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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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VOX AD30VT 'valve/tube' amp
Retro look of the 1960s Vox AC30 amp made probably 2004 with lots of SM
digital chippery for effects undreamt of in the 60s. One 12AX7 , but is it for show only ? Heaters have an AC supply but the anodes don't seem have any HV components attached to them. The speaker o/p is a non-retro National Semi LM3886T. I've not powered up yet as only poking around cold at the moment as I've never seen the like before, all seems DVM ok for power supplies etc. Apparently went pop between songs and then no more. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
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VOX AD30VT 'valve/tube' amp
"n cook" wrote in message ... Retro look of the 1960s Vox AC30 amp made probably 2004 with lots of SM digital chippery for effects undreamt of in the 60s. One 12AX7 , but is it for show only ? Heaters have an AC supply but the anodes don't seem have any HV components attached to them. The speaker o/p is a non-retro National Semi LM3886T. I've not powered up yet as only poking around cold at the moment as I've never seen the like before, all seems DVM ok for power supplies etc. Apparently went pop between songs and then no more. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I had one of these in for repair a while back. As far as I recall, the triode stage is genuine, but not run from a particularly high HT voltage. You can get away with some quite low anode voltages on these twin triodes. Elektor mag have published a few circuits in recent years, where they have run these at low HT. The digital simulations of various retro amp types, was actually remarkably good. Arfa |
#3
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VOX AD30VT 'valve/tube' amp
Arfa Daily wrote in message
... "n cook" wrote in message ... Retro look of the 1960s Vox AC30 amp made probably 2004 with lots of SM digital chippery for effects undreamt of in the 60s. One 12AX7 , but is it for show only ? Heaters have an AC supply but the anodes don't seem have any HV components attached to them. The speaker o/p is a non-retro National Semi LM3886T. I've not powered up yet as only poking around cold at the moment as I've never seen the like before, all seems DVM ok for power supplies etc. Apparently went pop between songs and then no more. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I had one of these in for repair a while back. As far as I recall, the triode stage is genuine, but not run from a particularly high HT voltage. You can get away with some quite low anode voltages on these twin triodes. Elektor mag have published a few circuits in recent years, where they have run these at low HT. The digital simulations of various retro amp types, was actually remarkably good. Arfa I'll get around to powering up tomorrow but from poking around there are no capacitors with greater than 50V dc working anywhere on the ps and o/p board, I've not undone the digital effects board. I've just noticed a 3.3V v. reg. |
#4
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VOX AD30VT 'valve/tube' amp
Arfa Daily wrote in message
... "n cook" wrote in message ... Retro look of the 1960s Vox AC30 amp made probably 2004 with lots of SM digital chippery for effects undreamt of in the 60s. One 12AX7 , but is it for show only ? Heaters have an AC supply but the anodes don't seem have any HV components attached to them. The speaker o/p is a non-retro National Semi LM3886T. I've not powered up yet as only poking around cold at the moment as I've never seen the like before, all seems DVM ok for power supplies etc. Apparently went pop between songs and then no more. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I had one of these in for repair a while back. As far as I recall, the triode stage is genuine, but not run from a particularly high HT voltage. You can get away with some quite low anode voltages on these twin triodes. Elektor mag have published a few circuits in recent years, where they have run these at low HT. The digital simulations of various retro amp types, was actually remarkably good. Arfa Damn hybrid O/P devices , -V rail to o/p short on the LM3886T. Not being abused and no audio troughput at all when it failed. Is there a learned file on WWW on why these sort of devices fail , a loudspeaker wire short or heavy throughput you could understand. So ten squid to replace rather than just a 3055 or 3773 -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#5
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VOX AD30VT 'valve/tube' amp
n cook wrote in message
... Retro look of the 1960s Vox AC30 amp made probably 2004 with lots of SM digital chippery for effects undreamt of in the 60s. One 12AX7 , but is it for show only ? Heaters have an AC supply but the anodes don't seem have any HV components attached to them. The speaker o/p is a non-retro National Semi LM3886T. I've not powered up yet as only poking around cold at the moment as I've never seen the like before, all seems DVM ok for power supplies etc. Apparently went pop between songs and then no more. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ I will probably use a 100W TDA7294 as I've a couple at hand, pinning swapped to match the 68W LM3886. Monitoring phones outlet, all effects and classic amp colourations are functioning so the valve is presumably an expensive and highly inefficient indicator, for show only, the maximum DC on any of its pins wrt ground is -15V -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#6
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VOX AD30VT 'valve/tube' amp
On Fri, 14 Apr 2006 13:34:42 +0100, "n cook"
wrote: Monitoring phones outlet, all effects and classic amp colourations are functioning so the valve is presumably an expensive and highly inefficient indicator, for show only, the maximum DC on any of its pins wrt ground is -15V No experience with the VOX amp, but in the 50's I do remember a pop'tronics article on using tubes "starved for voltage" They had a radio with a plate supply of +12 volts driving a single transistor class A transformer coupled output. I don't remember which tubes they used, but they were standard 6 & 12V filament parts. -- ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#7
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VOX AD30VT 'valve/tube' amp
I seem to remember the was PC motherboard with a 12A?7 on it a few
years ago -for that authentic valve sound - car radios with valve front ends and no vibrator pack, but, they were special valves with an extra grid I think. -- Neil J. Harris |
#8
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VOX AD30VT 'valve/tube' amp
"Neil J. Harris" wrote: I seem to remember the was PC motherboard with a 12A?7 on it a few years ago -for that authentic valve sound - car radios with valve front ends and no vibrator pack, but, they were special valves with an extra grid I think. -- Neil J. Harris That motherboard was made by Aopen, which is Acer computers. -- HELP! My sig file has escaped! ;-) |
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