Foreplay 3 amp no output (Paramount)

[Rob C]

It works for like a 1/2 hour and then stops so I go underneath and all I did this time was touch my needle nose to that bottom tab across from number 6 on PC2. The red wire that runs to the board with the 4 LED's when it's not working only one LED is lit when I touched my needle nose to it all 4 LED's came on and it started working.

[Rob C]

I'm still waiting on the manual so I could take proper voltage tests.

[Paul Joppa]

Just a thought:

It seems likely that red wire is not reliably connected at both ends. Sometimes a wire is nicked when stripping the insulation from an end, and it eventually breaks inside the insulation. So check both ends of the wire.

If it's the one that goes to pin 1 of the tube socket, the end in the PC board may have a cold solder joint - that goes to the collector of a power transistor, which acts as a heat sink and requires extra heat and/or time to make a solid connection. So check the transistor connection as well as the red wire.

[Rob C]

Hi Paul,  its the red wire that starts on the terminal Across from terminal 6 on PC2 tf,  it goes to the 5 tab Distribution brown board Which then splits to 2 reds, 1 red going to the i on the AB greenboard the other red going to the yellow capacitor board. Hope that's clear. I'll look into your suggestion.  It's been working for 3.5 hrs so far. Thank you

[Paul Joppa]

Hi Paul,  its the red wire that starts on the terminal Across from terminal 6 on PC2 tf,  it goes to the 5 tab Distribution brown board Which then splits to 2 reds, 1 red going to the i on the AB greenboard the other red going to the yellow capacitor board. Hope that's clear. I'll look into your suggestion.  It's been working for 3.5 hrs so far. Thank you

Took me a while, but I think I understand. (PC-2 is a plate choke; the terminal across from 6 is 5, the capacitor board is actually the power supply board). The wire connects the plate choke to the high-voltage power supply, so if it's not making good contact the output stage is not powered. The junction of the high-voltage power (under the green board) has several wires and is hard to see, so that's a likely spot for a marginal solder connection to happen.

These are just ideas for tinkering until the manual shows up; the real diagnosis starts when we have measurements, tinkering will then be much more likely to help!

[Rob C]

 I just took this video now I turned the amp on once I got home only only one red light was on this time instead of touching number 5 on PC2I touched the tab on the Brown 5 terminal distribution.

[Rob C]

I'm going to clean this up and resolder some points

[Rob C]

Clean it and got same results

[Thermioniclife]

Did you resolder the terminal you touched in your video?

[Paul Birkeland]

That is how a broken wire behaves.

[Rob C]

Yes soldered what I touched. Still looking for broke. Wires. Speaking of broken....300b socket. Maybe terminal is grounding out. Ceramic is broken see pic.

[Paul Birkeland]

You can very gently pull the tube out of that socket, then let super glue drip into all those cracks to keep it in place. 

You could remove all the wires from that socket and take the socket out and it wouldn't cause the problem you showed on your video.

[Rob C]

I will do glue. I think I have an extra socket. There were spare parts. So can i turn amp on without the 300? Is there anything I absolutely should not do? I wouldnt want to damage further. 

[Paul Birkeland]

Yes, you can run the amp without the 300B, but there isn't any reason to do that.  I'm just saying not to worry too much about the socket, as I believe you have a broken wire. 

[Rob C]

Cool thanks. Still can't find break. Here's another short vid. A little different result than last vid. Most likely picking up manuals today.