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2nd Mar 2019, 2:04 pm | #1 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,925
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Modern equivalent for Thorn 1500 transistors
Hi
Just tussling with a Thorn 1500 and it needs the IF transistors replacing. The manual's no help with its Thorn type numbers - what are good modern replacements for them? |
2nd Mar 2019, 2:08 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,966
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Re: Modern equivalent for Thorn 1500 transistors
Are they just RF bipolars? MPSH10s or 2SC2999s should be OK, and are cheap. Actually, jellybean general purpose types will probably be OK at those frequencies.
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2nd Mar 2019, 2:14 pm | #3 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,925
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Re: Modern equivalent for Thorn 1500 transistors
Oh yes, nothing special - usually nasty Lockfit types. I though I'd replace the lot - well, there aren't that many!
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2nd Mar 2019, 2:17 pm | #4 |
Pentode
Join Date: Sep 2006
Location: Wombourne, South Staffordshire, UK.
Posts: 225
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Re: Modern equivalent for Thorn 1500 transistors
The equivalents are listed in the manual I have.
Hope this helps. Tony
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2nd Mar 2019, 2:19 pm | #5 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
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Re: Modern equivalent for Thorn 1500 transistors
This any help ?
Edit: taken from page 276 of RTS 70-71
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2nd Mar 2019, 2:43 pm | #6 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,925
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Re: Modern equivalent for Thorn 1500 transistors
Thanks- plenty to choose from!
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2nd Mar 2019, 2:44 pm | #7 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,966
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Re: Modern equivalent for Thorn 1500 transistors
Actually, I've just had a look on eBay and MPSH10s are a lot more expensive than the last time I looked, even from China - maybe forum members have been buying them all up! 2SC2999s are still pretty cheap though.
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2nd Mar 2019, 4:05 pm | #8 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Modern equivalent for Thorn 1500 transistors
GQRP club are selling MPSH10 at 10 for 80p. Might panic buy some!
My goto is the 2n2369. Still available for not much money: https://cpc.farnell.com/unbranded/2n...-18/dp/SC06699 |
2nd Mar 2019, 6:37 pm | #9 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,966
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Re: Modern equivalent for Thorn 1500 transistors
The MPSH10 is a useful transistor and it's worth keeping a few to hand if you find a cheap source. The leadout is the same as a BF19x making substitution physically easy.
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2nd Mar 2019, 9:44 pm | #10 |
Heptode
Join Date: Jun 2007
Location: Durham, County Durham, UK.
Posts: 640
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Re: Modern equivalent for Thorn 1500 transistors
The 1500 is a bit fussy about the transistors used in positions VT7 & 8. There was a time when we ordered BF197s from Notts Stores BF199s were supplied and there was a small but noticeable drop in performance. Very slight crushing on peak whites and sometimes together with caption buzz which unlike the 1400 the 1500 wasn't prone to unless there was a fault, stick with a BF197. For the AGC controlled stages use a BF196 or a BF198.
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3rd Mar 2019, 7:04 pm | #11 |
Pentode
Join Date: Feb 2007
Location: Ventnor, Isle of Wight, UK.
Posts: 141
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Re: Modern equivalent for Thorn 1500 transistors
I would use the original types. If you don't like lockfits, there are the BF594, etc which have straight lead-out wires but are otherwise much the same with the same pin layout.
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