[Ron Ramirez]

Schematics:

Tuner and power supply - Click Here

Stereo amplifier - Click Here

Here's the power supply - click to enlarge.

[Image: http://www.philcoradio.com/images/phorum...s01_sm.jpg]

As you can see, with R19 open as it is, no B+ is going to get to the stereo amplifier. Point Z goes to the center taps of the audio output transformer primaries (and from there to each of the 7189 plates); point Y goes to the 7189 screen grids. Point Y also serves as the B+ source for the rest of the amplifier section.

[Ron Ramirez]

While searching for more information about the TA-600, I found this AudioKarma thread:

http://www.audiokarma.org/forums/index.p...on.676168/

I intend to perform the mods called for in the first post of that thread save for the part about 7199 drivers. I'm already using 7199s and had no intention of using adapters for alternate tubes, so point 3 in Dave Gillespie's post will not apply in my case.

I now understand why R19 is open in my TA-600 - the resistor was under-rated to begin with, and late production models switched to two 280 ohm 7W resistors in parallel to equal 140 ohms, 14W. I'm replacing mine with a 150 ohm, 20 watt resistor.

Loose parts ordered from Mouser, email from Tom at Hayseed Hamfest replied to with a request for total including shipping.

Now, while I wait for parts, I'll start DeoxITing the controls and switches.

[Arran]

Ron;
  I'm not familiar with that tube type, 7199, but I can't understand why someone would want to use an adapter unless the socket is mounted in a P.C board. Substitutes listed were a 6U8, 6BL8, and a 6GH8. If one could make a 6GH8 work there are bucket loads of those around, RCA and Brand Z TVs used to use several of them. Since it's used in audio circuitry it's not quite as critical as an oscillator-mixer type tube like a 1L6. It would seem to me that the 7199 was another of those tubes that RCA's tube division developed that was looking for a market, kind of like their 100 ma series string radio tubes, again I don't think I've seen a set that used them, at least in the Canadian market.
Regards
Arran

[TV MAN]

Dyna 70 used those 7199 tubes too. Bought a bunch of them from Sears for a couple dollars each years ago. A lot of folk use the 6GH8a to replace them, but the pinout is different. It's not a plug in replacement. I don't think your Fisher is going to burn up your 6BQ5 tubes if it's running right. I have a Fisher integrated amp (I don't recall the model) and it had the original Fisher tubes and sounded great. I used it quite a bit while I was in tech school. I have a set of JJ 6BQ5s but haven't auditioned them yet. Need to find that Fisher. It'll turn up one of these days and I can try 'em.

[Arran]

Yes;
  I forgot to mention that, you would need to rewire the sockets to swap a 7199 tube for a 6GH8 (or any other nine pin triode-pentode substitute, but I think that's a better course of action then using an adapter. It also need not be permanent, wiring changes are easy to change back with point to point wiring if need be. Of course I haven't compared the interelectrode capacities, transconductance, and electrical characteristics of these 7199 substitutes but one or more has to be close. If the 6GH8 is close that would be ideal, early colour TVs used to use fist fulls of them so millions of spares  were also made.
Regards
Arran

[Ron Ramirez]

Deleted.

[gregb]

I have tried subbing the 6U8 in for the 7199 only because I have been having trouble getting good 7199 tubes. The last few that I have gotten seem to be very microphonic and there are not cheap by any means. The 6U8 works very well and they are cheap and readily available. I do use the 7199 in my gear when ever I can, they would be my first choice for sure but sometimes we have to make exceptions.

Gregb

[Ron Ramirez]

Point well taken. I hereby withdraw my previous comment.

so are you saying the 6U8 is a Plug and Play replacement?

[gregb]

Sorry Ron, no its not plug and play, you have to buy an adaptor or rewire the socket. I went with adaptors as they are easy to use but I do try to stay with the original tube types when possible and use the adaptors when needed or for testing. The day may come when I have to rewire sockets as the 7199 tubes seem to be getting harder to buy for a reasonable price.

Gregb

[Ron Ramirez]

Interesting info. Thanks, Greg.

I just looked...Bob (findatube.com) has new 7199s for $20 each; used/tested for $9 each. So, yes...they are pricey. I've bought used tubes from Bob before and never had any trouble.

Edit: Holy Cow, they are $69.95 at Tube Depot...Jim at Vacuum Tubes, Inc. is out of stock at $45 each...$53.95 at Antique Electronic Supply...and Jim McShane has none listed on his website. I did not realize the 7199s were so..."rare, precious and beautiful"...

Fortunately my 7199s tested good.

Edit #2: Interestingly, late production TA-600 receivers use twin triode 7247 tubes instead of the pentode-triode 7199.

Now...back to the TA-600 restoration...

Parts arrived from Mouser today. I also received notification from Hayseed Hamfest that my new twist-lock caps have shipped. So it is slowly coming together. Three day weekend coming up, so I hope to at least get the parts from Mouser installed.

[gregb]

My problem here in Canada is add 35% to all those prices plus double the cost of shipping, makes it really expensive. And the other problem is like I was saying I am having problems with microphonics, the last amp I worked on had two Rogers branded 7199's that looked and tested like new but are so microphonic they are not at all usable.

Ron, good luck with yours and I hope the tubes are good when you have your first audition!

Gregb

[Ron Ramirez]

...microphonics...ugh...don't want to think about that...sorry to hear about the problems you had with them.

Yes, I know the cost is higher in Canada due to the exchange rate, but keep in mind Bob is almost always cheaper on every tube. Should I find that I need 7199s in the future I will contact Bob first.

[Ron Ramirez]

So the real work began today.

[Image: http://www.philcoradio.com/images/phorum...00_008.jpg]

I have replaced three electrolytics and some resistors, most notably R19 and R26.

[Image: http://www.philcoradio.com/images/phorum...00_009.jpg]

Following the recommendations by Dave Gillespie on Audiokarma (see post #32 above), I changed R19 to a 150 ohm, 20 watt resistor. I added new terminal strips to hold R19 and R26, and to get their ends away from audio section wiring as Mr. Gillespie suggested.

[Image: http://www.philcoradio.com/images/phorum...00_010.jpg]

A closer look at a couple of the 25 uF electrolytics I replaced, along with the resistors that also connected in the same areas:

[Image: http://www.philcoradio.com/images/phorum...00_011.jpg]

The twist-lock cap cans from Hayseed Hamfest are supposed to arrive tomorrow. I hope so. I only have a few more components to install other than those three cans.

[Ron Ramirez]

A nice CARE package arrived in today's mail from Iowa.

[Image: http://www.philcoradio.com/images/phorum...00_012.jpg]

[Image: http://www.philcoradio.com/images/phorum...00_013.jpg]

Three new Hayseed Hamfest twist-lock electroytics, custom made for the Fisher TA-600. This was my first order from Hayseed, and I must say these caps look great.

My goal for today: Get all three mounted in place.

The first one was easy:

[Image: http://www.philcoradio.com/images/phorum...00_014.jpg]

[Ron Ramirez]

The second can, C39, wasn't too difficult:

[Image: http://www.philcoradio.com/images/phorum...00_015.jpg]

[Image: http://www.philcoradio.com/images/phorum...00_016.jpg]

Next, I took a photo of C37 - just in case I forgot what went where, since so many wires and resistors connect to it:

[Image: http://www.philcoradio.com/images/phorum...00_017.jpg]