Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: SleepLess on October 07, 2013, 03:47:50 pm

Title: 5E3 strange issue
Post by: SleepLess on October 07, 2013, 03:47:50 pm
Hi!
I've just finished my tenth 5E3... And I have the weirdest issue I've ever had: only one of the 6V6s lights up... The other doesn't and remains as cold as ice... All the other tubes are well lit up. I have 3.4V on pins 7 and 2 of this tube (V3), just like on the other 6V6 (V4). B+ is higher on V3 with 385V, 365V on V4.

So I mean, it's getting its heater voltage right but doesn't light up, what the hell is this???
Of course I have tried other pairs of 6V6s (two more, so 3 pairs total!) and V3 never lights up.

I'm obviously going to recheck my wiring and everything, but if you have already seen this or know what it could be coming from, that could make me save some hours...
Thanks!!!
Title: Re: 5E3 strange issue
Post by: Slimtim on October 07, 2013, 04:31:06 pm
It would have to be the wiring right?Wouldn't hurt to post a pic. or 2 of it.
Title: Re: 5E3 strange issue
Post by: SleepLess on October 07, 2013, 04:32:22 pm
Quote from: Slimtim on October 07, 2013, 04:31:06 pm
It would have to be the wiring right?Wouldn't hurt to post a pic. or 2 of it.

My camera broke down two days ago...  :sad2:
Title: Re: 5E3 strange issue
Post by: Slimtim on October 07, 2013, 04:50:50 pm
i was just going to add maybe a bad socket lol.
Title: Re: 5E3 strange issue
Post by: HotBluePlates on October 07, 2013, 05:21:05 pm
Quote from: SleepLess on October 07, 2013, 03:47:50 pm
... it's getting its heater voltage right but doesn't light up, what the hell is this??? ...

Wires coming in have continuity with wires going out, but voltage on wires doesn't make it to 6V6 heater pins.

Maybe the socket doesn't grip both pins firmly (new socket, not reused?).
Maybe you don't have pins 2 & 7 (socket isn't an odd style, or 6V6 doesn't have a broken guide pin and is inserted incorrectly?).

Quote from: SleepLess on October 07, 2013, 03:47:50 pm
... B+ is higher on V3 with 385V, 365V on V4. ...

Heater didn't light up, V3 didn't draw current, B+ feed to V3 didn't drop voltage across OT's winding resistance, therefore V3 plate voltage is higher.
Title: Re: 5E3 strange issue
Post by: Ed_Chambley on October 07, 2013, 08:06:16 pm
Sounds like you have tried enough tubes eliminate anything with the tube.  I first would pull both power tubes.  Get voltages for both checking where it is soldered as well as inside the socket pin connection.

Measure your heater wires across each for 6.3vac, not one to ground.

Sorry if this seems simple and you have already checked this.
Title: Re: 5E3 strange issue
Post by: SleepLess on October 08, 2013, 04:07:09 am
Hi there.
It was a bad socket, I changed it and now it works and I have 355V B+ on both tubes... Thanks!!!