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Avery's "First" Maker: The TA-800

Hi all, is there a marked-up schematic available to show where to install and the values of:

1. Screen Stability resistors,
2. Cathode current sampling resistors
3. Individual bias controls

I am supposed to pick up a very tired TA-800 soon and it will need a total overhaul. Thank you.
 
The revised amplifier design is shown in a schematic I presented in post #249. Understand however, that the schematic also includes the revised driver circuit I developed to eliminate the use of the problematic 7199 tube in that position.

I hope this helps!

Dave
 
dcgillespie said:
The revised amplifier design is shown in a schematic I presented in post #249. Understand however, that the schematic also includes the revised driver circuit I developed to eliminate the use of the problematic 7199 tube in that position.

I hope this helps!

Dave
Click to expand...

Thank you, Dave. I see 100-Ohm screen stability resistors on the output tubes; 10-Ohm 1% resistors on cathodes. Is there recommendation on wattage for both? Screen stability I guess 1/4-watt will do; would the same work for cathode current sampling ones? For individual bias pots - your schematic shows connection to 'EFB' circuit. Is there a redline by any chance where the bias pots would be added? Are you replacing R153/R154 combination? Sorry, I only really started collecting info on the amp updates and upgrades.
 
I guess I never posted the power supply page -- but I'm sure I drew the details out, to be used in conjunction with the Fisher schematic. Sorry it didn't get posted. When I post schematics of modifications I've made to anything, I do so primarily with the intent of simply showing what was done, not so much with any great belief that folks would rush to apply the changes to their own units. It's flattering if they do, but I hardly expect it. Sometimes -- like with the Magnavox projects, it goes nuts. Other times, like with the TA-800, few if any will adopt the changes (since there's relatively so few of these units), so a page can get missed for (obviously) a long time. If it hasn't been archived, I should be able to get it posted shortly.

Dave
 
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