Sc

Re: U73b (drip) - 3 questions
« Reply #20 on: May 18, 2020, 02:17:45 PM »
Hi

You can use two relay sockets, cut off the two pins at the upper one and cross by wire. Another possibility is scraping the laquer of the board, scrape the ground connection of one pin off, and connect the other one to ground. Works fine. But be aware - I have a 2019 board with this bug fixed …..

good luck
Walter     


hugo

Re: U73b (drip) - 3 questions
« Reply #21 on: May 18, 2020, 07:21:48 PM »
Hi

You can use two relay sockets, cut off the two pins at the upper one and cross by wire. Another possibility is scraping the laquer of the board, scrape the ground connection of one pin off, and connect the other one to ground. Works fine. But be aware - I have a 2019 board with this bug fixed …..

good luck
Walter   

I checked the connection and it looks to be the 2018 edition, regarding the fact i have the same connections as your draw

hugo

Re: U73b (drip) - 3 questions
« Reply #22 on: May 19, 2020, 11:15:35 AM »
I don’t want to create multiple posts for a single unit so here is an other question. I replaced the 10k resistor of attack with a potentiometer of 100k. It seems to not have any effect..is there anything to do to have this potentiometer operational ?

Also, the freq resp in Comp mode is strange, is it normal ? pic attached
« Last Edit: May 19, 2020, 03:08:03 PM by hugo »

hugo

Re: U73b (drip) - 3 questions
« Reply #23 on: May 19, 2020, 07:39:15 PM »
Just in case your boards have the same bug, flipped lim and cmp at the relay, here´s a pic that shows where you should cross the contacts.

PS. again, thanks Walter!

Regarding the relay, and your picture : Is your picture showing a good or a bad board ? I have same connections as appearing on the picture.

Sc

Re: U73b (drip) - 3 questions
« Reply #24 on: May 20, 2020, 09:49:35 AM »
Hi Hugo

The pic shows the old version of the board. You have to interrupt lim - ground and connect comp - ground.


Sc

Re: U73b (drip) - 3 questions
« Reply #25 on: May 20, 2020, 10:12:51 AM »
I don’t want to create multiple posts for a single unit so here is an other question. I replaced the 10k resistor of attack with a potentiometer of 100k. It seems to not have any effect..is there anything to do to have this potentiometer operational ?

Yes - I believe an attack resistance could only be placed directly at the center tap of the side-chain transformer.  But it interferes with the release and even more with the eventual varicom connection. We changed to the original release and are now figuring  the varicom integration. So I can't help with a working attack.

Also, the freq resp in Comp mode is strange, is it normal ? pic attached
Compared to my (analog) measurements you seem to have a little more and a bit uneven loss beyond 100Hz, but not much. And it changes quite a bit with the input level.  IMHO it's still a very nice response - it's a vintage tube unit (and you know, how  speaker responses are .... ::). Any comparison out there ?
regards Walter

hugo

Re: U73b (drip) - 3 questions
« Reply #26 on: May 20, 2020, 11:27:04 AM »
Hi Hugo

The pic shows the old version of the board. You have to interrupt lim - ground and connect comp - ground.

I cut a leg and put some hard wire to modify the relays, I do have a « bad board » and it’s a shame to not tell this on the doc. 
Thank you for all infos

hugo

Re: U73b (drip) - 3 questions
« Reply #27 on: May 20, 2020, 01:53:44 PM »
Thanks a lot for the support, the unit now seems to completely work, or almost.
This 100k pot in place of attack resistor does not affect the attack of the comp..is that normal ?  How to make it effective ?
Also, is there a way to make a mod to not have this low end loss ?
Thanks again
« Last Edit: May 22, 2020, 11:06:22 PM by hugo »

Sc

Re: U73b (drip) - 3 questions
« Reply #28 on: May 24, 2020, 04:10:11 AM »
Thanks a lot for the support, the unit now seems to completely work, or almost.
This 100k pot in place of attack resistor does not affect the attack of the comp..is that normal ?  How to make it effective ?
Also, is there a way to make a mod to not have this low end loss ?
Thanks again

Hi
just in case you want to experiment with attack - try a pot at the point shown on the schematics . This will work, but interferes with standard calibration and fixed attack settings of the U73b (as well as the use of the 670 time constant - with the missing 800k the circuit has a much lower impedance). Both makes it a bit more complicated when you want to integrate a varicom. So we decided to quit this option and will use the original release setup.
Regards Walter
 

hugo

Re: U73b (drip) - 3 questions
« Reply #29 on: May 25, 2020, 04:44:43 PM »
Hi
just in case you want to experiment with attack - try a pot at the point shown on the schematics . This will work, but interferes with standard calibration and fixed attack settings of the U73b (as well as the use of the 670 time constant - with the missing 800k the circuit has a much lower impedance). Both makes it a bit more complicated when you want to integrate a varicom. So we decided to quit this option and will use the original release setup.
Regards Walter
 

Hi, I am also building the varicom so I will make it just as you.  I hope it’s not too difficult. So I have to remove this 220k and to find original values for the boards.. right ?


 

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