question about a 8-t-241

[Eric H]

You can replace the individual sections with Wirewounds under the chassis, depends on how many watts it is, you may need to get some that mount to the chassis for a heat sink.

I wouldn't worry about it just yet, the voltage could also be high because some parts of the set aren't working right, tubes not conducting due to bad caps and hence no load on the Power Supply.

[stusnyder]

Originally Posted by Eric H

You can replace the individual sections with Wirewounds under the chassis, depends on how many watts it is, you may need to get some that mount to the chassis for a heat sink.

I wouldn't worry about it just yet, the voltage could also be high because some parts of the set aren't working right, tubes not conducting due to bad caps and hence no load on the Power Supply.

Eric, the set has already been recapped, both e caps and paper caps.

[Penthode]

Because the voltage at the cathode of the 5U4 (pin 8) is high, I see one of two possible scenarios: either the resistive divider chain is open (R193A, R194 R210//R177, R193B and R193C) or else there is a short on the negative end of the chain (-120v to ground).

I suspect you may find an open resistor chain (bad connection or bad resistor). I have seen R193A open on a couple of these chassis. It is the big fella mounted on the rear chassis apron. In each case, I successfully replaced the one bad section with a big wirewound (ceramic tube type) mounted high up on the HV compartment cage on a home made bracket.

[stusnyder]

Originally Posted by Penthode

Because the voltage at the cathode of the 5U4 (pin 8) is high, I see one of two possible scenarios: either the resistive divider chain is open (R193A, R194 R210//R177, R193B and R193C) or else there is a short on the negative end of the chain (-120v to ground).

I suspect you may find an open resistor chain (bad connection or bad resistor). I have seen R193A open on a couple of these chassis. It is the big fella mounted on the rear chassis apron. In each case, I successfully replaced the one bad section with a big wirewound (ceramic tube type) mounted high up on the HV compartment cage on a home made bracket.

I'm having trouble deciphering that resister, to test use a ohm meter with a lead on one end and work down the line with the other lead?? Test out or in circut??? I have no formal training in electronics, just what I have read and experienced thru the years...radios I have no problem....damn televisions are so much harder.

[stusnyder]

I located the resistor on my sams, and checked it. It's in specification, nothing open on it.
But voltage does not match. Looking at the bottom of the chassis, transformer on the right, I hold 1 lead of my meter on the first resistor terminal, moving to the left with the other lead I get 139v, -200v, -188v, and the last to the left -176v

[Penthode]

The high voltage on the 5U4 cathode suggests that one of the resistors in the chain may be open.

If you check the resistance from pin 8 of the 5U4 to chassis, it should measure about 6400 ohms. If you check the resistance of the entire divider chain from pin 8 of the 5U4 to the metal can of C147 (located under the chassis under the power transformer), it should measure 7700 ohms. These resistances may vary +/- 20% but if they are considerably higher, then one of the resistors is likely at fault.

Lastly, try measuring from the metal can of C147 to chassis and it should be 1300 ohms. A short circuit to chassis of the C147 can could also lead to a high voltage on pin 8 of the 5U4.

[stusnyder]

Originally Posted by Penthode

The high voltage on the 5U4 cathode suggests that one of the resistors in the chain may be open.

If you check the resistance from pin 8 of the 5U4 to chassis, it should measure about 6400 ohms. If you check the resistance of the entire divider chain from pin 8 of the 5U4 to the metal can of C147 (located under the chassis under the power transformer), it should measure 7700 ohms. These resistances may vary +/- 20% but if they are considerably higher, then one of the resistors is likely at fault.

Lastly, try measuring from the metal can of C147 to chassis and it should be 1300 ohms. A short circuit to chassis of the C147 can could also lead to a high voltage on pin 8 of the 5U4.

resistance pin 8 to chassis 6460 ohm you said 6400
pin 8 to can c147 7720 ohm you said 7700
can c147 to chassis 1242 ohm you said 1300 ohm

[Penthode]

Originally Posted by stusnyder

I located the resistor on my sams, and checked it. It's in specification, nothing open on it.
But voltage does not match. Looking at the bottom of the chassis, transformer on the right, I hold 1 lead of my meter on the first resistor terminal, moving to the left with the other lead I get 139v, -200v, -188v, and the last to the left -176v

It is difficult to understand what you are measuring. Can you measure the overall chain resistance as I first suggested?

Further, could you identfy what you are measuring corresponding with what it should measure?

Correct ......... vs .......... Measured
Voltages ....................... Voltages

+215
+135
+88
-60
-120