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Old 24th February 2014, 07:28 PM   #181
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Quote:
Originally Posted by speedless View Post
Hi
Heres a quick test:A piece of cloth/paper with alchohol/acetone,try to wipe off the text.
If its stays on there proberly ok,if not they are without doubt fakes.
The print "MEXICO" also indicates a fake,originals : "MEX".
Anyone out there with a working amp. willing to try this easy test?

Jan
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
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Old 24th February 2014, 07:34 PM   #182
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Unhappy Prepare the lynch mob...

Quote:
Originally Posted by nautibuoy View Post
Now isn't that a coincidence! I live in North Taunton and cycled out to Monkton Heathfield a number of times.

They don't make them like JLH anymore do they. My abiding memory of visiting him was his lighting of a log/coal fire; he used what can only be described as a flame thrower that he had connected directly to a gas fire outlet that was next to the fireplace.

Ray
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
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Old 24th February 2014, 07:47 PM   #183
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Aargh! Now I don't know what to think. I just thought to check some know good MJ15003s and they do, indeed have just "MEX" printed on them.

Could this just be old stock vs new stock or should I consign them to the trash?
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Old 24th February 2014, 10:49 PM   #184
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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
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Old 25th February 2014, 05:31 PM   #185
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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
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Old 28th February 2014, 12:04 PM   #186
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I received my amplifier and power supply stuff today; nice PCBs. Thank you.

Ray
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Old 5th March 2014, 01:50 AM   #187
Shamron is offline Shamron  Norway
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Quote:
Originally Posted by Wildwater View Post
Aargh! Now I don't know what to think. I just thought to check some know good MJ15003s and they do, indeed have just "MEX" printed on them.

Could this just be old stock vs new stock or should I consign them to the trash?
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.
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Old 5th March 2014, 03:16 PM   #188
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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
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Old 7th March 2014, 02:08 AM   #189
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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
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Old 7th March 2014, 11:08 AM   #190
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Hi
Sorry
Just cant get used to WIN 8

Jan
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