Did you put a single diode or a bridge diode? (a bridge diode can give a higher voltage used with additional capacitors on the B +)
If your getting -27 volts then you may have a capacitor in backwards and shorting or draining (leakage)the plus side.
You could also monitor one of the center tube filament buy using a variac to slowly increase the A.C.input voltage and also watch the filament voltage with a volt meter and stop the variac when the filament voltage is 1.5 volts exactly. Dont go up any higher or you will blow the filament(s)
It may also be one of the tube capacitors are shorting the supply voltage.
Are you using the B - as ground reference or the chassis?
Also you may have restricted the current some how with a Bad capacitor or shorted resistor.
It's hard to tell without knowing or seeing the repair process you use.
how much current are you getting THU the DIODE?
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FOR REFERENCE JUST IN CASE.
HAVE # 673 AS PART OF THE MODEL NUMBERS
BEITMAN SCHEMATICS ALL
GE 637,VOLUME 16 PAGE 45
GE P673A,B,VOL 19 PAGE 54, VOL 20 PAGES 53-54
GE R-673 VOL 3 PAGE 153 UNITED MOTOR (MAYBE A CAR RADIO?)
GE RC 1673 VOL 24 PAGE 55
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RIDERS SCHEMATICS
GE L673 VOLUME 14 PAGE 61
GE LB-673 VOLUME 17 PAGE 25
GE R-673 VOLUME 10 PAGE 13 UNITED MOTORS (MAYBE A CAR RADIO?)
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SAMS SCHEMATICS
GE 19CC6733J01 SET 2494 FOLDER 2
GE 19CC6739J01 SET 2494 FOLDER 2
GE 19PF6730J01 SET 2494 FOLDER 2
GE 19PF6736J01 SET 2494 FOLDER 2
GE 673 SET 382 FOLDER 7
GE P6731A SET 411 FOLDER 9
GE P673AB SET 411 FOLDER 9
GE RC1673 SET 411 FOLDER 9
GE RC673A SET 674 FOLDER 9
GE RC673AB SET 783 FOLDER 6
GE RC673AB SET 783 FOLDER 6
GE RC6731BWDA SET 888 FOLDER 6
GE RC6732BMPA SET 888 FOLDER 6
GE S673G SET 1033 FOLDER 3
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