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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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26th Jan 2020, 4:56 pm | #1 |
Moderator
Join Date: Feb 2006
Location: Wembley, Middlesex
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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. |
26th Jan 2020, 7:08 pm | #2 |
Heptode
Join Date: Nov 2009
Location: London, Ontario, Canada
Posts: 675
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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 |
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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
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27th Jan 2020, 12:02 am | #4 |
Heptode
Join Date: Nov 2009
Location: London, Ontario, Canada
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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 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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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.
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27th Jan 2020, 4:35 pm | #6 |
Heptode
Join Date: Feb 2008
Location: Leven, Fife, Scotland
Posts: 823
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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
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28th Jan 2020, 2:03 pm | #7 |
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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 |
1st Feb 2020, 7:53 pm | #8 |
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Re: Beomaster transistors
I have successfully repaired the amplifier using TIP132 and TIP137 transistors.
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