Resistance check problem [fixed]

[chavac]

Hopefully someone can help me out here. Spent the last two nights putting my crack together and finally finished, but it seems a couple of my measurements on the resistance check don't check out. They would be 12->22 (reading infinite) and 12->nine pin center pin (which reads 0). I've look at and resoldered almost every connection looking for a cold solder but no dice so far. All of the other measurements seem pretty spot on. Any suggestions? Thanks.

[Paul Birkeland]

The center pin of the 9 pin socket should read zero.

So terminals 12-22 all read roughly infinity?

[chavac]

Ah ok, my manual says 90-100k

12
13 slowly creeps up to ~7.8
14 0
15 slowly towards infinity
16 0
17 infinity
18 ~2.4
19 ~2.4
20 0
21 creeps to 7
22 infinite/no movement

Everything below that and all the B terminals tested OK

[Paul Birkeland]

Ah, the center pin of the RCA jack is 0 Ohms?  That would indicate a short on the jack, look for metal or solder connecting the center solder cup to the outside of the jack.

12 - you gave no number?
13 - 7.8 Ohms, 7.8K Ohms, or 7.8 MOhms?
14 - this is supposed to be zero (as indicated in the maunal)
15 - climing to infinity is good
16 -  this is supposed to be zero (as indicated in the maunal)
17 - climbing to infinity is good
18-19 - 0 this means you probably have a short in the diode bridge.  Look for two metal UF-4007 leads touching each other, but going to different terminals.
21 - this confirms the short in the diode bridge
22 - this terminal is grounded, it should be at zero (how is T16?)

[chavac]

Oh my mistake about the center pin, I completely misread that and missed where is said RCA center pin.

And I didn't include twelve because I've been using that as the ground.

From what I can tell 16 is zero and grounded. One thing I didn't note, I lost the buss wire for my kit and substituted de-sheathed excess wire (don't know if that makes a difference).

7.8k ohms

and from what I can tell the diodes only touch where the enter the same terminal

[Grainger49]

It is possible that one of the diodes are reversed.  Double and triple check the diodes.  Then get someone else to check.  This is one of the most often mistakes assembling the kit.

[chavac]

I've looked at the amp for about 15 minutes this morning desperately trying to find an error. I did realize that the lower LED's direction was reversed. However it broke when I attempted to remove and reverse it from the center pin. Could that potentially be the cause? It still gives the same resistance now without the led attached (new one on order from mouser). Otherwise the diodes appear to be correct. On the inside 18L -> 21L with stripe towards 21, and and 20L->18L with white towards 18. The outside is 20L->19L with stripe towards 19, and 19L->21L with stripe towards 21.

Also noticed I had one smaller round lockwasher left over (one went to transfer screw closest to safety ground, other to nine pin). Don't know how that would affect anything.

Btw thanks so much for the help. This is my first DIY amp so not familiar at all with troubleshooting.

[Doc B.]

Yes the LEDs have definite direction and that one needed to be fixed. You can shoot an email to [email protected] and get a replacement sent. Get that part installed, redo the measurements and let us know if you still have readings that are off.

[chavac]

Alright so dropped in the new LED with correct orietation and got these resistances (with 12 as ground)


11: 0
13: slowly to~7.9k
14: 0
15: slowly to7k
16: 0
17: 0
18: 2.4k
19: 2.4k
20: 0
21: 6.7k
22: infinite

[Paul Birkeland]

Is the black wire crossing over the power transformer connecting to terminal 21 or terminal 20? I suspect you have a miswire here.

-PB

[chavac]

No, it's spanning 14u to 20u, the parrallel resistor abve it is 15u-21u

[Paul Birkeland]

Oops, I was off by a terminal.

So the issue is 22 not being 0.  That's not enough to not fire it up and recheck voltages.

[chavac]

Ok i'll check the voltages. Haven't actually even turned the thing on yet.
And thanks again tfor the help.

[chavac]

hmm only the smaller tube lights up

and only one led

[Paul Birkeland]

Those aren't exactly voltages...