Gretsch Rally "Sonic Boom" help

[maxwell]

Hi Guys,

I have a very messed up Gretsch Rally with the "Sonic Boom" treble boost feature. I found the Schematic for it but I'm struggling to interparate it. Would someone be able to turn this schematic into an easy to follow wiring diagram. Thanks in advance. Cheers

[maxwell]

[newey]

Oct 2, 2023 23:22:10 GMT -5 maxwell said:

I have a very messed up Gretsch Rally

So, does "very messed up" include missing some of the parts? Particularly, do you have all the switches shown in the schematic? If so, what do they look like?

I am sure a diagram can be done from this. I just want to be sure the diagram depicts something close to the actual switches. The treble boost circuit is treated as a "black box" in the schematic, so you'll be trusting to luck that it powers up and works as advertised, not much you can do if it doesn't.

[sumgai]

max,


I'm keen to help you out here, even though I'm pretty sure that the diagram was drawn by a technician during a serious psychotic break. Still, it was a matter of only a few moments to dope it out.

My problem is time. If you can hold out for a day or two, I'll generate what I think it is that you're asking for, but if other members here beat me to it, then that's fine by me. And also fine by you, of course.

HTH




sumgai

[sumgai]

max,


So here's a first-pass, but it's only a schematic, as drawn by an EE.... who has his good days and his not-so-good days.





All labels are for reference only. Component values are best determined by the owner/player/user/modder, not by some hack on the internet.

Also, I should note that the same warnings apply as written below the original diagram - do not ground either power supply lead, and do not ground both input and output cable shields. Instead, ground only one of those shields. This will help to reduce the risk of a ground loop. (And yes, the risk is very small, but if the manufacturer said to do it, might as well do it their way.)

EDIT:   A potential mod is to ensure that the 'OFF' is truly an OFF position, by virtue of grounding the output line - that's not happening in the original drawing, and thus a small amount of hum could potentially be heard from the amplifier while in OFF mode.  Simply ground the center lug of 'B', like so:





At some point, if no one else beats me to it, I'll find the time to do an actual layout for you. Keep in mind that I'm not all that gifted in "free-hand" stuff, things might not be all that easy to decipher.....

HTH





sumgai

[mikecg]

Hello Maxwell,

Are you making any progress with fixing up your 'Rally' ?

I have made a stab at producing a wiring diagram for you - it looks a bit like the London Underground (subway?) map - but the controls should be roughly in the right place when viewed from the back of the guitar. As it only has one small access hatch on the back I am guessing that you will need a trained mouse to access the connections in the upper bout! The Hilo'Tron pickups should have shielded twin (red/white) conductors and I don't know if the wiring beyond the pickup selector switch maintains the twin conductors up to the pots - so I have taken the easy way out and terminated the pickups' 'cold' ends at the selector switch. The other area of uncertainty is the battery wiring. On this version of the drawing, I have shown an isolated (micro-switch?) normally open contact operated by the insertion of the jack plug. The other version of this drawing uses a standard switched mono jack to close the circuit between battery positive (via the switched contact) and the jack sleeve ground connection. I guess that either way will work.

So, here's the drawing:







As previously mentioned, to minimize the output noise level when the output selector switch is in the 'mute' position an extra 'switched' position must be added, to ground the output connection. The 'centre off' 2 pole, 3 way switch, as shown above, is then replaced by a true 2 pole, 3 way switch, as shown below:

[maxwell]

Hi Guys,

my apologies I haven't checked in for a while. Thanks for all the info. I have it back together its all working however there is terrible hum / static noise most switching positions. I'm unsure about the grounding wires - do I ground all the pots and switches back to the bridge / tailpiece like you would a standard wiring setup? I can send a photo of the harness if that helps? 

Cheers,

Max.  

[newey]

do I ground all the pots and switches back to the bridge / tailpiece like you would a standard wiring setup? I can send a photo of the harness if that helps?

Is the hum reduced when you touch the strings?

Grounding the pots is probably more important than grounding the switches, but they should be grounded to the grounding point, where all of the grounds are before they are wired to the output jack sleeve lug.

Many hollow-bodied guitars don't ground the bridge/tailpiece, and I don't know if the Gretsch Rally does or not. If the guitar originally had a bridge/tailpiece ground, there would be a small hole for the wire, either beneath where the bridge sits or under the tailpiece- more likely under the tailpiece. If there is such a hole, then by all means try replacing that ground wire- the other end gets grounded to the grounding point, and then to the jack - . If there's no hole there, then there never was a factory bridge ground and I wouldn't worry about it. If there never was a hum problem before (and "static" sounds like a different issue anyway), you probably need to look elsewhere for the source of the noise problem.

Having said all that, hollow-bodied guitars without a bridge ground do tend to be a bit noisier than if they had it, but the noise level is usually not a big issue until someone wants to play one through high gain pedals or amp settings. If the noise floor is tolerable at clean settings at reasonable volume levels, and only becomes an annoyance when playing with high gain, then it may be one of those "nature of the beast" things. A noise gate pedal may help in that case.

[jpascal]

Hello

My name is JP.  50 years old .Newbie here

I ve got a rally with a strange behavior with the sonic bloom.
In lower position, I have the sonic bloom.
In the center I have the bypass circuit (normal mode)
In the upper position I have the kill sound.

2 positions are not corrects.

I have dismantled the hardness, but seems to be OK.

The switch seems to be original.

Any input on how this switch is supposed to work in terms of contact close and open?

[mikecg]

Hello jpascal,

I believe that the 'factory' positions for the 'boost' toggle switch are as follows:

Up = normal (bypass), middle = off (mute), down = treble boost

Whereas your guitar is wired to give:

Up = off (mute), middle = normal (bypass), down = treble boost

That's weird!

If the wiring is original, my guess is that when they came to wire up your guitar, the factory had run out of the standard 2 pole 3 position on-off-on toggle switches (6 lug), and instead fitted a 2 pole 3 position (8 lug) switch. My reason for suggesting this is that I can't find a way of getting your switch positions using the standard 6 lug switch. Either that, or the guitar has been 'previously modified'.

So - my guess is your switch looks something like this:
 




If your switch is wired as shown above, it will be an 'upgrade' on the standard 6 lug design, as the jack tip connection will be grounded in the 'Off' position. You can easily modify the wiring to get the 'factory' switch positions - or leave it 'as is'. 

[maxwell]

Hey fellas, 

I had given up on this and only just came back to it to see a whole lot of advice / work and diagrams. Thank you so much. I will have another crack and will let you know how I go. 

[perfboardpatcher]

Hi Maxwell & guys,

there is more info available

The complete document

[jimmymac3705]

May 13, 2024 19:42:55 GMT -5 maxwell said:

Hey fellas, 

I had given up on this and only just came back to it to see a whole lot of advice / work and diagrams. Thank you so much. I will have another crack and will let you know how I go. 

[jimmymac3705]

Hi would anyone know a technician in Melbourne who can wire up my 1967 rally. The sonic boom was repaired but when reinstall had a humming issue.
The guitar tech That tinkled with it tried everything but was unable to resolve the issue.

Thanks in advance

[mikecg]

Hello jimmymac3705,

Have you tried these guys? - replayguitars.com.au/

Unfortunately, as I live in the UK, I can't comment on their level of competence when it comes to repairing a vintage electronic module, but if they can't help, they may know someone local, who can?