Beomaster transistors - UK Vintage Radio Repair and Restoration Discussion Forum

Michael Maurice · 26th Jan 2020, 4:56 pm

I am repairing a Beomaster 901, it uses BD697 and BD698 complimentary transistors.

These have an odd case TO127 which appears to be unobtainable.

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I ordered some transistors from an online supplier and though these were marked BD697 and BD698, they were supplied in a TO220 package.

What could I use to replace these transistors. I was thinking of using TIP141/142 but these are thicker and the pins are spaced further apart.

So all suggestions welcome.

orbanp1 · 26th Jan 2020, 7:08 pm

Hi Micheal,

Those are complementary, darlington, 5A, min 60V, TO220 devices.
The TIP 120-121-122 and TIP125-26-127 transistors would do and are widely available.
I am sure the pins could be bent to fit.
The same for the TIP141 series.

Regards, Peter

Michael Maurice · 26th Jan 2020, 8:27 pm

The problem is that the TIP12x series are TO220 and the TIP 141 series are slightly thicker than the BD transistors which makes mounting harder because the transistors are sandwiched between the heatsink and a metal plate, I'll try and get a photo

orbanp1 · 27th Jan 2020, 12:02 am

Hi Micheal,

I did find the datasheet for the BD677A-679-682A and complementer transistors, and those have TO126 cases (at least the ST made ones).
Interestingly, the "All Transistors" web site lists them as TO220 cased!
The TO126 cased transistors are indeed skinnier (2.4mm - 2.7mm vs. 3.56mm - 4.83mm thickness of the TO220) and the leg spread is also closer.
Interesting mounting that they are sandwiched!
Any chance of spreading that gap? Even with a bit of "re-engineering" the mounting?

Regards, Peter

Herald1360 · 27th Jan 2020, 10:46 am

Picture of mounting?

Sounds like the transistors are clamped to a heatsink plate using a channel section bar or similar across all the devices. Tricky to replace individual devices with substitutes since all need to be the same thickness.

Norman Raeburn · 27th Jan 2020, 4:35 pm

Hi Michael, I came across a couple of pairs of these today when searching my junk for some thing else. Do you only need one pair as I would like to keep a pair for myself. Please let me know if you are still looking for them. Norman

Michael Maurice · 28th Jan 2020, 2:03 pm

Hi Norman,

I’m going to try replacing them with BD681/2 from RS which looks like it might just work with a little bit of packing.

Thank you for your kind offer

Michael Maurice · 1st Feb 2020, 7:53 pm

I have successfully repaired the amplifier using TIP132 and TIP137 transistors.

26th Jan 2020, 4:56 pm	#1
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,222	Beomaster transistors I am repairing a Beomaster 901, it uses BD697 and BD698 complimentary transistors. These have an odd case TO127 which appears to be unobtainable. I ordered some transistors from an online supplier and though these were marked BD697 and BD698, they were supplied in a TO220 package. What could I use to replace these transistors. I was thinking of using TIP141/142 but these are thicker and the pins are spaced further apart. So all suggestions welcome. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

26th Jan 2020, 7:08 pm	#2
orbanp1 Heptode Join Date: Nov 2009 Location: London, Ontario, Canada Posts: 675	Re: Beomaster transistors Hi Micheal, Those are complementary, darlington, 5A, min 60V, TO220 devices. The TIP 120-121-122 and TIP125-26-127 transistors would do and are widely available. I am sure the pins could be bent to fit. The same for the TIP141 series. Regards, Peter

26th Jan 2020, 8:27 pm	#3
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,222	Re: Beomaster transistors The problem is that the TIP12x series are TO220 and the TIP 141 series are slightly thicker than the BD transistors which makes mounting harder because the transistors are sandwiched between the heatsink and a metal plate, I'll try and get a photo __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

27th Jan 2020, 12:02 am	#4
orbanp1 Heptode Join Date: Nov 2009 Location: London, Ontario, Canada Posts: 675	Re: Beomaster transistors Hi Micheal, I did find the datasheet for the BD677A-679-682A and complementer transistors, and those have TO126 cases (at least the ST made ones). Interestingly, the "All Transistors" web site lists them as TO220 cased! The TO126 cased transistors are indeed skinnier (2.4mm - 2.7mm vs. 3.56mm - 4.83mm thickness of the TO220) and the leg spread is also closer. Interesting mounting that they are sandwiched! Any chance of spreading that gap? Even with a bit of "re-engineering" the mounting? Regards, Peter Last edited by orbanp1; 27th Jan 2020 at 12:08 am.

27th Jan 2020, 10:46 am	#5
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Beomaster transistors Picture of mounting? Sounds like the transistors are clamped to a heatsink plate using a channel section bar or similar across all the devices. Tricky to replace individual devices with substitutes since all need to be the same thickness. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

27th Jan 2020, 4:35 pm	#6
Norman Raeburn Heptode Join Date: Feb 2008 Location: Leven, Fife, Scotland Posts: 823	Re: Beomaster transistors Hi Michael, I came across a couple of pairs of these today when searching my junk for some thing else. Do you only need one pair as I would like to keep a pair for myself. Please let me know if you are still looking for them. Norman

28th Jan 2020, 2:03 pm	#7
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,222	Re: Beomaster transistors Hi Norman, I’m going to try replacing them with BD681/2 from RS which looks like it might just work with a little bit of packing. Thank you for your kind offer __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

1st Feb 2020, 7:53 pm	#8
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,222	Re: Beomaster transistors I have successfully repaired the amplifier using TIP132 and TIP137 transistors. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/