| revell |
Hi all
I have a problem with my brianGT kit: the chip produced flames and started smoking as soon as I connected the power. It's a dual mono configuration with 37 volts DC after rectification . So if anyone knows what I've done wrong: please let me know! |
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| Peter Daniel |
| I've heard about case like that before: the rectifiers were mounted the opposite way. |
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| jackinnj |
| also (and I have done this once) the caps will build up enormous heat if they are put in the wrong way. Diodes go "pop", pretty loudly, but capacitors go "bang". |
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| mcs |
Don't people use fuses anymore? :)
I had a problem with diodes (the voltage rating), but nothing much happened because of the fuse...
Best regards,
Mikkel C. Simonsen |
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| revell |
Ok thanks for the quick replies, but I've allready found my problem (I hope)
Both PSU work fine and have a fuse;) but the power entry at the amp box was poorly connected: v+ and GND measured 0 with an ohm meter so they probably connect somewhere.
One more question (for now): did I ruin the chip or does the internal protection work really well against stupidities like mine? |
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| mcs |
One of my chips has survived a shorted diode, so they are quite "robust". But some things will kill the chips - I don't know if your case is one of them.
Best regards,
Mikkel C. Simonsen |
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| Peter Daniel |
| The chip will not be damaged if one rail is missing. It also won't damage the speaker. |
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| Kelly McDonald |
If smoke and flames came out of the chip, then I would think it's probably toast.
Remember don't let the magic smoke out |
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| demogorgon |
| "If i could only get that magic smoke back in, i would be rich!" |
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| peranders |
| quote: | Originally posted by revell
Hi all
I have a problem with my brianGT kit: the chip produced flames and started smoking as soon as I connected the power. It's a dual mono configuration with 37 volts DC after rectification . So if anyone knows what I've done wrong: please let me know! |
Don't you have any fuses :scratch: |
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| JasonL |
| My question is do you have any pictures ? |
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| tiroth |
| This is evidently how real men test their PSU's max amperage. |
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| jackinnj |
| quote: | Originally posted by tiroth
This is evidently how real men test their PSU's max amperage. |
Yes, one of the great quotes in all cinemaphotography (homage to Humphrey Bogart in "Treasure of the Sierra Madre"):
Fuses, we don. need no stinkin' fuses
muchos apologias to our brethren in Europe who don't get to partake in the cinema noire |
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| neutron7 |
| everyone should get cameras ready when they start up their amps. it would be almost as cool as brianGT gallery! |
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| falcott |
| quote: | Originally posted by neutron7
everyone should get cameras ready when they start up their amps. it would be almost as cool as brianGT gallery! |
Nah, even cooler! Why do you think people watch motor sport? :clown: |
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| revell |
| Ok I have some pictures of really poor quality. I will make some studio quality shots when the amp works:cannotbe: |
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| revell |
one more
how many fuses should one include in a gainclone?? |
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| kmj |
| how about one on the primary winding and one on each secondary? |
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| karma |
| good plan:) nothing lasts forever what if you go away and leave it on by mistake and it fails. better safe than sorry:rolleyes: |
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| gmphadte |
This happened to me when I interchanged connections of the speaker and the transformer secondary.
Hurry makes worry |
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| peranders |
| quote: | Originally posted by revell
one more
how many fuses should one include in a gainclone?? |
You should at least have a fuse at the primary side. |
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| falcott |
| quote: | Originally posted by peranders
You should at least have a fuse at the primary side. |
That much is for sure. And if you really want to feel safe, a fast blow fuse on each supply rail. |
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| tg3 |
| quote: | Originally posted by revell
I have a problem with my brianGT kit: the chip produced flames and started smoking as soon as I connected the power. |
A good argument for a variac with a current meter on first power up.
Another trick is to put a mains voltage low wattage incandescent light in series with the transformer primary. Should nicely limit the current for electrical disasters like the above.
A problem with fuses is that they tend to die after the active electronics.
IMHO, YMMV, yada-yada. |
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| digi01 |
this simple circuit can avoid the mess current when power on the amp.any suggestions?
sch pic below,AC power soft start. |
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| mrlots2do |
| quote: | Originally posted by digi01
this simple circuit can avoid the mess current when power on the amp.any suggestions?
sch pic below,AC power soft start. |
Digi01, thanks for posting a simplified drawing of a a/c power soft start. I sure would appreciate knowing the component values and/or part#'s.
Phil |
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| digi01 |
thank you for your interest.
the values of R1,R2,C1 is mainly based on the relay parameter.
the others component values:
B1- 1N4007 *4
C2 - 470uf/250V safety value
R3 - *20W30(current limit)
here is the real stuff. |
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| mrlots2do |
| quote: | Originally posted by digi01
thank you for your interest.
the values of R1,R2,C1 is mainly based on the relay parameter.
the others component values:
B1- 1N4007 *4
C2 - 470uf/250V safety value
R3 - *20W30(current limit)
here is the real stuff. |
Q1 Based on relay parameters, would that be the coil rating voltage dc
Q2 AC-in, what voltage, 120vac (transformer primary), 18-25vac (transformer secondary), 4-18vac (another transformer used for this circuit)
Q3 Could you show me how to calculate R1, R2, C1 using an example of recommended AC-in?
Thanks Phil |
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| digi01 |
Hi Phil,
>>Q1 Based on relay parameters, would that be the coil rating voltage dc
there are two parameters.one is NOMINAL INPUT VOLTAGE,the other is NOMINAL RESISTANCE.
>>Q2 AC-in, what voltage, 120vac (transformer primary), 18-25vac (transformer secondary), 4-18vac (another transformer used for this circuit)
the soft start circuit should be set up before the transformer primary.
>>Q3 Could you show me how to calculate R1, R2, C1 using an example of recommended AC-in?
Ok,the soft function is achieved by C1 charging.
when you power on the circuit,C1 is in open,during the charging of C1,the voltage of the coil is raising...then it is full worked.
SO,R1>>R2.
R3,10-30 ohm,20W |
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| peranders |
Some calucations can be pretty hard but you can use my simulation files and put in simplifed values. Consider the relay to be a resistance, for instance.
I have used the free program LTSpice from www.linear.com
Notice that digi's circuit won't do in 230 VAC countries, unless he changes a little. A plain 0.6 W metall film resistor isn't safe in 230 VAC environment. |
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| mrlots2do |
Digi01
Sorry, I don't understand this. I have 120vac before transformer primary. I have 24vdc spdt & dpdt relays, don't know resistance since I'm at work.
Q1 How do I get from the 120vac to 24vdc in your circuit?
Q2 Could you tell me the values for R1, R2, C1
Peranders
I like what you did in your soft start circuit. K2 contacts delayed allows slow feed bypass to transformer.
Q1 How do you get from 120vac to 24vdc in your circuit.
Phil |
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| gmphadte |
Make some other circuit using DC supply.
Go ahead if u want to learn |
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| peranders |
| quote: | Originally posted by mrlots2do
Peranders
I like what you did in your soft start circuit. K2 contacts delayed allows slow feed bypass to transformer.
Q1 How do you get from 120vac to 24vdc in your circuit.
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If you already have 24 volts DC, just skip everything from the rectifier bridge and backwards
If you have 120 VAC (instead of 230 VAC), then you have to increase C1 and C2 in my design. I have written at the end of the page suitable values. |
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| kmj |
a bit OT but i would rather post this in an active thread than start a new one.
If you use the GC based on LM3875 with 2x24V psu unrectified, how much gain can you have on the preamp without driving the GC into clipping? Havin the bottlehead foreplay (19db gain) in mind.
I have i dim memory about reading something about it being a problem when using a CD as source. |
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| mrlots2do |
| quote: | Originally posted by peranders
If you already have 24 volts DC, just skip everything from the rectifier bridge and backwards
If you have 120 VAC (instead of 230 VAC), then you have to increase C1 and C2 in my design. I have written at the end of the page suitable values. |
Peranders, your website and write-ups are amazing. I've read the soft start pages several times now and find something additionally noteworthy each time read. Thanks.
BTW.... I have not yet purchased internationally and was not aware of money exchange charges. The charges listed on your webpages seem a bit high.
Phil |
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| Damon Hill |
Sigh.
I blew up my first LM4870 board last night; I'd just
gotten it together and was doing initial load testing.
There was a 1 volt offset on the output, and then
it just blew. No obvious distortion, but I had it running
at full power into a 4 ohm load.
You guessed it; no fuses!
It was a pain to get the chip out of the board, but I
didn't lift any traces or pull out any feedthroughs--looks
like a good quality board. The silicon is a pretty good
sized die--it completely separated from its heat sink.
The heatsink wasn't flat and I may have stressed the
package; will remount differently next time. I won't swear
100% that I had the right parts value in the right places.
Where's Brian these days? He hasn't answered email
and hardly seems to be online any more.
I've got a bunch of mica insulators that I cut down to fit;
holes are spaced correctly but it was intended for two
devices side by side. Holler if you need some and I can
put them in an envelope and mail them. I cut them down
for TO-247 packages, too.
--Damon |
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| Franz G |
Because everyone wanted to see some fotos (it is not from a Brian GT board): I like to smoke, but not the smoke from Ampères :rolleyes:
I really dont know, why this happened! Immediately after power on. The amp and the chip "burned in" before about 3 hours.
After replacing the chip: everything is O.K.
Franz |
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| digi01 |
The chip has died, but the spirit of DIY will never die:cool:
ZANG |
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| Franz G |
Thanks Zang!
I think, the reason was a little piece of soldering in the box. It looks like the Vcc+ was connected to the output of the chip.
Doe's someone want to repeat this experiment, to be sure? :clown:
Franz |
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| peranders |
| quote: | Originally posted by mrlots2do
BTW.... I have not yet purchased internationally and was not aware of money exchange charges. The charges listed on your webpages seem a bit high. |
99% of all americans use Paypal. Works fine.
The dollar is falling, I'm afraid.... |
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| WorkingAtHome |
Hi peranders
You think your curcuit will be ok at 25.7VDC?
-b |
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