Foreplay 3 amp no output (Paramount)

[Mr. Self-destruct]

Yes, it's staying in the family for sure.
Ok after the amp came on, I played music for about an hour. Sounds great, turned off,, went out for a few hours, wouldn't come on when I got back home. I once again touched the two meter leads, one on ground,  one on pc2 transformer red wire tab that goes to the first tab on the board w 4 red LED's. It came to life,, Nothing seems to be loose.

 

[Paul Birkeland]

Something is loose in the amp.  If you touch things and it magically comes on, you're moving the loose connection.

 

[Mr. Self-destruct]

I agree, just turned the system on, both amps working without probing. I'm going to meticulously check solders then voltages once I get manuals. Thank you

 

[Mr. Self-destruct]

Played for about 3 hrs, amp stopped, touched probes ground to tab on Pc2, the tab across from 6. Amp Came back on. Nothing loose.

 

[Paul Birkeland]

If you touch something in the amp with your meter probes and it magically comes to life, there's a loose connection or a broken wire. 

 

[Mr. Self-destruct]

It definitely feels like magic!  I still agree. Maybe a bad solder somewhere? I'm going to check around some more today.

 

[Thermioniclife]

if you touch a terminal and it comes to life, you need to heat that joint and apply just a little more solder.

 

[Karl5150]

What a wonderful gift, looks like there were plans to move the controls to the front of the pre base.
As for your volume question earlier, SF speakers (photo) aren't generally very sensitive (mid to high 80's) so 8W/ch probably won't rock the house.
Karl

 

[Mr. Self-destruct]

Karl, Indeed a great gift! I love em already.  Good eye on the control plan. Good info on sf speakers thanks. Paul, Found a loose connection as you said,  switch ground, thank you.

 

[Mr. Self-destruct]

Ah, spoke too soon. Back to the soldering board.

 

[Mr. Self-destruct]

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.

 

[Mr. Self-destruct]

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.

 

[Mr. Self-destruct]

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!

 

[Mr. Self-destruct]

https://youtu.be/-hmWCrbHgdc
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.

 

[Mr. Self-destruct]

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

 

[Mr. Self-destruct]

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.