VM breakdown

[sikter]

Get a new one and sell broken one to me.

[Burner]

As it is I promise you that you don't want it ;)

[sikter]

As it is I promise you that you don't want it ;)

Oh yeah, I want it!

[zvenamps]

all V/M is fault built !! you can not use ECC83 in v1 and V2 filament in series..

and put 26 volt dc power the 2 inner filament will breakdown in 10-200hours
though they see only 5,6 volts because of the series resistance of the outer filament (hot) side in each tube

Ecc83 is only for 6,3 or 12,6 volt filament voltage and not for use in series with other tubes... the tubes limits is 5,8-6,9 volt per filament under voltage will breakdown the cathode in the tube in about 10-200 hours...

[sikter]

Hm...
I play 20 hours per month ( give or take few hours)
so it will live max 10 months if your calculation is right.
Though, my tube broke after 48 months. I bought my VM used and have no
idea how many hours it was in use before I bought it.
(I play in HDR mostly)
I'm curious about statistics from other users...

[surlybastard]

Mine's a 2007, I purchased used in 2011. The guy I bought it from was *not* the original owner, said he owned it for 18 months. So I have no idea how much mileage mine had on it before I picked it up. Mine has periods of activity then largely sits with the cover on. When it's being used a lot it probably gets 10-12 hours of use a month, right now though, not so much maybe 2 hours a month. I replaced the power tubes a couple of months ago but otherwise the 12AX7's are stock and going on six years.

[Burner]

Feels like...

[MKB]

all V/M is fault built !! you can not use ECC83 in v1 and V2 filament in series..

and put 26 volt dc power the 2 inner filament will breakdown in 10-200hours
though they see only 5,6 volts because of the series resistance of the outer filament (hot) side in each tube

Ecc83 is only for 6,3 or 12,6 volt filament voltage and not for use in series with other tubes... the tubes limits is 5,8-6,9 volt per filament under voltage will breakdown the cathode in the tube in about 10-200 hours...

Could you please elaborate on this a bit or link to another site with this information? I'm not quite sure what you mean. V1 and V2 are wired in series and powered with -26v, with two 12.6V filaments in series this is a 0.4V overvoltage per tube, within the tolerance of the filament voltage range IIRC. Both tubes are cathode biased, so the cathodes are 1-2VDC negative anyway, and the design is well within the heater/cathode voltage rating of ECC83's. I can't see a problem here.

On the whooshing noise in the amp; I had a similar issue with my old Haze 40, in that case it was due to PCB contamination. With the high impedances and high signal levels, as well as high DC voltages, and all this on a common PCB, it is very easy to get contamination on the PCB and make stray current paths. Just make sure all of the PCBs are scrubbed clean of all flux residue, and hopefully that will help the issue.

[zvenamps]

Burner I have found some parts that's was failed ... around V2
testing is on its way... just putting back the card in the amp...

good tubes can withstand little more than 200 hours before they :gangsta and died

I have TFK Blue tip that's has 2000 hours on it and still in good shape

Chinese tubes fail quick in this filament underpower

[zvenamps]

There are some errors in such voltage supply

1.V1 and V2 have all four filaments are connected in series and supplied with 26V DC. NO H-e! ECC tubes are not as PCC television tubes. ECC filaments are designed to be connected in parallel, and a maximum of 2p filaments in series. 4 in series creates risk for under-and over-heating of the cathodes.

different voltage across each winding and then (twice the power) heats up some more and some less

[MKB]

There are some errors in such voltage supply

1.V1 and V2 have all four filaments are connected in series and supplied with 26V DC. NO H-e! ECC tubes are not as PCC television tubes. ECC filaments are designed to be connected in parallel, and a maximum of 2p filaments in series. 4 in series creates risk for under-and over-heating of the cathodes.

different voltage across each winding and then (twice the power) heats up some more and some less

If I understand, in a ECC83, are you saying that the resistance of the heater from pins 4 and 9 is different from 5 to 9? If you connect pins 4 and 5 to a 12.6v supply, that the voltage measured from pin 9 will not be 6.3V? If that is the case, and I could see why it could be, what you say makes sense. You infer that each heater in a ECC83 does not draw the same current as the other in the same tube.

However, the data sheet on Duncan's Amp Pages has ECC83's listed for 12.6V/0.15A operation, as does the PDF data sheets for Philips, Mazda, RFT, Telefunken, and Philips ECC83 datasheets. If any of these had asymmetrical heater current requirements for each triode section, I'd expect the tubes would not be rated for 12.6V operation (heater voltage from pins 4-5) without some sort of current divider to equalize the voltages, or at least they would give a warning. And I would expect that any current manufacture tube would need to meet this same design requirement. The only heater application warning I saw was that inrush current limiting was necessary for some of the tubes if operated at 12.6V.

The VM heater design for V1/V2 does imply however that you have tubes in V1/V2 that draw the same heater currents. Any tube that is designed as a ECC83 should have the same current requirements (6.3V/0.3A, 12.6V/0.15A), so if you plug the same tube in V1 and V2, each of the 4 heater sections should get the same voltage. Now if you installed a ECC83 in V1, but a tube with a different heater current draw in V2, both tubes would have the wrong voltage drops across each heater. This should not happen in most cases though as all the 12A_7/ECC8_ type tubes I can recall have the same heater voltage/current ratings.

[zvenamps]

the problem is not to use 1 tube at 12,6 or 6,3 volt the problem is when you use 2 tubes in series 12,6+12,6 volt you have a significant voltage drop between this 2 tubes the Russian understand this and they build one of the best tubes 6N2P-EV (12ax7) but only 6,3 volt filament and 5000h guaranty drift time

if you ask 2 of the world best guitar amp tech : Kevin o Connor at http://www.londonpower.com/ or alex at http://www.anacon-tech.com/

you can verify that V/M 26 volt line on 2 ecc83 is not a good thing ...
you can ask JJ electronic that makes JJ tubes I have asked them this question
and they say" you can not use ECC83 in this way" the tube will fail in short time under 500h ( ECC83 could last 1000-5000h )

[Burner]

The amp is still on the bench at "Zven", but he's getting closer to get rid of the major faults..
As said.. it was a breakdown..

Here's one of the things..
In the glue that hold one of the caps there was soldering "leftovers"(metalparts), result shortcircuit..
Also some relay(LDR/HDR) had gone due to this..

969223_10200627772311971_2075006220_n.jpg (78.49 KiB) Viewed 1447 times

Bonus pic...

[zvenamps]

now the amp is in working order

changed 3 caps in preamp supply AND the relays to LDR/HDR switching they was intermittent broken ,, changed them to Omron G5V-2 H1 and now it works !!!!

[sikter]

There is no bad soldering on any Marshall or other brand PCBs.
Could it be the result of previous mods?