Rocket redplating

[Gargoyle]

Guys,

Just fired up the Rocket this arvo for a practice and was ok for about 4 secs and the power tube furthest from the Trannys red plated...hmmm
Changed the tube for another Saratov and was fine prior to taking her off standby, soon as I flipped the switch the replaced tube redplated immediately.

Any ideas where I should start??

Cheers

[rooster]

Yeah, go to that socket and look for a cold solder joint - it's there, keep looking if you don't see it at first.

[Gargoyle]

Cheers mate, I'm on it..........

[Ian444]

There is another possibility, our line voltage in Brisbane is around 250V where I am, it can push the B+ up a bit. If you can't find any cold solder joint, try putting one of the tubes that redplated into a different position, and put a known good tube into the "suspect" socket. If the known good tube does not redplate in the "suspect" socket then the socket is OK.

[Gargoyle]

Ian,
Thanks for the feedback.. I did try another 2 tubes and they both redplated in that socket only.
Its with my tech at the moment, he is gonna go over the soldering on that socket and give her the once over.
You're right on the Brisbane power, its all over the place.
Cheers

[Ian444]

I have this voltmeter permanently plugged into the mains power
It's always near pegged, very rarely it gets to the low/mid 240's.

[guitarsnguns04]

if you tech doesnt have any luck...post some good pictures of it..these guys on tag have some great eyes and im sure we will figure it out..best of luck

[keewee]

I had a redplate problem, turned out to be the voltage rating on the 100 ohm resistors ...

[Gargoyle]

The tech rang me today (been busy), looks like a resistor as the bias on 2 of the tubes is around the 50ma mark.....

[rooster]

Er...keep looking at the socket where the redplating occured. If I heard you right, you didn't have two tubes redplating.

[Gargoyle]

Rooster, you're right. When I had it at home I only had 1 tube plating, the tech reckons there are 2 redplating...
I will reinforce that I want both sockets tested.

[ChrisM]

Just replace the two sockets, that's $10 in parts at most and about 30min of labour.

[Ian444]

It's quite possible that all your tubes are on the edge of red-plating with the high local mains. But we will wait and see. 50mA is way too hot. The amp isn't very old, if there is some sort of component failure I would be surprised.

[Gargoyle]

It's quite possible that all your tubes are on the edge of red-plating with the high local mains. But we will wait and see. 50mA is way too hot. The amp isn't very old, if there is some sort of component failure I would be surprised.

Ian, you could be right the mains is hovering up to 250v at times.
Chris, I will have a look at replacing the sockets.
Cheers
Gents

[Gargoyle]

Well I got her back from the tech today, with 2 replaced sockets and a fresh set of TAD's. There was some bias issues (50ma)

I must say it sounds quite different now but not in a bad way. it now has more head room. It used to break up at around 10 o'clock but now its up around 12 before it "lets the pigeons loose"
I am wondering if that bias has been screwy since I've had it.
Case closed.
Thanks guys