Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: dasman66 on March 03, 2018, 04:32:47 PM

Title: low resistance on RCA (Resolved)
Post by: dasman66 on March 03, 2018, 04:32:47 PM

I have a friend that asked me to troubleshoot his crack build.  After some resoldering, I've got all the resistances where they should be except the red RCA center pin.  Initially, he had too much solder and had bridged to the nut, so it was reading 0.  After removing the excess, removing and resoldering to the center, it's now reading 17-18k, rather than 90k. 

Does this mean the RCA jack is bad?  (doesn't look damaged, plastic isn't melted, etc)  or might this be something else?

If the RCA is bad, any recommendations on best place to pick up a replacement that might match appearance?  Or should I just count on replacing both of them to get them to match?

Title: Re: low resistance on RCA
Post by: Paul Joppa on March 03, 2018, 06:41:43 PM

Does it vary with the volume control setting?

Title: Re: low resistance on RCA
Post by: dasman66 on March 03, 2018, 06:53:51 PM

No, identical with min or max volume

Title: Re: low resistance on RCA
Post by: Paul Birkeland on March 05, 2018, 06:25:46 AM

That's an odd resistance to get on the jack.  You can heat up the joint on the center pin, then pop the wire out.  The center pin to ground should then read over limit on your meter and ideally you would get 100K on the pot.

You might also consider posting a photo of the pot.  Debris can enter the pot and it can actually be damaged if excessive solder is used.

Title: Re: low resistance on RCA
Post by: dasman66 on March 06, 2018, 01:50:48 PM

Ok... I popped the center wire back out.  Center pin to ground (12U), with meter set to 2M (I don't have an autoranging meter) starts at 1.3M area and then increases to off the chart (ie., 1 reading on the meter).  Center wire to ground (12U) is reading 97k.

Photo of center pot attached

Title: Re: low resistance on RCA
Post by: dasman66 on March 06, 2018, 01:58:44 PM

Well... I must have had a bad joint... For the hell of it I just resoldered the center wire back in again, and am now getting 90k.  Go figure.

Apologize for wasting people's time... thanks

Title: Re: low resistance on RCA
Post by: Paul Joppa on March 06, 2018, 02:22:02 PM

My guess would be that there was a bunch of solder flux in the RCA socket. Flux can be slightly conductive, and soldering those center pins can take a lot of heat and solder. And (in case anyone wonders) that's an experience-based guess ...

Title: Re: low resistance on RCA
Post by: Leland Hankins on March 06, 2018, 02:32:10 PM

I always drill a hole the size of the wire through the back of the RCA jack, then put the wire threw the hole and solder.  One is trying for a physical joint with jack and wire.  I do not like the sound of solder!

Title: Re: low resistance on RCA
Post by: dasman66 on March 07, 2018, 04:49:08 AM

That's a good idea... if I replace the braid on my crack at some point, I will remember to do that.

Since this one now works, it's going back to my friend.