5e3 help . Power Tubes pulsating . V1 not glowing =no sound

[Thenagual]

Hey guys , I'm having trouble with my 5e3 . I decided to rewire it and put in a negative feedback switch . I'm now not getting any sound , the power tubes are pulsating ( it can be heard through the speaker) and v1 (12ay7) is not glowing.

So last night I tried firing it up and had no sound . I went back in and discovered that I had the wires for the standby switch and pin 6 on a 6v6 switched. I corrected this and double checked the wiring under the board and my joints.

Here is the layout I am using and some pics.

The tubes were working before. I'm fairly certain all wires are connected correctly and joints are good.

I know checking the voltage would be helpful but with the pulsating of the tubes I'm not sure if I should . Any ideas?

 

[dan40]

If I am seeing your layout pic correctly, it shows the tip and sleeve connection on the output jack being bridged with a wire. This is incorrect as it should be the sleeve and ground that is bridged. Another thing that may pop up when adding nfb is the possibility of positive feedback instead of negative feedback. This usually shows up as a loud squeal or horn blast when you power the amp up or switch in the NFB. The cure for this is to switch the OT's connections at pin 3 on each power tube socket. Check out this link to Rob's sight which shows the correct wiring for the output jack when performing this mod....https://robrobinette.com/5e3_Modifications.htm#Switched_Negative_Feedback I would try getting the jack wired up correctly first and then see if the amp plays fine. If it squeals when you switch on the nfb you will need to swap the wires at the power tube sockets.

 

[dan40]

I am not sure what you may have done that would affect V1. Sometimes it may be hard to see the tube's filament glow but it should feel warm to the touch if it's working correctly. If the tube's filament is not lighting I would try a new tube first. If that does not help, you will need to start tracking down where you are loosing the 6.3vac that feeds the filaments. Maybe it's a bad solder joint or possibly a wire was broken internally from twisting them. The socket may also not be making a firm connection to the tube's pins and may need retensioning.

 

[Thenagual]

I just found the problem( s) I believe ... a heater wire came lose between pin 4 and 5 on v2 and was touching but had snapped. One of the switches I used was faulty and won't change position .. I should've made sure the switch Worked before soldering.

I fired the amp up - all tubes glow, nicely- amp is quiet until cranked only gaining slight noise . I'm draining caps as of now and going to swap out the switch . I'll post back when done.

 

[Thenagual]

Thanks for the help guys. I got it working , just in time too. My old lady's pissed that I spent both my days off on the amp...

 

[Thin69]

Congrats, glad you got it squared away!