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| Thread ID: 147406 | 2018-12-07 22:00:00 | Electronics Experts Wanted...............Amplifiers..... | SurferJoe46 (51) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 1456317 | 2018-12-09 17:45:00 | I can see the files now, but that schematic doesn't match up with the board, and the PCB layout is totally different. Your photos give the strong impression it's a class D amplifier. Maybe you have a newer, MKII version, or something? |
Agent_24 (57) | ||
| 1456318 | 2018-12-09 18:31:00 | I can see the files now, but that schematic doesn't match up with the board, and the PCB layout is totally different . Your photos give the strong impression it's a class D amplifier . Maybe you have a newer, MKII version, or something? Wow! I finally got them to be seen by persons other than I! Ye-gads! For a while I thought it was because the images had to cross a few time zones or stand upon their heads and I was not taking that into consideration . To the point: If anything, I would more likely have an earlier model . . . . although I, many times, see a few of the ones made before mine in pawn shops and they are truly different . It is a Class D ---> and this I state from interactions with others who own them - but the definition eludes me . I've never been clear on what constitutes a Class A or B or C and I don't truly understand that . However --- I've yet to perform the singularity-defining test to exclude the processor-side of the amp and take a Direct-Out (DI) signal and send it to another amplifier to see if the noise is still there . If so, then the noise should be in the pre-amp or power supply part of the whole product . Once that test is performed, I'll have a better idea what's going on . As far as I know - a transistorized amplifier or power supply can run open-ended with no load on it and still be OK . I know a tube system must 'see' a load on it constantly when it's turned ON . Are those two statements correct? :illogical |
SurferJoe46 (51) | ||
| 1456319 | 2018-12-09 18:38:00 | . I see a possible point of confusion with the visual as you mentioned . . . that these appear to be different units . I have just found that a couple of the special effect amplifier (or modelling amps) are not located on the main boards that exist in any of my pictures . These lie INSIDE the speaker/driver cabinet and as yet have not been photographed by me . That I shall try to accomplish in short order . |
SurferJoe46 (51) | ||
| 1456320 | 2018-12-09 18:45:00 | As I suspected, there are different versions. You have a newer version, while the schematic you have is for the older one. Have a look here; music-electronics-forum.com The "Max 115 poweramp 2012" schematic from there matches up far better with the photos you've shown. I expect it's 99% the same, except a bit higher power (I think 300 vs 200 watts for the Max 112?) |
Agent_24 (57) | ||
| 1456321 | 2018-12-09 19:10:00 | It is a Class D ---> and this I state from interactions with others who own them - but the definition eludes me . I've never been clear on what constitutes a Class A or B or C and I don't truly understand that The main difference between Class D and, well, everything else - is that the amplifier handles a digitized PWM signal of the audio, rather than the usual analogue . This means the speaker drive transistors are either fully ON or OFF rather than in linear mode, and use much less power and heat . The big coils and capacitors on the output to the speaker turn that digital signal back to analogue, otherwise all you'd hear is the speaker catching fire . The whole concept really behaves more like a switch-mode power supply than a traditional linear/analogue amplifier . However --- I've yet to perform the singularity-defining test to exclude the processor-side of the amp and take a Direct-Out (DI) signal and send it to another amplifier to see if the noise is still there . If so, then the noise should be in the pre-amp or power supply part of the whole product . Once that test is performed, I'll have a better idea what's going on . It looks like you could also try unplugging that grey ribbon cable in the photos you posted, then you'll completely isolate the Preamp/EQ/Effects section from the power amp . This should at least narrow down the fault between boards . As far as I know - a transistorized amplifier or power supply can run open-ended with no load on it and still be OK . I know a tube system must 'see' a load on it constantly when it's turned ON . Are those two statements correct? :illogical In general, and in most cases, yes, but it depends on the design - especially with power supplies . |
Agent_24 (57) | ||
| 1456322 | 2018-12-09 19:18:00 | OK - I've gotta go out for a couple of hours and as soon as I get back, I'll disconnect the EFX flatwire. | SurferJoe46 (51) | ||
| 1456323 | 2018-12-09 19:18:00 | I could not find that schem..... I was going a little crazy with the few that i DID find in that I had a miserable time posting them here - somehow that eluded me. Thanks - it's now downloaded into my files both here and on any other device I own. |
SurferJoe46 (51) | ||
| 1456324 | 2018-12-09 19:54:00 | Crackling noise : could be volume/tone pots : give them a good wiggle & see if that induces any noise otherwise could be almost anything, bad cable connections between boards , issues with any part of the digital circuits Class D & digital faults are really well beyond what a home DIY'er could hope to repair. Take it to an amp tech . |
1101 (13337) | ||
| 1456325 | 2018-12-09 19:57:00 | In the previous post on that thread, there is also a link to the rest of the circuit in a file "Max 112_115 Preamp_2012.pdf" which you'll probably also want a copy of. music-electronics-forum.com Crackling noise : could be volume/tone pots : give them a good wiggle & see if that induces any noise otherwise could be almost anything, bad cable connections between boards , issues with any part of the digital circuits Class D & digital faults are really well beyond what a home DIY'er could hope to repair. Take it to an amp tech . The preamp etc is just a bunch of opamps. However the fact that almost everything is surface-mount on a double-sided board is a bigger issue for a DIY'er, in my opinion. Only the power amp section is digital, and everything is integrated into a single IC. You'd just replace it. |
Agent_24 (57) | ||
| 1456326 | 2018-12-09 22:42:00 | Urgh! OK - the next nearest amplifier repair facility that Peavey recommends is in Idaho - the next state to the west of us. There WAS a shop in Missoula - a mere 60 miles or so away, but that phone number is dead now so I assume the worst. If I ship it - it would be very expensive at 50lbs and other fees, and me driving to Idaho would cost a few tanks of fuel and a couple of days for the round trip - then to pick it up with another round trip.... very spend-y. Would it be a gamble to just piggy-back another opamp over one of the suspect ones? Opamps themselves are pretty cheap. I've seen them cut off high on the legs and another opamp/IC chip just soldered to the existing leg-stumps. That way I am not on the solder-bath-flow side. I've still got to perform the test leaving the post-amp out of the chain and use another final amp - of which I have several - and see if the crackling thunder and hiss is still there that way. I'm totally sure it's not a pot making noise as they can be moved from post-to-post and nothing changes during the first 30 seconds or so. |
SurferJoe46 (51) | ||
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