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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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15th Sep 2017, 3:20 pm | #1 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,858
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CRATE GT80 Amp
Folks, my son has just acquired one of these for £20. Supposedly u/s, hence the plea - Dad, Dad - can you get it going ? Me - I'm out of my comfort zone - too modern, even though I'm guessing 1980's.
Has anyone got one, or has any info or experience, just to keep me straight. Its a hybrid Valve/ semi-conductor amp with a massive single 12" speaker. I reckon the speaker alone is worth more than £20. Regards, David |
15th Sep 2017, 3:28 pm | #2 |
Heptode
Join Date: Aug 2009
Location: Carshalton, Surrey, UK.
Posts: 735
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Re: CRATE GT80 Amp
Hi,
certainly worth more than £ 20-00 I would think. I know another Crate ( of a different model ) that I worked on had a faulty transformer, I can't remember if it was output or mains ? But the fault could be something much easier to fix.
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Regards Peter B |
15th Sep 2017, 3:48 pm | #3 |
Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,878
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Re: CRATE GT80 Amp
Circuit which I think is for the same model here https://elektrotanya.com/crate_gt-80.../download.html
The Output is all Solid state it has a few token double triodes of the 12AX7 12AU7 Varieties. Cheers Mike T
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Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk |
15th Sep 2017, 4:02 pm | #4 |
Octode
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,875
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Re: CRATE GT80 Amp
I have a Marshall version of this kind of thing ('valvestate') - it's very versatile, produces a lot of different sounds (clean / dirty and all stops in between, which is the main point of the valve pre-amp) and is a lot more flexible and reliable than other more highly regarded 60s/70s all-valve amps I have used. Fixed, this should be very useful for performance as well as practice.
Do you have some valves to try in it? If the driver turns out to be knackered I can sell you a good 12" unit for 20 quid! cheers Mark |
15th Sep 2017, 5:57 pm | #5 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,858
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Re: CRATE GT80 Amp
Thanks Guys for the info.
I've just got the Users Manual showing the spec & the block diagram. Its full of yanky teeny boppy ampy wampy language, which I don't understand :- "Funky Clean", "Bluesy Dirt", "Warm Tube Crunch", etc. I'll just stick with good old electronics fault-finding. Regards, David |
15th Sep 2017, 6:18 pm | #6 | |
Heptode
Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 762
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Re: CRATE GT80 Amp
Quote:
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George |
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16th Sep 2017, 9:53 am | #7 | |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: CRATE GT80 Amp
Quote:
How it sounds when new. How it sounds after a few years on the road. How it sounds after being tripped over by a drunken roadie.
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16th Sep 2017, 10:35 am | #8 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,858
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Re: CRATE GT80 Amp
Many thanks George for the circuit diagram link. I've heaps of spare ECC type double triodes, but I'm wondering if the BFP14/BFP9104 Mosfet PA's are easily acquirable these days, if needed ?
Regards, David |
20th Sep 2017, 5:58 pm | #9 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,858
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Re: CRATE GT80 Amp
More fault finding done - Mains T/F u/s , as are the two rectifying diodes (1N4087's) for the +175V HT line for the valves.
I found that someone had not changed the T/F tappings from 110V to 220V. The Pri now draws 1.5A when my Variac is just set to 40V ! I wonder how easy, if at all, one could get a replacement transformer ? Regards, David |
20th Sep 2017, 8:55 pm | #10 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,195
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Re: CRATE GT80 Amp
Hi David, probably a simple reverse engineer and rewind job (without a 110v tap).
Ed |
21st Sep 2017, 11:09 am | #11 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,858
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Re: CRATE GT80 Amp
Right enough Ed, I guess a rewind for just 240V should do. With the T/F completely disconnected - I used my variac to feed the 85V & 40V bridge rectifier circuits & they seemed fine.
There is loads of space on the chassis & in the cabinet to mount individual mains transformers for each of the three voltage rails (+175V, +&- 85, & +&- 40V). I'll see what I've available or can scrounge meantime. Regards, David |