Break down of pin connectors

[S Clark]

I put this under Amplification, but it's a broader issue.  I had reported a year or two back that a noise issue with a Dodd preamp was actually related to dirty pin connectors inside the unit. 
Now I can add to that the failure of a pin connection in a Moscode amp.  My Moscode 401HR has been my primary amp to drive my LS9 speakers for about a decade.  To my dismay it stopped sending a signal to either channel even though the center tubes lit. 
Credit to George Kaye (of whom I've been critical for how slow he works).  He ran me through a trouble shoot over the phone leading to a suspect and a solution.  The Moscode 401HR has a diode on a heat sink on the main board.  The 3 pins of the diode went straight to a pin connector... and as one leg began to increase resistance, it got hot, and then failed.  It was a PITA, but it's now directly soldered. 
The lesson is if anything with heat goes directly into a pin connector, it is subject to failure. 
Before, I had suggested that pin connectors should be cleaned annually.  Now pay special attention to anything that might conduct heat.   

[Folsom]

It may be a result of the pin to connector stress. Tube sockets operate all the time, but the BEST case scenario is that they free float in just the right way so that you get a high contact amount with good compression. When they don't have that it's a matter of time.

[S Clark]

But tube sockets are designed for heat... sockets in ceramic or that old Bakelite stuff.  Pin connectors are just plain plastic (I think).  Seems like running a diode that will dissipate heat into one is asking for trouble. 

[rollo]

  Good to know thanks

charles

[S Clark]

I do find it interesting that my last two major equipment failures were due to faulty connections in pin connectors...  And the things are ubiquitous in stereo gear.  Just like cleaning and tightening other connections, I'd certainly pull the covers off amps, preamps, phono stages, etc at least occasionally and use a little Caig (or equivalent) on them. 

[Folsom]

I'm saying some of the heat might be from a poor connection. It's like how a small wire will be hotter than a bigger one under the same load.

[S Clark]

I get what you're saying.  Except George seemed to know exactly where to go on this.  I'd put money that it's a bad idea to put a heat generating diode into a pin connector that isn't designed for heat.   My guess is that it was a poor design choice by George that was fixed in later models.  But to his credit, I was able to avoid the whole over the top box building to keep the apes at Fed Ex/UPS from destroying what ever is inside.  I can't tell you how I was dreading boxing and shipping that amp. 

[ejk]

I do find it interesting that my last two major equipment failures were due to faulty connections in pin connectors...  And the things are ubiquitous in stereo gear.  Just like cleaning and tightening other connections, I'd certainly pull the covers off amps, preamps, phono stages, etc at least occasionally and use a little Caig (or equivalent) on them. 

Plastic connectors like that are used in auto engine compartments for years and I would think they go through much worse conditions than in an amp. I wouldn't think the auto industry uses anything better.

Glad you fixed your problem

[S Clark]

Plastic connectors like that are used in auto engine compartments for years and ...

Yes, but I've never seen one plugged into a component with a heat sink.  You don't see a pin connector on a block or exhaust.