NBD 1967 Sunburst Starfire II

[wisconsindead]

Also, heres a link to my photobucket. Took a lot pictures of the pickups as I was trying to make sure I didn't forget where each wire went lol.

http://s1036.photobucket.com/user/ztwatson/library/?sort=3&page=1

 

[wisconsindead]

Hey guys. Ive been working on the wiring of my starfire. Ik ik...

Anyways, the pots aren't stamped with their resistance and all except for the Neck Tone pot measured 600-650 kohms. The neck tone pot was 198 kohms. This pot also looks much newer compared to the other pots. the wiring of the suck switch and the neck controls was pretty wacky. I had a friend who knows a bit about this stuff help me but as of now the neck circuit is messed up. No sound. I disconnected the master volume pot and put that where the neck tone pot was but that didnt fix it. In fact im not even sure if a volume pot would work in the tone spot (my assumption is they are the same thing). I took it to guitard center early today to have a guy take a look at the circuit and he gave me the "Idk whats going on, Id replace everything, take way too long and charge you up ***".

My photobucket^^^ has a lot of photos of the circuit. Its now looking different than that with the suck switch ripped out (the bridge controls are as they were). The master volume is out but that doesn't change much.

Im curious as to whether the capacitors that I have are correct now that the circuit has changed with the removal of the suck switch. I also am not sure if the neck tone pot is the problem. but ultimately I just do not understand the circuit (or circuits in general). However, I'd rather learn, save the money and have it likely take the same amount of time. Hence, I've taken it on myself.

 

[SFIV1967]

Interesting, two of the 3 capacitors and the one resistor seem to be part of the old suck switch circuit. I would just remove all that stuff.

The capacitors are old "vintage correct" capacitors, I guess I see a 0.022mfd cap (22nF or 22000pF).

This capacitor below is also original, it is a 10000pF (10nF or 0.01mfd) 200V Mullard 'mustard cap'.
Also you can see all the value of the pots written on the bottom of the pots.
I can give you an example what you might see (but with different pot code and dates):
Pot Code 137 6638 = CTS (Chicago Telephone Supply, manufacturer #137) = 38th week 1966
You also will see a Guild part number like 004019 or 004020 for 500kohms pots, or 004026 for 200kohms or something like this.

The correct wiring diagram with removed suck switch should look like this:

Mind that it is possible that your bass might have had a 200kohms neck tone pot or even an additional 200kohms bridge tone pot. That is perfectly correct!
(The Starfire IV had a 200kohms neck tone pot but a 500kohms bridge tome pot)

On the Starfire guitars usually the bigger capacitor value like 0.047mfd (or 0.033 or 0.022) is at the neck p/u tone pot and the smaller value, like 0.01mfd is at the bridge p/u tone pot. This should give you a "darker" "jazzy" sound for the neck pickup and a clearer sound for the bridge pickup. Now the lower resistance (200kohms) on the neck tone pot also means that more high frequencies go to ground, so the neck pickup is extra “dark”.

There were several possibilities how the pots and caps are connected, so this is just one version:

Ralf

 

[wisconsindead]

Very informative Ralf thanks! The neck tone pot is a 200 kohm pot then based on its stamp. And based off the capacitors and the pot values, maybe thats why its so dark/dull sounding. However the output should still be higher. Hopefully that will all get fixed with the redone circuit. Ill keep yall posted.

 

[fronobulax]

FWIW, in 1971 the suck switch managed components that were part of the circuit in either position. (Drawn from a 1971 JS I).

 

[SFIV1967]

FWIW, in 1971 the suck switch managed components that were part of the circuit in either position. (Drawn from a 1971 JS I).

But that version of the bass didn't include a choke, so the added components in the circuit did the job of the choke.
Ralf

 

[fronobulax]

But that version of the bass didn't include a choke, so the added components in the circuit did the job of the choke.
Ralf

Interesting, two of the 3 capacitors and the one resistor seem to be part of the old suck switch circuit. I would just remove all that stuff.

I was being literal and allowing for the possibility that the "extra parts" served some purpose that was still useful when the choke was removed. But I have already demonstrated that my ignorance in analyzing analog circuits exceeds my knowledge so maybe I'm speculating about something that cannot happen. Past discussions have suggested that merely removing the choke was sufficient.

 

[SFIV1967]

...allowing for the possibility that the "extra parts" served some purpose that was still useful when the choke was removed...

Ah, I see what you mean. Makes sense!
I don't know if those 3 green drop capacitors and the one resistor are factory original there or not, I have never seen other pictures of that circuit in other basses.
The vintage of the parts suggests they might be stock, but who knows.
Since the color of the used cables is different from the normal grey stock cables I am not sure what is original and what not.
What I would do (if I would have the task to fix it) is draw a full electrical circuit drawing of the current configuration to figure out what is going on by using the wiring diagram I posted and just draw in the connections to what wisconsindead has in his bass currently (including the choke he cut out so far).
Ralf

 

[wisconsindead]

Well heres some more info

Bridge Tone - 651 kohms - 004019 137 6748
Bridge Volume - 605 kohms - 004019 137 6744
Neck Tone - 198 kohms (this pot looks new, or it doesnt have the patina the others do) - 004026 137 6802
Neck Volume - 615 kohms - 004019 137 6748
Master Volume - 650 kohms - 004019 137 6744

The capacitor for the bridge is 0.01. +- 10% (off white colored, cylindrical)
The neck circuit had three capacitors all 0.022 10% (green colored, flat)

There was also a resistor in the neck circuit which is red, red, yellow, silver. I think this is 220 kohms. But resistors still confuse me. The bands are all equal distance from each other.

Anyways, I think it is original based on the pot dates (though it is odd that the neck pot looks so much newer). The capacitors (and potentially the resistor) make sense with the muddy/dull sound of the neck pickup. However I'm still not sure what caused the output issue. I rewired everything excluding the neck tone pot. The output is now equal between the two (screwdriver tap on poles as my test). Im actually really glad I decided to tackle this on my own. More knowledge gained. I will have rehearsal tonight and hopefully all goes well. It sounds OK on my 40 watt guitar amp, but the real test will come through my bass amp. It seems that the .01 cap for the bridge is kind of rare. Or not typical. Im thinking about getting one of them for the neck tone. Either way there is much more clarity (probably just treble) and the volume is where it should be.

I do have a question though....

When a tone pot is fully clockwise (at 10) then it is essentially off? or is it on? A friend was telling me that having your tone at 10 essentially turns the cap "off". Though this doesnt seem right as I think any capacitor whether at 0 or 10 will effect the tone or the circuit. Lil clarification por favor?

 

[SFIV1967]

Well heres some more info

Bridge Tone - 651 kohms - 004019 137 6748
Bridge Volume - 605 kohms - 004019 137 6744
Neck Tone - 198 kohms (this pot looks new, or it doesnt have the patina the others do) - 004026 137 6802
Neck Volume - 615 kohms - 004019 137 6748
Master Volume - 650 kohms - 004019 137 6744

The capacitor for the bridge is 0.01. +- 10% (off white colored, cylindrical)
The neck circuit had three capacitors all 0.022 10% (green colored, flat)

There was also a resistor in the neck circuit which is red, red, yellow, silver. I think this is 220 kohms. But resistors still confuse me. The bands are all equal distance from each other.

It seems that the .01 cap for the bridge is kind of rare. Or not typical. Im thinking about getting one of them for the neck tone. Either way there is much more clarity (probably just treble) and the volume is where it should be.

When a tone pot is fully clockwise (at 10) then it is essentially off? or is it on? A friend was telling me that having your tone at 10 essentially turns the cap "off". Though this doesnt seem right as I think any capacitor whether at 0 or 10 will effect the tone or the circuit. Lil clarification por favor?

Well I am glad some of my guesses about the use components were right.
So all pots are made by CTS (Chicago Telephone Supply, manufacturer code 137).
All, except that 200kohms pot are 500kohms pots (Guild part number 004019) made in 1967 in weeks 44 and 48.
Now the 200kohms pot (Guild code 004026) is made in week 02 in 1968.
That could be an indication that it was changed at some point in time. It's at least an original Guild pot.
As I explained before a lower value of the neck tone pot means that more high frequencies go to ground, so the neck pickup is slightly darker compared to the bridge pickup. All good and normal.

Now about the caps.
The round mustard green one on the bridge tone pot is a 10000pF (10nF or 0.01mfd) 200V Mullard 'mustard cap'. They are not rare and were made by Philips (Mullard belonged to Philips). There are various versions. You can get plenty on ebay. It was the "standard" capacitor at that time for the bridge. (lower capacitor value means less high frequencies go to ground, hence the bridge pickup is brighter). They are pretty good capacitors.
As I also said before the dark green flat or drop caps are 0.022mfd caps (22nF or 22000pF). If you connect caps in parallel, their value doubles, so two 0.022mfd caps in parallel are a 0.044mfd cap.
The usual value for a bridge tone pot in a Guild guitar at that time was 0.047mfd. But it could be as low as 0.033mfd or even 0.022mfd. All are possible as neck tone pot capacitors. The higher value of the capacitor just means more high frequencies pass to ground, so you hear a "jazzier", "darker", lower frequency sound. Don't get too excited as the differences are not that huge.
Usually you would NOT use a 0.01mfd cap for the neck, the lowest I would use is 0.022. And that is actually what I think is used in your bass as I believe the resistor and the two parallel caps belong to the suck switch circuit which you should remove. That's why I recommended you should draw where everything is connected to, so you see what was the tone cap and what was the suck switch circuit! (means which was 0.022 and which was 0.044).

Now how does a pot and a cap work together:
A tone control is a passive circuit that couples a potentiometer with a capacitor. The capacitor only allows higher treble frequencies to pass through it while blocking low frequencies. The guitar's signal passes through the tone cap, pot, and ultimately to ground. This resistor-capacitor (RC) circuit is called a low-pass filter.
When the pot is turned up all the way, it's at maximum resistance and doesn't pass the treble frequencies to ground. As you turn the tone pot down, the resistance decreases and some of the treble frequencies pass to ground instead of the amp.
When the pot is turned down all the way, the pot's resistance is near zero so all the treble frequencies pass to ground and you only hear the lower bass frequencies though the amp. This works because the guitar's signal always seeks the shortest path to ground.

Hope that makes sense!

Ralf

 

[wisconsindead]

Thanks ralf. You know I dont get how the tech at guitar center was unable to tell me the value of the caps with them right in front of his eyes. He acted like he had never seen a circuit before. Everyone I took it to looked at me like I was retarded to think there was a problem. Or for that matter why they wouldnt mention how different caps or pots will effect your tone. Its still a bit mysterious why it was so dull (it had to be due to the suck circuit) but I feel like I could have answered some of my concerns better than these guys (now). Can you believe the guy at GC said it would be at least $175 + parts to fix my guitar (even though I had already everything pulled out of the F holes, as I think to myself "theres no chance in hell you're touching my bass, I just want advice, and if its good I'll give you a big thank you and maybe buy the parts you suggested")

Thanks for letting me vent LOL.

 

[edwin]

Thanks ralf. You know I dont get how the tech at guitar center was unable to tell me the value of the caps with them right in front of his eyes. He acted like he had never seen a circuit before. Everyone I took it to looked at me like I was retarded to think there was a problem. Or for that matter why they wouldnt mention how different caps or pots will effect your tone. Its still a bit mysterious why it was so dull (it had to be due to the suck circuit) but I feel like I could have answered some of my concerns better than these guys (now). Can you believe the guy at GC said it would be at least $175 + parts to fix my guitar (even though I had already everything pulled out of the F holes, as I think to myself "theres no chance in hell you're touching my bass, I just want advice, and if its good I'll give you a big thank you and maybe buy the parts you suggested")

Thanks for letting me vent LOL.

Now you can take apart a few more instruments and then hang out a shingle as an expert! I think you do know more than 99% of the Guitar Center employees.

 

[wisconsindead]

Well there was one kid who works there and saw me pull the bass out and said "is that a guild?! nice, and flats! my man". I thought about trying to find him to see if he could tell me something lol.

 

[wisconsindead]

Had some free time last night and figured I'd get around to drawing up a diagram of the Suck Switch. Obviously its an amateur drawing, but the wiring is pretty clear. Anyone see anything obvious as to why it would suck treble? Whats up with the wiring of the capacitors? I'm sure If the value is right... 220? .022? Lets figure this thing out!

 

[fronobulax]

For reference...

Starfire II as published by Guild at an unknown date but best guesses are mid-1967 or earlier because there is no suck switch.

1971 JS II with humbuckers so there is no reason to expect similar values.

Suck switch toggles between a capacitor and a resistor.

There are some pictures floating around from fixit's work on twocorgi's green SF II that show the innards and I believe people preferred to call the "transformer" a "choke". I'm not going to pontificate on how the circuit might work because I got more wrong than right discussing the JS suck switch.

 

[SFIV1967]

Red Red Yellow Silver = 2 2 0000 ohms with 10% tolerance = 220kohms with 10% (The Gold or Silver band is always placed to the right. The resistor value is read from the left to right).

The green capacitors are 0.022mfd caps (=22nF=22000pF).

I am just wondering why some of wisconsidead's pictures show the suck switch between the neck volume pot and ground and some do not? Did you solder it out and solder it in again? I am confused.

As an improvement to your drawing I would draw all lines that are directly connected to ground in a different color.

Ralf

 

[wisconsindead]

Ralf, the second picture you refer to was the first attempt at disabling the suck switch. Disregard that image.

Crater at Talkbass helped me out by turning it into a circuit diagram so it might be more clear for you or others

I'm 99.9% the image of the circuit shown above is unaltered as I was very cautious to take images of everything before we made any changes. My drawing of it should be accurate.

 

[SFIV1967]

Ralf, the second picture you refer to was the first attempt at disabling the suck switch. Disregard that image. Crater at Talkbass helped me out by turning it into a circuit diagram so it might be more clear for you or others.

While you typed I still edited my message as I realized I wrote wrong things first. Basically what Crater came up with seems not to fit what you came up with as in your drawing the choke (=inductor) goes to ground on each end whereas Crater shows the left side to ground and the right side to the single 22nF cap and the switch. Is that the case? I don't see the choke (=inductor) between the 44nF (the two left) and 22nF (the one right) as Crater shows? But maybe I misunderstood what you show on the left side of your tone pot? Are all those things ground or not?
Ralf

 

[wisconsindead]

Just to the left of the tone pot you can see a square with a loop and T which is representative of one of those pot attachments that stick up (you can see it in the actual picture). The single 22nF cap is not ground to the bottom of the pot but connected to this attachment. The switch and lead for the switch are connected to the loop on top of this attachment. Hope that makes sense

 

[SFIV1967]

So this tone pot "attachement" on the left in your drawing is not soldered (I mean electrical connected) to the housing of the pot? I thought that is all soldered together. Maybe that was my mistake. So it is actually isolated from the housing?
And the 22nF cap is electrical connected to the choke and the switch, correct?
Well in that case Craters drawing seems to be right.
Ralf