7048300(BM0104) Transistors-Any info on these? - UK Vintage Radio Repair and Restoration Discussion Forum

'LIVEWIRE?' · 30th Sep 2010, 10:50 am

They are TO3 metal case power transistors, which APPEAR to be standard bipolar types, used in Peavey PA Amplifiers. In situ they measure ca. 48 ohms both ways between what I take to be the base & emitter connections.
The amplifier works OK except for a loudish 'crack' when first switched on.
I'm just curious about these odd readings!
BTW Both nos. quoted in the title of this post appear on the transistor case, and I'm not sure which is the type no. Googling either brings up 'no results found!!

neon indicator · 30th Sep 2010, 6:15 pm

7048310 aka 83100 is MJ-15015, 2N3055A
70483070 is MJ3055
http://www.ampix.org/albums/userpics..._Cross_Ref.pdf
http://www.***********/doc/29319120/P...Reference-List

I don't see 7048300

It's likely a variant voltage version of 2N3055.

BM0104 might be a date code. 2001 or 2004 week 1 or 4?

You didn't say what age or model.
Is the Base transformer driven?

What sort of meter did you use?

McMurdo · 30th Sep 2010, 7:09 pm

These are motorola devices (very early ones GE-RCA) with a Peavey house number, the BM.... is a motorola (now called ON Semi) batch code. More recent devices also say 'MEXICO' on them. The generic part number can be found on an 'emergency equivalents' list that Peavey provide on their website.

Peavey always use devices selected by Vbe and hFE and so off-the-shelf generics must never be used to replace them. The power amps that Peavey make use multiple current-sharing techniques that mean that standard devices tend to develop hotspots and coldspots (and early failure) unless the correct 'graded' (as the yanks say) devices are used. I've seen generics used in repairs.....and seen them fail spectacularly. Buy cheap, pay twice!!!!

The Peavey transistors obviously command a higher price than generic ones as they've been selected at the factory, they are of course for audio use.

'LIVEWIRE?' · 30th Sep 2010, 8:58 pm

Thanks, guys, for your answers. I have later checked the circuit involved. The 48 ohm reading is caused by the presence of 47 ohm resistors from the bases to center(ground via
the speaker)line, and 0.33 ohm emitter resistors, also connected to the center rail. Two of these transistors are wired in parallel in each 'half' of the circuit, hence the low readings.
I also seem to have misread/miswritten the type no. They are indeed 7048310s. Not that, on this occasion, I need to change any of the transistors, but I'll bear in mind for future reference, the fact that Peavey use selected(matched?)devices in their amplifiers.
I guess this could also apply to other manufacturers, too.
Neon Indicator- the amp. in question is a Eurosys 15PM, and the circuit is a totally DC coupled type, similar to many other PA & Hi Fi amplifiers, using a 55-0-55v split supply. Measurements were taken using a Fluke 77 DMM, and confirmed with an analogue meter on a low ohms range

neon indicator · 7th Oct 2010, 12:06 am

MJ-15015 is Motorola, now On Semi (Freescale is diffferent ex Motorola part)

Selecting and matching transistors isn't hard. I'd not pay extra for Peavey parts. Real "On Semi" MJ-15015 parts would be fine.

An DECENT design paralleling Bipolars uses Emitter resistors and local feed back or else you get thermal runaway. MOSFETS can be easily paralleled

The match only needs to be good for the parallel pairs, not between the halves.

30th Sep 2010, 10:50 am	#1
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	7048300(BM0104) Transistors-Any info on these? They are TO3 metal case power transistors, which APPEAR to be standard bipolar types, used in Peavey PA Amplifiers. In situ they measure ca. 48 ohms both ways between what I take to be the base & emitter connections. The amplifier works OK except for a loudish 'crack' when first switched on. I'm just curious about these odd readings! BTW Both nos. quoted in the title of this post appear on the transistor case, and I'm not sure which is the type no. Googling either brings up 'no results found!! Last edited by 'LIVEWIRE?'; 30th Sep 2010 at 10:53 am. Reason: To add comment about type numbers

30th Sep 2010, 6:15 pm	#2
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: 7048300(BM0104) Transistors-Any info on these? 7048310 aka 83100 is MJ-15015, 2N3055A 70483070 is MJ3055 http://www.ampix.org/albums/userpics..._Cross_Ref.pdf http://www.***********/doc/29319120/P...Reference-List I don't see 7048300 It's likely a variant voltage version of 2N3055. BM0104 might be a date code. 2001 or 2004 week 1 or 4? You didn't say what age or model. Is the Base transformer driven? What sort of meter did you use?

30th Sep 2010, 7:09 pm	#3
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,269	Re: 7048300(BM0104) Transistors-Any info on these? These are motorola devices (very early ones GE-RCA) with a Peavey house number, the BM.... is a motorola (now called ON Semi) batch code. More recent devices also say 'MEXICO' on them. The generic part number can be found on an 'emergency equivalents' list that Peavey provide on their website. Peavey always use devices selected by Vbe and hFE and so off-the-shelf generics must never be used to replace them. The power amps that Peavey make use multiple current-sharing techniques that mean that standard devices tend to develop hotspots and coldspots (and early failure) unless the correct 'graded' (as the yanks say) devices are used. I've seen generics used in repairs.....and seen them fail spectacularly. Buy cheap, pay twice!!!! The Peavey transistors obviously command a higher price than generic ones as they've been selected at the factory, they are of course for audio use. __________________ Kevin Last edited by McMurdo; 30th Sep 2010 at 7:15 pm.

30th Sep 2010, 8:58 pm	#4
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: 7048300(BM0104) Transistors-Any info on these? Thanks, guys, for your answers. I have later checked the circuit involved. The 48 ohm reading is caused by the presence of 47 ohm resistors from the bases to center(ground via the speaker)line, and 0.33 ohm emitter resistors, also connected to the center rail. Two of these transistors are wired in parallel in each 'half' of the circuit, hence the low readings. I also seem to have misread/miswritten the type no. They are indeed 7048310s. Not that, on this occasion, I need to change any of the transistors, but I'll bear in mind for future reference, the fact that Peavey use selected(matched?)devices in their amplifiers. I guess this could also apply to other manufacturers, too. Neon Indicator- the amp. in question is a Eurosys 15PM, and the circuit is a totally DC coupled type, similar to many other PA & Hi Fi amplifiers, using a 55-0-55v split supply. Measurements were taken using a Fluke 77 DMM, and confirmed with an analogue meter on a low ohms range Last edited by 'LIVEWIRE?'; 30th Sep 2010 at 9:06 pm. Reason: To add reply to 'neon indicator's' comments

7th Oct 2010, 12:06 am	#5
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: 7048300(BM0104) Transistors-Any info on these? MJ-15015 is Motorola, now On Semi (Freescale is diffferent ex Motorola part) Selecting and matching transistors isn't hard. I'd not pay extra for Peavey parts. Real "On Semi" MJ-15015 parts would be fine. An DECENT design paralleling Bipolars uses Emitter resistors and local feed back or else you get thermal runaway. MOSFETS can be easily paralleled The match only needs to be good for the parallel pairs, not between the halves. Last edited by neon indicator; 7th Oct 2010 at 12:15 am.