Ursa Major Space Station sst-282 problem

[fffaustino]

Hi,

I am in the process of restoring a nice Ursa sst-282. I have complete recapped all the machine cards, restored the PSU and replace one faulty opAmp in the analog card. Now the machine is working properly but i can not increase the reverb/echo feedback knob further than the two or three o´clock position without having a very high feedback noise. All voltages seem to be ok and i have checked all the IC´s too but i have had no luck...i would really appreciate any help..

Thanks!

 

[fffaustino]

to clarify, this high feedback noise only happens when the reverb/echo button is pressed, with the reverb option...if it helps

 

[Bo Deadly]

Well at least it sounds like it's probably an analog problem.

Which op amp did you replace, what was it and what did you replace it with?

 

[fffaustino]

Hi Bo and thanks for your reply. I replaced the analog card U10 IC, one faulty NE5534P. This opAmp is still in production so i intalled a brand new Texas NE5534P.

 

[Bo Deadly]

to clarify, this high feedback noise only happens when the reverb/echo button is pressed, with the reverb option...if it helps

Can you clarify further? You only get a brief moment of feedback during the pressing and release of the button? Or is it only when reverb is selected or when echo is selected?

Does adjusting the EQ affect the noise in any way?

 

[fffaustino]

Hi again Bo

I will try to explain myself properly and sorry for my English in any case…
The noise is the typical feedback noise that you get when you bring the mic near to the speaker or the guitar to the amp. It appears only with the reverb option (reverb/echo button pushed) and it begins at two o’clock position, (6-7 aprox in the panel numbers) and it goes louder as you increase the reverb feedback knob value (from 2 o’clock to the max, number 10 in the panel).

The noise volumen has no relation with the gain knob or the Eq section.

I am checking R25 in the analog card to see it has any effect with the issue, I will let you know if I get something

Many thanks!

 

[Bo Deadly]

The noise is the typical feedback noise that you get when you bring the mic near to the speaker or the guitar to the amp. It appears only with the reverb option (reverb/echo button pushed).

So then it's only when reverb or echo is engaged? Which one? Echo or Reverb?

It is strange that it only happens for one since there's really no difference other than how it pulls signal from the DAC.



Is one louder than the other? Meaning is the Reverb louder than the Echo or Echo louder than Reverb? Can you measure in dB?

It could be a grounding issue. There could be a bad solder joint. Maybe just reheat and add a tiny bit of solder with flux to each of the switch and dual pot leads.

Also, be very careful poking around in this type of gear. Old logic ICs can be fried with a little bit of static electricity. Make sure the case is grounded well while you're working on it and be vary careful when handling the boards. You could easily end up with more problems than you started.

Do you have a scope?

 

[fffaustino]

Hi Bo,

Thanks so much for your help and sorry for the delay. Finally I have borrowed another Ursa from a friend and I am going to try swapping the cards of both machines to identify the fault properly. It’s going to be easier for me since I have no experience with this machine.

Thanks so much again and I will let you know the results of my tests.

Best regards from Spain and nice Wednesday!

Alfredo

 

[Acoustic_Spaces_de]

Hi Faustino, my Ursa developed the exact same issue during the last weeks. I think so at least. The Meter shows the first 2 Lights on too. After 1 Hour of use the Noise did fade away but since today it´s (much lower in Volume) constantly there. Did you find out what it was with your Space Station?

 

[fffaustino]

Hi Faustino, my Ursa developed the exact same issue during the last weeks. I think so at least. The Meter shows the first 2 Lights on too. After 1 Hour of use the Noise did fade away but since today it´s (much lower in Volume) constantly there. Did you find out what it was with your Space Station?

Hi Acoustic_Spaces,

Yes, during these months I have fixed my machine and another one with a lot of faults, but I think it’s not an easy task without a good working machine for helping you to locate the problem, most probably a faulty ic.

If your machine cards have been properly recapped and voltages are ok I would start for checking ADS Card ic’s, which are related with memory address computation, and can cause some delay feedback mess.

 

[Acoustic_Spaces_de]

Do you have the Service Manual?

 

[fffaustino]

Hi again,

You have the manual for free at the web, but i will try to attach it here.

My first advice should be borrowing another machine in good condition and try swapping cards to locate the fault fastly. Do you receive Direct signal properly?...just to discard some fault in the ANA-card. If ANA card is working good i would go to check ADS card first which, in my recent experience, is related with those feedback problems...

 

[Acoustic_Spaces_de]

Thankyou
My Job daily Job is acoustician/Studiodesigner but sadly i have only little knowledge about electronics myself. I´ll try with my tech to find the issue with the service manual and report back.

 

[jensenmann]

Completely recap it first. Otherwise faultfinding is a waste of time.

 

[mkiijam]

I'm working on one as well. Mine had power supply failure that took out the RAM chips. After replacing those it mostly sounds okay now, but the very tail end of the reverb I can hear this little bit of noise. I don't think it is right, but I have no way to tell as I have never had one before and have no others to listen to. Should the trailing reverb(s) be perfectly clean all the way till the noise floor takes over?

 

[fffaustino]

These machines are not clean exactly.., but I maybe there’s something that is not working as it should. PM with some files to process if you want to compare them with another machine

 

[mkiijam]

Okay, cool. I'm just running a 1k tone out of Pro tools into it. I have the tone generator on bypass (silent) then just do a quick "click-click" with the mouse on the bypass button to give it a quick pulse of audio. I have all the controls, just kinda in the middle. If you read this and try it before I get back up there in the morning...

 

[fffaustino]

I have recorded your suggestion but i have changed parameters a bit because Reverb Feedback at the middle won´t give us too much info about the reverb tail.

I have recorded examples with Reverb Feedback fully clockwise and the rest at the middle, except Gain - at 3 aprox, to avoid distortion in the Ursa input -, Direct signal at 0, and room program number 1. Signal is 1k sine wave at -20 dbs, and i have just recorded the effect return sound (no Direct signal at the Ursa).

You will hear Medium Reverb program examples the first 45 secs, and the rest are Long Reverb examples....i hope this will help you.

Best


https://groupdiy.com/media/ursa_reverbtailtest1-mp3.13/

 

[mkiijam]

really appreciate this.

Here is mine. noise.mp3

 

[fffaustino]

I see…did you appreciate the same noise with delay programs?

In any case, check page number 9 in the service manual and try closing jumpers 2/3 to see if it’s something related with RAM or difficulties in conversion.