ART710A, RCF monitor speaker schematic/advice please

[zen]

HI all

It's yet another monitor speaker.

Trying to rebuild the audio circuitry.

The story so far, after removing loads of glue.

MOS3 & MOS4, both type IRFB4229, S/C

Also replaced Gate drive chip for them, U7 type IRS20955S, plus U3 which is same chip type for a different set of FETS.

Anyone have experience working on this model?

[zen]

Re: ART710A, RCF monitor speaker schematic/advice please

Require value of R63.

Measures 2K2 but has been corroded by glue & need to know if it's ok.

[zen]

Re: ART710A, RCF monitor speaker schematic/advice please

Suspect R63 is correct as there is no real link from it to damaged parts of circuitry.

Powered speaker by slowly increasing the AV supply using a variac.

Fully powered, but no audio for around 1 minute, then music from tweeter, but not main driver.

Shortly after spotted some smoke & hopefully powered off before damage occurred.

Suspect main driver faulty.

Tweeter coil measures 5R4

Drive coil measures 3R3

[zen]

Re: ART710A, RCF monitor speaker schematic/advice please

A previously found corroded resistor that I must have replaced by error with wrong value.

R62 which is on the VCC line to U7 is where I went wrong.

Used a 4K7, but when I compared the mirror circuitry for the tweeter drive value is 47K.

Replaced with correct value & now main driver producing audio, but the main output FETS getting quite hot.

[zen]

Re: ART710A, RCF monitor speaker schematic/advice please

One of the previously replaced FETS had shorted therefore swapped out both plus U7

[zen]

Re: ART710A, RCF monitor speaker schematic/advice please

MOS 3 seems to be the FET that keep failing, then DC finds its way to the tweeter, which has in turn blown it.Cannot seem to work out why.

Bass driver amp driver circuitry good.

[amingpx]

Re: ART710A, RCF monitor speaker schematic/advice please

Hi.
rcf art 415a protected.
The green and red lights are on together.* *Gate pin in Mosfets ate not enabled through IRS20955s...There is 12 volts in irs . The. I changed ADAU1701 but problem did not solve.

[zen]

Re: ART710A, RCF monitor speaker schematic/advice please

Hi & thanks very much for your input

Will update when i have the opportunity to work on it again.