIY. Just keep that in the back of your mind when ordering parts. Some may open up ideas for you.
-Chris
I usually do, indeed, although I guess I have less of a tendancy to collect spare transistors than say, ceramic capacitors and resistors. I have quite a bunch of those already...
halfgaar said:
Ouch! Oh well, I'd be willing to pay that price if they could be certified to be 100% genuine...
Street prices here for small-signal trannies may go for US$ 0.10 or 0.20... but, absolutely no idea where they come from...
Cheers!
Hi Clem,
My cost for those in quantity ran around 0.70~ 0.80 CDN each. But they were guarantied to be real.
Now I know why it's so important to you to find the good and bad ones! At those prices, I'd buy 100 per type as long as they were real.
-Chris
My cost for those in quantity ran around 0.70~ 0.80 CDN each. But they were guarantied to be real.
Now I know why it's so important to you to find the good and bad ones! At those prices, I'd buy 100 per type as long as they were real.
-Chris
Hi Chris,
Yeah, win some lose some... I can't even get any low-ESR capacitors to fix up my motherboard. No one knows what I'm talking about... sigh...
Cheers!
Clem
Yeah, win some lose some... I can't even get any low-ESR capacitors to fix up my motherboard. No one knows what I'm talking about... sigh...
Cheers!
Clem
Hmm, could it be possible they ordered a fake batch of those transistors, and that that's why two were broken and two had such different Hfe values? Perhaps I should inform the shop about it.
I don't know about other service desks around the world, but here, local support of MSI, abit, chaintech and all the others are willing to send you free replacement caps, without questions. I can just send them a list of caps and an address and the next day (or perhaps a bit later) they're here. It's a bit of an effort to find the correct support department, but it works.
I don't know about other service desks around the world, but here, local support of MSI, abit, chaintech and all the others are willing to send you free replacement caps, without questions. I can just send them a list of caps and an address and the next day (or perhaps a bit later) they're here. It's a bit of an effort to find the correct support department, but it works.
halfgaar said:
Wow, that's service! I don't think they even do that in the USA... Here, that is absolutely out of the question. Bigger sigh...
Send a couple of those caps to the Philippines! 🙂
Cheers
oops sorry for the off-topic posts guys...
Hi Clem, halfgaar,
SOP in North America is to send in the motherboard, wait for them to confirm the fault, then wait longer to (maybe) get a replacement. You have to get an RMA number before sending the board in. That translates to a few weeks without a computer.
BTW, your XP lic. is instantly bad and you then have to call uSoft and fight them.
Ever wonder why people just buy an entire new computer over here?
-Chris
SOP in North America is to send in the motherboard, wait for them to confirm the fault, then wait longer to (maybe) get a replacement. You have to get an RMA number before sending the board in. That translates to a few weeks without a computer.
BTW, your XP lic. is instantly bad and you then have to call uSoft and fight them.
Ever wonder why people just buy an entire new computer over here?
-Chris
Interesting..so many possibilities...i had not read the entire thread.
I had the problem once...was a resistor..broken inside...the lead was loosen...that was my noise.
The component was replaced, when dessoldered the lead was fixed in the pc board, and the transistor body was removed with only one lead attached to it.
Replaced the broken resistor everything runned fine...i suppose someone may have suggested to move resistors.
regards,
Carlos
I had the problem once...was a resistor..broken inside...the lead was loosen...that was my noise.
The component was replaced, when dessoldered the lead was fixed in the pc board, and the transistor body was removed with only one lead attached to it.
Replaced the broken resistor everything runned fine...i suppose someone may have suggested to move resistors.
regards,
Carlos
That will only work for boards with warrenty, of course. Warrenty claims are usually delt with by the shops themselves overhere, so you can instanty get a replacement board.
But I just repaired an MSI BX master (quite old...). Warrenty doesn't matter. I don't even have to say what I need the caps for, I can just get them...
Licences and corporate control... Am I glad I use Linux...
But I just repaired an MSI BX master (quite old...). Warrenty doesn't matter. I don't even have to say what I need the caps for, I can just get them...
Licences and corporate control... Am I glad I use Linux...
Re: Interesting..so many possibilities...i had not read the entire thread.
Good one!
I bought a 1W resistor just the other day - before I even put it into the pcb, the resistor's end cap (with the leg) came off...
Manufacturing may test the ohmic resistance for tolerance, but I wonder if there's a machine that gives it a 'wiggle' test before it goes out to distributors!
Cheers!!
Clem
destroyer X said:
Good one!
I bought a 1W resistor just the other day - before I even put it into the pcb, the resistor's end cap (with the leg) came off...
Manufacturing may test the ohmic resistance for tolerance, but I wonder if there's a machine that gives it a 'wiggle' test before it goes out to distributors!
Cheers!!
Clem