I have a late 60’s Silverface with an AB763 label.
Can someone ID the Actual circuit from the picture?
https://share.icloud.com/photos/0JIo...HGf-bG6Q#Lewes
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I have a late 60’s Silverface with an AB763 label.
Can someone ID the Actual circuit from the picture?
https://share.icloud.com/photos/0JIo...HGf-bG6Q#Lewes
One thing certain -- it is not the AB763 revision. Judging from the bias-balance circuit and the snubber caps on the power-tube sockets, it's likely an AC568, AA769, or AA270 circuit.
There is a Schumacher transformer with a stamp that seems to be from 1969. I wonder how to definitely ID the circuitry? Dad played this amp for years, and it still functions very well.
Use the data found here to determine the amp's pedigree and age......
http://www.superiormusic.com/page195.htm
Tube charts and circuit labels during the Silverface era are probably the least reliable info during that particular era of CBS Fender. And given that info, with only one picture what will you do? It's over 50 years old. It needs some work. based on your question, you should take it to a "qualified" repair tech. They should give you an estimate, and after completing repairs return the replaced parts. You should keep those replaced parts so you can include them if and when you sell the amp.Quote:
Originally Posted by phantomman
I apologize in advance for the "snarky" reply. Chalk it up to over 3 weeks in "social isolation".
The amp is approximately 50 years old. It should be gone over by a tech before you use it. Since you don't seem to be able to figure out which circuit you have, I would suggest you're probably not qualified to assess what needs to be done.
Your dad gave it to you, why not preserve it so you can give it to your son (or daughter}down the road?
Everything works and I am playing through this amp at home. Dad used it professionally, and I used it in a college band. I had it professionally serviced about 10 years ago and it has continued to work well. I don't want to sell the amp, and I have a good idea already what it isn't worth I just want to continue to enjoy playing it and learn more about the circuitry.
I was hoping that someone with knowledge of the vintage circuits might help me sleuth out the actual circuitry, since my research to date suggest to me that this isn't an AB763 SF. Perhaps there is a clue in the stamp on the power transformer - I believe the transformer stamp 606 is Schumacher. There is no chassis number, and there is no two digit production number on the tube label The amp has a drip edge. Perhaps the caps and components may reveal something.
I am posting more detail to see if I can solve the circuit mystery:
Front: https://share.icloud.com/photos/05UA...wz2VT6z5PnvrSg
Back: https://share.icloud.com/photos/0j8q...YMxbfyrkUVpZBg
Top of panel: https://share.icloud.com/photos/0DbY...HI5yRGnT48cfgQ
Choke: https://share.icloud.com/photos/0w65...yP6mr2vZ5_6Nng
Power Transformer: https://share.icloud.com/photos/0dL7...5y5NE1vUiPbxag
Closer details at power tubes:
https://share.icloud.com/photos/0fH9...G5zW3jNyD-KQ5Q
https://share.icloud.com/photos/0J7g...rUPJvf91PQNsvQ
https://share.icloud.com/photos/0oZN...RAl1dSJKeKLEWg
Blue Caps: https://share.icloud.com/photos/099N...QZLtGrq-GblInA
Speaker Detail: https://share.icloud.com/photos/0MAt...1kdpUY4NDUHv2w
Tube Label: https://share.icloud.com/photos/0SMv...Bm7-VkY9Zqq-wQ
Did you even bother to look at the detailed information provided in the link I posted previously?
:kick
Yes, thank you for posting the link. I was not able to ID the circuit from what saw there, but I would like to learn. I was hoping someone who has more experience with this vintage might steer me to a detail that would help the circuit ID. Please forgive my inexperience.
Correlate your amp's serial number to the tables listed and you shall have your answer.
Unfortunately, I do not see a serial number on the chassis. The year has to be late 1967-1969 based on the Silver face, the drip edge and other features. The trouble is, Fender used up left over AB763 labels (since the tubes were the same) in subsequent new circuit editions. A silverface with a AB763 (blackface) circuit is more desirable, but I suspect this is a newer Silverface circuit and not AB763. I would love to be able to pin down the circuit ID.
I'm done.
:wtf
If AC568, AA769, or AA270, how can I distinguish between those?
Auto save? seriously, I wrote a reply, but I'm not writing it again. Beginning to think I don't really belong here.:comp26:
No auto save. Drat!
I would say your amp left Fender as an AC568 circuit.
But now, it's questionable.
The electrolytic caps are questionable. the speaker wiring is questionable.
None of the electrolytic caps are serviceable. The "brown turd" caps are questionable, they need to be tested.
There is so much wrong it needs a qualified tech.
Sorry to be someone who might bring you down, but there appears to be a lot of work for your amp. If you wanted to sell it, your best bet would be a keyboard or pedal steel forum.
In it's present state it won't last long.
So there's a character limit post? Pretty sure I'm done here. I may drop in from time to time, but I have no interest in posting anything further. Asta la Vista.
Stay healthy,
Cheers,
Bill
JMO, but after all this is the internet. I'm sure you would get different opinions from Facebook, Twitter, or Instagram. And they would be just as unreliable.
Thanks Vinyl!
Perhaps a bastardized AC568 then.
Sounds like I better quit using it and find a qualified tech.
By “wrong” I’m thinking you mean it’s a Frankenstein. Also I deduce that although it works, it’s on borrowed time.