[Steve Mew]

I am building a JCM900 Marshall guitar amplifier from a schematic and I have
a parts list that I am not sure about, specifically :

Q1: Potentiometer Question --> I notice there are 8 potentiometers. There
are labelled VR1 - VR8:

VR1 - A1M
VR2 - A1M
VR3 - A1M
VR4 - A1M
VR5 - B220K
VR6 - B22K
VR7 - B220K
VR8 - B22K

Am I correct in assuming that A1M means Audio 1 MegaOhm ? Audio meaning
logarithmic ?
Also what does 'B' mean in VR5-VR8 ?
Does B mean linear ?

Q2: Capacitor Question --> I have a list of several Caps

C08 - RAD 30000uF / 30v*
C09 - RAD 33uF / 350v*
C11 - 22uF / 50v (NO POLARITY)*
C10 - RAD 33uF / 350v*

What does RAD mean ?

Any help greatly appreciated

Stephen Mew

 

[steve mew]

What does Radial Mean ?
Sorry for the Newby Questions

s

 

[Thierry C. \(NOOS\)]

[...]

What does Radial Mean ?

Both capacitor's leads are on the same side rather than on the opposite
sides (axial layout).

Sorry for the Newby Questions

But for the potentiometers with a "B", I don't know.

Thierry C.

 

[Jimmy]

A is for audio taper B is for linear taper

 

[Rick Cooper]

Jimmy,

First, the caps. RAD probably means radial leads as opposed to axial. That is,
like a can shape with two leads projecting out the same circular end cap and
placed part way from the center to the edge of the circle rather than a can with
a lead coming out each end and placed on the center axis of the cylinder.

wrt the variable resistors (potentiometers), I think A and B initial letters
more likely represent two different sections of the circuit. The only forms of
pots that I'm familiar are the logarithmic (audio) and linear. Can't see how a
B implies linear.

I agree with the interpretation that 1M, 220K, and 22K probably are the nominal
resistance values of the pots.

btw--an old (literally) friend once corrected my mistaken impression so let me
honor him by passing on that it's "megohm", *not* "megaohm". I was younger and
very sure, but when I checked I found he was right.

Rick

 

[Philip A. Marshall]

wrt the variable resistors (potentiometers), I think A and B initial letters
more likely represent two different sections of the circuit. The only forms of
pots that I'm familiar are the logarithmic (audio) and linear. Can't see how a
B implies linear.

whether or not you can see how it implies it, I can verify that that
is in fact the case

A = audio
B = linear

I've got a couple of each sitting right here, and i've seen plenty of
them in guitar effects circuits.