Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Tubes and Hybrids => Topic started by: Hawk on May 10, 2018, 11:06:53 AM

Title: Fender Deluxe AB763... vibrato not working
Post by: Hawk on May 10, 2018, 11:06:53 AM
Vibrato not working..can hear a very feint ticking sound. Suggestions?

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Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Hawk on May 10, 2018, 11:47:02 AM
According to the layout the voltages are correct on the "diode" side of the opto...there appears to be a resistive element in the opto, anyone know what value that should be?...

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Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Jazz P Bass on May 10, 2018, 12:14:44 PM
The resistive element should read around 1 Meg ohm when dark.

The reading should drop (not too sure how far) when light shines on it.
Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Hawk on May 10, 2018, 12:28:07 PM
Can't see a light. Should it be fairly obvious?

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Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Hawk on May 10, 2018, 01:15:09 PM
Definitely not seeing a light. Tried adjusting the intensity and nothing. Measured 68k not 1 meg...the plate end of the 10meg resistor  measures 190v whereas the layout shows 380v...the 10 meg is good and the voltage on the other side of the 10 meg is good...does a faulty opto effect the plate voltage?....I checked the resistance on the lightbulb side and found 13 Megohms...

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Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Enzo on May 10, 2018, 04:27:48 PM
It is a neon lamp in there, so no continuity expected.
Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Hawk on May 10, 2018, 04:30:23 PM
Thanks Enzo. I've ordered a new one. Hopefully it's the problem... haven't had any experience repairing these so first time for everything

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Title: Re: Fender Deluxe AB763... vibrato not working
Post by: Hawk on May 18, 2018, 11:27:07 AM
Opto installed. All is well!

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