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Need a Schematic? Check the Vault *MP-1 Classic Schematics Just Added!!

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Topics - Fdesalvo

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I posted this in the wrong area prior.

After installing a socketed OPA2604 into U4 the following occurred:

-On some patches, Master and EQ LEDs would light up. On some, the master led would turn off after lowering the master via the front panel.
-No changes in noise level when adjusting OD1 via the front panel
-Low, pulsating bass tone/oscillations on some patches

After installing the socket, I used a meter to confirm continuity between the pins and traces and also between the opamp legs and traces. I have a 4 pack of new BB/TI OPA2604AP’s and each one responded the same way.

Any idea of similar experiences?

Hi, all.

Long time lurker. So glad this site iis back up.

Ive got a v2 MP1 and am refreshing the caps and have moved on to the fets/jfets/etc. I have a couple of questions due to my ignorance of all things FET and the dearth of info for the v2 online.

1. I am unable to locate replacements for Q1/2: K364 GR91. Are these “2SK364’s” that I’m seeing referenced elsewhere?  I have some updated equivalents on hand (LSK170’s) if this is the case.

2. Q3/4 are MPSA92’s. I have these on hand, but is there a higher performing equivalent out there?

Many thanks for the help/education. I build all analog vacuum tube amps and do restorations on a variety of preamps, but venturing into the digital/ss realm has been eye-opening, if not exciting.

Best regards,

“Ruining good moments since 1975.”

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