Home Cinema active Subwoofer malfunctioning

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Put the bulb in series with the outlet on the wall and the primary of the transformer. Basically, In series with or in place of, the fuse.
Click to expand...

OK, got it! Thanks. So the idea is that the light will become brighter when things are about to get hot, before the 1A fuse burns out, giving me a chance to kill the power? I have 2 25W bulbs, and 3 40W ones. Getting more of those will be very tough now, they haven't been for sale since Dec 2009, so I hope I don't burn those out as quickly as I do the fuses!

What will my next step be? Do I dare switch the thing back on to see if the bulb gizmo works? Or should I lift some resistors and try to figure out what's happening?
 
While your doing your testing with a well-behaved amp, the bulb shouldn't even light as long as your not driving the speaker very loud.

If you switch it on briefly, you should get a glowing bulb. You won't be blowing bulbs. They will just glow. It could blink on power up. The cold resistance of a tungsten incadescent bulb is 10x lower than the hot resistance. So, as before, the speaker stays disconnected for a while. The bulb will break when you accellerate them to 9.8 m/s^2.

Here is a little blurb. Regavolt 8A Variac - UK Vintage Radio Repair and Restoration Discussion Forum I didn't sign up so I can't see the pictures. The Variac or autotransformer with a current meter can still replace the bulb. I built mine when I was maybe 10 ish years old when I built my bench. A 120V, 3A variac; front mounted fuse; ammeter; voltmeter; binding posts and chassis mount plug. It's plugged into a 120/120 (Mains are 120 V 60 Hz) isolation transformer (actually a step up/step down/isolation transformer). A center off switch either connects direct to the isolation transformer (1.5 KVA) or the isolation transformer + the variac.= (rated at 3A). Variacs don't provide isolated voltages, but the internal transformer in your amp does.
 
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You may have heard this: The transistor blows just in time to protect the fuse. So, now you know it's true.
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Heh, maybe I should throw in some transistors instead of fuses...

Making good progress on the cleaned up PCB pic (attached); still a few changes to make, might be a few errors (most likely), but it's getting there.

I have the bulb gizmo plugged in, a new fuse in place... Not sure I dare hit the power button though?!
 

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OK, so I tried it out. When I wack the power on (AC switch on the sub), the bulb glows. Voltage output is around 1.6V AC coming out of the transformer. I think Q10 (or Q11) gets very mildly warm, but LED1 doesn't show any light, neither red or green, regardless of standby switch position. I assume the bulb glowing is a sign that something is wrong with the circuit, and the bulb is taking the power surge instead of the rest of the PCB (burning out the fuse), right?

I'll await further instructions before testing anything else out...
 
Light on means that there is a BIG problem, as you already know. Basically, you have something seriously wrong, but you won't need a fire extinguisher. Voltmeter readings are useless. I need to get up and take my shower.
 
1. Pull Q8 and Q9, Test (leave out)
2. Test Q10, Q11 in circuit
3. Remove Q7; Test (leave out)
4. Test Q5, Q6 in circuit
5. Take a look at R11, r12, R13, R14 and R17 in circuit.
6. Pick up a couple of 10K, 1W Watt resistors

BTW: What do you know about Win 7 and wireless particularly "Red X through wireless icon with connectivity" and related issues.

5. Smoke test; turn off if light bulb glows bright
6. Check the power supply voltages 37, -37, 12, -12
 
Fantastic

1. Q8 is bust. Q9 fine.
2. I get unstable readings in circuit, not sure if they are meaningful (varying voltages)
3. Q7 is fine
4. Q5, Q6 : hard to judge, in circuit, not the usual behaviour. But they are consistant, I suspect those are fine.
5. Resistors tested out fine.

7. Smoke test: As I powered on, the bulb went on and then quickly dimmed to a very weak light Clearly my first point of action is to replace Q8...

8. Transformer output = 26V AC
Diode Bridge +- = 66V
Diode Bridge + GND = 33V
Diode Bridge - GND = 33V


BTW: What do you know about Win 7 and wireless particularly "Red X through wireless icon with connectivity" and related issues.
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General windows 7 wifi connectivity issues? Windows is always mysterious in the ways it works (or doesn't), but I can give it a go if you detail the problems, symptoms etc; I'm much more at ease with computers than I am with raw electronics, would be happy to help if I can.
 
I have to admit, I'm really impressed by the bulb gizmo. I was originally reluctant to trying it out, because for one, incandescent bulbs are rare and hard to come by, and two, I don't feel confortable messing around with live current... Would rather avoid any electric shocks, if possible. But now that it's in place, it's fantastic. I'll have to read up on it and get to grips with the concept better; so "simple" and elegant way of protecting a dubious circuit!

This is a fun learning experience. Tomorrow I have quite a few errands to do, including getting a new BD139 (Q8) and a few 1W 10k resistors; and later in the day I can replace Q8 and carry on with the slow progress. In the meantime, let me know if I can do anything to help with windows.
 
I'll be busy too.

I've formulated a plan for the AMP:

1. Procure two 10K 1W resistors (may not use them) Four 22K 1/2 will do too. Might even be better.

1a. Procure Q7

1c. Leave everything as is; Q7, Q8 and Q9 out.

2. Remove and match Q1 and Q2 and any NPN transistor that you have, that you don't have to remove.
Install Q1 and Q2. The two with the closest match. Hopefully, within 10% or better.

3. Possibly test the DIFF amp.

4. Work on turn-on ckt... (Let the power Amp section Chill)

5. Work on bias..

6. Set bias to zero and has correct range.

7. Assemble power stages. Bias still at zero

8. Other mods.

9. assemble, adjust bias and test.

I didn't explain them in detail. Somewhere HUM fits in. Might like to know the gains of the PNP transistors as well.

Win 7 Pro wireless Realtek card

If you do a search for "Red X through wireless ICON", you get lots of hits. I get wireless connectivity even with the X and so does many other people. I can fix it with, my fix, which puts "LOCAL SERVICE" in the Administrator's group. This isn't the right fix. What is?

When your in the mode above SOMETIMES it will re-connect to the preferred wireless network. Sometimes it will do the blue ball thing and end up with a yellow ball in the wireless ICON. Selecting and connecting manually works fine. Wireless G, no encryption. Repeater on the preferrred network.

There are SOMETIMES 5 or more networks available. I haven't checked the logs for expected buffer overrun errors (A Windows bug). I'm thinking it might be a dependency. Not sure.

The driver is: Realtek RTL8191SE Wireless LAN 802.11n PCI-E NIC , Driver version = 2019.1.1203.2010. There is nothing in the release notes that suggest an upgraded driver will fix this issue. I updated about 4 days before the next release.

I suspect a missing dependency. Started to investigate. Will try to upgrade to latest driver.

Other problem:

Sometimes when using wierd applications like PDANET or SYNCCELL, a tethering app, and even when not using one, sometimes "Media Disconnected" appears. In XP net start "Wireless Zero Autoconfig" fixed the problem and so does re-booting. In Win 7 Pro, stopping and starting "Wlan AutoConfig" doesn't work. Re-booting does.
 
Windows problems update
Found errors and warnings for: DHCP Client (1001, 1003) Address config status event and Warnings for 1014 (DNS Client event)
So, made NETBIOS over TCP/IP mandatory. Added my gateway address to list of DNS servers.
Restarted twice: Both OK
 

Good stuff, fingers crossed... I don't find the settings and config sections very intuitive with 7.

Pick up four 22K 1/2 W instead of the 10K 1 W.
Pick up a 1K 1/2 W.
Pick up a 2SA1015.
Click to expand...
Done.

1a. Procure Q7

1c. Leave everything as is; Q7, Q8 and Q9 out.
Click to expand...
Done, got a new Q7 underhand, ready to be soldered.

2. Remove and match Q1 and Q2 and any NPN transistor that you have, that you don't have to remove.
Install Q1 and Q2. The two with the closest match. Hopefully, within 10% or better.
Click to expand...
I have a few (3) spare C2240, so out of 5 transistors, should hopefully find a pair with a close match! Will go back to one of your previous posts to figure out how to match them, and let you know how that progresses.
 
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This is my next challenge. Will read up about this in more detail and decipher what has to be done.
 
KeepItSimpleStupid said:
Windows problem.
4 restarts/boots: 50% of the time worked.
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Have you tried reverting back to default settings? The following should reset settings:

1. Click Start, Run, devmgmt.msc
2. Locate the Network adapater for your wireless card
3. Right click, choose Uninstall
4. Click on any other entry in the device list
5. Click Action, Scan for Hardware Changes
6. Network card will be redetected and reinstalled at factory defaults

There's also a way of forcing the deletion of drivers, if you suspect it's driver related. No idea what causes that; does it interfere with the connection stability in any ways? if it's driver related you can over-rule an older or more recent driver...
 
The driver is: Realtek RTL8191SE Wireless LAN 802.11n PCI-E NIC , Driver version = 2019.1.1203.2010. There is nothing in the release notes that suggest an upgraded driver will fix this issue. I updated about 4 days before the next release.
Click to expand...

Hmmm, wifi N card, quite recent. Might be related to unstability? Have you tried any other OS?

I like to remove any realtek software installed and just use the default windows manager for network settings. I find that using other software can sometimes confuse it. You can uninstall realtek software, and reinstall only the drivers by manually chosing a driver folder to install.

Another thing to think about, there's a list of preferred networks somewhere, to which windows will connect to (in order of rpeference); could you have other networks in there that come and go?

Personally set a manual IP, disable DHCP, and manually configure DNS settings. Basically leave as little things as possible on auto. Then I gave up on windows and switched to Ubuntu... (Although I have dual-boot, I just don't use the windows 7 one anymore.) I know that hardly an elegant fix, more of a radical change which solved my stability problems, created some challenges (getting to grips with packages, drivers, etc) but that I don't regret now. I used to be a real expert a Windows XP stuff and then with Vista I just lost interest!

Finding equivalent software is sometimes a pain in Ubuntu. As a last resort, I use "wine", an emulator, or the overkill method, a virtualPC with XP installed, just to run photoshop or whatever I need.... Of course, last resort, I use my dual boot image. You could try to look at services ("services.msg" I think), google what must, and must not necessarily be booted at startup, and remove realtek etc useless stuff. Google yields a tonne of stuff on services to kill to optimize the PC, and in your case, you could possibly look for network services that might be conflicting...
 
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The last time I installed the driver, I uninstalled it first. It's not the latest and greatest as it was updated 4 days after I downloaded it, but nothing in the release notes would indicate that the problem I'm experiencing would be fixed. There is no effect on the stability of the driver, nor the ability to connect. With the LOCAL SERVICE user added it still can work, but it has an X. At least, currently, the icon reflects the state. If I remove the LOCAL SERVICE user, the behavior reverts. It seems as if the longer it takes to boot, i.e. Windows Updates to install, the better chance it has to connect the first time.

Realtek doesn't have any "special bits". Uses the standard windows configuration windows. Realtek is Laptop manufacturer installed. I would hate, that in order to use a "hotspot, I would have to reconfigure. I disabled all of the adapters but the wireless and the problem persists.

I've used Unix in the past, initially when it was first developed on the PDP-11 and more recently Solaris. I did create a stand-alone Knoppix CD, but haven't done much with it for my old XP machine. The wireless driver would have to be added manually and I never got that far. Win 7 boasts the ability to run virtual machines and eventually I plan to add a flavor of Linix. I did use Cygwin on XP. I do have XP mode running on Win 7. I lost the necessity to need to connect to a Unix system and credential management. I did set up a man-in-the-middle thingy to get around access rules until they fixed it with firewall rules so you must have DNS verification. Otherwise, I had to jump through other hoops that I rather not do like transfer big file to the tmp directory on the Solaris machine and then through ssh to the host.
 
Progress, parallel work:

- I checked all of the transistors on the PCB1; somehow when I switch AC on, RED light was fine, then tried turning on to GREEN light, and the light bulb went glowing like crazy (as crazy as a 40W can be). Checked all of the transistors, Q8 and Q11 had fried. Very surprised about Q11 frying as it really didn't have a chance to get warm, and was completely cold after the "incident". So I wonder if I don't have a dud zener diode somewhere in here, maybe? Anyway...

- Hfe matching. I have 5 C2240 transistors, I want to get the closest matching Hfe values for Q1 and Q2; was thinking about the circuit you described, googled it, tried to understand etc; then noticed some multimeters, including the DVM68, have a hFE mode... Can I simply use that to find the closest matching C2240s?
 
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