REDUCTION RESISTANCE ISSUE... bad cap?

[benrupp]

Hello all,

This is my very first build.  When I went to check the resistances I came across this issue... 13, 14 and 15 all read OL when I test them.  I tried resoldering the connections to no avail.  then I noticed the following.  when I check the resistance on the lead of the capacitor connected to 11L I get a reading of 00.00.  When I check the other lead of this capacitor I get a reading of OL.  Does that mean that this is a bad capacitor and the rout of my issue?  If not what advice would you give me to resolve this issue?

[Deke609]

Hi Ben - I am just a novice diy-er, but I doubt the cap is the source of the problem. The fact that you read 0L on one side of the film capacitor and 0 ohms on the other suggests to me that the cap is doing exactly what it is meant to: blocking direct current (DC). 

Unexpected OL resistance readings are likely due to a missed connection or bad solder joint. From your pics, one wire appears completely detached from its terminal and a couple of connections appear to have no solder. I have circled them in green. I would suggest inspecting all the joints from start to finish to make sure they are well soldered.

PB will likely have more detailed advice, but this is a good place to start.

cheers,

Derek

[benrupp]

Sorry for the confusion Derek.  I should have been more clear about the pictures.  I removed the two joints that you circled in order to get batter access to the joints where I was getting the bad readings.  They had the OL reading with and without these wires in place.  I have since reattached these wires.  I guess I will remove everything from these terminals and start over.

[benrupp]

So I think I know where I am at..... I need to redo all of these connections?  I actually work for KING 5 TV, where I have access to a couple of actual engineers (I'm in production) and when I asked them for advice they recommended that I take all of those joints apart.  I am new to soldering, and likely just failed there.  I ordered some new resistors to replace the ones I partially melted.  the one I can't find anywhere is the 10.k 1/8w (1072F) DALE resistor.  I don't want to bother Doc B since I know they are in the middle of moving to a new office.  anyone know where I can grab one? 

Ironically I am doing this for a video, where I am demonstrating the process and how anyone can do it...lol.  It'll be part 2 in this series I am making...  on vimeo  /mkhmfg/woodandwires1

[Deke609]

Hi Ben - Apologies are mine. That makes sense.  I should have deduced that.

I would hold-off on removing any components until PB (Paul Birkeland) or Doc B. of BH respond. Sometimes a symptom that manifests at a certain point in a circuit is caused by an issue further upstream.

But, anticipating that some resoldering will be necessary, you might want to ensure that you have some desoldering supplies - do you have a "solder sucker" or "solder wick"?  If not, I would suggest getting both -- they are fairly inexpensive. Each person has their preference -- I mostly use solder wick.  And just in case you haven't bought solder wick before, I'll mention that the solder wick MUST be labelled "Rosin". The stuff without rosin is useless. In contrast, solder wicker with rosin can leave you with a completely clean wire and lug in just seconds.

cheers,

Derek

[Karl5150]

It looks like a couple of the 0.01uf caps in the bundle got nicked by the iron.

[benrupp]

Indeed they did... I have ordered replacements for the nicked caps...I am assuming that they should be replaced?  I am very new to soldering and in the process of trying to fix the issue I  got them with the iron. 

[Deke609]

  the one I can't find anywhere is the 10.k 1/8w (1072F) DALE resistor. 

Mouser sells 1/8W 10.7 kOhm Vishay Dale resistors -- just search "1072F" on the Mouser website, and then further narrow your search by "power rating" and "in stock".  There are two varieties available - one that is labeled 100 ppm for $0.14 and one labeled 50 ppm for $0.25. Not sure which purity level might be called for, so I would get the 25 cent ones.

I think mouser also sells solder suckers and solder wick in case you need them.

cheers,

Derek

[benrupp]

Thanks Derek.  Ordered.  I believe that I now have replacements for all of the parts that are attached to my problem terminals, and everything that I nicked with the iron.  side note... $8 shipping for 20 cents worth of parts is awesome...lol

[Deke609]

  side note... $8 shipping for 20 cents worth of parts is awesome...lol

Yeah, I always end up scouring the electronic supplier's website for other stuff I could use/want to justify the shipping cost.

[Doc B.]

Hey Ben, before you get too much deeper into it I have asked PB to help you out. Also, I appreciate your respecting our move. We still have the packing stuff set up for one more day, so shoot Eileen an email at [email protected] and she can probably get what you need for replacement parts out to you. The rest of the office on the other hand, is looking pretty lonely. No more demo room, lab half empty, our offices down to just a desk, chair and computer. Had a marvelous crew come to help move the big stuff yesterday. Five studio tape decks, a tube console, a couple pairs of tower speakers and a bunch of amps down a couple flights of stairs, into the ambulance and unloaded at the other end. I think that was trip number seven to storage, and we still have a few more trips to go. I will be so glad when we are done!

[benrupp]

Thanks Dan.  I will shoot off an email. maybe I can cancel my order with parts direct before they ship.  I will also wait until I hear back from PB before I do much more.  I won't have much time this week to work on it anyway... so no worries.  This has been a learning experience for sure.  I am not really surprised that this side of the amp is a problem, I got a little better with soldering as I progressed.

[Paul Birkeland]

Hello Ben,

I'm down in SE King County if you want to bring your Reduction by sometime and I can help get you sorted out.

-PB

(pb(aht)bottlehead(doht)com)

[oguinn]

Ironically I am doing this for a video, where I am demonstrating the process and how anyone can do it...lol.  It'll be part 2 in this series I am making...  on vimeo  /mkhmfg/woodandwires1

I follow you in Instagram and have been waiting for this video to drop! I still think anyone can build these amps, but these phono preamps have a lot of little parts, and many of them are stacked on top of one another (as you're well aware). You probably would have had an easier time with a Crack - hindsight is 20/20 and all that.

[Paul Birkeland]

Also, terminals 13, 14, and 15 do not have any resistance value in the manual, so you can replace and resolder all of the parts on those terminals and it is unlikely to change your resistance readings.  As long as you don't have a number close to 0 for those terminals, there is nothing to debug.

-PB