Damaged shielded cable

polifemo

A would like to make those of you that are about to build the amp aware of the possibility of a damaged shielded cable in the kit.

One part of the cable was internally damaged (from the factory) causing a short circuit.
Unfortunately I did not notice this until it was to late, as this part of the cable happened to be used going from the phase inverter to one of the output tubes.
The tube got damaged...

One can see that the middle part of the cable is thinner and that the upper part is much thicker than the rest of the cable:

[Blockierte Grafik: http://i26.photobucket.com/albums/c109/prof2915/cable.jpg]

Hopefully I will receive a new tube from Klaus.

polifemo

2 months have passed, and I´m still waiting for my replacement tube...

(I´ve been really patient but I must say that if I ever buy another amp kit, it will be a Ceriatone: Quick shipping and fast replys to questions.
One does not get any of that here...)

MAD

Hi polifemo,

besides the fact, that the output tube can't be damaged by a short like this (it only means, that the input is grounded regarding AC) I'm sorry to hear that you have received a damaged tube from Klaus. Has he answered your request or have you got no answer at all? In this case perhaps he hasn't got your eMail at all...

Regards,
Martin

Lorak Alytjow

Hi Martin!

Zitat von MAD;236377

besides the fact, that the output tube can't be damaged by a short like this (it only means, that the input is grounded regarding AC)

That's not correct (as far as the A15MkII is concerned). If the g1 of the power tube is shorted to ground, the BIAS will be, too. I had a similiar situation (shielded wire "B" was shorted to a lead of C25) in my amp and the BIAS voltage was some volts higher (the lowest possible voltage was -21V ->50mA were flowing) at V6 than at V5 (-27V) and eventually the tube was destroyed.

lg, Matthias

MAD

Hi Matthias,
this is why the manual saysm that you should first measure all voltages and check especially the voltages at the cathode resistors before playing the amp. The tube will not be destroyed by another operation point immediately, but it will if you ignore the wrong voltage (and the bright glowing plate) and start using it, that's correct.
Regards,
Martin

polifemo

My tube DID get damaged somehow.

Klaus responded to my email about 2 months ago saying that he should ship things ( I ordered more stuff) as soon as possible, but still nothing has reached me...

I´ve been in contact with Klaus a couple of times during this period and I´m sure that I WILL get a new tube sometime in the future.
I´m just tired of waiting...

MAD

Hi polifemo,
I will contact him to speed up that a bit.
Regards,
Martin

Lorak Alytjow

Zitat von MAD;236389

Hi Matthias,
this is why the manual saysm that you should first measure all voltages and check especially the voltages at the cathode resistors before playing the amp. The tube will not be destroyed by another operation point immediately, but it will if you ignore the wrong voltage (and the bright glowing plate) and start using it, that's correct.
Regards,
Martin

I know:) (btw, when I measured the voltages, they were correct... and because the TAD tubes delivered with the kit are black, so I couldn't see the anode glowing. I only noticed loud noise, a bright blue glowing ( really nice fireworks ;D) from inside the tube and a blowing fuse when the tube was already damaged ).
But I just wanted to say that a short inside the shielded cables connecting the PI with the power tubes can damage the tubes.

-Matthew-

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