I don't think that the wire electrical insulation value necessarily corresponds to the heat resistance of the insulation. They are two seperate aspects of wire insulation properties. Wire can be purchased with many different types of insulation, some of which are specifically designed for high heat applications.
The top cap is connected to the tube anode. As I understand it some tubes (like the RCA 805's) have this design to isolate the high-tension circuit and allow higher voltages to be used. Isolating this circuit from the rest of the tube connections (socket) may provide greater circuit stability. I'm sure others have more detail about the benefits of this design.
After installing the 805's and running the amp for about 3 hrs I checked the bias and noticed it was running low - at just over 100mA without having adjusted from the stock tubes. It makes sense that I'd have to readjust the bias for the 805 tubes - back up to 120mA. It sounds even better now ;-)
RF Parts has both wire (30kV and 105 C rated) and ceramic caps. Amazon has spring loaded banana plugs. You will also likely need heatshrink tube for additional insulation.
All vintage 805 tubes have plate cup connector. Tube without it used to be called 838. For some reason modern tube of that type is labeled as 805.
well that was disappointing. I managed to score 2 WW2 era Amperex 805. They have the larger older style anode connection. Both looked good but one of them only bias to 60mA. Now what do I do?
I had similar thing with RCA 805 that I got yesterday. One of them go up to only 80mA which means it had be worn out or bad. The kind seller had shipped another one to me which will arrive this Saturday.
First Has anyone had a chance to compare the LM to the Willsenton r800? Would be interesting since the specs are very similar, the Willsenton even being a bit heavier (if that means anything) and much cheaper in US.
I am trying to see if I can return it. Blew the tweeter on my other speaker too. Not a good day today.
Just looking at the low res image of the internal, I think the 508IA is a better amp. The topology seems very similar, but the 508IA has much more substantial power supply. In a tube amp, have a good power supply is more than half the battle, esp for a high power 805 based SET.
Wow, so sorry you're going through that! Which platform were they purchased through? Did you pay with PayPal? If so, there should be no issues whatsoever in returning them.
I also saw listing in Amazon. The only interesting thing is balanced input which let long interconnect possible and prevent ground loop hum. But you never know until you try them yourself Both are made in China.
looking at the datasheet. they are similar, but 805 has a higher power dissipation and in general slightly higher limits than the 838. I just checked on the usual auction site, their prices are not that much different.
The direct replacement is pretty cheap, it is the lower end ALPS pot. less than $20. I'd rather do that than having to open it up and then still have a old pot. there is a better quality ALPS, has a totally different pinout (why would they do that?!). The current pot sits on its own PCB, and thus it is fixed to the current pot's pinout. I can try to adapt it, or try to make/find a pcb that can use the nicer ALPS. I still want the motorized function, it is so convenient.
Yeah. I was playing around with my other pair of speakers, the USB cable going from my laptop was slightly short and got yanked while I was trying to get from the floor to the couch. The DAC went nuts and blew up the tweeter. Damn expensive tweeter too. sigh.
To me, it sounds more like looking for trouble. Clean it and get onto better things. It doesn't matter if a pot is old as long as it's clean... and it should therefore perform perfectly well. Unless you're aching to tinker with *something*?
