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Author Topic: 7199 Tube Equiv. Re: w1vtp Eico 720  (Read 1216 times)
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KB3DKS
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« on: April 17, 2011, 01:34:33 PM »

w1vtp,Al
It's funny, when you mentioned needing a 7199 Sat afternoon I was working on an amplifier using the same type circuit 7199 X EL34s. There were too many in the QSO for me to throw a comment in so here is what I know.
  The 7199 phase inverter/driver is a very common circuit used in many Eico, Dynaco, and other amplifiers of the period. It is supposed to be a low noise tube that was probably designed specifically for those circuits. Dynaco and others also used the 6AN8, same type, different pinout but somewhat more common and usually cheaper. I believe there are Russian 7199s but not sure of the quality.
There are quite a few "upgrade ??" circuit boards for Dynaco amps being offered using a very common 6GH8, again same function/type different pinout, but they must be selected for noise with the usual yield of about 2 in 10 NOS suitable.
I prefer the 6AN8 altho it can be somewhat difficult to find.

Bill,
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w3jn
Johnny Novice
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« Reply #1 on: April 17, 2011, 01:37:13 PM »

6EA8 is I believe very similar, but has a different pinout.
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KB3DKS
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« Reply #2 on: April 17, 2011, 02:05:08 PM »

6EA8 is I believe very similar, but has a different pinout.

Yep,
For some reason there were quite a few triode/pentode combinations all with about the same spec just different basing. The 6EA8 never got bood audiofool recognition but was used extensively by Bogen and a couple other audio amp mfgs. Probably to get around design pat's. Same selection for noise performance needed as the 6GH8 but might have a better yield.
If my memory is correct this style tube was used extensively in the vertical sections
of TVs.

Bill, KB3DKS
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W2XR
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« Reply #3 on: April 17, 2011, 02:09:39 PM »

The 6AN8 is similar, too, but I believe the pin-out is different.

The Dynaco Stereo 70, and the SCA-35 both used the 7199, which has become somewhat difficult to find and quite expensive.

The Dynaco Mark III used the much cheaper and highly available 6AN8. A number of these circuits were modified to use the 6GH8 (I think that is the correct tube number) which supposedly offered a significant audible improvement over the 7199. If you need any 6AN8s, let me know, as I have zillions of the them from my Dynaco Mark III days.

The 7199 was a pentode/triode; the pentode section was used as a voltage amplifier, and the triode section as a phase splitter for swinging the push-pull grids in the output stage.

73,

Bruce
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W4AAB
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« Reply #4 on: April 17, 2011, 06:33:26 PM »

Another number for the 6EA8 is 6U8. I remember back in my TV repair days(early-mid '70's) that color TV's had many circuits that used 6GH8's.I MIGHT have a few 7199's around.
                                      Joe W4AAB
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KM1H
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« Reply #5 on: April 17, 2011, 07:04:54 PM »

The 6GH8 was a TV repairmans bane as they were always going bad; the 6GH8A was a whole lot better even tho the only stated difference was controlled warm-up for series strings...they had to have quietly fixed something else.

Carl
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kg8lb
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« Reply #6 on: April 19, 2011, 01:35:47 PM »

Pinout aside, the 6AN8 is a near identical replacement for the 7199 in the Eico 730. You should be able to use the 6AN8 by simply rewiring the socket to reflect the connection differences. The 6AN8 is in pretty high demand among the audio types but being a bit more common than the 7199,as mentioned, the prices are usually lower.
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w4bfs
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« Reply #7 on: April 19, 2011, 01:51:46 PM »

I believe the Ruskies have re-issued the 7199 ... I would usually change them to a 6GH8a, particularly in Ampegs for a small improvement in sound ....you might check with New Sensor for either ...73....John
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