Crate BV150H tube/valve amp

What is the voltage on the heaters? If this is excessive then the whole transformer is probably running too high.

Gareth.

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I didn't think of that, all valves out for testing at the moment

No mains voltage stated at the IEC inlet, just fuses for 110 or 240V, 7 wires to the primary side of the tranformer and jumper spade matrix inside. As the rep was going around Europe , not just the UK , I wonder if if it is internally set to 210V. Anyone know what the secondary voltages should be ? or how to unravel ? power up and look for voltages 30 or 40 V off from 0,110 or 240 I suppose. No smoothing choke for this amp it would seem, unless its in with the mains transformer .

As the mains switch is made for 110V use then anything is possible

The HT would depend on what tubes were in the output. The mains switch illumination is derived from where?

I've seen HT from 400 to 700 volts depending on the tube and manufacturer but if you have 450v caps your HT should be what minus 10 to 15% of the 450v caps..

What are the tube heater voltages?

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Testing the valves at the moment , next time I power up I will use a variac set for 210V or so and try and work out the 0/110/210/230 settings

Make sure the voltage selector is wired correctly. I didn't read this was a prototype first time around. Not that this normally portends of problems.

Curious what AC volts are at the filament and HT taps in the 230v/no variac setting.

Your best bet IMHO is trying to get the 6.3v heater winding correct via a variac and then make a judgement.

Gareth.

"BV" = Blue Voodoo series. 150 similar to 60 but with more O/P valves maybe ?

This also uses 350v and 450v rated caps and max quoted HT is 460v. This is coped with by 350v cap pairs series'd up, with v-share Rs across them.

Arfa

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I was wondering where the "B" came from and assumed V was for valve, despite USA amp. I will download that schema and compare

I should have said previously only the 110V and 230V fuse ratings stated on the chassis, not 2 separate fuseholders, so someone might erroneously think it was an "intelligent" ps , no external selector switch or helpful labelling of selector matrix inside, I'll explore that later today.

All valves test ok except one 6L6 which, apart from heater, is totally dead, no gain at all at any anode current. There is opaque stain on the envelope in area above pins 4 and 5, localised in that area, although it could pass beyond the non-round, mica spacers. I assume some metal melted and evaporated/jetted onto the glass like the getter process. I assume this could have been plasma arc to anode and excessive current and blown mains fuse, as that part of the amp history. What would have happened here ? I will break into the base/glass pip/cut-ring the envelope and remove the innards to have a good look as presently cannot see anything through the deposit. A melted hole in the anode? what would physically stop any valve action? the getter is still silvery. Not yet retubed (that one plus another removed for balance) and tried out on reduced mains yet.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Assuming no obvious internal o/c connections to electrodes, then a stripped cathode is about the only thing. However, I don't quite understand your statement "no gain at all at any anode current". It seems to me that if you are able to see *any* anode current, then the valve is, to whatever degree, 'working', and hence has at least some gain ?? How does the tester control the anode current ? By varying the g1 voltage ? If it does, then that would confirm that the grid is not o/c. Thinking a bit more, you might well see some anode current, but little 'gain' if the g2 connection was open ?

The schematic for the '60 that I pointed you at, has a detailed diagram set of the primary connection arrangement for different voltages. Probably a similar scheme to the '150 ?

Arfa

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Other than heater continuity it tests as though no valve placed in the socket.

Same colour code of primary, not secondaries , as that blue voodo and seemingly the same significances. But I'll have to take apart to check what is jumpered to what, and also the HT1 smoothing is different as it uses 3 , not 4 caps there. I forgot to check each voltage on the 7 primary wires, will do so next.

With the duff 6L6 and one other removed Putting 199V on the existing setting of primaries gives 5.65V ac so suggesting 6.53V ac if 230V fed in on existing internal set primaries. Is

The hum is present but with my variac I can lift the ground and doing that, the hum goes and amp works fine , normally testing an amp there is no hum and lifting the ground can introduce hum , so I wonder what other problem lurks. 1000V megga test on the mains Tx shows nothing amiss to ground.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Looks like the same colours but not necessarily the same taps.

Monitored the total primary resistance and marked, removed/replaced spade connections until 3 spade connectors blue , grey and black removed without affecting reading . Leaving blue+white stripe, white,brown and violet as the primary.

Powering up on 199V wrt to neutral the free wires read blue 190.3 grey 86.4 black 206

wrt live blue 8.3 grey 120 black 8.8V

is this the setting for 210V, 230V or 240V ?, I'm trying to get the maximum number of turns as the primary. I'm thinking I need to swap the blue+white with the black lead. If complete agreement with that Blue Voodoo 60 then the existing wiring is undefined on that chart, the J numbering does not tally with this one

Broke into the 6L6 , I thought the caesium getter went white immediately but takes a few minutes, envelope safely sealed separately now. The outer grey metalwork anode had a bright metal spot adjascent to where the black envelope staining was. Cutting half the anode away revealed a bare metal patch on the otherwise white coating of the cathode, no pools of metal or smoke trails, G1 winding looked fine. I'm surprised how tough the mica/composite ? spacers are compared to similar I've seen inside toasters

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Exploring the 6L6 a bit more there was continuity between the base pin and G3 but the internal contact to the cathode was missing. Presumably a deliberate weak fusible link in whatever occassions a plasma arc strikes between cathode and anode.

Looks as though the hum was associated with the input socket. This is designed to be isolated from chassis taking ground from screened lead. As it was turning round with tight bush nut I assume someone had been in there and changed the insulating bushes about so ground-looped, now isolated and tight and no undue hum.

Looked under the pa board and it is 2 seriesed 47uF,450V for HT1 and the other one with a dropper for another HT. date 2003 or later. Mains primary now set for presumably 250V as heater readings are still a bit high. So with full mains on there and all 8 12AX7 and only 4 of the 6 off 6L6 reads quiescent 6.6V ac and 470V HT1 from 356V ac, other secondaries or/or

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I cut the pins at the base of the 6L6 envelope to see that area and the ribbon that connects to the cathode tube is spark eroded to a ragged break. This ribbon is 0.5 x 0.04mm in section, if it was copper then I make the rupture current would be about 6 amps. Presumably failed at a weld spot so less than that

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on