Iron Pre Essentials Kits For The DIYA Store - Register Your Interest

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#4,104
I'm building an Iron Pre SMD, 2023 pcbs, version 4. I got my quad 10k pot a few days ago and finished the wiring and have a problem. I got through all of the adjustments just fine. The input switch leds light up appropriately when switching between inputs. I hooked it up to my system I got dead quiet instead of music. I remembered that I hadn't put the 4 jumpers on JP+ and JP-. When I did I got full ear splitting volume and the turning the pot didn't change that. Subsequently I reviewed my pot wiring and checked that the resistance between common and input; almost zero when the pot was in the full ccw position. All checked out. This is paired with an Aleph J. What should my next step be?
IMG_0773.jpg
 
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#4,106
Most likely scenario is miswiring or a wonky pot PCB, but I think ZM took a look at the PCB. Could... but unlikely... be a totally wonky pot.

Using the exact nomenclature on the iron pre PCB and no other nomenclature / abbreviations -

Turn the pot fully CCW and measure resistance for all four sets of pads -

Board 1
CCW- to WIP-
WIP- to CW-
CCW- to CW-

CCW+ to WIP+
WIP+ to CW+
CCW+ to CW+

Board 2
CCW- to WIP-
WIP- to CW-
CCW- to CW-

CCW+ to WIP+
WIP+ to CW+
CCW+ to CW+

Turn the pot fully CW and measure same -

Jot down / reply.
 
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#4,108
maybe this helps

this one is 2 section - usually used for stereo SE

yours - 4-deck is double that - having 4 sections, two channels, with 2 phases per channel


same principle

edit:

in case of Iron Pre - GND is GND, signal from source is signal from selector, signal to next stage is signal to buffer input






alps pot.png
 
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#4,109
@getgoin - also... if you can feed the iron pre a signal and measure it at the output before hooking it to an amplifier, that's always my best recommendation.

A 'simple' (but not always easy the first time) way to do it may be to hook your smartphone up to the inputs playing a 60Hz test tone and measure the output at various 'volume settings' before hooking it to your amp. Use a regular old DMM set to ACV.

That prevents (in many cases) damage to amps and speakers. Nice going getting it shut off quickly. My guess is that was a bit startling.
 
#4,110
OK. I found and fixed a number of wiring errors on pot. Volume at a loud but not awful level now but volume pot still doesn't do anything. No sound in one channel. No hum or odd noises. Here are the resistance measurements; they do look wonky. These were measured at the main PCBs. I checked that the pot pins were going to the correctly labeled input/output pads on on the pot pcb.
formatting went away when sent. First two numbers in each row are one channel; second two are the other.


Fully CCW
CCW-WIP + 1.3R - 1.6R +219K _ 1.6K
WIP-CW +9K - 9.6K +9.15K -9.2K
CCW-CW + 9K -9 k +228K - 9.3

Fully CW
CCW-WIP +8.7K - 8.7K + 218K -8.9K
WIP-CW +1.8R -1.7R + 1.6R -1.6R
CW-CWW +9.06K -9.06K +218K -8.7K
 
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#4,112
Took the pot out. Measurements:

Fully counter clockwise: CWW-WIP, WIP-CW; CW-CCW
A: 1.0R, 9.07K, 9.07K
B: 1.7R, 9.07K, 9.07K
C: 1.4R, 9.16K, 9.16K
D: 1.2R, 9.27K, 9.28K

Fully clockwise: CWW-WIP, WIP-CW; CW-CCW
A: 9.07K, 1.4R, 9.07K
B: 1.0R, 1.5R, 9.07K
C: 1.3R, 1.6R, 9.16K
D: 1.6R, 1.3R, 9.28K
 
#4,113
getgoin said:
Fully counter clockwise:
Click to expand...

by that, pot is OK

getgoin said:
Fully clockwise:
Click to expand...


by that, either your measurement sucks, or pot is bad

looking at data, it looks as your measurement is suspect; case B- if wiper is somehow shorted to CCW, then CCW-CW must be short too; same applies for C and D

so, repeat measurements and write here
 
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