Mullard Shmullard

[jaymanaa]

I like the Mullards with the mold/soot.
Always set those aside to collect!

Those seem to be really good tubes.
These definitely have a slot midway inn the plate, and a small slot in the plate next to each insulator/support. I'll try to find some other EL84s today for a comparison. It always gets me that they could, and would, label something as made in the wrong country, that's just so wrong. I would imagine it hurt Craftsman tools very much to start stamping their stuff made in china, but hey, that's the truth of it. I guess there is better consumer protection these days.

 

[jaymanaa]

I have a quad of Hammond that are "Japanese Mullards". You can make out the seams on the top of the tubes. They look exactly like that. They sound killer too. I have them in this stereo amp.
Mullard's el84 went from "sandy glass" rX1 , to smooth glass rX2 all with a circular locating hole in the center of the plate. I am not sure if the rX3 or rX4 they switched to the rectangular hole in the plate. Which looks exactly like the tubes in your Dyna. Sorry, i don't have a close up on the hammond el84s.View attachment 1078179

Is that a Maggie 9302? If so, did you add another gain stage, what tube number?

 

[primosounds]

I like the Mullards with the mold/soot.
Always set those aside to collect!

Woah, there big guy, those spots are radioactive! Luckily for you i have the only Mullard factory authorized radioactive dumpsite in the Northern hemisphere. Nominal handling fee of just 50.00 per tube applies.

 

[Leland47]

LoL!

 

[primosounds]

Is that a Maggie 9302? If so, did you add another gain stage, what tube number?

I am not sure what the donor amp for this build was. It is not a Magnavox. The actual circuit is a copy of the EICO HF86 which used 2 7247 for input/splitter. i wanted to do something different so i turned the circuit into a 12ax7 for input and 1/2 of a 12au7 for the splitter part. There is 1 12au7 per channel and only half or 1 section of the duotriode is used in each channel. Sort of a waste but if you used a 6C4 that would be the same. I was actually going to do that except the 7 pin socket is too small to secure it in the 9 pin socket hole. Other than its power output of about 12 watts it is an amazingly good sounding amp. Part of the good sound is attributed to the "Japanese Mullards". Here is a under the chassis shot.

 

[Tom_r]

... Also found a tin foil type sticker on the rear panel that said factory wired and had a serial number, so that shoots down my amateur idea.

...

Well not really. Factory assembly meant college students assembling stuff. Hmmm, in that era who knows what one might be high upon!

 

[Dswankey]

Jay,

Good to see you posting again and a Happy New Year to you.

Here's some links that might be helpful

http://blog.thetubestore.com/history-of-mullard-tubes/

http://www.tube-classics.de/TC/Tubes/Valvo EL84/EL84.htm

 

[Dswankey]

Those tubes are Japanese Amperex, Most Amperex EL84's are Japanese. They have to be pretty early to be actually made in Holland. same goes for amperex 12ax7's
Not that that's a bad thing..... Japanese Amperex are nice tubes....

As I understand it Amperex was the North American brand name for Philips tubes.

http://www.semiconductormuseum.com/...EarlyPowerTransistorHistory_Amperex_Index.htm

 

[Dswankey]

Here's an Amperex branded ECC83/12AX7, from a 1959 Ampex console RtR player.

Note it says "Made in Holland" however if you look at the codes at the bottom, based on this link*, it identifies as made in Hamburg Germany, more the likely a Valvo

* http://www.tube-classics.de/TC/Tubes/Valvo ECC83/ECC83.htm

 

[Dswankey]

Here's a Valvo labeled EL84 I have not sure what the codes on the top signify. The other codes ( rX3 D8L) would indicate late 50's made in Hamburg

 

[jaymanaa]

Good stuff D, I've had some tubes with that numbering on top too. Some of those also had a metal tag inside the tube with a two digit number. One thing seems for sure, it doesn't matter one iota where it says the tube is made. I had always thought that was a pretty big deal, to lie about that on a product that was marketed and sold in the USA.

 

[jaymanaa]

Well not really. Factory assembly meant college students assembling stuff. Hmmm, in that era who knows what one might be high upon!

I think you might be on to something here. The wiring is pretty bad on this guy. I've found a couple old kit jobs that looked like they were never used due to wiring errors, but this guy got by with a couple really bad things. There was an unintended solder bridge on an output tube socket between the screen and filament pins! There was also a short circuit on two legs of one of the PECs devices in the tone circuit, but I didn't take the time to figure out what the effect would have been. The guy didn't make any mechanical connections at all, just stuck the wire in the terminals an added solder. The kit manuals always made a big deal about making good mechanical connections before soldering, and I have thoughts, and have heard arguments about both ways. It's nice that in circuits this simple that by the time you get it re-capped and the switches replaced, there aren't many joints that you haven't hit. With any luck I should have this guy making noise this weekend.

 

[jaymanaa]

Jeesh, just found another short between two sections of one of the multi-tap power supply lytics. A resistor leg was un-trimmed and went clear through and had made a little carbon looking connection to it's next door neighbor. The power switch printing is rubbed off the face of this thing, so it definitely got some use. I kinda wish I'd have powered it on before I took it apart. I would think it would have had some issues. That said though, all the tubes tested perfect?

 

[jaymanaa]

She's coming along, and getting a new pretty facelift.

 

[jaymanaa]

Moving right along now, and looking at output tubes. I haven't done anything with this output iron on a scope in a long time, but I'm sure Dyanco rated it very conservatively like they did all their iron. I have an ST 70 that can do 70 a channel with EI 90s, and IIRC it was around 25hz before the outputs saturated. I have a bunch of Setchell branded Amperex 6GK6 that make a little more power than the EL84, but I did some checking last night and discovered that 6GM5s fit with about 1/2 inch in between. Whatcha think; https://frank.pocnet.net/sheets/084/6/6GM5.pdf I think the filament current is close enough, it's just that I've seen first hand that the PT is the week link in this amp bone stock, so I worry about putting the extra music demand on it. However, I did a trick once on a screen drive where I used the PA060 out of that 70 when I beefed it up. What I done, was use a buttload (like 10,000uf) capacitance for a storage tank and a CL 90 to protect the TX from inrush at start up. That amp makes some good power (6JM6s PP) and the PA 060 never gets past warm. I can't splain how it works, but it does, and I know there is no free lunch. I think what happens is the TX fills the big lytics on soft passages, then uses the "bank" on harder driving parts of the music?? I just happen to have a couple sleeves of NOS 6GM5s I had bought years ago to build a stand alone job that never took off. If it works, it would be a pretty cool SCA35. I have 3 or 4 of these, so this one is the test mule, and the next one won't have tone controls. The cat that makes these faceplates offers one without tone control holes.

 

[jaymanaa]

I bet these outputs would love 6GC5s or maybe the more conservative 7695. Trouble is changing the pinout on a circuit board sucks. It would look cool though if I could find a PT to push'em.

 

[sanford12]

Didn't some of the Mullards have a round hole that would get a smoke ring instead of the rectangle. Anyway heres a picture of some Eico tubes with a Made in Holland. Looks like similar construction. They have 3 digit # on the sides, yours is 315 mine is 351 and looks like it could have come off the same machine they look so close. Also looks similar to Amperex. These have etching on the bottom. The amp was mid 60's

 

[jaymanaa]

Hey Sanford, I think I remember getting a whole mess of those out of a Hammond organ once, and they were really good.

 

[sanford12]

I'd love to see your tube collection Jay. Do you still have all those 83's I sold you?

I've never had a 6BQ5 from Holland that didn't sound good. The Mullard 6BQ5's with the holes and smoke rings were outstanding output tubes.

 

[sanford12]

These are the Mullards I was talking about. They sounded excellent.