Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Return to Tube DIY Asylum


Message Sort: Post Order or Asylum Reverse Threaded

Arrrrrgh!

75.89.237.95

Posted on February 8, 2017 at 06:50:18
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
After waiting almost three weeks for the slow boat from China to bring my little 60 watt halogen transformers, it looks like neither one of them is working properly. At least i can not get 12vac out of them no matter what i do. I tried hooking them to my variac and bringing it up slowly. That got me about 0.8vac on each one. I then hooked them to the filaments of a 26 tube for a load, and measured the the voltage at the pins and got about 0.8 vac for both again. This is straight out of the box with no modifications yet. I did not have this trouble with the larger wattage units. Am I doing something wrong?

 

Hide full thread outline!
    ...
RE: Arrrrrgh!, posted on February 8, 2017 at 08:09:04
Triode_Kingdom
Audiophile

Posts: 6146
Location: Texas
Joined: September 24, 2006
I don't understand. You're connecting a 12V transformer to a 1.5V tube?







--------------------------
Buy Chinese. Bury freedom.

 

true rms meter, posted on February 8, 2017 at 09:42:10
RayP
Audiophile

Posts: 584
Location: Maryland
Joined: June 30, 2005
Are you measuring with a true RMS meter? I seem to remember you had one.

I did my initial testing with a large power resistor. I also used a thermistor and not a variac.

ray

 

RE: Arrrrrgh!, posted on February 8, 2017 at 11:10:20
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
Just to give it a load. I was running the transformer with my variac and watching the results on my true rms meter. I had planned on stopping when it got to 1.5 volts ac output or so. Never made it that far. I just wanted to test the transformers before I started modifying them to reduce the output voltage.

 

RE: true rms meter, posted on February 8, 2017 at 11:18:07
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
The meter says true rms on it. It's a fluke model 179. I will try a resistor, but I used a tube when I checked the larger units I modified to run the 813 filaments.
What is a thermistor?

 

thermistor, posted on February 8, 2017 at 11:24:13
RayP
Audiophile

Posts: 584
Location: Maryland
Joined: June 30, 2005
http://www.mouser.com/Circuit-Protection/Thermistors/_/N-axfus?Keyword=CL-190&FS=True

An inrush current limiter. More about them in the link below.

They are often used when using toroid power transformers.

ray

 

RE: Arrrrrgh!, posted on February 8, 2017 at 12:19:21
deafbykhorns
Audiophile

Posts: 674
Location: Florida
Joined: October 17, 2003
This power supply wont work at low voltage. Takes about 70-80v for it to start working, by that time you will have blown your 26 tubes

 

RE: Arrrrrgh!, posted on February 8, 2017 at 12:26:11
Triode_Kingdom
Audiophile

Posts: 6146
Location: Texas
Joined: September 24, 2006
Didn't we discuss this previously? The oscillator in the halogen ETs either oscillates to saturation, or it doesn't oscillate at all. It also needs a substantial load to start up. Has anyone here successfully modified one of these for 1.5V out?


--------------------------
Buy Chinese. Bury freedom.

 

RE: Arrrrrgh!, posted on February 8, 2017 at 14:05:23
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
I have not seen anyone say they were not able to, so I thought I would give it a try.

 

RE: Arrrrrgh!, posted on February 8, 2017 at 14:06:58
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
Ok, let me try it with a resistor instead, or a tube with a 12v filament.

 

update, posted on February 8, 2017 at 16:38:53
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013



well drat.... just doesn't seem to be my night. I hooked the halo up to the filaments of an 813, and got a bit of a glow from it, and it was measuring 4.5 volts on my dvm. I started taking loops off the torroid and got down to about 1.4vac with 4 loops left on the torroid. then I hooked it up to a 26 and compared the brightness of the filament to a 26 in my preamp that I know is set at 1.5 vdc and they looked pretty close. Decided to try it in the bread board and was rewarded with a loud hum, so decided to put the same 550uf cap in that I used on the halos for the 813's. Got that set up and when I turned the juice on there was a bit of a crackle and then silence. No glow on the filament any more. Could it be the cap is to big for this little guy? Pic attached. Looking at the picture I just thought of another possibility too. On the 813 halos there are 4 diodes in front of the greedn cap and the wires were attached to the back pair. Could it be these wires should be attached to the diodes behind the cap? If so, I have one left I can experiment with tomorrow. At least they were cheap; just wish it didn't take so darned long to get them.

 

RE: update, posted on February 8, 2017 at 17:03:11
RayP
Audiophile

Posts: 584
Location: Maryland
Joined: June 30, 2005
I think if you look at the back of the pcb that you will see that the diodes on either side are connected to each other at the edge of the pcb. they are also connected to the large green caps. It is just a simple diode bridge.

Presumably you remembered to observe the cap's polarity.

It's interesting that you got to such a low voltage. Perhaps next time you could start with the 550 uf cap attached and then remove the turns. Or as you suggest you could try a lower value cap.

ray


 

RE: update, posted on February 8, 2017 at 18:27:07
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
So it doesn't matter which pair you hook up to? I did observe the polarity.

 

RE: update, posted on February 8, 2017 at 18:34:18
RayP
Audiophile

Posts: 584
Location: Maryland
Joined: June 30, 2005
If you measure the resistance between the diodes at the edges of the pcb, the resistance should be zero if your's are like mine. So you can connect to either.

ray

 

RE: update, posted on February 8, 2017 at 21:28:01
Triode_Kingdom
Audiophile

Posts: 6146
Location: Texas
Joined: September 24, 2006
The 1 ohm (or similar) surge resistor burned open because of the capacitor. I can see it in the photo, next to the output toroid. This has all been discussed multiple times, I strongly suggest you go back and read the previous posts on using these devices. You need to replace the resistor with a standard 1/2W or 1W approximately 1 to 3 ohms. I also recommend using a smaller cap than 550uF. I've never attempted to power one of these with such a large filter. Again, discussed previously within the last month or so...





--------------------------
Buy Chinese. Bury freedom.

 

RE: update, posted on February 9, 2017 at 03:57:36
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
I don't think we discussed that particular item, and besides it would take me forever to go through all the posts that particular thread generated. Certainly a whole lot longer than it took you to type your post.
When I did the halos for the 813's I first used a cap that was way too small, so I thought I would start with a larger one this time.Thanks for the info.

 

RE: update, posted on February 9, 2017 at 04:45:45
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
thanks!

 

update 2, posted on February 9, 2017 at 09:39:12
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
I am beginning to think I will just stay with the dc switching supply on the 26. It is fairly small and easy to adjust for the right voltage with just a couple of resistors and the adjustment screw. I can get a good measurement of the voltage and I can get it very close to the 1.5vdc I need. The halo is giving me a hard time as I have no way of accurately measuring the output as far as I can tell. Been trying to adjust it with resistors but it seems to very sensitive to the value. Just a few tenths of an ohm can make it go from working to not working, and with no way of measuring the output I am reluctant to waste 26's trying to see if it is right. Oh well, I got close and it only cost a few bucks to try it out. If anyone else figures out a way to use them for under 2 vac please post your method.

 

Yes, that's how they behave, posted on February 9, 2017 at 14:35:04
Triode_Kingdom
Audiophile

Posts: 6146
Location: Texas
Joined: September 24, 2006
Vinnie, the halogen transformer won't work if you remove the number of output turns necessary to theoretically produce 1.5V. Two of us did that test at two different times, less than two months ago, and I thought you were involved in at least one round of those discussions here on the forum.

I'll also go on record again to say that no one should apply high frequency AC of this type to driver or preamp stages. The possibility that residual energy will be amplified and mixed in subsequent stages cannot be ignored if the goal is high fidelity sound.





--------------------------
Buy Chinese. Bury freedom.

 

RE: Yes, that's how they behave, posted on February 9, 2017 at 17:10:12
vinnie2
Audiophile

Posts: 2809
Joined: September 28, 2013
Sounds like the dc transformer is the way to go then. Thanks.

 

RE: Or Rod Coleman supplies, posted on February 9, 2017 at 18:37:33
deafbykhorns
Audiophile

Posts: 674
Location: Florida
Joined: October 17, 2003
.

 

Page processed in 0.027 seconds.