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Old 19th Mar 2018, 3:20 pm   #1
Electrical Rod
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Default Telequipment D54 ?

New to the forum so I thought this would be a good place to ask a few questions.
I purchased the D54 scope a couple months ago and was working good, all of the front controls seem to have no problems.
Over the last couple weeks I lost the sweep and all I get is a vertical trace that can be controlled but will not display a 6.5 volt AC sine wave. I can control the length of this test voltage by the volts division and position from both ch. 1 and ch. 2.
Going by the May 1974 manual which is not exactly correct for this scope but close, I have TR107 shown as a 3 pin FET transistor and this scope uses a 4 pin FET.
TR107 in this scope is bad. I`m trying to figure out exactly what this transistor is and if I can find one. Seem to be obsolete for the most part, but i`m sure something may work.
More information will be included as needed.
Thanks
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Old 19th Mar 2018, 7:12 pm   #2
karesz*
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Default Re: Telequipment D54 ?

Hi,
my manual is June,1970 dated, has Mullard's BFW0265 listed for TR107, but that is unknown for me.

Karl
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Old 19th Mar 2018, 7:34 pm   #3
Electrical Rod
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Default Re: Telequipment D54 ?

OK I'm working out of the wrong manual, looks like several changes were made by May 1974. The 1970 manual must be it.

I will need to find a BFW0265 or a substitute. This manual shows TR107 as a 3 pin BFW1052

Thanks, Rodney.
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Old 19th Mar 2018, 10:09 pm   #4
Electrical Rod
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Default Re: Telequipment D54 ?

No luck finding a BFW0265, the metal case of this bad transistor has the #'s (00734) on it, no luck with that # either.

The May 1974 manual shows TR107 as a type of FET, a Mullard BFW 1052, but that transistor looks to be obsolete also. Besides it's a 3 pin and the BFW0265 is a 4 pin. I hate to toss this scope out over one transistor, it had a new CRT put in about 15 years ago and used very little since. Any idea of something else that may work, (modification of that circuit)? etc. etc?

Thanks.
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Old 19th Mar 2018, 10:35 pm   #5
WME_bill
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Default Re: Telequipment D54 ?

Input FET in Scopes. Telequipment D54.
The FET used in the input stages of scopes are selected. The manufacturing process leaves wide variation in characteristics, so the FET manufacturers do some selection, varying also on packaging (TO18,TO92,TO72, 3 pin or 4 pin) to give a range of commercial type numbers.
Then the scope manufacturer specifies closer tolerance, and his supply is specially selected, at extra cost. Hence the strange numbers which no-one can recognise.

I have checked the characteristics of them in several Telequipment and Tek scopes and others.
In general, they appear to be low Vp (pinch off voltage) and moderate Idss (Zero bias gate current) eg Vp =1.5v. Idss = 3.5ma, with a wide variation. If you want something exact, try the makers.

I have seen in Telequipment scopes (some may be servicing substitutes):
151-1051=2BFW1051. dual clipped together for D54.
151-0242 = BFW0265 for S54
151-1052 = BFW1052 for DM63 & D67
151-1036 = SU2351, 2N4393, TFD1551 dual for DM63
151-1125 = SU2603K,SU2603M Dual DIL (different pinout, but board of D1010 accepts either), BFW1118 dual.
All as the input stage on the Y amplifier.
If you want something which works so that you can use the scope, then try commercial types such as:
BFW13, BFT46 (used frequently by Philips in their scopes, as ON471), 2N3823, 2N4117, BF245, BF256, 2N5246, 2N5457.
If dual, then you can use two with common clip holding them together, as BFS21, or make up your own clip.
wme_bill.
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Old 20th Mar 2018, 12:21 am   #6
MotorBikeLes
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Default Re: Telequipment D54 ?

Like WME-Bill, I have tested many of these in the past. For a failed dual FET, I select a pair, I wrap some silver plated copper wire round one, carry it to the second and wind there - gives good thermal equivalence. -- I have a CT71 curve tracer, but there are many simple test circuits that will provide FETs characteristics. Don't forget with a faulty dual FET, one half may still be good to provide correct data.
BFW0265 -- I have not tested any, but it appears that they were UC products, under type No. KEM103. I MAY have one somewhere. They were used in the type JD plug-ins as used on D53, D53S, DM53A as well as your D54.
BFW1052. IDss range 8 - 11, -VGs, range 0.9 - 1.5. UC734 a good candidate, maybe also UCS2410 or BF245B.
If you buy a few plastic encapsulated BF245A,B and C, you can probably select something for any job. Similarly, a good range on metal clad BW10,11 and 12s will cover a wide range.
Les
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Old 20th Mar 2018, 2:42 am   #7
Electrical Rod
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Default Re: Telequipment D54 ?

Thanks for all of this extra information, I'm sure other people may find it beneficial also. Over here it looks like the 2N numbers are a lot easier to find. I will take a good look at all of this information. A good working dual FET substitute is good enough as far as I am concerned, just used as a hobby scope anyway.

I do have a good many old Tex scope transistor pull outs, but I am not sure if any of those will work for this input, and the time trying to figure it out could take a while. So does this 4 pin Mullard BFW 0265 that I need have a 2N number to look up and try to find?

I also see no reason why I can`t wire two 3 pin FET's together to make a dual FET to fit the four pin socket. Which 3 pin FET would be the question?

Thanks, Rodney.
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Old 20th Mar 2018, 12:57 pm   #8
Electrical Rod
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Default Re: Telequipment D54 ?

I will be looking at these Tektronix pull outs that I have from about the same period. I do know that all of them are three pin and I'm not sure if any are FET's.

Any 2N number for the Mullard BFW0265?

Rodney
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Old 20th Mar 2018, 7:01 pm   #9
MotorBikeLes
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Default Re: Telequipment D54 ?

I have just read your first two posts again. These 4 legged devices are NOT dual Fets, they are a normal 3 electrode device plus a shield.The BFW10 is a Mullard product (but could made by others as well) so you should find the specs online easily. Any decent equivalents book should show most of them.
You say your BFW0265 is marked 00734. This suggests to me it is a Union Carbide type UC734 or equivalent, not a date code, but almost certainly a selected value. When manufacturers mark their semis as BFW0265, and you can not find the info in a data book, you should conclude it is a BFWxx device, selected for properties, and marked 0265. Telequipment was a British company, and at that time Tek had little or no influence as far as I can guess. So they MAY have asked Phillips (Mullard) to supply them, with their "personal" markings. The same would apply to BFW0303, BFW1051, BFW1052
Other FETS you could select from might be TIS59Y, similar to these, as used in Dynamco Y-amps, WD212, and all the others I mentioned previously.
Les.
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Old 20th Mar 2018, 7:37 pm   #10
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Default Re: Telequipment D54 ?

Just an addendum to something I wrote earlier. The "presentation" parts of TQ scopes of this era appear to be very British "TQ", as were the selected semis, BUT TQ were by then using TEK part numbers, so you MAY be able to get more info from TEK sites. For example, the 2BFW1051 used in the S54A (a two FET package I assume) has the TEK part number 151-1051-01, so a search for a 151-1051-xx may come up with what you want. I don't have any other appropriate manuals to hand, but you could try adding the 151- to any of those numbers (0203, 1052 etc.)
Hope this helps.
Les.
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Old 20th Mar 2018, 10:10 pm   #11
Electrical Rod
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Default Re: Telequipment D54 ?

After many, many hours of searching I haven`t found a substitute for this transistor yet, I may be looking in the wrong place, but I will keep looking.
From my stash I did find a high speed switching transistor out of the sweep circuit in a old Tek scope, a 3 leg 2N2369, so that one will not work.
My eyes feel like a million numbers stuck inside, thanks for the help.
Rodney
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Old 21st Mar 2018, 3:28 am   #12
Electrical Rod
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Default Re: Telequipment D54 ?

OK solved, looks like that 00734 number I gave that was on the side of this bad transistor,, and a member picked up on it was the kee to finding the correct one.
Union Carbide 00734 goes over to 2N4416 a four lead FET for this scope,, should work just fine, a little pricy, but shows we have them in the United States.
thanks,,
Rodney
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Old 21st Mar 2018, 8:36 pm   #13
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Default Re: Telequipment D54 ?

The 2N4416 is a jfet with a small input capacitance.

It was a good starting point if you wanted to design a wideband high impedance amplifier.
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Old 21st Mar 2018, 11:08 pm   #14
Electrical Rod
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Default Re: Telequipment D54 ?

Do not have the, 4416, 4116,3823,3452,5104,5105, or 5485 and any of the others, told obsolete. Mouser said obsolete and so did many others.
I found one that cost 3 times as much as this scope. May try to figure out if a tube(valve) will work and make the modifications. I have plenty of time.
Thanks,,
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Old 22nd Mar 2018, 12:29 am   #15
karesz*
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Default Re: Telequipment D54 ?

Rodney,
you can search for that at Sphere, Qservice, SMC, EEVblog, Tek, and epay too of course...
rgds, Karl
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Old 22nd Mar 2018, 4:14 pm   #16
WME_bill
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Default Re: Telequipment D54 ?

FET for D54.
I am a bit nervous at offering you something which is not exactly a metal cased 4 lead FET,as you seem to be concerned about finding the original types for something made nearly 40 years ago, in spite of lots of alternatives still available from second rank manufacturers in USA or India or China, via ebay or similar. I see from about 1.50 upwards each. Lots of BF245, 2N3823, 2N5245.Even a single UC734 at 5.00.
To save you the effort of searching, I will gladly send you for the postage cost two UC734, TO18 FET, with 3 leads. The fourth lead has been chopped off.
I have chosen two from my stock which are fairly closely matched:
no 17, Idss 10.5ma, Vp 3.3v, Gm 5.1
no18, Idss 9.8ma, Vp 3.1v, Gm 5.3
They came I think from some RACAL counter/voltmeter panels.
Telequipment are not going to buy closely matched pairs, as it would have been too expensive, so they provide a setting up adjustment with the preset balance control in the circuit, so that differences in standing current can be taken up.
The manual tells you how to adjust this is you are in doubt.
Send me a private message with your name and mail address so we can discuss.
wme_bill

Last edited by WME_bill; 22nd Mar 2018 at 4:20 pm.
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Old 22nd Mar 2018, 6:11 pm   #17
Electrical Rod
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Default Re: Telequipment D54 ?

Thanks Bill, I was still looking, may have been looking in the wrong places. I did call Tek and several other places and they did not have a replacement.
I was not aware that a 3 lead JFET would work in place of this four lead, and with that extra lead that is connected in this scopes circuit.
If a 3 lead will work that is good, I wasn`t exactly sure about the wording of all this. So to make the 3 lead work what needs to be done is my question?
I have no problem ordering a couple etc., just got in several new NPN transistors for this scope, from SkyCraft, those were not hard to find.
Rodney
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Old 22nd Mar 2018, 7:08 pm   #18
WME_bill
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Default Re: Telequipment D54 ?

FET for D54.
Three leads are needed to make a FET work. Source, Drain and Gate. The 4th lead is substrate or screen.
On a TO72 metal case transistor, counting from the tag, comparable pins are emitter, collector, base, substrate-screen. If using the FET as a VHF amplifier, then the screen may be helpful.
For this particular use in the D54, no need for the screen. That is why the 4th lead is often cut off, as an alternative to finding somewhere to solder it to keep it from straying. The TO18 case is identical but with 3 leads only.

Many of these FET use the same chip, and the type number changes for the packaging, and sometime as a selection of closer characteristics.
The UC734, 2N4416, 2N3819, 2N3823, 2N5245, 2N5435, BF245, MPF102, J304 all use the same chip, in either TO72 (4 led metal), or TO18 (3 lead metal) or TO92 (3 lead plastic) package.
The TEK 151-1031 is 2N4416, and 151-1042 is one of a pair of 2N4416 matched for Idss within 0.5ma. 151-1070 is same but more closely matched.
Matching is to simplify set up in when manufacturing. Not important to us, as we can spend the extra 10 minutes setting up the preset controls individually. And temperature effects are not likely to worry us, unless you want to move it from -40C to +70C in an hour, and still expect readings to remain constant.

Incidentally, with most FET, the Source and Drain can be interchanged, so don't get worried if the pcb layout seems inverted.
wme_bill.
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Old 22nd Mar 2018, 7:45 pm   #19
Electrical Rod
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Default Re: Telequipment D54 ?

OK, that solves my question completely. Found the 2N3823 on ebay, so I will be ordering it. I may purchase two, what the heck. (Pricey)
I`m no expert on semi-conductors but your last post Bill solved this.
Just curious, will a Nuvistor 8056 work in that circuit. I know it uses a 6.5 volt heater. I have a few of those, but no i`m not going there.
Hi Karl, you sent me a private message about the D54 manual, for some reason my reply back did not work; but anyway if my scanner works I may be able to scan some pages to your email when I get time .
Rodney
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Old 22nd Mar 2018, 9:44 pm   #20
MotorBikeLes
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Default Re: Telequipment D54 ?

Rod, most of your questions were answered many posts up if you read them carefully.
The D54 is a dual S54A, but there was an S54 (mentioned but then "unmentioned" in the Tek (US version) Telequipment catalogue back in the '70s. The S54 had nuvistors 13SD4 from memory, the 12v heater equiv of the 6SD4.
Two in the Y amp (dual Fet in S54A/D54) and one in the T/B in the TR107 equivalent position. I found it simple to replace all 3 with FETs, saving the cost of expensive nuvistors. Of course it does mean I have good tested nuvistors in stock today.
Les.
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