The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
33609J calibration help Equalisers (HW)
Old 7th February 2017
  #1
Gear Maniac
 
Stéphane's Avatar
33609J calibration help

One side is hotter by one dB, I ran a 1KHz into the unit and turned on RV1 trim pot, worked great but when I ran a 100Hz tone, one side is leaning again at 20Hz too.
Is there any calibration routine I’m missing here @ Jim Williams @ Geoff_T ?
I set the unit IN while calibrating
Thank you all.
Attached Thumbnails
33609J calibration help-33609-20hz.jpg   33609J calibration help-33609-1000hz.jpg   33609J calibration help-33609-100hz.jpg   33609J calibration help-33609j-3.jpg  
Old 7th February 2017
  #2
Lives for gear
 
Geoff_T's Avatar
 

Hi

Most likely a bad electrolytic capacitor around the output amplifier. That's the only gain stage in the whole module so check the coupling caps around it.

Don't expect it to be dead flat at 20Hz!



Quote:
Originally Posted by Stéphane View Post
One side is hotter by one dB, I ran a 1KHz into the unit and turned on RV1 trim pot, worked great but when I ran a 100Hz tone, one side is leaning again at 20Hz too.
Is there any calibration routine I’m missing here @ Jim Williams @ Geoff_T ?
I set the unit IN while calibrating
Thank you all.
Old 7th February 2017
  #3
Gear Maniac
 
Stéphane's Avatar
Hello @ Geoff_T ,
thanks a lot for your quick reply,
I live in the south of France, the best I can do is to send the unit to audio maintenance guy? Even if he doesn't know the unit? I need to find the schematic then…
Thx again
Old 7th February 2017
  #4
Lives for gear
 
Geoff_T's Avatar
 

Hi Stéphane

This is the info re the 33609 I found on the web....

http://www.thehistoryofrecording.com...%2033609jd.pdf

The most likely culprits are C16 and C18 on the main motherboard.

While that was being looked at, a tech could remove stupid 600 ohm input terminations R24 and R25 on that relay/logic board.

If you can't find a tech you could always try contacting our Paris distributor and mention my name... his tech could easily fix it.

Floating Point Audio SARL T



Quote:
Originally Posted by Stéphane View Post
Hello @ Geoff_T ,
thanks a lot for your quick reply,
I live in the south of France, the best I can do is to send the unit to audio maintenance guy? Even if he doesn't know the unit? I need to find the schematic then…
Thx again
Old 7th February 2017
  #5
Gear Maniac
 
Stéphane's Avatar
Thanks a lot @ Geoff_T , it's so nice of you sharing your knowledge.
So I just have to order some new c18 & c18 and replace them.
shouldn't be a big deal for a tech around me I think.
Do we have to calibrate again after? If yes, is there any special procedure?

Does removing theses 600 ohm input terminations R24 and R25 improve the sound of the unit?

Thanks again sir.
Old 7th February 2017
  #6
Lives for gear
 
Geoff_T's Avatar
 

Hi

A tech should check that C16 or C18 might be the cause of the low frequency response issue before you pay for new capacitors.

I'm puzzled why those 600 ohm resistors were added because not every piece of equipment in the world has a low enough output impedance to drive 600 ohms without some loss, particularly at low frequency. The unit was originally 10Kohm input impedance which virtually any device could drive without difficulty and, if not, it ain't a pro-audio product!

So snip them off (if fitted) and try the response test again.

Regarding recalibrating, I highly recommend your just adjusting RV1 and not touching anything else as they adjust thresholds and meter readings.... not related to your level issues.







Quote:
Originally Posted by Stéphane View Post
Thanks a lot @ Geoff_T , it's so nice of you sharing your knowledge.
So I just have to order some new c18 & c18 and replace them.
shouldn't be a big deal for a tech around me I think.
Do we have to calibrate again after? If yes, is there any special procedure?

Does removing theses 600 ohm input terminations R24 and R25 improve the sound of the unit?

Thanks again sir.
Old 8th February 2017
  #7
Gear Maniac
 
Stéphane's Avatar
I’ve been surprised to see 2 different pair of (C16 & c18) caps (different brands) for each channel in a 4000€ compressor, such a bummer, could you explain why please?
same as well for c23
see attached @ Geoff_T
Attached Thumbnails
33609J calibration help-photo-1-1.jpg   33609J calibration help-photo-2-1.jpg   33609J calibration help-photo-3-1.jpg  
Old 8th February 2017
  #9
Lives for gear
 
Geoff_T's Avatar
 

Hi

I don't know if you bought the compressor from new but, if not, they may have been changed by a tech subsequent to purchase.

Otherwise, I don't know... they should both be 470uF 16v





Quote:
Originally Posted by Stéphane View Post
I’ve been surprised to see 2 different pair of (C16 & c18) caps (different brands) for each channel in a 4000€ compressor, such a bummer, could you explain why please?
same as well for c23
see attached @ Geoff_T
Old 8th February 2017
  #10
Lives for gear
 
Geoff_T's Avatar
 

Hi

They would be perfect but heed my advice re checking in case the fault is somewhere else. Those capacitors were my best guess as the amplifier has a lot of gain to make up, close to the maximum allowed when boosted 20dB for extra make up, and those electrolytics are critical to that stage...

But I'm not there so can only guess....

It would not do harm to change them provided you or your tech were good at soldering and desoldering and won't damage the tracks. Don't use the soldering iron to lever up folded over component legs. Desolder the joint fully and then prise them up.






Last edited by Geoff_T; 8th February 2017 at 11:56 PM.. Reason: typo
Old 8th February 2017
  #11
Lives for gear
 
Lumbergh's Avatar
 

That blue (Rubycon?) C16 looks a bit bulgy to me ...
Old 8th February 2017
  #12
Lives for gear
 
Geoff_T's Avatar
 

Hi

Well spotted!

Yes, it looks like a gas build up is pushing the top upwards.

That one is a prime suspect for change!







Quote:
Originally Posted by Lumbergh View Post
That blue (Rubycon?) C16 looks a bit bulgy to me ...
Old 8th February 2017
  #13
Lives for gear
 
Lumbergh's Avatar
 

Hey

Yeah it looks like its been selectively recapped. Strange thing is I assumed that all the black Nover caps were the originals as I have some Alice mic pres of the same vintage and they are full of them (they all still look and sound good.)
Top Mentioned Products
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump