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Very low sound coming through δ1

delta1

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Re: Very low sound coming through δ1

Postby linux-works » August 20th, 2012, 9:41 am

lets start with the input. when you set the atten to 0db, do you see a 0 ohm (or close) connection from input pad to output pad?

what's the resistance like from the input (and also output) to gnd, at 0db?

now, as you vary things, how does that change? does the resist from input to gnd change?

if you are not hearing much sound, you could be shunting most of the audio to gnd, so check for that. or, the connection in series is always too high.

however, you said you reversed in and out and you got 'very loud' output. that sounds like you do have some continuity from input to output.

double check the output resistors (the last ones on the d1 board). make sure they are HIGH value (25k or something) and not low values. I've seen that happen before.

for testing, I find that you don't really need audio thru the system. putting a dc power supply on the input and watching the output on a voltmeter can save your ears and also give you all the info you need. but be sure that you don't have input shorts to gnd at any atten setting or you'll hurt your voltage source (good idea to current limit it anyway; put a series R in so that even if you short your 'input test' power supply, it won't burn itself out.
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 10:26 am

When connecting the multimeter between the input and output I get 49.7k at -127db, 63.2k at -6db, 227.8 k at -1db and no connection at 0db. The readings are identical on both channels.

Between input and ground I get 24.4k at -127db, 38.0k at -6db, 202.6k at -1db and no connection at 0db.

Between output and ground I get a constant 25.2k at all db settings.

Regarding the "very loud" bit, I had jumper 4 in so it effectively bypassed the attenuator when I switched the wires.

RTR & RTL are 25.2k. I tested each resistor with a 4 wire ohm check prior to installation also.
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 10:49 am

I've just checked the coils on the 7 relays each are reading 203R which is on spec.
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 10:55 am

Also, just confirmed that pin 1 on the driver section has continuity with pin 1 on the attenuator section. So the harness appears to be correctly set-up.
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Re: Very low sound coming through δ1

Postby amb » August 20th, 2012, 12:08 pm

Are you sure you used all the correct value resistors? e.g., Ω vs. KΩ
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 12:56 pm

Yes, I checked them all with my multimeter prior to installation and they're all the correct value in the correct place. What about if I configure the δ2 driver board as the driver for the δ1, swap the harnesses and see if there's a problem with the driver section?
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 3:04 pm

I swapped the addresses on the δ2 & δ1 along with the harnesses. I still get almost the same reading:

between the input and output I get 49.7k at -127db, 76.0k at -6db, 227.8 k at -1db and no connection at 0db. The only one that is different is 76k at -6db.

Is it normal that the line you're editing in the "menu" mode on the LCDuino flashes?
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Re: Very low sound coming through δ1

Postby amb » August 20th, 2012, 3:46 pm

How did you measure the resistors? Onboard in-situ? If so, in order to get correct readings for all the Rs resistors you need to set the volume to -127dB. To get correct readings for all the Rp resistors you need to set the volume to 0dB. Otherwise the relays will short out some of these resistors or cause other resistors in the circuit to become paralleled and affect the readings.

If you measure the resistance from input to output with the volume set at 0dB, you should get ~0 ohms. Also, at 0dB, the resistance from the output to ground should be equal to the value of Rt (with nothing connected to the input or output).

Yes, the menu item being edited should flash -- see the LCDuino-1 website "Setup" section.

EDIT: I missed the "prior to installation" part of your post above. I recommend that you re-check the resistances as outlined in this post.
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 4:24 pm

I checked them with Kelvin Clips prior to installation. The values are clearly written on them so I can see the values are in the right places. I checked them in situ and with volume at 0dB, the Rp resistors all show very near to the correct values (identical on both channels):

RP0 (200k) - measured 200k
RP1 (94.2k) - measured 94.2k
RP2 (41.7k) - measured 41.7k
RP3 (16.2k) - measured 16.2k
RP4 (4.59k) - measured 4.59k
RP5 (634Ω) - measured 635.4Ω (exactly the same on both channels), which is strange considering it was bang on when I installed it.
RP6 (15Ω) - measured 16.4Ω, again, this was bang on 15Ω when I installed it.

However, the Rs resistors, at -127dB show the following (identical measurements found on both channels):

RS0 (2.67k) - measured 2.68k
RS1 (5.05k) - measured 4.94k
RS2 (9.09k) - measured 8.76k
RS3 (14.7k) - measured 10.47k
RS4 (20.5k) - measured 8.83k
RS5 (24k) - measured 3.89k
RS6 (24.6k) - measured 621Ω

Could it be that either K5 or K6 relays are jammed and shunting to ground? I have one spare relay, how can I find out if one is not working?

Output to Ground matches RT at 25.2k.

Many thanks to both yourself and linux-works for taking the time to assist me with this.
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Re: Very low sound coming through δ1

Postby astrouk1 » August 20th, 2012, 4:32 pm

What if I remove the IDC connector and apply 4.5VDC to the pins for K5 & K6, and see if they click? Does reversing the polarity reset them?
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