Gents I think I have finally found a genuinely buggered amplifier in the local classifieds.
It’s being sold for practically nothing and this time the chap assured me it is faulty and is being sold for spares and repair.
I’m waiting for a description of what is wrong with it but as suggested by Mr Babin, is there anything in particular to watch out for with these amps?
It’s being sold for practically nothing and this time the chap assured me it is faulty and is being sold for spares and repair.
I’m waiting for a description of what is wrong with it but as suggested by Mr Babin, is there anything in particular to watch out for with these amps?
These are very complex amps. They use a lot of surface mount parts which can complicate repairs if you're not used to working with them. If you have to pull a driver board, I'd strongly recommend using ChipQuik and buying a good desoldering pump (DS017).
If it has comex switches, they can give a lot of trouble but can generally be cleaned with a good contact cleaner (deoxit D5 is OK).
Has it been under water?
Is it complete (no one has tried to repair it)?
Do a search on the forum for 300/2 and 300/4 to see what you're in for if you buy it.
If it has comex switches, they can give a lot of trouble but can generally be cleaned with a good contact cleaner (deoxit D5 is OK).
Has it been under water?
Is it complete (no one has tried to repair it)?
Do a search on the forum for 300/2 and 300/4 to see what you're in for if you buy it.
My dad has a hot air soldering thing and a soldier pump I can borrow. He has a few oscilloscopes too but has given me a Fluke 105b scope meter to keep, I’m reading the manual and learning how to use that at the moment.
Complexity isn’t a good thing for a starting project but then I suppose the end result is worth it. Will do some searches.
Complexity isn’t a good thing for a starting project but then I suppose the end result is worth it. Will do some searches.
I have a hot air station and only VERY rarely use it for SMD parts. A good soldering iron works better for me.
A scopemeter is better than nothing and the fact that is can be run from batteries (no connection to the mains) makes it useful for checking drive signals. If you can borrow a scope with a CRT display, that's what I'd suggest you do. It doesn't have to be anything more than 20MHz. Actually, a 2MHZ like one of the tek 5100 series would work if in good working order.
A scopemeter is better than nothing and the fact that is can be run from batteries (no connection to the mains) makes it useful for checking drive signals. If you can borrow a scope with a CRT display, that's what I'd suggest you do. It doesn't have to be anything more than 20MHz. Actually, a 2MHZ like one of the tek 5100 series would work if in good working order.
Thanks, it seems that corroded vias, dodgy 47ohm resistors on the driver boards and fired output transistors in the main.
I understand your question about water damage in consequent.
I do some more research but from what I understand it’s a decent amp and it might be worth a punt.
I can borrow any number of crt oscilloscopes if necessary, he had a good Philips DSO that I can use if necessary.
Is it worth thinking ahead and ordering some power resistors to make a dummy load for testing amps more generally? I have a few hifi amps to repair/restore too...
I understand your question about water damage in consequent.
I do some more research but from what I understand it’s a decent amp and it might be worth a punt.
I can borrow any number of crt oscilloscopes if necessary, he had a good Philips DSO that I can use if necessary.
Is it worth thinking ahead and ordering some power resistors to make a dummy load for testing amps more generally? I have a few hifi amps to repair/restore too...
Where are the corroded vias?
Some cars flood with the amps in the 'boot'. If an amp has power applied and is in water, it's often impractical to repair.
DSO is only VERY rarely needed. I can't force you to use a simple oscope but that's what I recommend you use. If you read the basic repair page, you saw the waveforms from a 100MHz scope and one from a VERY simple 2MHz scope and there was virtually no difference.
Worth a punt? For me, punting an amp means choosing not to repair it.
Some cars flood with the amps in the 'boot'. If an amp has power applied and is in water, it's often impractical to repair.
DSO is only VERY rarely needed. I can't force you to use a simple oscope but that's what I recommend you use. If you read the basic repair page, you saw the waveforms from a 100MHz scope and one from a VERY simple 2MHz scope and there was virtually no difference.
Worth a punt? For me, punting an amp means choosing not to repair it.
Around the power and grounding terminals, according to what I have seen on an admittedly cursory search.
I also have access to a simple tec 20mhz oscilloscope, I can use that. 🙂
The main issue for me is that the chap is an hour and a half away, my Texan cousins would drive that far on a Wednesday just for barbecue it here it is considered a serious journey...
I also have access to a simple tec 20mhz oscilloscope, I can use that. 🙂
The main issue for me is that the chap is an hour and a half away, my Texan cousins would drive that far on a Wednesday just for barbecue it here it is considered a serious journey...
Can you use a middleman, like a mail service (for a small fee) and have him mail it to you? A lot of mail services also serve as money transfer stations. I don't know if that's true there.
Don't get stuck on this one. You may be find some at thrift shops or pawn shops. Be careful at pawn shops unless you know how they work. Only go in asking for amps that don't work.
Even car audio shops may have some laying around that they will give you just to get rid of them. A good relationship with a car audio shop can get you business doing repairs if you like the work and they don't have a tech.
Don't get stuck on this one. You may be find some at thrift shops or pawn shops. Be careful at pawn shops unless you know how they work. Only go in asking for amps that don't work.
Even car audio shops may have some laying around that they will give you just to get rid of them. A good relationship with a car audio shop can get you business doing repairs if you like the work and they don't have a tech.
I hear you but the trouble is we don’t really have that sort of shop in London, not like the states anyway.
The only way to get one’s hands on knackered gear is to scour the internet small ads.
I shouldn’t be complaining I suppose, I have in the last month bought a “faulty” JBL BP300.1 that works perfectly and a “faulty” Kenwood KAC 9104D that also works perfectly for a grand total of the equivalent of 30 dollars...
I’m running out cars to put amps in...
The only way to get one’s hands on knackered gear is to scour the internet small ads.
I shouldn’t be complaining I suppose, I have in the last month bought a “faulty” JBL BP300.1 that works perfectly and a “faulty” Kenwood KAC 9104D that also works perfectly for a grand total of the equivalent of 30 dollars...
I’m running out cars to put amps in...
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