I wonder if we are all referring to the same components... polsol reported a problem with the MJ15003s and Siliconray believe they did receive a problem shipment. I have four of these from two unbuilt kits which all have MEXICO printed in them (which you suggest is a sign of a fake). However, I tested their gain at 1 amp and they all seem to work fine. Two are branded ON and two are Motorola.
Does the MEX(ICO) text test apply to 2N3055 only?
I wasn't pleased to find that the Motorola ones were second hand even though I paid for new but as these had the best gain figures (97 and 80, when the new ON's measured 62 and 55) I guess it is a wash. My kits were ordered mid-September and arrived in early December (the post was having a BAD time). I also measured the big capacitors and they were within spec and well OVER their nominal value so that's good too..
So, I've no complaints about my shipment
Prepare the lynch mob...
At the time I am afraid I was far more interested in his daughter. Such an opportunity missed through the hedonism and foolishness of youth! Ever the generous teacher he would explain his designs to me (appropriately simplified) but I wasn't paying more than the politic amount of attention
At the time I am afraid I was far more interested in his daughter. Such an opportunity missed through the hedonism and foolishness of youth! Ever the generous teacher he would explain his designs to me (appropriately simplified) but I wasn't paying more than the politic amount of attention
Hi
Wildwater:
Try the "quick test".
The ones marked "MEX" applies only to the original MJ15003.
See pic. in my last post,the 2N3055 looked exactly like the original!
(untill the "quick test")
and/or read this:Counterfeit Transistors
Yes the fakes may work or not, but cant compare in any way.
Jan
Wildwater:
Try the "quick test".
The ones marked "MEX" applies only to the original MJ15003.
See pic. in my last post,the 2N3055 looked exactly like the original!
(untill the "quick test")
and/or read this:Counterfeit Transistors
Yes the fakes may work or not, but cant compare in any way.
Jan
Thanks speedless. Tested with acetone (spouses nail varnish remover) and I now have four much cleaner cases all with their printing still intact. The second hand Motorola ones did fade just a bit - but I guess they must have be pretty old since ON semiconductor was spun off 15 years ago.
I think that makes me happy again It's an emotional roller coaster ride on this thread
I think that makes me happy again It's an emotional roller coaster ride on this thread
I bought 50 Mj15003's from Farnell last year and i have used 18 of them. All of them are used in Class A amplifiers and have proven to be genuine. And they all have "Mex" written on the third and last line, NOT in the middle, which a lot of the fakes have. The base plate is about 1mm thick, the "cover" have a totally flat top, not rounded, and the print is sharp and deep black, but does not look like lazered on, like a lot of the 2n3055's i've seen lately have.
Hi
Just got some 2n3055 from RS .
Marked "ON" & "MEX"
First the " wipe test",the text went clean off ! ?
With a suspicion rising I desided to cut one.
See Att. pic.
A nice surprice,the cooling "coin/mint" (axeformed) is present and the assembling dosn't looks like its made in hand.
Still it could be a fake! The dice is very small. See:Counterfeit Transistors
But I think these are actually ok.
The "wipe" test is apparently no longer usefull for exposion of fakes.
Neigther is the dimensions.Base thickness,flat top,diameter of insulation around pins......
These pirates know there dirty work .
Seems the only way to check is testing a few to/over the limits.Hoping the rest is similar.
Jan
Just got some 2n3055 from RS .
Marked "ON" & "MEX"
First the " wipe test",the text went clean off ! ?
With a suspicion rising I desided to cut one.
See Att. pic.
A nice surprice,the cooling "coin/mint" (axeformed) is present and the assembling dosn't looks like its made in hand.
Still it could be a fake! The dice is very small. See:Counterfeit Transistors
But I think these are actually ok.
The "wipe" test is apparently no longer usefull for exposion of fakes.
Neigther is the dimensions.Base thickness,flat top,diameter of insulation around pins......
These pirates know there dirty work .
Seems the only way to check is testing a few to/over the limits.Hoping the rest is similar.
Jan
Hi Siliconray,
Quick question for your power supply ; Hi-End Power supply board with speaker protecting - Boards | Kits | Components | Modules | Tools
My power transformer is +- 25Vac, 300VA. Could I use your power supply with my power transformer so I can get +-22Vdc ?
There are very minor details from your web site, does your circuit allow the user to adjust the output voltage (I need +- 22Vdc) or is your power supply board simply a rectifier + some filtering caps ?
The rectified 25Vac will give about 35Vdc, to get down to 22Vdc will require a 13Vdc voltage drop at a few amps...I don't see any heatsink on your PCB.
Thanks,
Eric
Quick question for your power supply ; Hi-End Power supply board with speaker protecting - Boards | Kits | Components | Modules | Tools
My power transformer is +- 25Vac, 300VA. Could I use your power supply with my power transformer so I can get +-22Vdc ?
There are very minor details from your web site, does your circuit allow the user to adjust the output voltage (I need +- 22Vdc) or is your power supply board simply a rectifier + some filtering caps ?
The rectified 25Vac will give about 35Vdc, to get down to 22Vdc will require a 13Vdc voltage drop at a few amps...I don't see any heatsink on your PCB.
Thanks,
Eric
Power supply for JLH 2005
Can someone help please.
I have read on this forum that the JLH 2005 works wonder at +- 19Vdc, 1A bias and it's better to use a regulated supply vs unregulated.
I have built the Amp Camp with the proposed 19Vdc switching mode supply and it sounds amazing therefore I was thinking of the following for the JLH 2005 ;
Buy two small switching mode power supply each rated 19Vdc, 3.5A but I would make sure to buy the double insulated version..i.e. the type with the floating output this way I can easily create a bipolar supply while using two unipolar +19Vdc supply.
I know this would work but do you think that having a supply of +-19Vdc, 3.5A enough to power a stereo JLH 2005 amp ? I could simply buy a 36Vct, 160-200VA but it wouldn't be regulated...this is the reason I would really like to use these Switching power supply.
Most of the supply (19Vac, 3.5A) are available without a ground pin and if properly built they are double insulated with floating output. The more powerful one like the 19Vdc, 90W are mostly grounded on the primary side and the DC output is tied to ground so a bipolar supply can't be created without blowing something ;-)
Thanks for your help.
Eric
Can someone help please.
I have read on this forum that the JLH 2005 works wonder at +- 19Vdc, 1A bias and it's better to use a regulated supply vs unregulated.
I have built the Amp Camp with the proposed 19Vdc switching mode supply and it sounds amazing therefore I was thinking of the following for the JLH 2005 ;
Buy two small switching mode power supply each rated 19Vdc, 3.5A but I would make sure to buy the double insulated version..i.e. the type with the floating output this way I can easily create a bipolar supply while using two unipolar +19Vdc supply.
I know this would work but do you think that having a supply of +-19Vdc, 3.5A enough to power a stereo JLH 2005 amp ? I could simply buy a 36Vct, 160-200VA but it wouldn't be regulated...this is the reason I would really like to use these Switching power supply.
Most of the supply (19Vac, 3.5A) are available without a ground pin and if properly built they are double insulated with floating output. The more powerful one like the 19Vdc, 90W are mostly grounded on the primary side and the DC output is tied to ground so a bipolar supply can't be created without blowing something ;-)
Thanks for your help.
Eric
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Hi e_fortier with 38v across the rails you will have close to 13v RMS max at the output. So a nominal 8 ohm load will draw slightly over 1.5A for an output power close to 21w. Your supply looks fine for one 8 ohm channel but getting a bit tight for a 4 ohm load or for two channels.
Over many lunchtimes at work I have read the main thread on this amp and there is a recurring theme that current to spare is a GOOD thing and the experienced builders that tried out different supply rails use 2A or more so that dips in the loudspeaker's impedance are well catered for.
It doesn't seem a common view that a regulated supply is needed just a low noise one as these amps don't have the highest Power Supply Rejection Ratio. The Cap Multiplier is a good, historical, match as that was the authors recommended supply for the original design.
I am (VERY) slowly building a Siliconray 2005 version and an original (single rail) version as the mid and high amps for a 3 way active system and research on this site has led me to have big heatsinks and plenty of current.
Over many lunchtimes at work I have read the main thread on this amp and there is a recurring theme that current to spare is a GOOD thing and the experienced builders that tried out different supply rails use 2A or more so that dips in the loudspeaker's impedance are well catered for.
It doesn't seem a common view that a regulated supply is needed just a low noise one as these amps don't have the highest Power Supply Rejection Ratio. The Cap Multiplier is a good, historical, match as that was the authors recommended supply for the original design.
I am (VERY) slowly building a Siliconray 2005 version and an original (single rail) version as the mid and high amps for a 3 way active system and research on this site has led me to have big heatsinks and plenty of current.
is that the size of a real 3055 chip?
Are all the different source but genuine 3055 the same size chip?
Hi,
WOW this really helped me, I was under the impression that the JLH 2005 was also rated 10W output just like the 1969 version...boy was I wrong ;-)
I'm aiming for 10W output power, 22W is way too much. The 1969 would be great since I already have a 27Vdc, 8A power supply but I want to avoid the output cap.
Thanks to your text I did some calculation, with a +- 12Vdc supply with 1A bias I would get 9W at the output...I just wonder if using a different voltage will screw up the bias and sound...
Rgds,
Eric
WOW this really helped me, I was under the impression that the JLH 2005 was also rated 10W output just like the 1969 version...boy was I wrong ;-)
I'm aiming for 10W output power, 22W is way too much. The 1969 would be great since I already have a 27Vdc, 8A power supply but I want to avoid the output cap.
Thanks to your text I did some calculation, with a +- 12Vdc supply with 1A bias I would get 9W at the output...I just wonder if using a different voltage will screw up the bias and sound...
Rgds,
Eric
Ok, I am confused. Are we talking about two different products in this thread? I ordered the above and got a headphone amplifier kit. The power transistors were not in the TO-3 case.
The amp will produce power according to the rails you use (within limits,
) and have heatsinks able to to keep it cool. With +- 12 volts you will have +- 11.4 v swing available (caused by the 1 diode drop across each output transistor) 11.4/sqrt(2) = 8v rms so closer to 8W than 9 but this is an inaudible difference.
With this PSU you'll be dissipating 12W per output transistor which shouldn't be exactly hard to keep cool, just decide the approximate heatsink temperature you are comfortable with and size accordingly.
Since its a class A amp you are going to pull 1A from the PSU all the time so you need to be happy that this is its continuous rating. I am pretty sure that what siliconray supply can pull up to 1.5 times the quiescent (bias) current so you may be limited by the PSU if you are driving something that can look like a lower impedance than it's nominal 8 ohms.
You shouldn't be concerned that a low power version won't be as good; siliconray also supply a headphone amp which is pretty much the same circuit way less powerful that you are intending to use and is also very well regarded.
As long as your PSU and heatsinks are a reasonable match for whatever level you decide to run at you'll not be disappointed.