Modern equivalent for Thorn 1500 transistors - UK Vintage Radio Repair and Restoration Discussion Forum

Welsh Anorak · 2nd Mar 2019, 2:04 pm

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?

paulsherwin · 2nd Mar 2019, 2:08 pm

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.

Welsh Anorak · 2nd Mar 2019, 2:14 pm

Oh yes, nothing special - usually nasty Lockfit types. I though I'd replace the lot - well, there aren't that many!

G8KBG Tony · 2nd Mar 2019, 2:17 pm

The equivalents are listed in the manual I have.

Hope this helps.

Tony

Red to black · 2nd Mar 2019, 2:19 pm

This any help ?

Edit: taken from page 276 of RTS 70-71

Welsh Anorak · 2nd Mar 2019, 2:43 pm

Thanks- plenty to choose from!

paulsherwin · 2nd Mar 2019, 2:44 pm

Quote:

Originally Posted by paulsherwin

Are they just RF bipolars? MPSH10s or 2SC2999s should be OK, and are cheap.

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.

MrBungle · 2nd Mar 2019, 4:05 pm

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

paulsherwin · 2nd Mar 2019, 6:37 pm

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.

jayceebee · 2nd Mar 2019, 9:44 pm

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.

Vectamart · 3rd Mar 2019, 7:04 pm

Quote:

Originally Posted by Welsh Anorak

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?

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.

2nd Mar 2019, 2:04 pm	#1
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,921	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? __________________ Glyn www.gdelectronics.wales

2nd Mar 2019, 2:08 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	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.

2nd Mar 2019, 2:14 pm	#3
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,921	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! __________________ Glyn www.gdelectronics.wales

2nd Mar 2019, 2:17 pm	#4
G8KBG Tony Pentode Join Date: Sep 2006 Location: Wombourne, South Staffordshire, UK. Posts: 225	Re: Modern equivalent for Thorn 1500 transistors The equivalents are listed in the manual I have. Hope this helps. Tony Attached Thumbnails __________________ G8KBG - BVWS Member - BATC Member

2nd Mar 2019, 2:19 pm	#5
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,475	Re: Modern equivalent for Thorn 1500 transistors This any help ? Edit: taken from page 276 of RTS 70-71 Attached Thumbnails __________________ I don't suffer from Insanity. I enjoy every minute of it.

2nd Mar 2019, 2:43 pm	#6
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,921	Re: Modern equivalent for Thorn 1500 transistors Thanks- plenty to choose from! __________________ Glyn www.gdelectronics.wales

2nd Mar 2019, 4:05 pm	#8
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	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
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	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.

2nd Mar 2019, 9:44 pm	#10
jayceebee Heptode Join Date: Jun 2007 Location: Durham, County Durham, UK. Posts: 640	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.