hi,im trying to identify this cap for replacement but don't know the value ect... can you help me,thank you this is in a AB763 Deluxe Reverb guitar amp
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Which tube is this socket? -
Looks like it is a .001 maybe 250 volts the voltage should be below the value, replace with a .001 1kv ceramic disc should be fine.
Here is a .005 3kv with the same markings for referenceAttached FilesLast edited by R_J; 08-08-2024, 03:49 PM.Comment
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I don't see the caps in AB763 pics, and it's 6V6 all the way to quad 6L6 though. Nor in any schematics- that cap does not go across the control grid, after the stopper resistor unless you want a Tesla coil.
So I say it's somebody's mod, and it would kill the high end. There should be two of them and they need to be the same, replaced in a pair.
The AA769 has them as 2,000pF. At the control grid even 100V part is OK. I would use a low distortion dielectric C0G or PP.
If the socket arced and carbon tracked, I would replace it with a ceramic one. Maybe add (Marshall) protection diodes if it's heavy overdrive on the output stage to protect it.
Upsize the 470Ω screen resistors too to a few watts. Looks alike somebody played metal on it lol.
Fender amp schematics, layout etcLast edited by redwire; 08-08-2024, 07:50 PM.Comment
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Just adding this information, I found
I did find pictures with those caps installed (maybe AA1069 model or were added later?) and I found this site that has many mods where they remove those disc caps ( All the Differences Between the AB763 Vibroverb and AA1069 Bandmaster Reverb) AB763 Mods (robrobinette.com)
Seems to be endless modifications as usualLast edited by R_J; 08-08-2024, 10:10 PM.Comment
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thank you everybody for these response,and yes i think it was a mod...since i was not finding anything on diagram also. socket v8 6v6gt tube is the bad one.all 2 resistors 740 and 1.5k are burn,this cap is burn,and did have a couple wires to change ,and tube is ok,so hope to replace them and work again,thank you for your helpComment
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The 1,500Ω grid-stop resistors should never burn up! If they did then something is very wrong.
The 470Ω screen resistors will burn if the amp is overdriven too hard. People upsize to 3W parts.
If someone was in there doing mods, check if they are done right or not. That cap is only on two models and none with 6V6, it's not necessary.
Bad mods can make the amp malfunction and it's a mess. People try copying other circuits from other models and if you don't know what you are doing, it's a mess.
Fender was very good giving layout drawings. I would check the chassis you have close for other changes, if a guy did bad mods then I pull that garbage out.Comment
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thanks redwire i will do as said,i will check with the owner what mod where made and where.Comment
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