Rivera f-55 - Octal sockets?

[H Chandler]

What's the deal with these amps. Do they all melt the solder on the el-34 tube sockets or are they all under-biased?. The sockets are PC mount and the ears are tapped for screws. Are these sockets available?

Thanks

[Le Basseur]

Hey,
I'm glad you opened this theme!
(see my Rivera Fandango thread in this forum section)

What's the deal with these amps. Do they all melt the solder on the el-34 tube sockets or are they all under-biased?

I'm not sure what are you talking about...in my case,I didn't find any melted/cracked solder,neither a wrong bias but,of course,both can happen when a tube or both fail or if someone with little knowledge turned "by ear" the bias trimpot.

The sockets are PC mount and the ears are tapped for screws.

Yep,the're some sort of Frankensteins as the screw-tapped ears are most common for chassis mount.
I suspect this mount type to be the primary reason for the output tubes' mechanical destruction (they become microphonic in no time).The loudspeakers'/box/chassis vibrations are merciless transferred due to the sockets' tightness.

Are these sockets available?

I've seen them once in a while (ebay and some small web stores) but,AFAIK,there's no steady source.
Regards,

[H Chandler]

I share your suspicion about improperly set bias. I was curious though to see if there might be something inherent in the design of these amps that causes this, and if anyone else has noticed problems like this.

It's strange though. The owner of the amp mentioned that it has had a history of this happening. You'd think the tech who fixed it would have taken measures to cool down the bias.

Thanks for the response.

[H Chandler]

Still thinking out loud.

Could it be that the excessive vibrations are causing the tubes to get loose in the socket, causing the tube to lose bias and fry the PC board?

Don't know if this will help but I'm going to put some spring tube retainer clamps on just in case.

[Le Basseur]

Could it be that the excessive vibrations are causing the tubes to get loose in the socket, causing the tube to lose bias and fry the PC board?

I see this issue coming up from time to time on this forum...frankly,I had very few situations of loose socket contacts but maybe I'm just lucky.Theoretically,this might appear on any amp but in Rivera's case I'd rather look at the bias circuit for a faulty component.

Don't know if this will help but I'm going to put some spring tube retainer clamps on just in case.

Thanks for reminding me of the good,ol' tube clamps!
I'll give them a try...maybe,combined with the tube dampers I intend to install,they'll solve my microphony problem!
Regards,
Le Basseur