Need some 7591 info.

MCS Guy

The MCS hoarder
I just wanted to make sure these voltages were right.

Pin 1= Not used (Cathode feeds Supressor Grid from this pin internally)
Pin 2= 0 (Cathode/Heater GND)
Pin 3= 504 VDC (Plate)
Pin 4= .400 VDC (Screen Grid)
Pin 5= 0 (Supresor grid)
Pin 6= -21 VDC (Control/Bias Grid)
Pin 7= 7 VAC (Cathode/Heater Power)
Pin 8= .400 VDC (Screen Grid)

These readings were taken after 10 minutes of run time. Just wanted to make sure these readings are healthy before buying new outputs and the big caps.

Also, Output Trans A resistance was 138ohm and Output Trans B was 142ohm (measuring from center tap to pin 3). Is this OK?
 
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MCS Guy said:
I just wanted to make sure these voltages were right.

Pin 1= Not used (Cathode feeds Supressor Grid from this pin internally)
Pin 2= 0 (Cathode/Heater GND)
Pin 3= 504 VDC (Plate)
Pin 4= .400 VDC (Screen Grid)
Pin 5= 0 (Supresor grid)
Pin 6= -21 VDC (Control/Bias Grid)
Pin 7= 7 VAC (Cathode/Heater Power)
Pin 8= .400 VDC (Screen Grid)

These readings were taken after 10 minutes of run time. Just wanted to make sure these readings are healthy before buying new outputs and the big caps.

Also, Output Trans A resistance was 138ohm and Output Trans B was 142ohm (measuring from center tap to pin 3). Is this OK?

I forget what amp are we talking about ?
Everything looks good except the .400 VDC on pin 4 and 8 I hope that is a typo and its really 400 VDC. Another possible source of a problem is the 500V on the plates that is on the extreme side for a 7591
 
those look about right to me. the most important voltage is the negative supply for the control grid. Before you replace the tubes, check to see if the amp uses a selenium rectifier for the negative supply and replace it with a silicon diode if it does. This will give you a larger negative supply, and you will probably have to adjust the bias or change resistors to get enough bias current. but the selenium rectifiers go bad, leaving you with no negative supply and that will over bias your tubes and maybe kill your output transformers.
Not sure about the resistance of the output transformer, but I think if you don't read a dead short it's probably ok. If you can look at the output with a scope, running into an 8 ohm load, with a 1KHz sine wave input and it looks clean, then the trannies are fine. the voltages are ok to run a safe checkout.
 
It was a typo. Its 400VDC on the 4/8 pins.

According to this website (http://rummageads.com/tstereo/KenwoodKW220/).

"This amp has some unique features such as seperate fixed bias power supply from the DC filament power supply"

The KW220 and the KW1100u use the same amp section
 
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I took a look at the pictures and I don't see any selenium rectifiers in there, so I think you are ok. I agree the gray axial japanese electrolytics seem to go bad alot.
 
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