Tube Rolling w/Crack

[cddc]

No etching or any marks. Here’s a link to another tube from the same batch:

https://www.ebay.com/itm/CV5008-6080WA-Tungsol-double-O-getter-metal-base-Amplitrex-tested-3251002-/203028310018

I imagine they got a stack of these Chelmers and decided to test them as Tung-Sol for lack of any other solid information. I just noticed the word Brimar also somewhere in the ad. Ha.

So buyer beware.The one I got is not bad at all, it just may or may not be not be the exact thing I thought I bought.

This one looks like an RCA 6080 to me. Tested pretty low and way overpriced.

 

[monsterdonkey]

I’ve found some photos of Raytheon 6080s that look very similar as well, down to the white base. I’ve left feedback on eBay suggesting it may not actually be a Tung Sol tube. Oh well!

 

[cddc]

I’ve found some photos of Raytheon 6080s that look very similar as well, down to the white base. I’ve left feedback on eBay suggesting it may not actually be a Tung Sol tube. Oh well!

Raytheon never made any 6080 tube, all Raytheon 6080's are rebrands, mostly from RCA 6080's.

So they do look very similar, in fact, exactly the same except the label...

 

[cddc]

It is for sure not a Tung Sol 6080 tube, not even close.

 

[Paul Birkeland]

I haven't ever seen the grid coolers up top on a Mullard 6080.

 

[cddc]

You mean the black shields between the top micas?

Some earlier Mullard 6080's do have the RCA-like shields, like the one on the left.

 

[monsterdonkey]

I like the Mullard idea. A rebranding company based in the UK could just pick up some tubes from down the road and do their thing, avoid the overseas shipping. I’ll call it a Mullard then. Nothing against RCA. Some of my favourite tubes are RCAs.

 

[Deluk]

I note the very poor quality of the brown base and the rather crude crimps on the right hand tube. View full screen. What is the supposed identity of that one?

 

[Paul Birkeland]

That's what a typical CV2984 looks like.

 

[cddc]

Hi PB, can you help to identify if this Dayton 100uF cap is an oil film cap? I don't see "oil" or "film" mentioned anywhere in the specs.

https://www.parts-express.com/dayton-audio-dmpc-100-100uf-250v-polypropylene-capacitor--027-447?utm_group=%7Bgroup%7D&msclkid=ea1cc11e262d1eb95fa59e787a1d394c&utm_source=bing&utm_medium=cpc&utm_campaign=DSA_Dayton-Audio&utm_term=dayton%20audio&utm_content=Dayton%20Audio

 

[Paul Birkeland]

It's a metalized film cap with no oil.

 

[cddc]

Great, thanks a lot for the confirmation, PB!

I was suspicious about the cap because it is smaller than those 100uF oil film caps, thought it does look like an oil film cap.

 

[Paul Birkeland]

The lack of oil should not prevent you from using them. 

 

[cddc]

That's for sure, I'm pretty new to caps, so not sure what magic these "oil" and "film" bring  :-[

 

[Paul Birkeland]

Oil is helpful for cooling, filling voids, and arc protection.  These aren't really an issue for coupling caps in a Crack.

 

[tintin]

I've recently picked up some ECC31 as well as some nice looking 6N7G tubes. I have an ECC31--> ECC32 adapter, and was wondering if this would work for the crack. Would R1 on the speedball board at 470 ohms work for the ECC31, just as it does for the ECC32, or are there other considerations with the single cathode? 

 

[Paul Birkeland]

470 ohms for the R1 on the small board may work for the ECC31.  You'd have to use an EC31->EC32->12AU7 stack of adapters. 

 

[tintin]

470 ohms for the R1 on the small board may work for the ECC31.  You'd have to use an EC31->EC32->12AU7 stack of adapters.

Thanks Paul for the confirmation. I've installed a switch to go between 117, 235 and 470 Ohms and testing it out today. For reference, fresh 12AU7 on 235Ohm reads 65V OA/OB, 6SN7s similar. Very used ECC32 on 470 Ohm tests 90V.

ECC31s on 470Ohm tests 85-93V. 6N7Gs seem to be higher testing at 90-95V. They are all pretty fresh but seem to test a little higher but still barely within the acceptable range. Should be ok for long term use, or should I try up the 470 Ohm resistor value? To me so far, they sound just as good as the ECC32 for a non-silly price.

 

[Paul Birkeland]

Maybe you could nudge the 470 ohm resistor up a bit more to bring the plate voltage down a bit.

 

[Markkr]

I’m absolutely loving this amp.... lets just say I was interested in picking up a couple tubes for them.... Can anyone recommend what to start with? Is there a tube upgrade that is guaranteed to please? (Budget would be less than $200 per amp)