Two EL95 Tubes to Single ELL80 Adapter

[maxhifi]

If gadget has one, and it has film capacitors, i think it's safe to assume yours does too, and they won't be any problem. I was concerned it may have those shiny dark brown German capacitors which are known for failure, that's why I wanted to see a photo.

For the time being I would focus on the tube as the most probable cause of red plating. It does it in both sockets, and if the capacitors were bad, every tube would red plate in the socket with bad capacitors.

Those Polish adapters do say they rotate, which in my opinion makes them more useful than the circuit board version, as it could make them easier to fit.

If it's a no go, could always just spring for some used ELL80, I checked ebay and prices are high but not insane.

 

[gadget73]

I think they are the "dog turd" ones, but mine aren't leaky. No guarantee they can't be but they seem to more or less work until disturbed.

 

[Jim 2018]

Hey Gadget. Right. That might be a problem depending on how "fat" the particular adapter is I'm getting. Ugh. Well, one way or the other I have to deal with this because ELL80 tubes are not going to be suddenly plentiful and cheap. Plus I'm hooked on the Fisher since I got it work. And while I was hoping I'd have years on the ELL80 tubes I have, that clearly t won't be the case now.. And this problem definitely follows the tube. As a sidebar that might relate to this, I have a questionable audio output transformer in there. One problem is it would cut out and go low but if squeezed it would stop. A solid work around for that was tight wire tie where I would squeeze. But a second problem that developed after a few weeks is an intermittent hum. And I could get it to stop or reduce with putting tension on the wires and/or squeezing the transformer but that was hard to do.

Anyway, I'm wondering if a marginal audio output transformer can hose a tube in the way mine is. Mind you, when I discovered the red plate, it was NOT installed in the socket with the bad transformer. HOWEVER, it could have easily lived in the socket with the bad transformer decades ago when the system last operated. Or could have been installed there at times when I took tubes in and out during phases of work, troubleshooting and experimentation since recapping in November. If an audio output transformer with the idiosyncratic symptoms of mine could hose the tube, then I've got to deal with that problem sooner rather than later. Another ugh.

MaxHiFi: I missed that they rotate. That's good to know. Maybe I'll get lucky and fit those in without a ton of grief.

 

[Ziradog]

I have a Fisher Allegro that uses the ELL80 tubes, and had a second unit that used them for a little while. I had no problems rounding up a dozen over 3 months, all old stock. Various branding (Lorenz seems most common) but all marked Germany and almost all look identical. Most I paid was $15 but many were less than $10.

 

[Jim 2018]

Ziradog: You're lucky. I don't think you could get those tubes today especially at those prices from reputable suppliers.

 

[maxhifi]

Jim, If you're a bit resourceful, it could be easier than you think. Once people know you like old electronics, it seems to materialize out of thin air.

 

[Ziradog]

"reputable sellers" is probably a stretch. I bought as many as I did to make sure I had 2 pairs of good ones that reasonably matched, plus some spares. One pair went when I sold that amp, but I should have enough to keep the Allegro going for a long time.

 

[maxhifi]

I've also read about people using the QQE03/12 as a substitute, with some socket rewiring. You may want to do some research on that, it's a fairly common military surplus tube.

https://frank.pocnet.net/sheets/128/6/6360.pdf

 

[Jim 2018]

MaxHiFi: Well maybe so. But nobody knows me. If the standard of knowing someone is that of old electronics, that's going to take a long while! By that time I'll be worried about finding NOS transistors for vintage solid state equipment I want to keep around. And I will look into the QQE03/12. If that looks like it might work I'll run it by the gurus on the Fisher forum.

Ziradog: Part of the substance that underpins my reference to "reputable sellers" has to do with the temptation of humans to sell used, bad, or forged tubes when they become valuable (in a way that is far less likely when it is cheap and available). So I think reputable or quasi reputable sellers are more important for rare or expensive tubes. And these ELL80s are approaching scarce and valuable if not there already. Every really expensive and/or rare tubes had a period where it was at one time available for reasonable prices and gradually transitioned to relatively expensive hard to find. Seems to me ELL80s are minimally in the later stages of this transition but maybe perhaps not completely there. If nothing else, the writing is on the wall for the future of these tubes. I think you were smart to stock up when you could.

 

[maxhifi]

If you scroll down on this page, you will see an interesting way to convert an ELL80 to the tube I referenced above. It is in German, but the pictures tell the story

https://www.radiomuseum.org/tubes/tube_ell80.html

 

[jaymanaa]

Sorry if I missed it, but what are needing 6HU8s for, a Fisher I presume? Ya know, a really fussy guy might be better off going with EL95s as they are dirt cheap, so you buy enough to get a really tight match. Not too many of us have a deep enough wallet to buy a bunch of 6HU8s to find matched sections, I think Ziradog must be living right. I've been buying these little mono Telefunken RTRs when they come up cheap just for the tubes, iron, mu metal, etc.... The single 12AX7 in them that never seems to be even worn, more than pays for the machine. Point being, they use a EL95 in SET mode and have iron just a tad smaller than Maggy console iron. Since the iron and EL95 are pretty much worthless, I've been thinking of stamping out a few amps (true dual mono for stereo). I'd definitely get rid of any Aero Caps, but I've been curious about the precision resistors. They look to be top shelf, but wirewound. Seems like I remember being told that WW Rs aren't so good as they "by nature of design" create induction. So, use'm or trash the beautiful things?

 

[Ziradog]

That is interesting. Looks like his first mod was using a MOSFET (transistor)? Wish my German was better,

 

[maxhifi]

That is interesting. Looks like his first mod was using a MOSFET (transistor)? Wish my German was better,

That's where Google translate is a big help,
I just copy and paste the url into the box and select German to English.

After doing that and reading the whole thing, I think the EL95s really are the best! I just happen to have a number of those other tubes, and reading the data sheet made them look appealing.

Jay, you could always get some mono reel to reel tapes! I feel guilty taking apart the old tape recorders, they're such nice machines.

About wire wound resistors, I recently repaired a video projector, and thinking I was doing an upgrade, put some wire wound 5W resistors in place of burned out metal films in the convergence circuit. Result was very weird, solid white areas got a pattern of swirling dots on them. It took me a bit of time to figure out that it was the resistors, but 2W metal films cured the problem complely.

In audio I doubt it would be so easy to notice, and in power supplies they're perfect.

 

[jaymanaa]

That's where Google translate is a big help,
I just copy and paste the url into the box and select German to English.

After doing that and reading the whole thing, I think the EL95s really are the best! I just happen to have a number of those other tubes, and reading the data sheet made them look appealing.

Jay, you could always get some mono reel to reel tapes! I feel guilty taking apart the old tape recorders, they're such nice machines.

About wire wound resistors, I recently repaired a video projector, and thinking I was doing an upgrade, put some wire wound 5W resistors in place of burned out metal films in the convergence circuit. Result was very weird, solid white areas got a pattern of swirling dots on them. It took me a bit of time to figure out that it was the resistors, but 2W metal films cured the problem complely.

In audio I doubt it would be so easy to notice, and in power supplies they're perfect.

Yep, I know what you mean, and right now I',m in moving crap through phase. Don't ya hate it when you're spring cleaning and find a box with a part,or parts inside. These units have more craftsmanship in putting the ele. emblem on that some of these cheap things at WalMart and the like. They don't mind swapping them out forever, but who wants to drive into town every other day. When I lived down in Baton Rouge, I did a little air conditioning work on big old diesel cranes. They were having me do a bracket (kit thingy) on the engine, and do it all up right. They had been using window units and the cranes would sake them to pieces after a couple or so day. Walmart, or Maybe it was Kmart, cut them off, no more free window units.

 

[jaymanaa]

That's where Google translate is a big help,
I just copy and paste the url into the box and select German to English.

After doing that and reading the whole thing, I think the EL95s really are the best! I just happen to have a number of those other tubes, and reading the data sheet made them look appealing.

Jay, you could always get some mono reel to reel tapes! I feel guilty taking apart the old tape recorders, they're such nice machines.

About wire wound resistors, I recently repaired a video projector, and thinking I was doing an upgrade, put some wire wound 5W resistors in place of burned out metal films in the convergence circuit. Result was very weird, solid white areas got a pattern of swirling dots on them. It took me a bit of time to figure out that it was the resistors, but 2W metal films cured the problem complely.

In audio I doubt it would be so easy to notice, and in power supplies they're perfect.

I might just be lying to myself to justify scrapping these things out, but I try to envision someone with more time, breathing new life into them. You've got all the tubes, iron, and even a schematic to help you with a new one. Then you have a wonderful little pair of monos, that maybe have a better chance of getting used than a tape recorder. It's fairly incredible to me that these Tele tubes, save one EL95, outlasted the tape heads to a degree. I haven't looked closely at the schematics yet, but why all the front end gain? Is that a tape / NART B thing? Each one has a dual triode 12AX7, and an EF86 pentode pushing that teeny weeny little EL95. I suppose I should take another look see, but I could see the little amps that could be built, would go wonderfully with Altec 19s, or 17s for that matter. Was Telefunken known for iron, or "meh" iron, I've never used any.

 

[maxhifi]

They need all the gain because a tape head has similar output to a magnetic phonograph stage, with a similar curve to RIAA called NARTAB. In record mode, the same preamp stage is used for a mic pre.

I wouldn't expect miracles from the iron, it will be similar to a table radio. Germans tended to use fairly small output transformers. Realistically it could sound quite nice through horns, but i would not count on it giving a 2A3 any real competition.

That said I have not actuslly tried a telefunken, only the similar Philips machines, nordmende console amplifier, etc.

 

[larryderouin]

I've been looking for that adapter for almost 8 years now for my Hybrid 49A and 59A amps (65 Custom Electra and Futura Consoles). I just got 2 on Ebay. Will follow up when I get them and the tubes from ABCVacuumtubes.com ($5.00 ea.). I don't buy tubes on E-bay.

 

[jaymanaa]

I've been looking for that adapter for almost 8 years now for my Hybrid 49A and 59A amps (65 Custom Electra and Futura Consoles). I just got 2 on Ebay. Will follow up when I get them and the tubes from ABCVacuumtubes.com ($5.00 ea.). I don't buy tubes on E-bay.

You got some nice amps right there, real nice in the 59, but it does have one weak link, the emitter variable resistors. Whatever you do, don't try to adjust these while they are powered on. Chances are real good of letting the smoke out of those Germanium transistors, and if you aren't fast enough with the power switch, they will take that unobtanium interstage TX with them (don't ask how I found that out). If you want to do them justice, I'd change those variable R pots out and adjust the ohms before even trying to run them. Those little 10 cent pots are junk in an otherwise, all precision component amps. Some of them that got warranty repair, will have a regular WW power resistor there, but I like to be able to adjust them. Just a decent 5 dollar pot would do fine I think. Those amps have some real power output, and a pretty nice power supply to boot. I think they are definitely under the radar as far as price and availability. I have 3 or 4 of them tucked away for a rainy day project.

I think you probably nailed it on the Tele amps Max. I wonder if they'd make a decent practice guitar or harp amp? You'd have to mic it for gigging, but a guy only would if it had some sort of magic mojo tone.

 

[jaymanaa]

Ha, I turned around and there one was, lurking under my 28 Majestic curb find. Somebody had already put a battery replacement power pack in the Majestic, it's a pretty good old radio.

 

[Jim 2018]

So one of my ELL80s is red plating (follows the tube, 100% so not the stereo). So I want to use the stereo while I wait for my replacement EL95s and adapter. And discovered something screwing around that is interesting to me and wanted to find out if this makes sense.

Turned on the stereo and load a record. Sounds great but then it's a Fisher. I'm keeping my eye on the tubes. Within about 5 minutes or so, the bad ELL80 tube red plates. You can tell it's hot because I can sort of "smell" the heat". Then I wondered what happens if I put a fan on it and compare the temp with a infrared thermometer.

As expected, it cools it down a ton. Temps came down from high 200's to high to mid 100's. Then I wondered, how much power is it taking? I know as a point of reference on my kilowatt meter after it was recapped, it was drawing between 68 and 75 watts (its rated for 90). So I put the meter on and its drawing 148 watts!!! Yikes! So I immediately pull the plug. Let it cool off. Then I tried with with the good tube only. About 68 watts. Okay, so I know I probably have nothing else wrong but this one tube. Then I wondered, well how long does it take to ramp up wattage with the bad tube in there? The key difference this time is I have the fan already running on it from cold start. With in a couple minutes it ramps up wattage more than usual but peaks around 91 watts. And most interestingly, the bad tube is NOT red plating.

So, it looks like to me if you have a bad tube that is going to red plate and it otherwise works, you can buy some time using that tube keeping it cool (from the start) and this stops the negative feedback loop of heat run away and the red plating. If I'm right, then this only works if you apply cooling before the tube gets too hot. If the tube is red plating when you first apply cooling, it won't stop it.

Does this make sense? I'm new to tubes...I'm just asking. If experienced tube people would expect this, then this is no big discovery. But if not, then perhaps it's something to keep in mind if one has a bad tube that works (for the moment) but is red plating...that is to keep the tube cool from startup until the replacement tubes arrive.