Series 1 Bass Electronics Problem

[strangeboy]

Hello, all.
My '78 Series 1 Bass suddenly and quite randomly, began making loud popping sounds when played. It's very strange and it's not something I can force to happen. Today I picked it up and began to play and it was perfectly clean. Then, after about 20 minutes, the popping sounds began with every note I played. I've tried to isolate the cause:
- Removed 5 pin cable and switched to 1/4" battery powered jack. No change.
- Exercised all switches. No change.
- Exercised all volume and filter pots at 50+ revolutions each. No change.

The only other clue is that it only happens when the filters are at or near wide open.
And then, it will suddenly stop... completely.

Losing my mind.
Any thoughts will be most helpful.
Thanx!

[pauldo]

Hi Strangeboy,
Are you the original owner of this bass?
Best I know is there may be an upgrade available for the Series electronics.
Sit tight, there are smarter people here who will assist you shortly.

Pics?

[David Houck]

Two things off the top of my head.  Are the pots tight against the body/not loose?  And check inside the control cavity that nothing is shorting against the shielding.

[KR]

Hi,
Others will soon way in here. Be sure to check, unplug and clean the jacks of whatever device you're plugging the bass into making sure it's not the device first before tearing into the bass. If it's not your device....
A good start is to clean all the output jacks on the bass and also clean the cables connectors (1/4 & XLR) with a Q-tip dunked in contact cleaner or alcohol--if alcohol is all you have it will work fine. Wring out the q-tip so it's not dripping before cleaning the barrel of the 1/4" jack and XLR jack on the bass. Unplug the Alembic power supply box and clean all those jacks, too. Further, you can unscrew the bass back plate, expose the cavity, and then unplug each of the pickups and single humcancellor connectors on the preamp card, clean them, re-attach them, and then be sure to slide the plastic cover/tubes back over each of the pickup connection points on the preamp card. Also, while in the open cavity, unplug the big black square connector on the preamp card, (the black connector with an arrow on it) and very, very, gently clean the pins being careful not to bend the pins so it will re-attach properly. If you're worried about this just carefully unplug and replug the black square connector a couple of times without cleaning.
If this problem happens with both the 1/4' output and the XLR outputs, I would assume it's not a problem with the Alembic power supply box. If your problem only happens when using the XLR with power supply, and works fine with 1/4" jack I would look into a faulty power supply needing a capacitor-replacement, maybe.
After checking and cleaning everything, but still having a problem, you can unplug the pickups and the black square connector from the pickup card and send just the preamp card in to Mica and Ron.
Lastly, a broken or compromised 1/4" jack on the bass will cause problems when using --either-- the XLR or 1/4" connector, so check the 1/4"  jack housing while in the cavity with a flashlight, watching how it behaves when wigglying a plugged in 1/4" jack.
As always, fully rotating each of the pots 100 times or more, and moving the switches quite a few times is always recommended.

[rv_bass]

I have experienced this loud popping with two different Series basses. 

For one of them, the screws on the five pin jack became loose and the jack sunk into the cavity when I plugged the cable into the bass, causing the connectors on the back of the five pin jack to make contact with other things in the cavity, presumably shorting and causing the loud popping sound.  I tightened up the screws, securing the five pin jack and it resolved the problem.

For the other bass, the connector on the ribbon wire inside the cavity came loose, I assume shorting things out and causing the loud popping sound.  I resecured the ribbon connector and it solved the problem.

So those are two things you might want to check on your bass.

[strangeboy]

Hi Strangeboy,
Are you the original owner of this bass?
Best I know is there may be an upgrade available for the Series electronics.
Sit tight, there are smarter people here who will assist you shortly.

Pics?

Yep. Original owner. I've considered the electronics upgrade, holding that as a last resort.

[strangeboy]

Wow. Thanx, everyone. It's sounds like I'm "going in." Dave, Keith and RV... thank you for the details. I'll report back.

[strangeboy]

Well...
Disconnected pickup and ribbon cables, lightly cleaned with 90% alcohol. Gently "massaged" all other connections.
So far so good, I'm happy to report.
Again, thank you all!

[pauldo]

Yeah!

Now how about a few pictures that we can drool over? 

[strangeboy]

Yeah!

Now how about a few pictures that we can drool over? 

Here are some recent monochrome pics from my Instagram page:

[strangeboy]

Yeah!

Now how about a few pictures that we can drool over? 

My files are too large. Try visiting:
https://www.instagram.com/p/B5Eh6YYJUHc/?igshid=e48nwrfmwpgs

[pauldo]

Saw it, loved it.  Beautiful lefty.  Loved the story you posted with it also.

[strangeboy]

Saw it, loved it.  Beautiful lefty.  Loved the story you posted with it also.

Thank you, Pauldo.

[mica]

I sent this over to your Facebook message request as well, but here's some troubleshooting advice direct from Ron:

-----------------------------------------------------------------------
using the output in stereo, determine if the pop sounds are equal in both channels or predominately in one channel only.

if it is in one channel only, check the connector for the pickup, and suggest unplugging and plugging in again on that channel in case that connection is intermittent.

think this might be early enough that the connectors are the coaxial microwave connectors.  they sometimes have an issue with the ground contact where the tiny tines that detent the connector in the fully mated condition are slightly too loose to make a reliable ground connection.  can't be corrosion since they are heavy mil-spec gold plated.

if the pop sounds are equal in both channels, then it's the hum pickup since the hum cancelling signal is distributed to both channels.

###

another possibility is either one of the input FETs or one of the op-amps.  that is less likely if the frequency and sound character of the pops are the same regardless of the voltage (22 volts bipolar on power supply or 9 volts bipolar on battery).

also possibly what is called fretting corrosion (which is caused by vibration really) on the gold contacts on the 14-pin ribbon connector where it plugs into the circuit card, but this is very infrequent.

-----------------------------------------------------------------------

Looks like you've got some work to do, then report back to us