EQN build thread

[JBVries]

Two EQNs........

No Smoke!!! ;D but no sound either....... the hunt begins.

How are we supposed to set the two variable resistors?

Also, nowhere on the boards including the heatsink are showing any expected temperature variation almost as if voltage were present at the tabs but not going any where beyond that. Anywhere I can poke to make sure voltage is getting to the right place? If so, proper value expected?

Cheers! 

 

[canidoit]

Two EQNs........

No Smoke!!! ;D but no sound either....... the hunt begins.

How are we supposed to set the two variable resistors?

Also, nowhere on the boards including the heatsink are showing any expected temperature variation almost as if voltage were present at the tabs but not going any where beyond that. Anywhere I can poke to make sure voltage is getting to the right place? If so, proper value expected?

Cheers! 

I set mine at 750r from what I recall, because that was like the safe zone as discussed in a few of the posts but I recall only discussing 1 resistor to adjust. Are we both on the same page?  ???

 

[JBVries]

No, you are thinking of the bandwidth resistor. I am talking about the variable resistors pots (the ones with a set screw).

 

[canidoit]

No, you are thinking of the bandwidth resistor. I am talking about the variable resistors pots (the ones with a set screw).

You mean the little blue trimmer pots? If so, you are meant to use an oscilloscope and measure for clipping.

I do not recall having to change any resistors besides that 750r one.

Have a look at the BOM I have, I referred to two parts list I received from two builders here before making my own parts list. Maybe the solution is in there??

I would like to know as well incase I did something wrong?

 

[peter purpose]

jbv,
Are you 51x, or standard?

 

[JBVries]

I was testing with +-16v on my test little jig. I do use 51x and when I threw one in the rack I had no difference in results.

 

[peter purpose]

I'll re-phrase... is it fully populated, or are you in 51x mode?

 

[JBVries]

Ahhh, 51x.

 

[peter purpose]

Then plus and minus 16v is nfg. Feed it 24v.

 

[JBVries]

Bollox!! (and i'm not taking the piss I do say that all the time, even though I'm coastal Californian, haha )


C60 started to go as soon as I jumped that spot on CC6 and fed it 24v. I heard it first then saw it start to bulge so I killed power. If I find the problem will that cap still be ok, or is it shot already?

and  Orientation and general assembly form aside(as I'm triple checking that now), any advice on where to look would be greatly appreciated.

 

[peter purpose]

any advice on where to look would be greatly appreciated.

C60 and everything else..!!

 

[JBVries]

So close I can taste (or hear) it.....

Is there supposed to be significant level coming out of the OUT(-) of the input transformer? When probed I see very little signal.

When I poke around I do see signal various places all over the board. Plenty of signal out of the op amps, but still nothing at the output.

Any thoughts much appreciated.

 

[crisotop]

Plenty of signal out of the op amps, but still nothing at the output.

Follow the schematic from the opamps to the output - somewhere along these lines you might have got a problem.

Good Luck!
Christoph

 

[peter purpose]

Is there supposed to be significant level coming out of the OUT(-) of the input transformer?

No. The negative output goes to ground.

 

[JBVries]

I did get one of them running..... Sounds beautiful. Thank you much for the great projects Peter!

 

[Marcocet]

Okay, ran up on a problem I can't solve.

On one of my EQs the High Pass filter is WAY too high. As in when it's set to 45 its cutting at like 4k. I've replaced caps 11-18, all the resistors on the switch and the two tantalum caps and nothing's changed. I can't figure out what else in the circuit it could even be. Anybody have any insight?

Thanks

 

[ruairioflaherty]

Okay, ran up on a problem I can't solve.

On one of my EQs the High Pass filter is WAY too high. As in when it's set to 45 its cutting at like 4k. I've replaced caps 11-18, all the resistors on the switch and the two tantalum caps and nothing's changed. I can't figure out what else in the circuit it could even be. Anybody have any insight?

Thanks

Hi Marc,

Don't have the schemo handy and mid session anyhow but it sounds like a component factor to me, it's probably cutting at 4500Hz, ie 100 times what it should be.  Are all the high pass values on that one unit similarly elevated?  If so then it could be a rogue resistor in the wrong bin or even marked wrong.  Did you measure them all when fitting?

Cheers,
Ruairi

 

[Marcocet]

Okay, ran up on a problem I can't solve.

On one of my EQs the High Pass filter is WAY too high. As in when it's set to 45 its cutting at like 4k. I've replaced caps 11-18, all the resistors on the switch and the two tantalum caps and nothing's changed. I can't figure out what else in the circuit it could even be. Anybody have any insight?

Thanks

Hi Marc,

Don't have the schemo handy and mid session anyhow but it sounds like a component factor to me, it's probably cutting at 4500Hz, ie 100 times what it should be.  Are all the high pass values on that one unit similarly elevated?  If so then it could be a rogue resistor in the wrong bin or even marked wrong.  Did you measure them all when fitting?

Cheers,
Ruairi

Stupidly I didnt on this batch. I swapped out all the resistors and caps that I know are in the hpf section though. I'm gonna keep trying to trace it and see if I spot anything else.

 

[ruairioflaherty]

Hey Marc,

If you pulled the parts from the same bins as the other builds the chances are small but still there that you grabbed a 100R instead of a 10K or something like that, or your cap is 100 times too small....  The other thing it could be is short around the resistors, a very low resistance there would elevate the HPF frequency. 

Are all the HPF frequencies out or just the 45Hz?

Is there a schemo somewhere for the EQ-N, can't find it (and I have a pair to build at some point)

Cheers,
Ruairi

 

[Marcocet]

it was an inductor! Anybody have a source for 9043's in the states?