Fake valves

[smangus]

Hi All

I was browsing the net and came across this article about fake valves and what to look for , seems pretty comprehensive and well written , may be of use to someone especially those that are into Telefunkens! Its quite an interesting site anyway also.

cheers :)

http://www.jacmusic.com/nos/images/Fakes/index.htm

[montesquieu]

Great site, thanks for that. Some scary shit going on!

[richmain]

Just had a look at this site,makes you think twice.

[smangus]

Yeah , my valve use is pretty minimal compared to some on here. Just 2 small ones in my fb monos so if I got ripped of it wouldn't be for huge amount. but if some one is looking to buy a set of 4 or 8 larger ones then that's a different kettle of fish. I guess the moral of the storey is to buy dorm reputable dealers if in doubt.

Its got some interesting bits for sale that site though.

Sent from my SM-G950F using Tapatalk

[Barry]

Fascinating read.

I was already well aware of the existence of counterfeit Telefunken and Siemens & Halske items, especially the positive embossing of the Telefunken 'diamond', but was surprised there was no mention of the quality of the ink used for the printing on the glass envelope.

[JohnJo]

I’m sure Marco posted a link to this same article years ago. It’s a fascinating read and it makes complete sense that stocks of something that went out of production 30 to 50 years ago just don’t exist any more and what’s for sale is largely rebranded modern equivalents.

I think the only way to put an end to this is for a modern day manufacturer to produce new products that match or out perform the golden oldies. Even if they charged a premium price for them at least you’d know what you were buying.

[struth]

I’m sure Marco posted a link to this same article years ago. It’s a fascinating read and it makes complete sense that stocks of something that wen out of production 30 to 50 years ago just don’t exist any more and what’s for sale is largely rebranded modern equivalents.

I think the only way to put an end to this is for a modern day manufacturer to produce new products that match or out perform the golden oldies. Even if they charged a premium price for them at least you’d know what you were buying.

yup or go back to good old fashioned solid state :eyebrows::sofa:

[JohnJo]

yup or go back to good old fashioned solid state :eyebrows::sofa:

Hehe :D

[Barry]

yup or go back to good old fashioned solid state :eyebrows::sofa:

But what about counterfeit power devices that are no longer made? As you can't look inside a transistor or FET package, counterfeits could be easily made to "pass muster".

I think fake SS devices are unlikely, but then a few years ago there were a lot of counterfeit 50p pieces in circulation, as later there were £1 coins. Wouldn't have thought it worth the effort.

[User211]

Jac is my EML dealer and yeah that page has been around for some years.

Jac is recommended as a valve supplier by me for what that's worth i.e. not much but he has been very good with me.

[southall-1998_mk2]

Some folks should list some genuine valve sellers here.

S.

[Barry]

I believe all the suppliers mentioned here: https://theartofsound.net/forum/showthread.php?3285-On-The-Net-Valve-Databases are genuine, but if there are others then I will add them to the list.

[spendorman]

But what about counterfeit power devices that are no longer made? As you can't look inside a transistor or FET package, counterfeits could be easily made to "pass muster".

I think fake SS devices are unlikely, but then a few years ago there were a lot of counterfeit 50p pieces in circulation, as later there were £1 coins. Wouldn't have thought it worth the effort.

Apparently, a lot of fake semiconductors around. A few years ago I was looking for original RCA output transistors for a Quad 303. Got very confused.

Here is an original

https://farm9.staticflickr.com/8558/29078093394_2c8c32b2d9_z.jpg (https://flic.kr/p/LiwQ6Q)Early 303 output transistor (https://flic.kr/p/LiwQ6Q) by A60man (https://www.flickr.com/photos/41679262@N02/), on Flickr

In the end, I used these, bought from a UK supplier, amp was fine after.

https://farm9.staticflickr.com/8265/29737811125_68bf0cae40_z.jpg (https://flic.kr/p/MiQ4ct)2N3055H (https://flic.kr/p/MiQ4ct) by A60man (https://www.flickr.com/photos/41679262@N02/), on Flickr

[struth]

good thing about them is you may never have to change one, whereas valves....:eyebrows:

[Barry]

Apparently, a lot of fake semiconductors around. A few years ago I was looking for original RCA output transistors for a Quad 303. Got very confused.



In what way were you confused? Were you offered fake RCA 2N3055 devices? How did you know?

Actually my post was 'tongue in cheek' - whilst I'm aware of counterfeit copies of advanced integrated circuit chips, I can't imagine
it is worth the trouble to fake simple transistors or FETs.

[spendorman]

There were certainty fake Motorola 2N3055's out there, printing on case wrong, and other details too.

[Primalsea]

I thought that Motorola has not manufactured any semiconductors for many years 15+, so unlikely that any new looking motorola semis are genuine.

However, with modern production techniques even fakes can be quite good, if they come from one of the better factories. Possibly we could have a situation like the counterfit artists who became famous and in some ways more skilled than the artists whose work they forged.

[spendorman]

Some interesting stuff here

http://sound.whsites.net/fake/counterfeit-p1.htm

[spendorman]

Some folks should list some genuine valve sellers here.

S.

http://www.ebaystores.co.uk/LANGREX

[Barry]

There were certainty fake Motorola 2N3055's out there, printing on case wrong, and other details too.

Can you provide links?

[spendorman]

Can you provide links?

It was a few years ago, so no.

[Barry]

Some interesting stuff here

http://sound.whsites.net/fake/counterfeit-p1.htm

Ah - just read this. I take back my scepticism about fake Motorola TO-3 packaged power transistors. Still begs the question why go to all that trouble?


Fortunately I have loads of genuine Motorola 2N3055 devices knocking about here to support the several Quad 303 and 50E amplifiers of mine.

[spendorman]

Ah - just read this. I take back my scepticism about fake Motorola TO-3 packaged power transistors. Still begs the question why go to all that trouble?


Fortunately I have loads of genuine Motorola 2N3055 devices knocking about here to support the several Quad 303 and 50E amplifiers of mine.

I have a load of genuine Motorola 2N5055H, but have just discovered that they are not really a direct replacement for the RCA 38494.

See the capacitance test here. I have just done that test on mine.

http://www.amplabs.co.uk/quad%20303%20parts.htm

[spendorman]

Yesterday I ordered one of these, I expect that it will pass the capacitance test.

https://www.ebay.co.uk/itm/38494-RCA-POWER-TRANSISTOR-FOR-QUAD-303-AMPS-ETC/311459653603

This historically has been a reliable supplier

[Barry]

I have a load of genuine Motorola 2N5055H, but have just discovered that they are not really a direct replacement for the RCA 38494.

See the capacitance test here. I have just done that test on mine.

http://www.amplabs.co.uk/quad%20303%20parts.htm

Why does the article (and others) go on about Motorola MJ15003 devices? I'm talking about 2N3055s, which Quad themselves have stated as being the device used as the third part of the output 'triple'.

What Cob did you measure on your Motorola 2N3055s?

[spendorman]

Why does the article (and others) go on about Motorola MJ15003 devices? I'm talking about 2N3055s, which Quad themselves have stated as being the device used as the third part of the output 'triple'.

What Cob did you measure on your Motorola 2N3055s?

The early 2N3055 were Hometaxial, so high capacitance (low ft) like the 34994, so OK.

Later 2N3055 were Epitaxial, so low capacitance (high ft), so not really suitable for 303.

My Genuine Motorola 2N3055's gave similar low capacitance reading to the "fake Transistor" shown in their picture (Amp Labs).

I guess that the MJ15003 is a good "modern" transistor that could be used apart from the low capacitance.

I have repaired one of my amps using a single Motorola 2N3055H and although low capacitance, I didn't get any oscillation when checked with a scope and sig gen. Perhaps just lucky.

[Barry]

I've been doing a bit of research on this.

According to Quad's 303 Service data, the final output transistors (Tr1 and Tr2) are either 2N3055 or (RCA) 38494 for amplifiers having serial numbers up to 11500, and 38494 devices thereafter.

This would tally with the later 2N3055 being epitaxial devices. It would seem that Motorola (and also RCA) moved to epitaxial fabrication to achieve faster devices, but also to increase yield.

Of the Motorola MJ15003, whilst I have to believe the Amplabs report concerning supersonic parasitic oscillation, two companies which concern themselves with Quad 303 upgrade and repair (Quad Spot and Dada), do not report any problems in using 15003 devices and in fact Dada prefer the 15003 to the 2N3055/38494.

Genuine RCA 38494 devices can be obtained them from Langarex https://www.langrex.co.uk/products/38494-rca-power-transistor-for-quad-303-amps-etc/, though I don't know how they ascertain provenance. Perhaps they measure the Cob.



Whilst I have been aware of the existance of fake and counterfeit valves for many years now, learning of fake and counterfeit transistors is new to me and somewhat shocking news!

[spendorman]

Genuine RCA 38494 devices can be obtained them from Langarex https://www.langrex.co.uk/products/38494-rca-power-transistor-for-quad-303-amps-etc/, though I don't know how they ascertain provenance. Perhaps they measure the Cob.

My new 38494 arrives from Langrex next week, I'll measure the capacitance.

[spendorman]

I have four 303's, thought I'd take a look at the latest production one's power transistors, probably from the mid to late 80's. IEC mains socket.

https://farm8.staticflickr.com/7877/33559112838_846173082c_k.jpg (https://flic.kr/p/T8ve4L)DSCF1030 (https://flic.kr/p/T8ve4L) by A60man (https://www.flickr.com/photos/41679262@N02/), on Flickr

[Barry]

I have four 303's, thought I'd take a look at the latest production one's power transistors, probably from the mid to late 80's. IEC mains socket.

https://farm8.staticflickr.com/7877/33559112838_846173082c_k.jpg (https://flic.kr/p/T8ve4L)DSCF1030 (https://flic.kr/p/T8ve4L) by A60man (https://www.flickr.com/photos/41679262@N02/), on Flickr

Yes - that concurs with what I quoted from Quad's 303 Service Data: all 303s with serial number 11500 and above were fitted with RCA 38494s. If it is fitted with an IEC mains socket it will have a SN > 80500. The serial number should be stamped on a small plate on the underside and towards the rear of the amp.

I have two 303s (one is a 303K, that is one where all the connectors are replaced by XLR types, including the mains connector). However they are packed away at the moment and I can't be bothered to get them out to have a look at their SNs, let alone open them up to inspect the power transistors.

I admire your diligence in this matter, and ask did you buy a new 38494 to replace a damaged one in one of your four 303s?

[spendorman]

My late 303 is serial 83114, my early 303 is of very early production, v low serial number. All my 303's were fitted with 38494s, one 38414 failed, that was replaced with Motorola 2N3055H, yes the Langrex purchased 38494 is to replace the 2N3055H, but no rush to do that!

[spendorman]

The RCA 38494 arrived today from Langrex, measured it's Cob and found it to be 1287pF.

The Motorola 2N3055H's that I have measure in the order of 410pF.

This sort of ties in with Amp Lab's findings.

[southall-1998_mk2]

Sorry for the silly question. Are Langrex a good company to deal with? Are their NOS tubes genuine etc?

S.

[Jazid]

Yes, I've used them several times, all decent. You can 'phone up James if you want something odd or to ask about quality, provenance &c.

[southall-1998_mk2]

Smashing stuff James. Thanks!

S.

[karma67]

Yes, I've used them several times, all decent. You can 'phone up James if you want something odd or to ask about quality, provenance &c.

same here and they are only down the road from me,i bought NOS ec881 from them,had to take them back twice,the last time was to get my money back,they refunded me with no problems.

[spendorman]

same here and they are only down the road from me,i bought NOS ec881 from them,had to take them back twice,the last time was to get my money back,they refunded me with no problems.

That doesn't seem so good. but I suppose NOS could be unreliable.

[karma67]

That doesn't seem so good. but I suppose NOS could be unreliable.

i suppose these things happen,both times one tube out of the pair had a sort of wind rushing noise in the background,im no expert but shouldn't that have a result when testing which they say they do?

[spendorman]

i suppose these things happen,both times one tube out of the pair had a sort of wind rushing noise in the background,im no expert but shouldn't that have a result when testing which they say they do?

Testing may not have revealed that, the ear is super sensitive.

Some years ago I repaired a vintage valve amplifier, fitting a non standard output transformer, had to adjust the negative feedback. The good, amp worked, and measured OK using a scope and signal generator. The bad, listening tests proved that the repaired channel sounded different and inferior to the un-repaired channel.

[Jazid]

Often it's valve bases, or oxidised pins, and in the case of some WE 417a where I obviously wasn't in a rush to bin them the issue resolved itself (and for several years to date). So not perfect but NOS is a risk as it's old stock, and testing isn't perfect. I've had all sorts off Langrex and they have never been less than helpful and honest.

Sent from my BLA-L09 using Tapatalk

[spendorman]

Here is the card that came with my Langrex order

https://farm8.staticflickr.com/7900/32543553547_8dd514526a_c.jpg (https://flic.kr/p/RzLdEP)Langrex (https://flic.kr/p/RzLdEP) by A60man (https://www.flickr.com/photos/41679262@N02/), on Flickr

[anthonyTD]

The one main thing you have to establish, where either fake valves, or semiconductors are concerned is; are they actualy the same "electricaly" as the device they are pretending to be ?
For example, there were a lot of a well know make of ECC88/E88CC's being sold as the real deal years ago, [when everyone and his dog seemed to be building equipment using them] on physical inspection,they looked to be the real deal, however; after thorough testing, they turned out to be a variable mu version!!! :doh:
A...

[Mixc]

Hi what would the effect of "variable mu" be if the ecc88 was installed?

[anthonyTD]

In Audio aplications, the diffrence between fixed, and variable mu triodes is not always obvious, however; one should not be substituted for the other, especialy in radio, or test equipment aplications, as the affect of the diffrence in grid spacing character [which is the main diffrence between each type] can be considerable.
Hi what would the effect of "variable mu" be if the ecc88 was installed?

[spendorman]

Stumbled across this, long, but interesting

https://www.youtube.com/watch?v=BXAjspPLzRQ