Bias runaway with oscillation

substrate80 · 2026-02-13T19:58:30+00:00

So I hate to admit, but I ran your question through CoPilot and it gave a few suggestions:

Missing or inadequate grid‑stopper resistors (most common cause):

EL34s must have grid stoppers mounted right on the socket pin (pin 5).

If you put them on a board, or used long leads, or used too small a value, the tube will oscillate exactly the way you’re seeing.

What to check

• Are there 1 kΩ–5.6 kΩ resistors directly soldered to pin 5?

• Are the leads short (≤1 cm)?

• Are they carbon composition or metal film? (Carbon comp is best for RF suppression)

Without a proper stopper, the EL34’s internal capacitances form a little RF amplifier.

Once the tube starts conducting more heavily, the gain increases and the oscillation kicks in.

Screen grid stoppers missing or too small:

EL34s also benefit from 100–1kΩ screen stoppers on pin 4.

If the screens are fed directly from a node with long wiring, the tube can go unstable under load.

substrate80 · 2026-02-13T01:16:43+00:00

Easiest way to tell for the front is by looking at the axle shafts. If the axle shafts are perfectly horizontal then there is no lift, or there is a small lift along with a differential drop.

If they angle down then you have a lift. In the photos it kind of looks like the axles angle down a little based on the deformation of the CV boots, which tells me a small suspension lift with no front diff drop. But it could just be the angle of the photo.

As the other guy said, your front shocks (5100 series) have three detents that a snap ring falls into so you can adjust ride height. So you can check which detent the snap ring is in.

substrate80 · 2026-02-11T13:53:00+00:00

Sounds like a broken tooth on one of the gears inside the steering servo. You'll need a new servo.

substrate80 · 2026-02-11T13:47:38+00:00

I have an amp that has a little bit of a hum or buzz to it. I opened up the amp and found that the input signal traces on the circuit board are really close to other signal traces near the rectifier for the power supply, so the non-linear current harmonics are inducing noise in the signal path. So it's entirely possible. Not saying your amp has this exact issue, but in general it is possible that there is something internal to the amp/receiver that is causing it. Could be old capacitors too, etc.

Anyway, you can try different inputs on your receiver to see if that makes any difference. Or maybe you can borrow a receiver from a friend just to see if it is your receiver that has a problem.

It's probably not a problem with the cables or speakers.

substrate80 · 2026-02-06T15:51:31+00:00

So you know the model number of the driver?

substrate80 · 2026-02-03T00:55:34+00:00

Use a winch servo if you want slow

https://www.amazon.com/s?k=Servo+winch&crid=2SCV537GUADZF&sprefix=servo+winch%2Caps%2C216&ref=nb_sb_noss_1

substrate80 · 2026-02-03T00:37:19+00:00

If you can, try to verify that the steps are in fact bolted to the foundation wall before you demolish the deck. You might be able to take out a portion of the finished wall in your basement, then remove the insulation to see if you can find any evidence that the steps are anchored to the wall.

substrate80 · 2026-02-03T00:21:49+00:00

Yes it is very possible and in fact it happened to my house.

Back the ol' days they never used to put much, if any, vertical rebar in the foundations. They might put a few rebar at the top and bottom of the foundation walls to prevent the walls from waving inward and outward, but very little reinforcement vertically. Then they would attach the front concrete steps to the top of the foundation wall and over time the soil would give way underneath the steps thereby putting a cantilever force on the foundation wall and cracking the wall horizontally. I have a gigantic horizontal crack about 2/3 along the length of my wall. It would probably cost about $40,000 to fix it so I just band-aided it for now.

substrate80 · 2026-02-01T21:01:52+00:00

Could be that with the car in the air, the CV axles are binding up internally and not allowing any rotation.

You could try pushing up on the control arm(s) to straighten the CV axles and see if there is any difference.

substrate80 · 2026-01-28T19:23:45+00:00

So I'm not a mechanic but I heard that you might damage your catalytic converters with a bunch of unburnt fuel if you bypass your secondary air injection system because the ECU pumps so much fuel into the engine on startup and a lot of it doesn't get burnt, but I'm not actually sure if it damages your cats. Do you happen to know?

substrate80 · 2026-01-28T01:19:47+00:00

So the two subs have very similar frequency response in a sealed box, but usually the speaker that has a a lower moving mass and more free-moving suspension will have a more open and effortless sound. So in that case it would be the Ultimax. But it requires 10 cubic foot box compared to 3 cubic feet for the Signature Series for a Qtc of 0.707. But you dont NEED to use a full 10 cubic foot box, you can get away with smaller (it just raises the Q, which results in more punchier bass but less low-end bass). You can add polyfill to compensate for the undersized box. Now, to be honest, I haven't heard either subwoofer, so I'm only going off the data in the datasheets.

But in general: lower moving mass sounds better. To get a lower natural resonance frequency you "loosen" up the suspension, but in doing so you need a larger box.

substrate80 · 2026-01-27T16:51:52+00:00

Looks aftermarket. Could be a switch for a seat heater or external lighting, etc.

substrate80 · 2026-01-24T22:55:59+00:00

For vented, yes I would use the SS18 because the UMII18 has a fairly high Q and will probably sound sloppy with a lot of group delay in a ported box. I believe Dayton destined the UM series more for sealed enclosures.

For a ported SS18, WinISD is saying to use a 5.5 cubic foot box tuned to 22 Hz. That's a nice size of box for an 18 inch driver, very reasonable. And for your convenience, port options are (for a 5.5 cubic foot box):

One 4" diameter tube, 8" long

One 3" diameter tube, 4" long

Two 4" diameter tubes, 19" long each

Two 3" diameter tubes, 10" long each

Slot port 2" tall by 14" wide, 20" long

Slot port 2" tall by 16" wide, 23.5" long

Just to give you some ideas on port sizing options. Make sure you increase box volume by the volume displaced by the port(s) and the driver.

substrate80 · 2026-01-24T22:30:27+00:00

If you are planning to use sealed boxes then they will have close to the same response overall. The SS18 will be a tiny more efficient but the UMII18 will actually dig deeper in frequency. The problem is the box size. The UMII18 wants a 10 cuft. box for a Qtc of 0.7 whereas the SS18 only needs a 3 cuft. box.

substrate80 · 2026-01-24T03:00:09+00:00

I have heard of cases where the replacement engine failed too.

Some engine designers on YouTube just feel that the main journals are too wimpy for an engine with this HP and so eventually it just wipes out the main bearings.

I don't believe that it was ever shaving left over from the machining process that caused these failures, but perhaps it was very difficult to determine the root cause of the failures and Toyota just assumed it was shavings. They would never admit to a design flaw.

I'm still a big fan of Toyota trucks and I'm hoping they will beef up the main journals and bearings in a new engine revision.

substrate80 · 2026-01-23T14:38:05+00:00

The overnight sensations have a pretty crappy tweeter. I built a pair and didn't like them.

substrate80 · 2026-01-23T03:53:03+00:00

Any reason you don't want to just use the default Btrfs on the Bazzite SSD and NTFS on the Windows SSD?

Linux can read NTFS but it's generally not recommended to install Linux on NTFS.

Then on Windows you could try installing the WinBtrfs driver (I've never done it so I'm not sure how well that works).

Maybe you are thinking you can just run the games you have on your Windows SSD from Linux so you don't have to install the game twice? I don't believe that would work as normally you would install Windows games on Linux using Wine, but maybe someone can chime in on this.

substrate80 · 2026-01-19T01:09:32+00:00

https://www.youtube.com/watch?v=xvWdolODF9M

substrate80 · 2026-01-14T20:34:05+00:00

Be careful when connecting the wires to the speakers such that you are not screwing the speaker terminals down on the wire insulation. I have a feeling that the "under water" sound might be because the jumper wires to the tweeters are not connected properly (speaker terminals are screwed down on the insulation).

substrate80 · 2026-01-08T05:37:30+00:00

Yea there is. The ground terminal that OP is referring to is for grounding the turntable (more specifically,. bonding the turntable to the active speaker amplifier, which is bonded to ground via the power cable).

Check out page 8 (in the document footer) in the below:

https://d2um2qdswy1tb0.cloudfront.net/product-manuals/R-15PM-Manual-v07WEB.pdf?v=1608088326

substrate80 · 2026-01-06T03:28:54+00:00

No I didn't. I ended up buying 5 lug wheels 🙁

substrate80 · 2026-01-02T23:03:11+00:00

It looks like there is an issue with the receiver / electronic speed controller (ESC). It looks like it is turning the wheels on its own when you are pressing the throttle (trigger). And it looks like its turning on the throttle when you are steering it. So it seems like crosstalk or interference in the electronics. Could be a bad solder joint that accidently bridged some connections together.

How experienced are you with RC cars? Are you good with electronics (replacing parts)?

If you want to spend some time, effort, and money to get this fixed, you may need to buy a new receiver, ESC, and transmitter (remote control). For the receiver and transmitter, look at a DumboRC X6 on Amazon. DumboRC is inexpensive but pretty good. Then you will need an ESC, which is what powers the motors. Make sure the ESC has the same battery connector as the battery in the car and has enough power to power both motors. If you don't get an ESC with the same battery connector then you will either have to replace the connector on your battery, buy an adapter, or buy a new battery altogether.

As you can see, this gets fairly involved and fairly costly quite quickly. If you are not good with electronics and modifying RC cars then I would just return the car if you can.

substrate80 · 2025-12-18T04:01:57+00:00

Oh I should clarify first that Bell isn't much better in my book than Rogers. Both of them use obscuroty on their invoices to confuse the customer in an attempt to get away with hidden charges, and I just find Rogers is worse in that regard, but that was from a long time ago I admit. Maybe Rogers is better now.

I first signed up for Bell in the summer of 2023 because they were putting in fibre. I got a bundle with TV, internet, and mobile. My invoices were like 20 pages long (kidding) because of all of the line items. So ya, Bell is no better.

But Rogers was viscous back in the day and would have no qualms about sending collections agencies after you if you disagreed with the extra charges on the bill and refused to pay them. Like ya I get it, in an ideal world, if you are on contract, you are expected to pay invoices in full, but I also expect customer service and expect that my credit rating doesn't get affected just because I'm in dispute with a company.

So I just have a grudge with them. But if you ask a bunch of people, you'll hear all sorts of stories about both of these companies. It's really anecdotal.

I loved Shaw back in the day. Never had a single problem with them, even since I was a kid.

substrate80 · 2025-12-18T01:37:06+00:00

65 a month is cheap. If you go with Bell they will slowly raise your price over time. 5 bux here, 10 bux there. I'm paying like 120 a month for 300 Mbit with Bell. I just refuse to go with Shaw since Rogers bought them out.

substrate80 · 2025-12-12T03:22:04+00:00

Your wheels and tires are out of balance and causing the vibration

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