Thanks 🙂
I think you have a very dead multimeter but to make certain, I'll repeat the experiment myself, I also have a couple multimeters like that one (2 AC scales) and they are all the same.
Don't know whether there's a giant factory churning out millions with different brands or it's a straight from the datasheet "multimeter on a chip" application and many make them, but they all have the same specs, so my results should match what you should be getting.
I sort of got used to them 🙁 , because my customers are Rock bands and sometimes I'm onstage , they have some problem, I didn't bring my toolbox and when I ask for a multimeter they smile proudly and say: "yup ... we got one" (usually to check batteries and cables or whether an outlet is live) ... and bring one of these 🙁 .
Oh well, still better than testing batteries with the tongue 😱
I think you have a very dead multimeter but to make certain, I'll repeat the experiment myself, I also have a couple multimeters like that one (2 AC scales) and they are all the same.
Don't know whether there's a giant factory churning out millions with different brands or it's a straight from the datasheet "multimeter on a chip" application and many make them, but they all have the same specs, so my results should match what you should be getting.
I sort of got used to them 🙁 , because my customers are Rock bands and sometimes I'm onstage , they have some problem, I didn't bring my toolbox and when I ask for a multimeter they smile proudly and say: "yup ... we got one" (usually to check batteries and cables or whether an outlet is live) ... and bring one of these 🙁 .
Oh well, still better than testing batteries with the tongue 😱
I'll measure a working amp as well to make sure.
And it measures house AC @ 123 v ac just fine.
Cool.
Srinath.
And it measures house AC @ 123 v ac just fine.
Cool.
Srinath.
I got 0 out of my working denon avr97. 0 in both channels.
You know how the meter can meaure AC where there is DC and vice versa - maybe I have a dc offset that shows as AC in the louder channel ... which means the louder channel is bad.
Thanks.
Srinath.
You know how the meter can meaure AC where there is DC and vice versa - maybe I have a dc offset that shows as AC in the louder channel ... which means the louder channel is bad.
Thanks.
Srinath.
Interesting. I never knew antimony and bromine could enhance purple plague. Thanks.
I thought most power semi manu's used a glob top to protect the metalization and the bonds, and that most used aluminum for gates and bases, at least in power product.
jn
TO-3 and TO-39 are hermetic - no glop-top. Early non-molded TO-220's were glop-top with epoxy, then the case was glued on separately. I hated those - the leads liked to break off easily. Fakes use silicone for glop top in pretty much everything. Their TO-3 cans fall apart easily so they can't possibly pass gross leak let alone hermetic. And they use the cheapest possible epoxy for the TO-264, so I'm sure Tg is on the low side. In either case the silicone probably helps to an extent.
They really don't like using gold in Si devices. They're pretty much all aluminum with some copper. Bond wires are aluminum.
They really don't like using gold in Si devices. They're pretty much all aluminum with some copper. Bond wires are aluminum.
I got 2.7v ac out of another working amp.
I have no idea why its reading what its reading.
Cool.
Srinath.
I have no idea why its reading what its reading.
Cool.
Srinath.
Circuit attached.
Is there something like a "pre amp section" in this amp.
Does a transistor (pre driver) work to strengthen the signal before the C4000/5000 work to make it more ??
Which is it ?
I see FT317, 417, MJE3055, MPS8, MPS8097 (or whatever that scrawl is).
Any of those being dead - would it make one channel lose 3 db ?
Thanks.
Srinath.
Is there something like a "pre amp section" in this amp.
Does a transistor (pre driver) work to strengthen the signal before the C4000/5000 work to make it more ??
Which is it ?
I see FT317, 417, MJE3055, MPS8, MPS8097 (or whatever that scrawl is).
Any of those being dead - would it make one channel lose 3 db ?
Thanks.
Srinath.
Usually when both channels appear to be working and there's a difference in output levels the feedback path is the first thing to look at. But you don't have a scope or signal generator to look at any of the signals so I don't know what to suggest, I'm not a throw parts at it until it's fixed type guy. You sure can't learn anything by throwing parts at it willy nilly. You seem to go thru lots audio equipment but without test equipment I'm amazed you get anything repaired, or at least correctly. What's up with the last Carver?
Craig
Craig
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I'm surprised the whole thing hasn't gone up in smoke yet. One solder bridge, lifted PCB trace, or shorted TO-3 insulator and you have real problems to deal with. When you get those with one of these triac-controlled power supplies, you *won't* fix it without proper test equipment.
Add in the typical PITA Carver mechanical layout you have still a challenge even if you know your way around them.
Craig
Craig
I tried to repair a "cube".... once. Never again. It ended with "Let me re-build this with a conventional power supply with three toroids in series". The mag coil just didn't like the light bulb limiter, and I wasn't touching it with a 10 foot pole (or 100 foot extension cord) without one.
Yes, the "cube" is a real PITA. Trying to do a neat job with the heat sink compound is next to impossible. That's one of the amps you have to disassemble, HOPE you find all of the problems, reassemble, and plug it in and hope for the best. Impossible to measure anything as you can't get to anything. Setting the idle current is pretty exciting too.
Craig
Craig
He he he ... I will fix it, I am not as crazy as I sound. I come form a non electronic background, however I have fixed in the last few days, an Akai AA 6600, am pretty much close to analyzing a Kenwood KR 9600 for why one channel is dead and so on.
I'll probably follow the same method on this that I used on the AA6600.
Find left channel transistor 1 and right channel transistor 1 and swap the 2.
If it flips the weak channel - you found your culprit, if it didn't, go on to the next. In fact I'll put both of em in my transistor tester ... the AA6600's C931 from the bad channel read bad on it, so I know before I put the one form the other channel it was bad so it prevented me from putting it in the good chanel.
Stuff wont go up in smoke in my hands ...
OK yea that carver M 1.0 t was a mess. However I have eliminated that it was fine before I got it.
The M 200 I brought back from the grave.
Its now alive, but limping along.
I was just looking for the most likely source for the missing 3 db.
Oh yea the accurate DMM arrived, though I think I'll not need it quite, I can hear the problem just fine.
Cool.
Srinath.
I'll probably follow the same method on this that I used on the AA6600.
Find left channel transistor 1 and right channel transistor 1 and swap the 2.
If it flips the weak channel - you found your culprit, if it didn't, go on to the next. In fact I'll put both of em in my transistor tester ... the AA6600's C931 from the bad channel read bad on it, so I know before I put the one form the other channel it was bad so it prevented me from putting it in the good chanel.
Stuff wont go up in smoke in my hands ...
OK yea that carver M 1.0 t was a mess. However I have eliminated that it was fine before I got it.
The M 200 I brought back from the grave.
Its now alive, but limping along.
I was just looking for the most likely source for the missing 3 db.
Oh yea the accurate DMM arrived, though I think I'll not need it quite, I can hear the problem just fine.
Cool.
Srinath.
If it turns out to be a bad pot or oxidized input jack you will probably hear the laughter from the other side of the world.
No pots in this bugger, oxidised RCA - unlikely.
Why ? You do realize that I have been beating on this for weeks now - nothing like that is on this amp.
I've swapped all 4 power transistors 1 at a time, to try to isolate this problem, and generally replaced quite a few components just to get it working even before the differential output issue.
The first step is to figure out if its the zobel.
Then I'd swap the pre drivers methodically.
Cool.
Srinath.
Why ? You do realize that I have been beating on this for weeks now - nothing like that is on this amp.
I've swapped all 4 power transistors 1 at a time, to try to isolate this problem, and generally replaced quite a few components just to get it working even before the differential output issue.
The first step is to figure out if its the zobel.
Then I'd swap the pre drivers methodically.
Cool.
Srinath.
But with the right test equipment it's a 10 minute job. You can't hear different parts of the circuit with your ears but you can see them with an o'scope. Swapping parts from channel to channel is a good way to end up 2 bad channels.
Craig
Craig
Yea true. But I dont know how to use an O'scope.
I have I tihnk 2 of em, but dunno to use em. I have my eye on a digital scope, so I can connect it and it will do the rest.
I however eliminated the Zobel from the equation.
Swapping the wires to the speaker terminals flipped the side that was weak. So the Zobel is off the hook.
Cool.
Srinath.
I have I tihnk 2 of em, but dunno to use em. I have my eye on a digital scope, so I can connect it and it will do the rest.
I however eliminated the Zobel from the equation.
Swapping the wires to the speaker terminals flipped the side that was weak. So the Zobel is off the hook.
Cool.
Srinath.
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Put the parts from that circuit please
Could you tell me which parts are in the feedback circuit ?
I would be moving it left to right basically, evaluvating it against itself.
Thanks.
Srinath.
Could you tell me which parts are in the feedback circuit ?
I would be moving it left to right basically, evaluvating it against itself.
Thanks.
Srinath.
A bad transistor never never never results in the symptoms you describe (gain imbalance between channels) if it is not oscillating. I thought we made that clear on the first page.
If you've swapped "other stuff" - perhaps a feedback resistor or just something in the front end signal path got dyslexic? Swap two bands and it's a totally different value. Green often looks like blue, and orange like red or brown. If a resistor got stressed it can even change value. Bad electrolyic in the signal path or feedback could also be at fault. That's the sort of thing you should be looking for - before you blow up both channels by accident swapping perfectly good transistors.
With an oscilloscope it would be a 10 minute job.
No I didn't swap anything between channels or even replace any of those to get it working. Of course who knows what was done to it before I got it.
Transistor swapping gave me 6 db less at one point. I had to unswap it to get 3 db.
Let me put it this way, the best, highest output transistors are in the weak channel and its 3 db under. I can lose 3 more db now at will in minutes. I just swap the 2 in the middle to the other side and voila ... even crappier.
Cool.
Srinath.
Transistor swapping gave me 6 db less at one point. I had to unswap it to get 3 db.
Let me put it this way, the best, highest output transistors are in the weak channel and its 3 db under. I can lose 3 more db now at will in minutes. I just swap the 2 in the middle to the other side and voila ... even crappier.
Cool.
Srinath.
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