Dynaco-Doctor Forum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to Dynaco-Doctor Forum

Message Sort: Post Order or Asylum Reverse Threaded

Heat effects on components

209.179.51.93
Posted on May 26, 2003 at 00:59:00
Pat


 
I have just gutted my two (functional) ST-70's in prep for a complete rebuild using CAE driver and cap boards, sockets, and wire. I did my best to de-solder and clean the components with as little heat as possible. I am now wondering how much heat the 15.6 ohm bias set resisters and the 3 leaded ceramic capaciters can actually take before they are damaged. I used heat sink clips on the ceramic caps, but they got very hot and expelled oil by the time I got them unwound from the 7-pin terminal strip. The leads are pretty short too. The bias resisters test just fine, but I am worried about the ceramic caps. Has anyone found a replacement for these? A source would be greatly appreciated. Thanks, Pat.

 

Hide full thread outline!
    ...
Re: Heat effects on components, posted on May 26, 2003 at 06:03:26
airtime
Audiophile

Posts: 11287
Location: Arizona
Joined: February 4, 2003
 I would assume you can test the cap for damage. There should be infinite resistance between the common leg and the two others. If you get some resistance of try comparing it to another ceramic of the same value. And I don't know why you can't 2 ceramics anyway?? What is it a 0.02uf 500v??
charles

 

Re: Heat effects on components, posted on May 26, 2003 at 07:47:10
Joe Curcio
Manufacturer

Posts: 1261
Location: Northern CA
Joined: October 10, 2001
 Unlike semiconductors, passive components are very tolerant of the heat encountered in soldering. In particular the ceramic resistors on the output tubes pins 1&8 are very tolerant of heat. On the other hand they are somewhat susceptable to damage if you place too much mechnical force on the leads.

The same goess for the ceramic caps - the "oil" is actualy wax coating and is of no consequence. Again, be careful to not place too much stress on the leads.

In cleaning the sockets and resoldering (hopefully you are installing new ceramic sockets) you should be certain to use the heat necessary to thoroughly clean and remove all old solder(an Edsyn solder sucker and some solder wick is recommended - see our DIY bible on the tech support page). Above al don't try to simply re-apply new solder over the original. The only heat intolerant component is the original PVC insulated wire - it melts very easily and is one reason why we recommend Teflon insulated wire.

 

Re: Heat effects on components, posted on May 26, 2003 at 11:51:29
Pat


 
I do get infinite resistance between the common and each of the other two legs, and they tested good at the local tube shop this morning. I was just worried that all the heat I used to remove them would reduce longeviety. Indeed...he sold me (2) 0.02uf 500v ceramics for each unit, but said the old would work just fine if the leads are not "worked". I don't have the experience to start swapping out components without advise. I figured they doubled those caps up for a special reason, but I guess not. Thanks for taking the time.
-Pat

 

Re: Heat effects on components, posted on May 26, 2003 at 12:32:45
Pat


 
Yikes Joe! I started this weekend with two good St-70's, and am now left with two piles of parts. Slight anxiety attack last night had me wondering if you dispense Prozac too! Well, the chassis's both polished up very nice and the transformers ar sitting pretty with two coats of high temp semi-gloss acrylic enamel. Somehow I missed the DIY bible..wonderful resource. It answered so many questions I had.

And yes...I did order ceramic sockets along with the boards. I bought the wire, switches, and little stuff from the local tube shop. They recomended your components, and have been so helpful testing tubes and giving advise.

Can't wait to get my kits. I think I went the right route in upgrading everything at once. It is a little frightening though!

-Pat

 

Page processed in 0.019 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]