recaping an altec 1567a

Hi there,
I am in the process of recaping this unit which schematics is available here:
http://alteclansingunofficial.nlenet.net/proelectronics/rackmixers/1567a.zip

Aside the power supply stage where I will use electrolytic 105 caps, I am having problem to decide what king of caps to use for the sound stage; I will take polypropylene caps where I can but I have small values that I can't find:

These will be polypropylene caps:
C1 50uF 5V
C2,C3,C4 and C5 0.1uF
C6,C7,C13 and C15 0.022uF
C16 0.15uF
C17a 125uF 25V
C18 1uF

and here are the ones I am having problem with; on the orginal unit there are ceramic caps:
C8 150pF/0.00015uF
C9 ad C12 1500pF/0.0015uF
C10 390pF/0.00039uF
C11 6800pF/0.0068uF
C14 3.3pF/0.0000033uF

I could thanksfully use your help.
Thanks
Alex

As much as I agree with the need to replace the old electrolytics, i don't see the point in replacing the other caps, unless you think that newer types may give a better sound (a very debatable and dubious subject).
In particular, the tiny caps (3.3pF) that are used for stability issues; replacing them may be detrimental.

Do you know what dielectric the ceramic caps are supposed to be? NPO, X7R etc?
Electro's eventually dry out and their ESR goes up, causing problems in PSU and amp stage decoupling. These should be replaced by good low-ESR caps.
Ceramics, mica, polystyrene, polypropylene etc don't usually need to be replaced unless there has been a fault which has destroyed them. Sometimes a particular dielectric is chosen in the design procerss for particular reasons. Unless you know this you could alter the operation of the circuit and make a real mess.

I don't know about the dieletric, how can I find out ? There is no such information on the document of the altec unit.

After reading the doc, no particular dialetric is mentionned on any cap. There is a part list quite detailled though.
I will start recaping the PS and see how it goes before changing any other cap.

alexidoia said:

I don't know about the dieletric, how can I find out ? There is no such information on the document of the altec unit.

Click to expand...

Cap markings are usually an indicator and also how and where they are being used in the circuit.

do you mean what is written on these tiny ceramic caps ?

Yes, that and the colour codings on them (case colour, top colour etc).

And where do I get the reference of the color ?
Thanks for your time.

Manufacturer's data.
Philips etc.