Many of the 4kw+ amplifiers that have the transistors mounted vertically should be avoided. They have a tendancy to break the leads on the transistors due to poor support of the heavy components.
Many times, the amplifiers will arrive with a single transistor that has a broken leg and it's causing the amp to go into protect. Some people would replace only the 3-5 transistors in the paralleled group of components (and that would be OK on many amps). The problem is... many of the other components have weak leads. If the others begin to break soon after you repair it, you could be married to the amp if you give a warranty because other components' leads will begin to break (and may break during the warranty period).
If you do it correctly and replace all of the weak components, you may have to replace ~$300 worth of parts (actual cost of the parts). If you provide a warranty and the owner blows the amp again, you'll have to buy and replace the parts again.
Some of these amplifiers have 300+ volts across the rails so extreme caution is required when working on them.
Many times, the amplifiers will arrive with a single transistor that has a broken leg and it's causing the amp to go into protect. Some people would replace only the 3-5 transistors in the paralleled group of components (and that would be OK on many amps). The problem is... many of the other components have weak leads. If the others begin to break soon after you repair it, you could be married to the amp if you give a warranty because other components' leads will begin to break (and may break during the warranty period).
If you do it correctly and replace all of the weak components, you may have to replace ~$300 worth of parts (actual cost of the parts). If you provide a warranty and the owner blows the amp again, you'll have to buy and replace the parts again.
Some of these amplifiers have 300+ volts across the rails so extreme caution is required when working on them.
Reeeeeally old amps, ones that have point to point hard wiring.
Sure as sh-t, as soon as you touch it those wires start breaking, one after the other.
Brands,
none really, they all have their own little quirks for dissasembly, known faults, etc.
Worst I've done was an alpine V12.
Part of the fibreglass board was burnt.
I had to cut out the burnt section (5cm square), lay new tracks, drill holes, replace smd's etc.
Took several days, but the customer really wanted this amp fixed.
Sure as sh-t, as soon as you touch it those wires start breaking, one after the other.
Brands,
none really, they all have their own little quirks for dissasembly, known faults, etc.
Worst I've done was an alpine V12.
Part of the fibreglass board was burnt.
I had to cut out the burnt section (5cm square), lay new tracks, drill holes, replace smd's etc.
Took several days, but the customer really wanted this amp fixed.
Perry Babin said:
Clipped said:
grjr said:
MadMutt said:
I agree with all of you. They did all those things to save money and ease construction, and bolster profits
Heres a solution of mine for PPI amps. Lots of work but worth it in the end run...I will have these in quantity shortly. PM me if you have questions or needs
Attachments
justonemoreamp:
Where did you find connectors to fit the tiny holes in the main board? I started to do this but not being able to find a connector put an end to it.
I also found that someone else was selling repalcement boards so that made it less interesting.
Do you have a price on them yet?
Where did you find connectors to fit the tiny holes in the main board? I started to do this but not being able to find a connector put an end to it.
I also found that someone else was selling repalcement boards so that made it less interesting.
Do you have a price on them yet?
Perry Babin said:
Morning Perry,
This is a beta unit, its built on some very exotic 20 gig rated board material. I am currently getting bulk pricing for the boards from several different suppliers both here and offshore, so a per unit price has not been set.
But its in the works, and PPI owners will now have a source to keep their beloved Art, PC, and PCX series amps running forever now.
Currently we have standard spaced gold pins that will right angle mount front or back to the card so as to permit offsetting the card to accommodate the many main board layouts PPI used over the years. Please see attachment, pins are reversible for mounting differences.
I also have pin arrays that slip on and can be soldered with thru hole connections from front to back < these pins are exact matches for the original PPI pins.
I found a batch of 30,000 pieces at a shop local to me here in Silicon Valley.
As soon as board pricing has been setup I can talk cost numbers,,,,,
Attachments
i hate class D amplifiers that use surface mount "direct fets" (i think that's what they're called)
they're not user serviceable due to the absolute tiny size they are...
i think the Alpine PDX series of amplifiers use them...That's how alpine was able to make a powerful amp w/ a small footprint.
they're not user serviceable due to the absolute tiny size they are...
i think the Alpine PDX series of amplifiers use them...That's how alpine was able to make a powerful amp w/ a small footprint.
turbo_slug said:
Most bench tech's are hating on SMD technology but once you get use to it and using tweezers and a SMD rework station, it goes pretty quick and easy.
A fair piece of advice is to get use to it and quick, as things are never going back to the way they were. SMD is not a fad, it's the future and that includes Direct mounted Fets in class D amps. Machine loaded boards, and high speed low cost manufacturing.
Its all about fast cheap assembly time, and in the case of class D amps it has a lot to also do with proper design to prevent parasitic instability and outright amp failure.
SMD is here to stay, and its actually very easy to work with once you get some practice in on it. The real pain is the code markings on the semi's, and no markings on many of the passives. And the big mag lamp in front of your face all day long < makes you lose your tan
grjr said:
Ceramic boards are a pain cause once the 'board' is damaged it's pretty much over.
Extremely hard to repair tracks etc.
And if the 'board' gets a hairline fracture, forget it.
Other problem is they normally wedge them inbetween other components so trying to trace signals on/through them is like trying to pin down a contortionist.
In response to 'justonemoreamp'
I agree that smd is here to stay.
Personally I have no issues with it.
But then I'm used to working with smd.
Just look at headunits. full of smd.
smd can be so much more reliable IF it's done right.
Problems only come when parts are damaged to a point where you can't read the numbering, but that applies to all parts be they smd or not.
This only really falls apart if the faulty part is a 'jungle' smd ic.
But this is more the case of head units, and then you just replace the board (if economical).
justonemoreamp said:
Most bench tech's are hating on SMD technology but once you get use to it and using tweezers and a SMD rework station, it goes pretty quick and easy.
A fair piece of advice is to get use to it and quick, as things are never going back to the way they were. SMD is not a fad, it's the future and that includes Direct mounted Fets in class D amps. Machine loaded boards, and high speed low cost manufacturing.
Its all about fast cheap assembly time, and in the case of class D amps it has a lot to also do with proper design to prevent parasitic instability and outright amp failure.
SMD is here to stay, and its actually very easy to work with once you get some practice in on it. The real pain is the code markings on the semi's, and no markings on many of the passives. And the big mag lamp in front of your face all day long < makes you lose your tan
how do you service a fet that has all the solder joints under the chip? it's like trying to resolder a ball grid array ic. it's much more difficult than soldering a regular surface mount part. basically it's a throwaway item once it's dead. it's also not really something someone can do in a home workshop...
I've tried repairing a brand new harman kardom class d (good ol' crappy harman quality on a receiver which retailed for $2500ish) receiver w/ direct fets...everything was mounted on a coated aluminum board then coated w/ another layer of conformal coating+a huge honking heatsink was glued to the fets. there's basically no way of replacing blown fets. first you'd have to rip off the glued heatsink w/out breaking the board, then you have to get past the coating on the board, then if everything is still fine and dandy, you have to somehow get get the fets off. And that's only half of the work. You still have to somehow figure out how to solder new fets to the board. Sounds easy but the solder joints are unaccessible with any type of regular soldering iron because the joints are under the component like a ball grid array chip. Harman's service manual says to replace the entire daughter board which is basically the entire receiver minus the power supply and DSP stuff.
turbo_slug said:
MadMutt said:
Correctamundo MadMutt, Its all SMD technology and hot air rework stations are the rule not the exception. Reflow ovens have been used for years by rework specialists. Your computer motherboards were all reflowed, along with RF MESHA panels, and just about every automated device built today.
My cards were hand done using pro solder stations that incorporates reflow wands
May I suggest the following brand names: Metcal for hand wand soldering and Hakko 850 series ( affordable) for general purpose hot air rework.
Be prepared to spend between $300.00 to $1,000.00 for good soldering tools.
I have two Metcals, with over 40 different tips, and a Hakko 850 reflow hot air wand with 15 different tips, and a dual Hakko 930 series on my bench for regular grunt solder work. And a small tip no name for passives.
5 different solder suction devices and of course good old solder wick.
I have ultra low temp solder for hot air rework and of course super grade liquid flux, along with 5 different sizes of wire solder. Acetone and pro flux removers and alcohol. Plus the assorted brushes and wands and pic tools.
My bench has more solder tools that anything else on it, and all my tech toys are on a upper shelf.
PS I love my Metcals, most folks do, trouble is the 20 hour tip life or less
Very expensive, but PRO soldering always was...I remember getting beat up by some Canadian fella claiming to be Rockford Fosgate service for Canada, He said it did not take special tools to rework MESHA panels, Later on I found out he was using a 150 watt wedge iron mounted into a bench top drill press to repair MESHA panels . I laughed so hard I hurt
I hope it made you chuckle also
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.