Hi All..
I usually work on Comms equipment and Lab/test gear and avoid Tv.. Radio.. Laptop.. and Amp repair like the plague but a neighbour took advantage....
So this ALTO T-212s is a class D Amp delivering enough power to get to the Moon (according to the makers
).. just 'broke' the guy said. So reluctantly I said ok leave it and when I get some time I'll take a look.
So.. eventually i did some tests.. preamp/input circuit is fine.. smps is working.. 2 pairs of o/p mosfets also fine. All regulators working except the -12v reg.. so I renewed that and got the rail back.. but still no output.
Problem is.. this 'b thing' is wasting my time because I can't find a schematic or service manual and to make matters worse there's lots of black goo all over the pcb hiding smd components from view so whatever is under the goo I don't know and can't test..! Of course I know they had to put the goo there for stress reasons.. but now it's stressing me..!
Originally before even opening the Amp up I was expecting to find dead Mosfets in the smps or output stages.. but no.. and now many sets of 2hr stints and testing what I can get at hasn't helped.
The output drivers are a pair of IRS2092s which I've not worked with before and I'm old-school class A/B bred. So although I know how class D works I had to do some reading up on the IRS2092s and the strange choice of a ballast IC for the switcher in the smps. The output pairs of mosfets being driven by the IRS2092s's are all IRF4020's. Testing on their gates with the scope I got no squarewave so turned to the 2092s driver chips. So it looks like I should find around ±45v~62v on pins 1 & 6 of the 2092s's but I'm only getting around ±14v and because of all the black goo on the board can't get at the 'hidden' nearby components. I started removing some of the goo but it's wasting my time and this is a freebee repair for a neighbour(!)..
It's wasting my time but I hate to be beaten..!
So has anyone got a schematic or some info relating to this specific Amp that might help me nail this problem..? ..or anyone who's worked on the T-212 Amp and can offer up the 'usual suspects' for failure..?
I'd be very grateful
as it would save me wasting hours more removing the goo.. because my ocd wont let me give up!
Tony
I usually work on Comms equipment and Lab/test gear and avoid Tv.. Radio.. Laptop.. and Amp repair like the plague but a neighbour took advantage....
So this ALTO T-212s is a class D Amp delivering enough power to get to the Moon (according to the makers
).. just 'broke' the guy said. So reluctantly I said ok leave it and when I get some time I'll take a look.So.. eventually i did some tests.. preamp/input circuit is fine.. smps is working.. 2 pairs of o/p mosfets also fine. All regulators working except the -12v reg.. so I renewed that and got the rail back.. but still no output.
Problem is.. this 'b thing' is wasting my time because I can't find a schematic or service manual and to make matters worse there's lots of black goo all over the pcb hiding smd components from view so whatever is under the goo I don't know and can't test..! Of course I know they had to put the goo there for stress reasons.. but now it's stressing me..!
Originally before even opening the Amp up I was expecting to find dead Mosfets in the smps or output stages.. but no.. and now many sets of 2hr stints and testing what I can get at hasn't helped.
The output drivers are a pair of IRS2092s which I've not worked with before and I'm old-school class A/B bred. So although I know how class D works I had to do some reading up on the IRS2092s and the strange choice of a ballast IC for the switcher in the smps. The output pairs of mosfets being driven by the IRS2092s's are all IRF4020's. Testing on their gates with the scope I got no squarewave so turned to the 2092s driver chips. So it looks like I should find around ±45v~62v on pins 1 & 6 of the 2092s's but I'm only getting around ±14v and because of all the black goo on the board can't get at the 'hidden' nearby components. I started removing some of the goo but it's wasting my time and this is a freebee repair for a neighbour(!)..
It's wasting my time but I hate to be beaten..!
So has anyone got a schematic or some info relating to this specific Amp that might help me nail this problem..? ..or anyone who's worked on the T-212 Amp and can offer up the 'usual suspects' for failure..?
I'd be very grateful
as it would save me wasting hours more removing the goo.. because my ocd wont let me give up!Tony
I hate to loose like that too...............struggle on and you will be victor.......i sat once two days fitting new 2092s chips........only to be told by a friend that the five 2092s chips i bought were fake ...........i waited 3 days for another order from another spares supplier and guess what happened ......it took me 5 fives to remove the fake spare and replace it ..and switched on ........the amp module started idling .......DAM FAKE SPARES ..... ...MY ADVISE ...BEWARE OF FAKES PLEASE!
You will find the black goo is now conductive due to it being porous.
Not a lot can be done with these substandard builds. The circuit is fine but the glue they use is not.
If the 2092 is not running, there will be about full rail on pin 16. Pin 10 is negative rail and pin 12 must have +12volts with respect to pin 10, or t won't work.
No idea of your particular schematic but it won't be far from Infineon's layout; https://www.infineon.com/dgdl/irs2092.pdf?fileId=5546d462533600a401535675f1be2790
Not a lot can be done with these substandard builds. The circuit is fine but the glue they use is not.
If the 2092 is not running, there will be about full rail on pin 16. Pin 10 is negative rail and pin 12 must have +12volts with respect to pin 10, or t won't work.
No idea of your particular schematic but it won't be far from Infineon's layout; https://www.infineon.com/dgdl/irs2092.pdf?fileId=5546d462533600a401535675f1be2790
Thanks for the reply and encouragement..
I will keep going back to it but it has taken a back seat to more important things since my post..Fakes.. yes.. had my share of them too. Fake MC145106 PLL chips and fake SRF7043's of which I bought several and they weren't cheap too.. oh and recently fake 1N34A Germanium diodes of which I bought 50!
For everyone.. a genuine Germanium diode will be 7mm in length and no less !!
I'm thinking to take a closer look at this ballast chip being used for the SMPS because it has an inhibit pin.. so I'll take a look at that to make sure it's not being activated.. maybe tomorrow.. or the next day...
cheers
Tony
Hey thanks for the information
I will test those 2092's again to see what voltages are there and compare with your info.
Thanks also for the link which I will take a look at after posting this reply to you.. Hope it will renew my enthusiasm as I can't even stand to look at that amp at the moment and have been actively avoiding it.. haha..
Interesting about the goo and I will have a test of that with the HiRes Fluke. Have heard of glues going bad many times but it didn't actually cross my mind to test the goo in this amp which is everywhere!.. Also there are thermal pads for all the mosfets but someone has put thermal paste all over the place too.. and that is annoying because it got on everything.. including me
I'll have a look at that link and then I'll test a few things and post back maybe tomorrow..
cheers
Tony
Just to update...
Owner bought another Amp and failed to tell me until weeks later. So another time-waster.. and this is why I didn't want to take the repair on in the first place and why I don't do repairs for individuals..!
Thanks to all who contributed.
@Tdlunsfo: If he doesn't collect the Amp I may still investigate the fault but only as time permits and just because I don't like to be beaten..
Owner bought another Amp and failed to tell me until weeks later. So another time-waster.. and this is why I didn't want to take the repair on in the first place and why I don't do repairs for individuals..!
Thanks to all who contributed.
@Tdlunsfo: If he doesn't collect the Amp I may still investigate the fault but only as time permits and just because I don't like to be beaten..
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