7591A International Servicemaster in Fisher 800C

[Jim M]

Hi All
I have a line on a good local guy to update my Fisher 800C Receiver. It plays very well but it needs to be updated. Before it goes off I am going to take lots of pictures including what tubes are where.
Looking over the tubes I am fortunate that they all seem to be Fisher branded tubes (Made in West Germany) except the four 7591A.

V11 is an RCA
V10, V13, V14 are branded 7591A International C Servicemaster.

What brand might these be?
What is your advice on this 7591A quad?
Other than the 7591A International C Servicemaster markings, there is a 7591 in an octagon, and to the lower right in the octagon are the numbers 234. The base is marked Japan and below that is marked O-K three times.
Other than the usual 1 thru 8 pin numbers no other marks seems to be molded in or etched.
103172 103173

[FalconEddy]

ICC / International Servicemaster didn't make tubes. They're all rebranded.

These were made in Japan. That list of 7591/7591A manufacturers included Hitachi and Toshiba. I don't believe that Masushita made 7591's (I've never seen any); but, if so, they would be a third possible Japanese producer.

Your 7591's happen to be Toshiba which is evident from the hexagon printed on the glass envelope with the tube number inside, and the three round holes in the plates instead of three square holes.

. . Falcon

[Jim M]

Thanks for the info Falcon. Good to know who manufactured them.

Were these Toshiba's considered worthwhile tubes?
Any idea on the date they may have been manufactured?

The guy I have lined up is an old audio guy who runs a TV repair shop that has been around since the tube days. I hope to talk to him in person next week some time.
Hopefully he has a good quad of 7591/7591A's laying around from the old days. All the other tubes are original Fisher branded stock so like everyone else I would like to get a quality quad to match up with them. This receiver was well taken of and loved over the years so I think it deserves a good set of 7591/7591A's.
What would you guys be asking for in this situation as far as New Old or Used Stock?

[FalconEddy]

Were these Toshiba's considered worthwhile tubes?
Any idea on the date they may have been manufactured?


Yes, the Toshiba 7591 is generally an OK quality quality vintage tube.

The actual manufacturing date would be tough to pin down without a manufacturing code of some type. The production peak years were generally between 1960 to 1965, but they also made the 7591A for several more years.

I also misspoke myself earlier. Mullard actually set up the tooling and production lines for Matsushita Electronics in Kyoto Japan, and not necessarily for Toshiba or Hitachi. Sorry, my bad.

What would you guys be asking for in this situation as far as New Old or Used Stock?

There's a lot of speculation about whether TRUE NOS vintage tubes are actually unobtainum in this point in time, or not. So, here's some more speculation. . . There still are many true NOS vintage tubes available out there. The trick is finding them, and then hoping they're not just rejects from some technician's tube carrying case. But, the bad ones are usually pretty easy to find when (and if) they're actually tested out.

I've seen, and purchased, a matched full sleeve of 1966 NOS GE 7591A's that tested out at 122% of new for transconductance, and all drew 57mA of total current when tested at standard 'operational' voltages. (i.e. An excellent set!)

However, I also recently purchased a matched pair of 1965 Westinghouse 7591's that were labeled Hammond; and they tested at nearly 105% of new. Barring mechanical accidents, they should last for a very long time So, it's really up to you as far as what you prefer for your amp.

Here's a close up of the LK-72A running with those '65 Hammond 7591's on the left:

http://www.falconeddystudios.com/images/LK72a-Hammond7591.jpg

. . Falcon

[Jim M]

Thanks again for all the info Falcon. That was just the kind of info I was looking for.
This is a small old time TV repair shop that has been in the same family since the late 50's, early 60's and they have not forgot the tube stuff. We will see how it goes next week when I see them face to face. Hopefully they have some old stuff stashed away or have some good sources.
If nothing else, I feel a bit better about the 7591A's that are in there now.

So ilets see if I understood your previous statement.
Mullard actually set up the tooling and production lines for Matsushita Electronics in Kyoto Japan (that did not make any 7591's), but they were not involved with the Toshiba or Hitachi production lines?

Nice Pic. Nothing like the glow of clean tubes that are working well.

[FalconEddy]

So ilets see if I understood your previous statement.
Mullard actually set up the tooling and production lines for Matsushita Electronics in Kyoto Japan (that did not make any 7591's), but they were not involved with the Toshiba or Hitachi production lines?


Ok, I can see where that sounds a bit confusing now that I read it. Here's the down and dirty details. . .

'Mullard' was actually Philips-Mullard, and Philips owned/co-owned/part owned manufacturing facilities all over the globe. They were part owner (35%) of Matsushita Electronics for both the Kyoto factory and the Takatsuki factory in Japan, when they first formed a joint business venture in 1953. Which, as I understand it, they used many of Philips-Mullard tooling machines to produce several different type of tubes. Philips-Mullard directly assisted them in re-designing and setting up tube production lines, plus valve research and testing labs. Philips sold their portion of Matsushita Electronics Corporation (MEC) to Matsushita Electric Industrial Company (MEI) in 1993, for the tidy little sum of $1.67 billion.

Based on my research a little over two years ago, they also were part owners of both Toshiba and Hitachi (couldn't find documentation on the percentages); both of which were located in Japan. In my last post I meant to say 'not necessarily for JUST Toshiba or Hitachi'. Anyway, Philips-Mullard tubes produced and labeled 'Toshiba' or 'Hitachi' will many times (but not always) have a code that tells which plant in Japan actually made it.

The Toshiba factory was designated by a 5, the Hitachi factory was designated by a 7, and the Kyoto Matsushita factory's code was an n while the Takatsumi factory's code was N.

Sorry for the confusion earlier.

. . Falcon