identifying all ceramic disc caps

[mikepukmel]

Im trying to identify all ceramic disc caps in the Deluxe REvereb AB763 circuit. I think one is on the back of a pot, maybe? I found a bunch of photos, but it looks like one with 'brown turd' caps must be later, maybe 70's, has one brown cap instead of a ceramic?

[mikepukmel]

Question for you all, has anyone built a Fender Deluxe Reverb clone with all caps as close to original, meaning ceramic disc instead of mica? If so, any idea if it has an effect on tone?

[pdf64]

Sorry, I thought I’d already replied - the caps marked 4 and 3 would typically be film types, rather than ceramic.

Regarding your second query, a flaw in trying to lump all ceramic caps together as one thing is that they aren’t. Class 1 types are very linear and temperature stable (eg NP0 dielectric), whereas other classes can be the polar opposite.
See https://en.m.wikipedia.org/wiki/Ceramic_capacitor
Typical tube guitar amp suppliers don’t tend to note the spec of the ceramic caps they’re selling, thus compounding confusion and misunderstanding when the topic is discussed on tube guitar amp build/repair/modify forums.

[Enzo]

And I say again, it is just a guitar amp, not precision lab gear. You might find film caps in one amp and ceramics in another in certain spots. The 63 in AB763 means 1963, if you amp is from 1970, chances are it is not identical. So don't assume there is some cosmic "correct" cap for each component. Old Fender amps were built with 20% tolerance resistors, and the tolerance on caps back in that era was all over the map. And pots? A 250k pot might measure at 400k. Ballpark is as close as it gets there.

[The Dude]

^^^^^^^^^^ That...... and

1uF = 1uF

[mikepukmel]

Sorry, I thought I’d already replied - the caps marked 4 and 3 would typically be film types, rather than ceramic.

Regarding your second query, a flaw in trying to lump all ceramic caps together as one thing is that they aren’t. Class 1 types are very linear and temperature stable (eg NP0 dielectric), whereas other classes can be the polar opposite.
See https://en.m.wikipedia.org/wiki/Ceramic_capacitor
Typical tube guitar amp suppliers don’t tend to note the spec of the ceramic caps they’re selling, thus compounding confusion and misunderstanding when the topic is discussed on tube guitar amp build/repair/modify forums.

Thanks for the links and info PDF! yeah, and for me (amateur/hobbyist) its even worse, since I don't have the background. I'll check the 'class' on some caps I have bought for previous projects. Re 4 and 3, so I tried looking at lots of photos (lots of photos!) of 60's era fender chassis. Found a bunch. Some, I was surprised, e.g. 0.003 on the plate of the reverb output. Some amps had one of those 'brown' caps, look like old film, and a few had ceramic. Maybe it was a later repair ,that put ceramic in this spot?

And thanks Dude, looked as hard as I could, could not find two 1uf Are those the caps that sometimes appear on output tubes?

[pdf64]

Haha, I think The Dude just meant that electrons behave the same, whatever the cap dielectric.

[vintagekiki]

Fender Capacitor Codes
CAP AE = Aluminum Electrolytic
CAP CA = Ceramic Axial
CAP CD = Ceramic Disk
CAP MPF = Metalized Polyester
CAP MY = Mylar
CAP PFF = Polyester Film/Foil

http://www.thevintagesound.com/ffg/deluxe_reverb_bf.html

https://images.reverb.com/image/upload/s--Ot5_DUXJ--/f_auto,t_supersize/v1598934362/efto7rcc2lbnq8xma58n.jpg

[pdf64]

And the class types of those ceramic disc / axial caps are???
Without that detail, it’s pretty much pointless, non-info.

[Helmholtz]

And the class types of those ceramic disc / axial caps are???
Without that detail, it’s pretty much pointless, non-info.

If two ceramic disks have similar size and voltage rating, they are probably the same class. The better ceramics have lower dielectric constants and thus need to be bigger for same capacitance and voltage rating.
Measuring the capactive Q-factor with an LCR meter might give some info.

I also use the Q to tell between polyester/mylar, polypropylene and PIO caps.

[vintagekiki]

And the class types of those ceramic disc / axial caps are???
Without that detail, it’s pretty much pointless, non-info.

Fender Deluxe Reverb has no Ceramic Axial capacitor (CA)
http://ampwares.com/schematics/65_Deluxe_Reverb_RI.pdf

1)
Fender uses coded naming convention in the description of certain parts.
The codes and what they mean are described on page 2 SM.

[pdf64]

That seems to provide the voltage rating, cap nominal value and tolerance, but not the class type / acceptable limits for parasitics, eg temperature coefficient?

[vintagekiki]

Guitar amplifiers koriste consumer electronics parts.
Most likely something like

https://portal.edge-group.com/~edgegro1/members/marketing/datasheets/nte/90000.pdf

[The Dude]

Haha, I think The Dude just meant that electrons behave the same, whatever the cap dielectric.

Yes, that was the point. Sorry if it wasn't clear.

[vintagekiki]

Every serious manufacturer (amplifier) in the process of development connect for some supplier of parts, and according to chosen parts makes its own coded naming their own built-in (spare) parts.
The parts to be installed supports the minimum design and technical requirements, both in voltage (capacitors) and in power (resistors).
Transformers generally follow technical datasheets recommendations from good old handbooks (vademecums) for projected tube (s).
Everything else is technology and modern design.

About spare parts ... ...

https://portal.edge-group.com/~edgegro1/members/marketing/datasheets/nte/

https://portal.edge-group.com/~edgegro1/members/marketing/datasheets/nte/89000.pdf

https://portal.edge-group.com/~edgegro1/members/marketing/datasheets/