| Electronics > Repair |
| What more i can do? |
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| 222Lab_Test222:
--- Quote from: Harry_22 on December 12, 2024, 06:09:31 am --- What makes me despondent is that sooner or later the topic will be closed and our communication will end. --- End quote --- Why will it be closed? :scared: :scared: |
| Harry_22:
--- Quote from: 222Lab_Test222 on December 12, 2024, 07:52:21 am --- --- Quote from: Harry_22 on December 12, 2024, 05:41:23 am ---Ok, good! Where the trace? --- End quote --- I don't have 10K resistance, I need to buy one. --- End quote --- Take another one from 1k. Take several in series, parallel. |
| m k:
--- Quote from: Harry_22 on December 09, 2024, 09:19:26 pm ---On the working machine the data sequence is ODE9h, 00F8h, 0000h, 0000h... On the not-working is 0D0Dh, 0000h, 0000h... --- End quote --- 2 1 4 3 data would be JMP(rel16) F80D. Faulty machine is doubling other side of 16 bit data. |
| Harry_22:
So, the results of signal collection from the Address and Data buses of BIOS EPROM were processed. We found out the following: 1. The Address signals on the working and non-working machines are the same for the first eight clock cycles. 2. Data signals on the lower EPROM differ from the first clock cycle. 3. In the case of mechanical removal of the lower EPROM, all data signals are set to logic level 1. That is, they are pulled up to the power bus by resistors. 4. It follows that it is EPROM chip that sets logical 0 at D5 line in the first clock cycle. 5. I am sure that today you will confirm that nothing prevents the chip from setting logical 0 on D2 bus. Conclusion: Data from EPROM IC16 is loaded with an error despite the fact that all incoming signals are correct. I know that you checked IC16 on a working machine and everything was Ok. It seems that the “Don’t believe your eyes” situation has arisen, but this is not so. I assume that one or more address signals do not reach the chip body and are lost in the crib contacts. The fact that on a non-working machine you see a different breakpoint every time indicates the contact bounce. At high frequencies a fraction of an ohm is sufficient. This is my current version. But I admit that I could be wrong. PS I usually detect bad contacts with a milliohm meter because I need to determine the exact point of failure. Cleaning and reassembling is not the right approach if you are working with customer equipment. Possible solution for you: Check the clamping force of the collets with a some chip leg. Read the working IC16 EPROM with programmer, compare it and make a copy of new 27C2001 for test. |
| CaptDon:
I was given a butchered up Peavey Classic 100 series (there are several similar models with the same name) that uses a pair of 6L6GC tubes as the 50 watt power amp. I restored it back to factory new condition. The combo amp is a twin 12" using the Eminence (code 67 12820PA) speakers. All of the preamp / predrive stages are solid state. Overall the amp indeed has a smoother more pleasing sound than my all solid state twin 12. My friend recently played his Martin acoustic through the Peavey and he said it had a 'nicer sound' than his Fishman. The tube amp although mostly solid state is more pleasing to the ear possibly because it sounds like it has a bit more pronounced low mids without sounding muddy. The amp sounds fast and articulate but not shrill or glassy on the high end. Perhaps the push/pull tube finals add a bit of even harmonic distortion giving all individual notes a fuller and richer sound? The all solid state twin twelve seems glassy and brassy but when reducing the mid and treble controls it goes quickly to a muddy sound. The all solid state amp just doesn't seem as rich or full, overall very lifeless compared to the tube amp. All of my P.A. gear for front of house and monitors are solid state using SMPS power supplies and class G multi-voltage output laddering. Many of the amps are Carver PM-2.0T models. They are Clair Brothers Touring modified with additional mods by me. |
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