Neumann LV-66 Replacement Transistor

[Gold]

The BSY24C that are the power transistors in this power amp are difficult to find. I have a stash and there is one place that has them but I don't know how long that will last. I'd like to find a substitute. That's a little above my pay grade.

Two LV-66 are bridged to form the cutter head drive amplifier. It is DC coupled. Needs to drive an a 10M cable. The cutter head is a heavily inductive load.

I can't find anything that exactly matches it and am unsure of what parameters to look at.  Schematic and data sheet below.

 

[Khron]

Are you sure you searched for the right part? Because unless my eyes are playing major tricks on me, i'm seeing BDY24C on the schematic, not "BSY24".

That datasheet you posted screenshots for is for a 40V 500mA rated part, capable of a flimsy 0.6W dissipation. The actual BDY24Cis a TO3 metal can package, rated for 90V, 6A and 85W, much more appropriate for driving a hefty load.

https://alltransistors.com/pdfdatasheet_comset/bdy23_bdy24_bdy25_180t2_181t2_182t2.pdf

TO3-can transistors in general are likely to get more and more difficult to find overall - metal's expensive! More expensive than a small fleck of metal and a dollop of resin, anyway

But just about any transistor rated for at least 90V and 6A should do the job just fine - might wanna keep an eye on the minimum gain, the BDY24C's spec'd for a minimum of 75 (higher gain = easier to drive for the stages "upstream" of it). Going for parts rated for more than the original's 10MHz might be risking HF oscillation.

 

[Gold]

Are you sure you searched for the right part? Because unless my eyes are playing major tricks on me, i'm seeing BDY24C on the schematic, not "BSY24".

Ooops. I'll fix that. It is a BDY24. There are a lot of BSYxx in the rack.

Edit:
Fixed above

Thanks Khron

 

[Gold]

But just about any transistor rated for at least 90V and 6A should do the job just fine -

As has happened when I've tried this in the past I can't find any transistors that meet all the relevant parameters as far as I can tell. This is why I've asked for help. Do you have any specific part numbers of currently manufactured devices?

 

[Khron]

Not sure there's anything "currently manufactured" in TO3 packages, so if you want non-unobtanium / non-obsolete parts, you'd better be ready to MacGyver the wiring / connections of the replacement transistors, since they'll be in TO220 / TO247 / TO3P packaging.

 

[Gold]

Not sure there's anything "currently manufactured" in TO3 packages,

How about "easy to get". The BDY24's are next to unobtanium. I don't want a kludge. I want a drop in replacement.

 

[Khron]

Well then, you're gonna have to pony up whatever the holders of the "last" stocks of this transistor may ask.

Do understand, it's a literally ancient part, in a package that's been on its way out since a couple decades ago, so expecting a compatibly-specced part, in that exact same package, nowadays, is a tall order.

I'm afraid it's an either/or situation, ie. deal with lack of supply and/or associated high costs on one hand, or what you call a "kludge" (using a different-packaged transistor and deal with the different mounting solution required), on the other hand.

For what it's worth, Mouser still seem to have some stock of 2N5038G's, but they're considerably lower-gain (min. 20 vs 75), and Ft's unknown.

https://www.mouser.fi/ProductDetail/ON-Semiconductor/2N5038G?qs=vLkC5FC1VN%252BMcNSLV00nCQ%3D%3D

Digikey has nothing in TO3 packaging, but Newark seems to still carry some items. Mostly from off-brand manufacturers, but some OnSemi parts as well (MJ15015).

https://www.newark.com/w/c/semiconductors-discretes/transistors/bipolar-transistors/single-bipolar-junction-transistors-bjt/prl/results?transistor-polarity=npn&collector-emitter-voltage-v-br-ceo=90v|100v|120v|140v|150v|180v|200v|250v|300v|325v|350v|400v|450v|500v|700v|750v|800v|850v&transition-frequency-ft=80khz|2mhz|2.5mhz|2.8mhz|3mhz|4mhz|5mhz&dc-collector-current=7a|8a|10a|12a|15a|16a|20a&transistor-case-style=to-3&sort=P_PRICE

 

[Gold]

I just went through a bunch of available transistors. I couldn't find any 2Nxxxx that looked like they would work. Many of the 2N had a max voltage of 80V. I tried:
2N3714
2N3716
2N3773
2N5038
2N5629
2N5631
2N5884
2N6328

I couldn't find any MJxxxxx that looked like they would work. I tried:
MJ15003
MJ15015
MJ15024

The only thing that looked like would work and I can find is a BDY28. A close second was a BDY56.

 

[moamps]

How about "easy to get". The BDY24's are next to unobtanium.

5 pcs original for about USD30 including shipping to USA

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=BDY24C&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=meanwell

Direct replacement is 2SD189

https://www.ebay.com/itm/2SD189-Original-New-Panasonic-Silicon-NPN-Transistor-D189/120976308075?hash=item1c2abff76b:gUgAAOxyakdRE29s

Higher price, but you don't change output transistors every year.

This one also would be perfect:

https://www.ebay.com/itm/Transistor-di-potenza-182T2C-NPN-140V-6A-85W/224036205540?hash=item34299933e4:g:9gkAAOSwMste20~Z


Also BDY25,26,27,28  grade B or C would be fine.

One more:

https://www.ebay.com/itm/Composants-electroniques-ampli-radio-components-Transistor-183T2B-NOS-X1/143558739584?hash=item216cc48680:g:Zp4AAOSwkeBbZXFJ

 

[Gold]

5 pcs original for about USD30 including shipping to USA

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=BDY24C&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=meanwell

I have a medium sized stash but i want to keep them for personal use. I have to repair these for other people.

Direct replacement is 2SD189

https://www.ebay.com/itm/2SD189-Original-New-Panasonic-Silicon-NPN-Transistor-D189/120976308075?hash=item1c2abff76b:gUgAAOxyakdRE29s

That looks like a TO220 case. I need the same form factor.

This one also would be perfect:

https://www.ebay.com/itm/Transistor-di-potenza-182T2C-NPN-140V-6A-85W/224036205540?hash=item34299933e4:g:9gkAAOSwMste20~Z

That looks very good.  I'll look to see if quantities are available.

Also BDY25,26,27,28  grade B or C would be fine.

What spec do you look at for noise? The BDY24C is a low noise version of the BDY24. How do you know how the 182T2C compares to the BDY24C for noise?

 

[moamps]

2SD189 has TO3 case.

Grades A,B,C  are used for hfe, not for noise IMO, it's output transistor however, without letter means "not selected".

https://datasheetspdf.com/pdf-file/725716/ComsetSemiconductor/BDY24/1

 

[Gold]

2SD189 has TO3 case.
Grades A,B,C  are used for hfe, not for noise IMO, it's output transistor however, without letter means "not selected".

Ahh, the 2SD189x is a TO220.  I thought I was told that A,B,C meant they were graded for noise but hfe make sense because there is a large range. I can test for hfe so I guess I'll have to grade them myself.

Thanks for the help.

 

[cyrano]

Some stock still seems to exist:

https://electols.com/shopping/nl/transistors/1494-bdy24.html

There's even companies advertising with them, it seems.

 

[Conviction]

How about the good old 2N3055? It's listed as a suitable replacement in one of my books.

 

[Walrus]

I wouldn't want to run the 2n3055 on 70V rails.......

 

[Conviction]

I wouldn't want to run the 2n3055 on 70V rails.......

Oops. Didn't notice the 70VDC to the right.

2N5069. It's listed next. Still rather scarce/expensive.

... But as Khron it would probably be wise to find a modern equivalent, different package, and practice some DIY.

On another note: does the output of LV-66's break down often? Why? A 2 euro per BDY24C investment seems like quite a OK deal. They're still out there.

 

[Gold]

Some stock still seems to exist:

https://electols.com/shopping/nl/transistors/1494-bdy24.html


There's even companies advertising with them, it seems.

I once bought some “custom made”  BDY24 that didn’t work out very well.  This place didn’t turn up in my search. I think 50 pcs would be a lifetime supply. If they have over 100 pcs I’m set.

I cleaned out Cricklewood which is my go to place.

I work on these VG66 racks for other people.

 

[Gold]

How about the good old 2N3055? It's listed as a suitable replacement in one of my books.

I have found them used as replacements before. I guess if they don’t blow up right away they “work”. They are as slow as dirt and don’t help sound wise.

 

[Gold]

Some stock still seems to exist:

I just ordered 50. When I went to set up an account it said I already had one. Turns out I bought BDY24’s from them before. I totally forgot. All good now.

 

[JohnRoberts]

I found exactly one to-3 power NPN close to those parameters at digikey but it is a 50A part...  https://www.digikey.com/products/en/discrete-semiconductor-products/transistors-bipolar-bjt-single/276?k=&pkeyword=&sv=0&pv74=380569&pv2103=u100V&pv1291=413593&sf=1&FV=-8%7C276&quantity=&ColumnSort=0&page=1&pageSize=25

0nly $1200 ea  never mind.  :

JR