Supro 1650 rt

[Big chief]

Power tubes red plating changed tubes did not help
Can’t find schematic on internet
Any help would be appreciated
Have to travel to my home where I work in my little shop due to flood at my house

Please help

[shooter]

self biased or fixed bias?

[Big chief]

Fixed bias as there is no bias pot that I can find

[shooter]

fixed bias doesn't NEED a pot
IS THERE a cathode resistor on the PA tubes, if so what value

[Big chief]

I’ll go over tomorrow and take readings with tubes out and post this thing has a pcb
Thank you

[shooter]

post a pic of the PCB

[Big chief]

Voltage on power tubes
V2 p1 0     V3 p1 0
     P2 8.         P2.8
     P3 0.         P3 0
     P4 512.     P4 508
     P5 0          P5 504
     P7 3.7.      P7 .5
     P8 .4.        P8 .5
Can’t get photo to post.  Hope I did not get junk

[Big chief]

Pin 5-54

[Big chief]

Photo

[Willabe]

Voltage on power tubes
V2 p1 0     V3 p1 0
     P2 8.         P2.8
     P3 0.         P3 0
     P4 512.     P4 508
     P5 0          P5 504
     P7 3.7.      P7 .5
     P8 .4.        P8 .5

Somethings wrong. Power tubes are 5881/6L6GB?

If so, pin 4 is the screen grid, that looks pretty good, then pin 3 is the plate, should be the same or a little higher than the screen grid dcv.

Pin 5 is the input/control grid, should be the -bias dcv, maybe ~ -45? 

[Big chief]

Rectifier tube cold 5u4
Pin 4 122
Pin 6 128


Pin 2 .05
Pin 8 .05
Have no idea from here

[shooter]

with no schematic, PCB built, strip it and build something new, otherwise we're just blindfold duck hunting

[Big chief]

Thanks

[Willabe]

Rectifier tube cold 5u4
Pin 4 122
Pin 6 128


Pin 2 .05
Pin 8 .05
Have no idea from here

With all tubes out, measure for 5acv across rectifier tube pins 2 and 8. That's the acv for the rectifier tubes heater. If you have 5acv, then try different rectifier tube, that tubes heater went out.

If no 5acv then make sure there's not a bad/broken 5acv heater wire, or a cold solder joint, might be a push on spade luge.  Or lastly the PT's gone bad. 

And pin's 4 and 6 look low, but you do have some acv from the PT's secondaries B+ high voltage wind.

And please put acv or dcv when you post voltages.

[Big chief]

Thanks for the info I’ll go over tomorrow and measure and post

[Willabe]

Pins 2 and 8 should have both a 5acv and the B+ dcv.

For the 5acv for the heaters measure across pins 2 and 8. For the hi B+ dcv, measure for dcv from pin 8 to ground. 

[Big chief]

Pin 2-8 ac 0.6
Pin 8 to ground 522 dc
Pin 4 127 ac
Pin 6 131 ac

[Willabe]

I was out of town for the weekend. Somebody should have replied on this.

The 0.6acv has to be wrong because your getting 522dcv at pin 8.

Pin 4 with 127acv and pin 6 with 131acv seem low since you getting 522dcv at pin 8.

131 x 1.3 = 170.

Somethings wrong with these readings/voltages.

[Willabe]

And;

Voltage on power tubes
V2 p1 0     V3 p1 0
     P2 8.         P2.8
     P3 0.         P3 0
     P4 512.     P4 508
     P5 0          P5 504
     P7 3.7.      P7 .5
     P8 .4.        P8 .5

Somethings wrong. Power tubes are 5881/6L6GB?

If so, pin 4 is the screen grid, that looks pretty good, then pin 3 is the plate, should be the same or a little higher than the screen grid dcv.

Pin 5 is the input/control grid, should be the -bias dcv, maybe ~ -45?

Those #'s show no plate dcv. And the V3 pin 5 502dcv has to be wrong.

Measure for negative dcv at pins 5 on both tubes. That is the -bias dcv.

And put a new battery in your meter. See if the readings change.