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 Post subject: 3M Germanium Transistor part numbers
PostPosted: Apr Thu 20, 2017 9:15 am 
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Is anyone familiar with the part number markings of 3M branded Germanium transistors? I cannot find a cross reference for the part number printed on these output transistors from the 1960s.

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Thank You


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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Thu 20, 2017 2:38 pm 
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What product are the in? Could be an in-house number and you'll have to get a Sam's for reference.


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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Thu 20, 2017 4:48 pm 
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466 EIA number is Delco, IIRC.
If you are sure they are germanium, here's Delco's data:

http://www.33audio.com/enter/data/Delco1963.pdf

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 5:14 am 
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Tbirdkid wrote:
What product are the in? Could be an in-house number and you'll have to get a Sam's for reference.


This is an 8 watt amplifier chassis out of a 3M Cantata 700 Background Music System model 94BG from the mid to late 1960s. There is no Sams Photofact information on this product. 3M USA explained that they "divested" all of their audio products information in 1988. I've also been in contact with 3M in Canada which was originally 3M Sound Divsion Products, and they did not have anything about the product in their old technical manuals.

It is possible that the same output transistors were used in one of the transistorized 3M Wollensak Reel to Reel machines of the 1960s, namely the 1500SS but I have not been able to dig that far as of yet.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 5:20 am 
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Findm-Keepm wrote:
466 EIA number is Delco, IIRC.
If you are sure they are germanium, here's Delco's data:

http://www.33audio.com/enter/data/Delco1963.pdf


Thanks for the link! :mrgreen:

The 3M Cantata 700 Model 94BG was the first generation model. It was first manufactured in the early 1960s up until a point where the MK2 was introduced which I believe is the Model 293AH.

The other transistors are RCA Germanium types 2N2613, 2N2614 and 2N2953. If I remember correctly from what I have read, Silicon transistors were available in the 1960s but incredibly expensive. It would be great to at least have a circuit diagram of the amplifier unit, but I've not been able to locate that information.

Like I explained previously the 1960s Wollensak 1500SS (Solid State) service docs may also help shed some light.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 5:32 am 
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Findm-Keepm wrote:
If you are sure they are germanium, here's Delco's data:

http://www.33audio.com/enter/data/Delco1963.pdf


I downloaded and viewed the datasheet. There seems to be no 2n466 listed, though I could have misread the information?

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 7:26 am 
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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 1:59 pm 
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Hi Donald,

There is a simple but useful (initial) sizing technique for output transistors for amps with AB output stages:

The Vce0 of the replacement transistor should be about 20% - 30% higher than the rail-to-rail voltage (or the supply voltage, if it is a single supply amp) of the amplifier.

The max peak current through a transistor would be the rail voltage (or half of the single supply voltage) divided by the load impedance.
The max current rating of the transistor should be about 2 - 3 times as much, the load of a speaker is not simply resistive.

The other parameters of the transistors would probably be just fine, the early germanium transistors were manufactured pretty much with the same technology.
This initial sizing rule of thumb is also true for Si devices.

Hope this helps,

Peter


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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 7:05 pm 
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Isn't the Cantata the player that takes large tape cartridges, and has pinch rollers that turn into soft, sticky goo? I used to work for a Muzak franchise, an=d serviced them. Never had to do an electronic repair, just mechanical.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 21, 2017 10:44 pm 
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The 2N466 is a small TO-5 GE PNP intended for audio driver/output at a voltage of about 25 volts. Those in your picture look like TO-3 and probably PNP. NTE 121 is a brute that I use in most cases and they work well. If you can not find a matched pair you will need to match them as far as resistances go to get them into the ball park.Also NTE 104 is similar. The NTE and older ECG numbers are the same. Many transistors cross into these such as 2N176, 2N301, 2N155, 2n3614 and many many more.


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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Sat 22, 2017 10:08 am 
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stromberg6 wrote:
Isn't the Cantata the player that takes large tape cartridges, and has pinch rollers that turn into soft, sticky goo? I used to work for a Muzak franchise, an=d serviced them. Never had to do an electronic repair, just mechanical.


Yes that is it. The pinch rollers in this one kind of bubbled and sagged against the mechanism plate. I find it odd that the pinch rollers in this turn soft, but the idler wheels are all in perfect condition, just like my Wollensak T-1515 and 1500SS.

Sound Products Canada (Formerly 3M Sound Products) also explained that the electronics were never a problem. Unfortunately of all their older documentation they did not have anything on the Cantata 700.

This unit was stored for many years. I suspect the condition of all electrolytic capacitors. There is also one Tantalum capacitor on the board, a 10uf 15v. They do like to go bang. I intend on replacing all of the resistors, capacitors etc. The mechanism plate is stamped, 1967, therefore it's due for a rebuild. I have been advised by experts who regularly restore transistorized jukebox amplifiers that if the bias is wrong the output transistors will go poof.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Sat 22, 2017 10:23 am 
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Audioman wrote:
The 2N466 is a small TO-5 GE PNP intended for audio driver/output at a voltage of about 25 volts. Those in your picture look like TO-3 and probably PNP. NTE 121 is a brute that I use in most cases and they work well. If you can not find a matched pair you will need to match them as far as resistances go to get them into the ball park.Also NTE 104 is similar. The NTE and older ECG numbers are the same. Many transistors cross into these such as 2N176, 2N301, 2N155, 2n3614 and many many more.


These are the standard sized transistor packaging, which as far as I know are packaged as TO-3 types.

In my search in NTE for the 2n466 it suggested the NTE 102 and NTE 103 which are "Germanium complementary transistors designed for me- dium–speed saturated switching applications".

This is what threw me off.

I suspect that 3M used this transistor in many of their Wollensak reel to reel products during this time period. The 1500SS was manufactured, mid to late 1960s (I think). I suspect it used the same output transistor. I am waiting to find a high quality reprint of the 1500SS service manual. It may be the closes thing I find to match the playback circuit in the 94BG Cantata 700 MK1.

I downloaded the NTE121 data sheet and it specifies that you can purchase matched pairs. This would save me great headache in that I wouldn't have to buy a bunch of these and then try to match them on my Triplett 3490A transistor analyzer.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Sat 22, 2017 6:51 pm 
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There is some mis-communication here. Findm-Keepm posted that 466 is the EIA manufacturer code for Delco. I think that was misunderstood as a transistor type number and led you down the wrong path. NTE 102 and 103 are not what you are looking for. NTE121 would probably be the way to go.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Sun 23, 2017 11:24 am 
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Tim wrote:
There is some mis-communication here. Findm-Keepm posted that 466 is the EIA manufacturer code for Delco. I think that was misunderstood as a transistor type number and led you down the wrong path. NTE 102 and 103 are not what you are looking for. NTE121 would probably be the way to go.


In the research I did online, a reference showed that the Delco 466 code is for loudspeakers not transistors.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Tue 25, 2017 2:20 pm 
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Audioman wrote:
Those in your picture look like TO-3 and probably PNP. NTE 121 is a brute that I use in most cases and they work well.


I had remembered that simple tests on transistors could be done with a multi-meter how it was done escapes me. It was high-school (1970s) that my electronics shop teacher showed me how to test (very quickly) a power transistor with a Simpson analog VOM.

Glad we have the internet.... By finding this:
http://www.electricalbasicprojects.com/how-to-identify-npn-and-pnp-transistor-using-multimeter/

I was able to determine that these are indeed PNP transistors. Something else I had previously noticed and let slip my mind is that the sides of the caps are stamped with the letters ST. I suppose they could have been manufactured by ST Microelectronics, yet I have no real proof.

When I un-soldered and removed the transistors, I found that they were was no heat sink grease on either the mica insulators, transistor casing or the heat sink plate. I suppose at only 8 watts output maximum they would not get very hot. The Mica insulators are rather thick compared to what I have have in extremely old NOS.


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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Thu 27, 2017 3:36 am 
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Quote:
Silicon transistors were available in the 1960s but incredibly expensive.


RCA and Westinghouse (where I worked) were selling 2N3055 silicon TO-3 for under 70 cents in 1968.

ST Microelectronics did not exist until the 80s. Before that it was Thomson CSF of France and SGES-ATES of Italy. They combined to form ST.

The ST on the can could be a manufacturer code (Solitron, maybe) or just to indicate a steel case, or could have been a special selection, like for Hfe.

Delco did make germanium TO-3 power transistors in the 1960s. 466 might be the universal EIA code for Delco. If you look at Mallory (235), the same code is used for capacitors and resistors. http://www.triodeel.com/eiacode.htm

http://audiophool.com/Misc/1962_EIA_codes.pdf

Rich


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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Thu 27, 2017 8:24 am 
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Rich, W3HWJ wrote:
Quote:
Silicon transistors were available in the 1960s but incredibly expensive.


RCA and Westinghouse (where I worked) were selling 2N3055 silicon TO-3 for under 70 cents in 1968.

ST Microelectronics did not exist until the 80s. Before that it was Thomson CSF of France and SGES-ATES of Italy. They combined to form ST.

The ST on the can could be a manufacturer code (Solitron, maybe) or just to indicate a steel case, or could have been a special selection, like for Hfe.

Delco did make germanium TO-3 power transistors in the 1960s. 466 might be the universal EIA code for Delco. If you look at Mallory (235), the same code is used for capacitors and resistors. http://www.triodeel.com/eiacode.htm

http://audiophool.com/Misc/1962_EIA_codes.pdf

Rich


I saw the codes however it did not lead me to a data sheet as to which transistor these are. The number 8918-1 does not appear to be something I can find information for either. Unless of course I am missing something in my search effort.

Unfortunately, like everything else money makes the world go around. I'm waiting for payment from a customer. I'll then purchase a copy of the Wollensak 1500SS (solid state) service manual which was manufactured during the same time period. The chassis of this background music system has a stamp of 1967. If the date code on the transistor is correct (6625), 3M must have bought a ton of them for use in their products.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Thu 27, 2017 6:54 pm 
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EIA codes have nothing to do with part numbers. They indicate who actually manufactured a part. 3M did not make these transistors. They are undoubtedly "house numbers." Equipment sellers had component manufacturers mark parts with proprietary numbers, so that repair techs could not easily buy cheaper replacement parts and had to deal with the original equipment manufacturer.

When I was in the semiconductor business (Westinghouse and Siliconix) we occasionally had to make agreements with customers that we would not sell their "proprietary" parts to others and would not provide a cross reference. This makes good economic sense. You take care of the customer who buys 100K pcs., not the tech who buys 2 pieces.

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 28, 2017 6:23 am 
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Rich, W3HWJ wrote:
Quote:

RCA and Westinghouse (where I worked) were selling 2N3055 silicon TO-3 for under 70 cents in 1968.



If this was the case why did so many manufacturers choose to continue the use of Germanium transistors?

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 Post subject: Re: 3M Germanium Transistor part numbers
PostPosted: Apr Fri 28, 2017 6:36 am 
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Rich, W3HWJ wrote:

When I was in the semiconductor business (Westinghouse and Siliconix) we occasionally had to make agreements with customers that we would not sell their "proprietary" parts to others and would not provide a cross reference. This makes good economic sense. You take care of the customer who buys 100K pcs., not the tech who buys 2 pieces.

Rich


I understand that 3M did not manufacture the transistors.

I had read some of the same information about "house" part numbers somewhere else. I can't help being curious as to which transistor was re-badged for this purpose. Without a schematic, it's probably near impossible to tell.

With circuits being quite complicated these days and where the ICs may be common, the embedded software is not, a manufacturer can still have guaranteed obsolescence.

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