Gibson RD Artist Bass---Moog Electronics inside..not working

[nevetslab]

My client who owns the White Fender Super Bassman that I just got woriking has picked up a Gibson RD Artist Bass, whose Moog Electronics inside don't appear to be working. I haven't yet seen it, but I did open the first Webpage that appeared when I googled it.

https://www.flyguitars.com/gibson/bass/RDartist.php

https://www.flyguitars.com/gibson/ba...t_techinfo.php

I found on the techinfo page photos of the large Moog PCB as well as a schematic, for it, and additional details. The schematic shows some selected Moog FET's used thruout...SFB1234, along with a normal CD4007 IC. No idea yet what does and doesn't work. Appears to be powered via 9V battery.

























The web pages are intereactive, revealing more details on it. The Front Pickup does appear to work, or so he was told by one tech who looked at it. None of the shops that he's visited have been able to do anything with it, and contacting both Gibson and Moog didn't lead to any success either due to it's age. So, it's now cycling down to our world of wizardry and craft to see how to bring it back to life.

I'll know more when I see the instrument.

Meanwhile anyone out there familiar with the electronics and the selected FET's? I do at least have a curve tracer Hameg HM8042 that I connect to my scope. Might just be oxidation issues, bad caps, switch contacts....who knows. This is the first one I've ever seen, so somewhat intrigued. My first bass was a short scale Gibson EB-O, which I should never had sold.

[nevetslab]

I found some additional support images hunting on the internet & one of the forums...Bass Talk, I think it was.

[nevetslab]

Yesterday our former Guitar Dept mgr here at CenterStaging, LLC in Burbank, CA finally came in to pick up his 'free' White Tolex-covered Fender Super Bassman. He also brought over his Gibson RD Artist bass that he bought from someone across the country. That former owner indicated everything was working fine at his location, but something must have changed by the time it got here.

When Chuch came in yesterday, I removed the rear cover of the instrument (after first gawking at the very cool looking bass in person), and after looking close at the toggle switch directly behind the bridge, I found it had a lot of battery corrosion present on the Switchcraft leaf springs. The 9V battery sits right next to the contacts of the switch, so that might have something to do with it. Photos of that to follow.






Now, I did take the time to clean up left-over solder flux on the back side of the PCB on the two IC's, a couple FET's, and a few other locations. But, what I found on the toggle switch is nasty.



So, I'm thinking, after I remove this switch and carefully unsolder the wires from it, I'll disassemble it so I have full access to the leaf springs of the switch assy and tackle cleaning off that corrosion. What's the best solution on cleaning that? Baking soda and vinegar? I've usually resorted to using a brass bristle brush and a small scraper to pick all that stuff off the battery contacts and other nearby metal parts that got infected.

When I get the Main PCB lifted up, and the switches, jack and pots lifted out, I'll get a full spread of photos for the top side of the PCB. I figured I'd tackle the most obvious thing first, as this might be where the problem is. That little fiber coupling joining the two wiper contacts together wasn't in contact with both wipers, just the outside one. Interesting project.

[Jazz P Bass]

Awesome circuitry.
Good luck.

[nevetslab]

Now having some $$ coming back in, I'm back inside the electronics housing of this instrument, and have the corroded Toggle Switch lifted out for close inspection. Got the wire colors identified, found the Switchcraft data sheet on the Switch...type 12015L 3-pole/3-position switch, Locking. I took more detailed photos so I have the roadmap to reassemble it, once I desolder the wires.






Switchcraft 12000 Right Angle Toggle Sw-1.pdf

Switchcraft 12000 Right Angle Toggle Sw-2.pdf

Switchcraft 12000 Right Angle Toggle Sw-3.pdf

Now the fun begins. LORD, don't let me screw up!

[Jazz P Bass]

YIKES!

[Jon Snell]

I have seen and worked on worse.
If you use a thin strip of wet & dry 1200 grit, those contacts will clean up nicely.
Finish them off with a contact lubricant strip; https://uk.rs-online.com/web/p/elect...aners/1015564/

I have even rebuilt a couple of these by removing the fastening screws, separating the contacts, cleaning the contacts and rebuild the switch, not forhetting where the spacers go!

[nevetslab]

The switch contacts (Palladium) cleaned up nicely. I completely disassembled the switch so I could deal with each contact arm. I used both Vinegar as well as baking soda in water...tiny little containers to go between them. I let them soak in the vinegar to begin with. All but the two wiper contact arms, which had the most corrosion cleaned up nicely. Those took a lot of effort, and had lost the plating from the corrosion. I also screwed up on one of the contact arms, using a brass bristle brush, and knocked off the welded Palladium contact. I fashioned a contact with two turns of #28 AWG Silver plated wire, soldered to the opposite side, leaving the 'contact' untouched. Over time, that will probably oxidize. After I had gotten the corrosion off, and had to live with the somewhat pitted surface on the two wiper arms, I reassembled the switch assy. Then, I used Caig Gold Wipes (which have a contact lubricant to help preserve the contact surface), cut into a narrow strip, and worked it across all of the contacts with them closed as a finishing touch.

I had to use some RTV to glue the fiber coupling arm of the two Wiper contact arms on the one side. Not pretty, but held the fiber piece in place. Not sure if that one arm had fractured, as the other end had a square hole to fit the tiny piece into place. It wasn't staying in place when I first started the project.





I also cut a small piece of thick cardboard to form a wall between the battery compartment and the switch. It's presently glued into place and drying.

Before I could get the cover back on and borrow one of the amps I just serviced to see if this operation was successful, the client for the six amps I just completed came by to pick them up. So, for the moment, all I have are the amps yet to be repaired. For all I know, this corroded switch had nothing to do with the Bass pickup electronics not working. Though after seeing it, and having heard all was working with the prior owner before it was shipped across the country to my client, who found out it's NOT working now, seemed like the place to start. So, I'll know soon. Not perfect, having lost the plating on the two long wiper arms, but a lot better than it was. I did zero out my Fluke 8060A DMM in Ohms mode, and got 0.00 ohms reading on all of the switch contacts before reassembly, so at least I know the switch is healthy.

Now waiting for glue to dry. Like watching grass grow.

[nevetslab]

I've finished the glue-up of the battery compartment wall, then painted it black. After a couple coats, letting it dry, I've re-installed the switch and battery, finally closing the lid, and turned the instrument over to do some touch-up on the scratches adjacent to the knurled mtg nut that was there when I began the project.





Now, the crucial question. Does it work after all this effort?

[nevetslab]

I finally plugged it in. Not surprisingly, that switch was NOT the problem. Still no output from the Neck pickup, so now onward with the main PCB assy.

[nevetslab]

Yesterday, I pulled the Moog Preamp PCB assy out of the body for inspection, as well as photo documenting it for my database. The Neck Pickup's PCB connector had a broken Signal lead on it's connecting cable plug. I wasn't impressed with the cable quality Gibson selected as their shielded signal cable. I did loosen the strings enough to lift up the pick guard/pickup-mounting assy, but found those cables disappear into a sealed plastic pickup cover assy, no access for disassembly that I could see, so put it back into place. So much for the thought of replacing the cables with some appropriate Mogami cable I have.

The Connectors they use (0.100" ctrs/pitch, 0.025" square pins) don't have just one locking tab on the connector shell inserts. There are two...one on each side of the inserts. I've never seen this connector before. I've opened a separate thread on that to see if anyone can identify the mfgr of that connector family. I've never seen it. I tried using my Erem 45-deg flush cutting dikes to release both sides at once, but thus far, no luck. Special tool, and I don't find what I thought I might have had tucked away to solve it.

At any rate, repaired the Neck pickup cable, I put it back together to see if I had a working bass.

Everything worked....Neck pickup working in all three Function Switch settings, so as I was getting used to what was available in settings....now about 5 minutes into this....I lost the neck pickup on the Forward and Middle Function Switch setting positions. But, I did have it on the rear setting. Messed with the Function Switch, but nothing came back on. Gave up and set it aside.

This morning, I came in, and first, spent time taking photos of the Component side of the Moog PCB assy.





So, while I've just ordered replacement connector housings & inserts from Digi-Key, my next task is to find out WHAT is shutting down slowly to take the Compressor/Expander functions out after it's been powered up for for several minutes. Probably one or more caps....of which there are plenty.

While it WAS working, I did like what I was hearing. First thing I did when I pulled it apart was to apply some Red Grease onto the nylon actuator of the 3-position Switchcraft Toggle Switch (Function Switch), which helped considerably with the feel of the switch.

[Greg Robinson]

If you'd like to replace the switch:
https://www.philadelphialuthiertools...-neck-guitars/

[nevetslab]

If you'd like to replace the switch:
https://www.philadelphialuthiertools...-neck-guitars/

Thanks, but that isn't the same switch. It's a 3-Pole 3-Way switch, using three Form C switch contacts + Frame Ground.

[nevetslab]

The Molex connectors arrived yesterday. I did first swap out some electrolytic caps, as I had seen 8VDC buss dropping when I inserted an open circuit phone plug into the output jack to apply battery power. I began with just replacing all the 47uF/10V caps with fresh 47uF/50V parts and checked again. That stopped the 8VDC supply from dropping, so I put the cover back on and checked it out. Now I had NO output from the Neck pickup in the middle and forward Function switch positions...where before, I had both pickups in all three positions for a few minutes...before loosing the Neck pickup.

As I still can't read the cap values or designation numbers on the schematics I have, and, knowing there's 40+ year old electrolytic caps here, I changed out the rest of the caps with fresh stock. That didn't make any change. So, this morning, I first checked the high pressure Molex connectors I bought, which have full enclosure around the 0.025" square pins, and have a nice tight fit. So, armed with the pinout chart of the 9-pin connector from the Function Switch, along with the other two 3-pin connectors (only using 2 pins), I successfully cut, stripped & crimped the new connector inserts, loaded them into the housings and shoved them into place. The new connector fit is much nicer than the original connectors. I did extract one terminal, and I'd say changing was a definite improvement. Did it restore the Functions?


NO. Sigh...........

All of the 2N3904 NPN xstrs measure ok, as do the selected N-Ch FET's. The leaves the CD4007AE or CD4007UB CMOS IC that's in the Expander/Compressor circuit.

Now, while I don't have the Neck Pickup present in the Middle and Forward Function positions, it does sound like I have the Expander in the Rear Position (both pickups active there).

So, I've ordered fresh CD4007's, along with fresh TL022CP Low Current Dual Bifet Op Amps, just in case that's where the problem is. I did like what I was hearing for the brief period that all three Function positions were working.

So, back to waiting.

[Greg Robinson]

Thanks, but that isn't the same switch. It's a 3-Pole 3-Way switch, using three Form C switch contacts + Frame Ground.

Sorry, that'll teach me to skim. Annoying they'd use a custom part like that.