Wiring help needed - Strat with series blender

[stratman323]

I hope one of you clever people out there can help me with this one, because it's beaten me! I'm trying to wire up a Strat using this diagram.

I'm sure I've connected everything up OK, but it doesn't seem to work properly. There's probably something blindingly obvious to one of you, but not to me, I'm afraid.

With the blender pot turned anti-clockwise, the series wiring seems to work. The problem is in the normal position with the blender fully clockwise - the only position that works is the middle position, which selects the middle pickup.

Can anyone please work out what the problem is here? Is there a fault with the diagram? Have I read it wrongly? I'm baffled here, so all help will be gratefully accepted.

Thanks.

 

[rlyacht]

I've done the regular blender diagram from acme a few times, but not this one. The first time I did it, I made a mistake, which I'll pass on in case you did it too. I misinterpreted the wiring of the tone (2nd) pot and wired the cap incorrectly. One end of the cap goes on the first lug of the pot, and the other is soldered to the top of the pot. My mistake was that I also wired it to the ground (3rd) lug! That's unlikely to be what you did, but FWIW ...

Beyond that, I don't know enough electronics to say that the circuit in the picture is right or wrong, though considering the source I'd be pretty confident that it is correct.

You might consider posting on thegearpage.net, as I've gotten useful help on wiring there too (not to knock strat-talk of course).

Good luck!

 

[Algynon]

Had a quick look at the circuit. In 'Parallel' mode - control fully anticlockwise- it works like a normal Strat. In 'Series' mode - with the control fully clockwise it is supposed to connect the neck or bridge p/u in series (ie daisy-chain fashion) to the middle p/u. This should give you a sort of humbucker tone but my guess is that it'll sound pretty weak. Maybe it has worked properly but you hadn't noticed the difference. Check this by selecting position 1 with the blend control fully clockwise - this connects bridge and middle in series. Tap the pole pieces of each of the bridge and middle p/us with a screwdriver to see if you get a sound from both. If not then I'd check the connection between the blend control and the selector switch.

In the in-between positions [2 & 4], the control will simply adjust (mix) the level of the neck or bridge p/u in relation to the middle. Eg when in position 2 [bridge & middle] the blend pot gradually reduces the volume level of the bridge p/u the more you turn the control clockwise. So by the time it is fully clockwise, only the middle p/u is heard.

 

[stratman323]

Had a quick look at the circuit. In 'Parallel' mode - control fully anticlockwise- it works like a normal Strat.

Presumably you meant parallel = fully clockwise, as the diagram states?

And if it had done that, I would have been happy. The problem is that it didn't, as I tried my hardest to explain in the original post.

 

[Algynon]

Sorry for the confusion stratman323. The earth wires from the bridge and neck p/us should be connected together and soldered to the middle terminal of the blender pot as shown in the diagram. With the blender pot fully clockwise, it connects those earths from bridge and neck p/us to ground.

If you are only getting the middle p/u working in this mode, it looks like the earthing on the other end of the blend pot [looking from the back, it is the one on the right] is not properly earthed. If you have soldered it to the case of the blend pot like it shows in the diagram, I would check that the pot itself is earthed.

You can test that with a multimeter. Fix it by soldering another wire from the earth terminal of the blend pot to any of the other earth points (eg the tone or volume pot cases). If this doesn't do the trick, it would be helpful to upload a pic of your work.

 

[stratman323]

OK, well this is going to have to go on hold until next week as I'll be away for a few days. Because it didn't work, I wired the blender up as a parallel wiring blender (using an Acme diagram, & it works fine), but I would prefer to try the series wiring. I'll have another go next week.

Here are a couple of pics of what I had.

 

[Algynon]

Well, everything looks to be connected in accordance with the Acme diagram. When you say it works in the [fully anticlockwise] series mode, have you checked that in position 1 both the bridge and middle p/us are active?

If so, it means that the earth connections of the bridge p/u has been connected OK to the middle p/u by the blend control. The blend control acts like a three way switch; fully anti-clockwise it connects the earths of the neck and bridge (black wire, middle terminal) to the hot of the middle p/u (white wire between blend control and selector s/w). Turned fully clockwise it should connect the middle (black wire) terminal to the other terminal - the one that is soldered/connected to earth or ground (ie soldered to the blend pot case). The fact that you are NOT getting a signal when the selector is on position 1 and the blend control is turned fully clockwise means that the earth (black) wire of the bridge p/u is NOT getting connected to earth.

If you have a multimeter (you can pick em up pretty cheap these days and they're useful for jobs like this) you can test this easily by measuring resistance (ohms) between the middle & left (earth) terminal when the control is turned fully clockwise. It should read zero (or very nearly zero) ohms.

If you don't have a multimeter you can temporarily short the two terminals with a spare piece of wire. If this results in connecting your p/u then you need to check your solder joints between the blend pot earth terminal and the rest of your guitar's earths.

 

[stratman323]

Well, everything looks to be connected in accordance with the Acme diagram. When you say it works in the [fully anticlockwise] series mode, have you checked that in position 1 both the bridge and middle p/us are active?

If you have a multimeter (you can pick em up pretty cheap these days and they're useful for jobs like this) you can test this easily by measuring resistance (ohms) between the middle & left (earth) terminal when the control is turned fully clockwise. It should read zero (or very nearly zero) ohms.

If you don't have a multimeter you can temporarily short the two terminals with a spare piece of wire. If this results in connecting your p/u then you need to check your solder joints between the blend pot earth terminal and the rest of your guitar's earths.

By position 1 you mean the "normal" bridge position? In that case, the answer is yes, both bridge & middle worked together with the blender in series mode.

I do have a multimeter, which I have only ever used for measuring the resistance of pickups. I've never worked out how to use it for anything else. It's automatic, which means I don't seem to be able to set it up the way people tell me I should do for testing circuits, switches etc.

Anyway, I'm away for a week from today, so I'll have another go at the series circuit next week & see if I can work out what you are suggesting above. It might make more sense to my poor old brain if I have the guitar in front of me!

It may well be that I will need your help again next week, so please stick around! Thanks.

I WILL crack this......

 

[Algynon]

Eureka!

stratman323, When I looked again at your pic something hit me; I noticed that your blend pot is shiny and new compared to the other two and is a CTS pot with a dimple in the case. If I,m not mistaken it is a no load pot which means it is designed only as a tone control and the right hand terminal is not connected internally - its a dummy terminal and I'm afraid that is why your circuit doesn't work as it should. :cry:

Another 'design feature' of this type of pot is that when turned fully clockwise, the middle (wiper) terminal disconnects itself from the circuit. There's a thread on this site Strat neck pickup blender ... - Telecaster Guitar Forum explaining how and why they work this way.

If you bought it from Acme specifically for this circuit, then I guess you could claim a refund/exchange. If not you'll need to replace it with a standard tone or volume pot.

I do have a multimeter, which I have only ever used for measuring the resistance of pickups. I've never worked out how to use it for anything else. It's automatic, which means I don't seem to be able to set it up the way people tell me I should do for testing circuits, switches etc.

To confirm your blend pot is a no load version you could test it with a multimeter as follows:

Set up your multimeter as you do to measure a pickup - not sure what you mean by 'automatic' but if you've measured pickups before with it , use the same setting which should read off ohms or k ohm units.

First test the multimeter, switch it on and put the two test prod ends together and it should display zero. If its digital it will show 0.00, if its analogue (like a v/u meter) the pointer should swing from left to right and rest at the 0 (zero) ohms position.

Next, put one prod on the middle terminal of the blend pot and the other prod on the right terminal [the one thats earthed]. If it is a standard pot, turned fully anti-clockwise, it should show zero ohms. If it doesn't, it is a no load type.

If you want to test what it would be like if it was a standard pot, try shorting the two terminals (with a short bit of wire or a wide enough screwdriver blade that touches both the middle and right terminals together) until the meter shows zero. Your bridge pickup (with selector at position 1) should then be active.

Obviously if its a no load pot it will stop working when you remove the short (or screwdriver blade).

 

[stratman323]

stratman323, When I looked again at your pic something hit me; I noticed that your blend pot is shiny and new compared to the other two and is a CTS pot with a dimple in the case. If I,m not mistaken it is a no load pot which means it is designed only as a tone control and the right hand terminal is not connected internally - its a dummy terminal and I'm afraid that is why your circuit doesn't work as it should. :cry:

Another 'design feature' of this type of pot is that when turned fully clockwise, the middle (wiper) terminal disconnects itself from the circuit. There's a thread on this site Strat neck pickup blender ... - Telecaster Guitar Forum explaining how and why they work this way.

If you bought it from Acme specifically for this circuit, then I guess you could claim a refund/exchange. If not you'll need to replace it with a standard tone or volume pot.

All the pots are new, I'm using Alpha 250k pots for volume & tone (much better pots than CTS, IMHO) & a Fender no-load pot which I bought as I read that you need to use a no-load pot for a blender.

So are you saying that an ordinary pot is the correct thing to use for a blender? Now I AM confused! It works fine as a parallel blender using another Acme diagram.



I'll come back to the rest of your post when I'm home again next week.

 

[Algynon]

Whether you use a no load pot depends on the circuit you want to use.

If your no-load pot is also 250k (you didn't give the value), you could simply swap it with your tone pot which, as you can see, doesn't need the right hand terminal wired up. The no load pot will work fine as a tone control - which is exactly what it's designed to do.

On your Acme circuit, the blend control needs to be a standard (non no load) type control that has continuity from end to end [meaning the the left and right terminals are internally connected to a fixed resistor eg 250k ohm].

Your tone pot (in the pic) looks to be a standard pot and you should therefore be able to measure its resistance with your multimeter. Put your meter prods on the left & right terminals - it should read off the same value usually stamped on the case - in your case, 250k ohm.

On the no load pot you won't get any reading because the right hand terminal is not connected to anything.

The middle terminal (wiper) of a standard pot, sweeps from one end of that fixed resistor to the other as you turn the shaft/knob. Your Acme circuit needs the wiper to sweep to the earthed end of your blend pot to connect the earth wire of your p/u when in parallel mode - otherwise it won't work.

Hope this enables you to get everything up and working. It's been quite a journey

 

[stratman323]

OK, well I have a couple of spare Alpha 250k pots (linear & log) which I could use for the blender - would linear or log be better? If the series blender circuit will work with a standard pot, I'll try it when I get home. I'm sure I read somewhere that a blender must be no-load pot so that there isn't any bleed-through when it's turned off?

The other puzzling thing for me is that the exact same 250k no-load pot seems to work fine as a parallel blender using this circuit.

Does that make sense?

Thanks for all your help with this - I do appreciate it.

 

[Algynon]

Hi stratman,

I'm not an expert in this stuff - I only picked up what I know as I went along.... While in danger of turning into an electronics teach-in, as you seem to appreciate it, I’ll carry on for you and others in search of enlightenment

Log or Linear blender pot?

In the Acme series/parallel wiring diagram you have been copying, the same pot type is used for volume, tone and blend controls [magnify the Acme diagram, you'll see that all three controls are all stamped "ACME 250k CTS 0718". As far as I can tell (that part no is no longer listed on Acme site) it’s an 'audio taper' ie logarithmic type pot.

With a logarithmic taper, depending on which way round you wire it, everything happens either at the start or end of travel. A linear taper pot changes proportionately to the travel (eg when the control is half-way you get half the output). I would've suggested using a linear pot for your blend control but Acme shows otherwise so it's down to personal taste.

When should a ‘no load’ be used for a blender pot?

The reason why the [blender only] wiring diagram you just posted above uses a ‘no load’ pot is that it doesn’t involve a series/parallel “switch” like your circuit.

In the “blender only” circuit all pickups remain in parallel mode and the three earth [ground] wires remain permanently soldered to the volume pot. The blend pot connects the bridge hot wire to the neck hot wire via the blend control. It uses only the left and centre terminals of the blend pot; left hand terminal through its internal resistor to the centre (wiper) terminal. And while the diagram says the blend control case should earthed, the RH terminal does not need to be. So a ‘no load’ pot (in which the RH terminal is not internally connected) is fine for the purpose.

Why yours works in series but not in parallel?

Your series/parallel circuit involves disconnecting the earths from the neck and bridge pick-ups because to wire something ‘in series’ you have to connect them end to end in a chain. So your circuit uses the blend control as a ‘switch’ as well as a ‘volume’ mixer. That is why it needs all three terminals on the blend control to be [internally] connected to each other. And it is why your series/parallel circuit worked in the series mode but not in the parallel mode; it is down to that 'no-load’ pot you used for the blend control.

In your guitar, as currently wired, turning the control anticlockwise,as the wiper moves towards the left hand terminal (middle p/u) it de-creases the resistance between bridge or neck p/u and the middle p/u. In other words it is gradually blending the middle p/u in series with the bridge p/u [when the selector switch at position 1] or the neck p/u when selector switch on 5. When it is fully anti-clockwise, there is zero resistance between the earth of the bridge p/u [when the selector is at position 1] and the middle p/u. Bridge and middle are therefore connected in series and both are active.

However turning the control clockwise, the centre wiper moves away from the left terminal and moves to the right hand one. With it being a 'no load' type, however:

a) the right hand terminal is not even connected to the internal resistor AND
b) the wiper terminal disconnects itself from the resistor when turned fully clockwise.

So, even though you had [externally] connected/soldered the RH terminal to earth (the blend pot case), there is no connection internally with the resistor track and no connection with the wiper terminal. Hence your bridge p/u is not connected to earth and in what should be ‘parallel’ [normal] mode, it is 'open circuit' and no sound comes out :cry:

Here endeth the lesson. Go forth and swap your pots so that you may bring harmony, if not peace…....

 

[stratman323]

Algynon.

You, sir, are the cleverest person on this forum (and a couple of others I tried too). Changing the third pot to an Alpha 250k B (linear) pot & re-doing the series wiring just as I originally had it seems to have been a complete success. The circuit now works as described in the Acme diagram - series wiring in positions 1 & 5 when the third knob is turned down to 1, & standard Strat wiring when it's turned to 10.

The series sound is fatter (as expected), & time will tell how much use the series options are in practice. But of all the extra wiring options that are possible on a Strat, this one seems like it will be the most useful as it gives the option to fatten up the sound when needed.

So, after all that frustration initially, I'm now very happy & also very grateful to you for taking the time to help me with this - I do appreciate it.

Thanks.

8)