[JimK]

Yesterday I finally found some time to sit down and get back on this project. The goal was to finish the installation of the resistors and move on to the next step, but I hit a snag:



I've been checking each and every resistor both before and after installation, but resistor R6R is acting weird. On the bench, or out of the circuit as seen here, it measures 4.71 ohms. But when it is in the circuit it is approximately one-third that (1.04 ohms). When I check it's counterpart (R6L), I get 4.71 ohms either way.

I've had this resistor in and out of that socket three times now, and the results are consistent.

Question: Is this normal? My gut tells me "no". Also, noting that the trace for this resistor goes to the RH chip marked "LSK398" (upside down), is it possible I damaged the chip in some way? I've tried to be careful....

Thanks.

[avahifi]

Just as a general guidline, when you measure a resistor value out of circuit, your meter is looking at the resistor only.

When you try and measure it in circuit, you are also measuring all the resistance paths connected to it.  On in the case of an attached capacitor in the circuit, your meter may slow a slowly dropping or raising value, as the meter is trying to charge the capacitor or discharge it depending upon the polarity of the way your meter probes were attached.

In general, if you are measuring the same resistor in an identical circuit (one of two stereo circuits for example) and you get different readings from one channel to the other in circuit, this is telling you that likely there is something else defective in the circuit.  Unfortunately the parts don't have little pop up red flags like turkey thermometers to tell you "I am cooked now".

This sounds like a back to the vendor issue unless you have the schematic and can apply the necessary logic to trace down the associated part or connection that is causing the differences in readings. Hopefully Jim can give you enough help to avoid needing to do this.

Regards,

Frank Van Alstine

[analog97]

On the bench, or out of the circuit as seen here, it measures 4.71 ohms.

Jim,

I have built 3 PICCOLOS.  That resistor should test 4.75K ohms out of circuit.  Are you sure you have the correct value resistor or was you meter on the correct setting?   In circuit, (completely built PICCOLO), my reading about 735 ohms for the location you specify.  Sounds to me like you may have put in the wrong  value resistor??   Hope this helps.

[JimK]

The resistors are PRP units, sourced from Parts Connexion as per a recommendation given to me by Jim/"tubesforever". Since they don't make a 4.75k resistor, I asked Jim about this and he said the 4.71k should be fine.

When I took delivery of the resistors I double-checked all of their values and made sure I wasn't mixing-up the 47.5, 475, 4.75k, and 47.5k resistors (sometimes paranoia can be a good thing!). I'm absolutely certain of what I have, and what I installed, and I've gone over this numerous times. After all, I'm a rookie and I've been taking this very, very slowly and methodically....(and Frank- it was the comparison between the RH and LH resistors that tipped me off on this). (Also, I was at the Audio Research tour with you a few weeks back, although you wouldn't know me from Adam).

Plus, although I don't care to appear foolish (I can do that well enough on my own, thank you very much!  ), I checked everything I could think of (including consulting the schematic) no less than three times before finally "caving in" and posting this.

So, there you have it. I've managed to mess things up on just Step 1!

Oh, and I'm checking things with my trusty Fluke 79, an auto-ranging DMM which served me well during my years as an HVAC service tech (controls and control troubleshooting being my areas of expertise).

Thanks for the responses so far!

[MusicMtnMonkey]

Shipping costs can be painful, but at the price of one or two PRP resistors, there might be argument for just replacing the part that doesn't test "perfectly"??

(Take some time to remove all the old solder, clean up with flux and then test, add a new resistor??)

[tubesforever]

Jim if it measures fine off the board use the resistor on the board.  When the build is complete then you can go back and double check the resistance values of the caps on the board.  Be careful.  Its best to simply use the test points. 

I say check the resistor values, solder them in and trust your build! 

Continue on and enjoy the process.  Its easy to let audio nirvosa set in.  When you have every resistor properly soldered up you just might find that the right and left channel resistance (on the board) all match up. 

You are too early into the build to worry about measuring the loaded value of your uncompleted board.

[Bill Epstein]

I'm with Jim.

[JimK]

Jim & Bill,

Thank you for your input, and know that I value each and every piece of advice I get, but I've come to the conclusion that until I hear from "The Man" himself I'm quite leery of going any further. I would hate to put this whole thing together, only to find that I screwed-up something that can't be fixed, and then have to either junk it or de-solder everything and put it on another board. The biggest reason for the "hold" is because the LH and RH resistors measure so differently, and I have a sneaky suspicion that something is in parallel with the RH resistor causing the (possibly) low reading. Plus, if I messed thus up, what's to say I won't fry something else?

Sounds like I've gotten "gun shy" (which is partially true), but it's also a "time invested" thing as I'm quite busy in my other life.

Hopefully Jim H. will chime-in with his opinion...

[Bill Epstein]

I took down my Piccolo and in the completed circuit board, the R6 resistors both measure 750 ohms, which is why we say move ahead and complete the board. If you then have an issue, your trouble shooting can begin with R6.

[JimK]

Ok, ok!  Christmas has been unofficially canceled around here as 15-20 inches of snow is supposed to fall within the next 48-72 hours, so it looks as though I'll have some time on my hands this weekend....

(But I'm still keeping my fingers crossed!)

Thanks.