I'm working on a Fender Sidekick Keyboard amp circa 1990, made in Taiwan. Both volume pots for Input 1 and Input 2 need to be replaced. Looks like the originals were linear taper, correct?
Yes, it's a feedback type gain control, so the pot taper is linear.
The tone pots are A taper, log type.
The tone pots are A taper, log type.
Yup.
https://eepower.com/resistor-guide/resistor-types/potentiometer-taper/
If you didn't know for sure, all you have to do is remove the old pot, set the pot at 50% of rotation,
and measure the resistance from the wiper to one end. If the measured value is about half the rating,
it's a linear pot.
https://eepower.com/resistor-guide/resistor-types/potentiometer-taper/
If you didn't know for sure, all you have to do is remove the old pot, set the pot at 50% of rotation,
and measure the resistance from the wiper to one end. If the measured value is about half the rating,
it's a linear pot.
Helo Enzo, Do you remember the time when A was Linear and B Logarithmic.
Then, who decided it, they changed it in wat it is today.
Very confusing if you get repairs from before the 80'ties.
Therefore, to be sure, measure the pot, allways...
Then, who decided it, they changed it in wat it is today.
Very confusing if you get repairs from before the 80'ties.
Therefore, to be sure, measure the pot, allways...
Thanks guys. I would have measured from wiper at mid-point to one of the legs, expect both pots are pretty mangled-- wipers ripped out of the bodies, legs broken. . . . Apparently, someone thought they really could crank them up to 11.
And that switcharound from A to B, B to A linear and log Tarzan mentioned always makes me wonder.
Linear it is.
And that switcharound from A to B, B to A linear and log Tarzan mentioned always makes me wonder.
Linear it is.
Yes, A stands for linear in Europe. Until somewhere in the 80's it became B.
Similar with B, logaritmic.
But the lesson learned: allways test the pot unless you're 100% sure it's A or B.
But I do not want to confuse DBXDX5. There is also a C, D and if I'm not mistaken, an E pot.
Not very much used, but still interesting for some applications.
Similar with B, logaritmic.
But the lesson learned: allways test the pot unless you're 100% sure it's A or B.
But I do not want to confuse DBXDX5. There is also a C, D and if I'm not mistaken, an E pot.
Not very much used, but still interesting for some applications.
WHICH "Sidekick"? Fender made at least seven....
You may be able to read the old pot without wiper or ears. All you need is the C-shape black stripe on the phenolic wafer, in not too many pieces. Measure from center to each end. (If fragmented, read the fragments and add.) Yes, imprecise, but you only need to tell 50:50 from 80:20.
Another path. Look on the schematic (or in the chassis) for a pot with similar marks. See what it does, or how it reads.
I saw the 3-band tone control. This type has equal + and - resistors (though here is 2.7k and three of about 8K) and will use LINear pots (or S-bend, but not in a popular-price product). These are noted "L", so the "L" in the input gain is also LINear.
Seeing this schematic I would have bet a dime that the input pots are LIN because that is one of the benefits of this t pe gain/loss stage: the curve is semi-LOG even with LIN pots.
I fear the Keyboard and Keyboard 60 are different amps. His photo shows two input channels, the Sidekick Keyboard 60 has three.
MY factory file is called Sidekick Switcher/Bass/Keyboard. But only schematics for the Switcher and Bass versions. My paper files probably cover it, but they are buried in storage.
I include the file in case it be useful.
MY factory file is called Sidekick Switcher/Bass/Keyboard. But only schematics for the Switcher and Bass versions. My paper files probably cover it, but they are buried in storage.
I include the file in case it be useful.
Nevertheless, this is the same "10KL" input stage gain control. Now paired with the classic Fender tone-stack, best rendered with Audio taper, here marked "A".
Right, I had come across that schematic and it isn't the same. But PRR, if you say the input stage gain control is the same, I'll take your word for it. So we're still looking at Linear taper for those 10KL pots.
Pots replaced. Something I just noticed. The green wire from the transformer is disconnected/hanging in the air. Looks like it was purposeful. Any thoughts?
The wire comes from the rear of the transformer as you're facing the back of the amp. Hard to make out (or get a good photo). You can see it here in the bottom of the shot.
Sadly that does not show where it comes from.
We need some resistance measurements.
Schematic shows 5 "active" wires: 2 primary, 2 secondary and their center tap, 1 "screen"
Picture shows 2 Black ones (secondary?) and a Red one (center tap?)
It does NOT show (or does not identify) primaries nor screen.
*WITH AMP UNPLUGGED FROM MAINS AND PLUG ON THE TABLE, ALWAYS IN SIGHT
draw a "transformer map" showing all wires exiting from it and resistance/continuity between them, we want to i9dentify primaries, secondaries, center tap nd screen/shield.
OK, now you have a homework to do.
AGAIN: AMP UNPLUGGED FROM MAINS; turning it OFF is not enough.
Please, actual ohms in numbers, not basic "continuity" or "it beeps".
We need some resistance measurements.
Schematic shows 5 "active" wires: 2 primary, 2 secondary and their center tap, 1 "screen"
Picture shows 2 Black ones (secondary?) and a Red one (center tap?)
It does NOT show (or does not identify) primaries nor screen.
*WITH AMP UNPLUGGED FROM MAINS AND PLUG ON THE TABLE, ALWAYS IN SIGHT
draw a "transformer map" showing all wires exiting from it and resistance/continuity between them, we want to i9dentify primaries, secondaries, center tap nd screen/shield.
OK, now you have a homework to do.
AGAIN: AMP UNPLUGGED FROM MAINS; turning it OFF is not enough.
Please, actual ohms in numbers, not basic "continuity" or "it beeps".
