Hello,

I am trying to bring an old B600 back to life and am stumped. All tubes test good. All voltages are on the mark. All tubes except for the 50A1 are not lighting up or heating up. There is no sound from the speaker. The chassis is out of the cabinet. I dont think there is a safety lock on it. I have no clue what is happening here.

Greg, you said all voltage ok and tubes ok but they don't light up or heat! Assume you checked voltages of heater string and found correct voltage at socket.
If the voltage is there (across heater)tubes have to light up and heat unless tube heater shot or voltage not getting from socket to pin of tube. I could see one or two pins not making contact but every tube in set? If tubes in series how did you get correct voltage across heaters? Some thing does not add up here. PL

:Hello,
:
:I am trying to bring an old B600 back to life and am stumped. All tubes test good. All voltages are on the mark. All tubes except for the 50A1 are not lighting up or heating up. There is no sound from the speaker. The chassis is out of the cabinet. I dont think there is a safety lock on it. I have no clue what is happening here.

Hi, I get about a 1.2V drop across all tube elements accept for the 3V4 tube which is getting a 2.7 voltage drop. The voltage going into pin 7 of 3V4 is 7.5 just as the schematic says. One of the 1U4 tubes does acutally light up but very faintly.

Any thoughts?

: Greg, you said all voltage ok and tubes ok but they don't light up or heat! Assume you checked voltages of heater string and found correct voltage at socket.
:If the voltage is there (across heater)tubes have to light up and heat unless tube heater shot or voltage not getting from socket to pin of tube. I could see one or two pins not making contact but every tube in set? If tubes in series how did you get correct voltage across heaters? Some thing does not add up here. PL
:
::Hello,
::
::I am trying to bring an old B600 back to life and am stumped. All tubes test good. All voltages are on the mark. All tubes except for the 50A1 are not lighting up or heating up. There is no sound from the speaker. The chassis is out of the cabinet. I dont think there is a safety lock on it. I have no clue what is happening here.

:Hi, I get about a 1.2V drop across all tube elements accept for the 3V4 tube which is getting a 2.7 voltage drop. The voltage going into pin 7 of 3V4 is 7.5 just as the schematic says. One of the 1U4 tubes does acutally light up but very faintly.
:
:Any thoughts?
:
:
:
:: Greg, you said all voltage ok and tubes ok but they don't light up or heat! Assume you checked voltages of heater string and found correct voltage at socket.
::If the voltage is there (across heater)tubes have to light up and heat unless tube heater shot or voltage not getting from socket to pin of tube. I could see one or two pins not making contact but every tube in set? If tubes in series how did you get correct voltage across heaters? Some thing does not add up here. PL
::
:::Hello,
:::
:::I am trying to bring an old B600 back to life and am stumped. All tubes test good. All voltages are on the mark. All tubes except for the 50A1 are not lighting up or heating up. There is no sound from the speaker. The chassis is out of the cabinet. I dont think there is a safety lock on it. I have no clue what is happening here.
Hi Greg,
It seems your turbe are lighting. Sometimes you can't see the filamens on these.
I have a B600. It had been working with poor sensitivity. The tuning turned out to be way off. If tuning had been off more I would have gotten nothing. I think you will need a signal generator to go further with troubleshooting.

Best Regards,

Bill Grimm

:Hi, I get about a 1.2V drop across all tube elements accept for the 3V4 tube which is getting a 2.7 voltage drop. The voltage going into pin 7 of 3V4 is 7.5 just as the schematic says. One of the 1U4 tubes does acutally light up but very faintly.
:
:Any thoughts?
:
:
:
:: Greg, you said all voltage ok and tubes ok but they don't light up or heat! Assume you checked voltages of heater string and found correct voltage at socket.
::If the voltage is there (across heater)tubes have to light up and heat unless tube heater shot or voltage not getting from socket to pin of tube. I could see one or two pins not making contact but every tube in set? If tubes in series how did you get correct voltage across heaters? Some thing does not add up here. PL
::
:::Hello,
:::
:::I am trying to bring an old B600 back to life and am stumped. All tubes test good. All voltages are on the mark. All tubes except for the 50A1 are not lighting up or heating up. There is no sound from the speaker. The chassis is out of the cabinet. I dont think there is a safety lock on it. I have no clue what is happening here.

I'm no expert but, I've just restored one of these. Filament voltages should be around 1.4v except the 3V4, in my set it's filament voltage is 3v. The 1L6 will not operate correctly with a low filament voltage. These tubes do not light brightly, since they're designed to operate from battery voltages. Some like to substitute the 1L6 for a 1R5 while working on the set to avoid burning out the filaments with a misplaced probe. Don't pull any tubes while the set is powered up. Hopefully other will join in and help you.

I have a G500 Transoceanic with a similar tube lineup, I just don't have the 50A1 regulator in mine. The filament string is a complex circuit with series and parellel resistances along the path. As 'directly heated' cathodes, these tube filaments bear that circuitry as well.
I have lost a 1L6 before and I strongly recommend the 1R5 substitution idea during service.
With the tubes out, check your filament string resistors. Some of mine had drifted as high as 70% above spec. These voltages need to be as accurate as possible. Adding a filament protection zener for surge/overvoltage issues is also worthwhile for safety.

: I have a G500 Transoceanic with a similar tube lineup, I just don't have the 50A1 regulator in mine. The filament string is a complex circuit with series and parellel resistances along the path. As 'directly heated' cathodes, these tube filaments bear that circuitry as well.
: I have lost a 1L6 before and I strongly recommend the 1R5 substitution idea during service.
: With the tubes out, check your filament string resistors. Some of mine had drifted as high as 70% above spec. These voltages need to be as accurate as possible. Adding a filament protection zener for surge/overvoltage issues is also worthwhile for safety.

Hi Again,

I had another look last night and inspected the wiring on the speaker because there was no sound at all. I noticed there was an ear phone jack in the schematic and saw that the jack on the cabintet was not conntected because the chassis was removed from the cabinet leaving the speaker connections open. I temporarily rewired the output coil directly to the speaker and turned it on. It works fine!! :)

Thank you everyone for your input. Cant wait to get her all back together!!