Racking two Telefunken W695 modules

[weiss]

Hey guys,

i'm currently fixing up two recently acquired W695 to rack them in a case.
I heard the quality of the power supply has some importance to the function of the modules so i wanted to ask if you know something i should keep in mind?

I was actually going to look for min. 1 A supply so it wouldn't lack headroom and has enough current

would this combination work?

toroid: https://www.ebay.com/itm/112613323749
psu: https://www.ebay.com/itm/273605707539

Max. current is 1,5A... is this good enough or should i get another psu?

thanks for your answers! 

 

[[silent:arts]]

You only need one voltage (+24V).
Current consumption is 70 mA max (each module @ 22dBu into 300R).

Your eBay links don't match each other very well so yes, you should get another PSU.

 

[weiss]

You only need one voltage (+24V).
Current consumption is 70 mA max (each module @ 22dBu into 300R).

Your eBay links don't match each other very well so yes, you should get another PSU.

thank you volker.

so correct me if i'm wrong. basically this would be sufficient to drive the modules?
https://www.reichelt.de/schaltnetzteil-open-frame-15-w-24-v-0-625-a-eps-15-24-p170926.html?&trstct=pol_4

 

[[silent:arts]]

I would go with a linear PSU.
Those cheap switch mode PSUs are not filtered very well (and haven’t been around the day your modules have been designed).

 

[TwentyTrees]

And Volker is too much of a gentleman to say it here, but he does sell a high quality PSU board which is designed exactly for these +24V broadcast modules, with tons of filtering! I’ve got a couple for some Telefunken & Neumann preamps in the build queue.  ;D

 

[weiss]

I would go with a linear PSU.
Those cheap switch mode PSUs are not filtered very well (and haven’t been around the day your modules have been designed).

alright thank you!

And Volker is too much of a gentleman to say it here, but he does sell a high quality PSU board which is designed exactly for these +24V broadcast modules, with tons of filtering! I’ve got a couple for some Telefunken & Neumann preamps in the build queue.  ;D

oh good to know! i'm gonna take a look there. thx

 

[weiss]

Finally managed to get the modules running with help by volker and his neat little psu 

One of them works completely fine, the other one gives me a massive 50Hz hum. Is this due to bad capacitors? I wired them completely identical and also changed connectors and xlrs to rule out any errors on my side.
Does it need a recap or is it a grounding issue? Still waiting for the case from frank.

Would be happy about some ideas  ??? ???

thanks

 

[weiss]

 

[dmp]

You might have to recap the modules. The electrolytic caps are pretty old and could be going bad.

 

[weiss]

You might have to recap the modules. The electrolytic caps are pretty old and could be going bad.

oh alright, they are pretty old indeed..
best all of the capacitors i guess?

thank you!

 

[dmp]

No, not all the caps. Just the polarized electrolytics. 

 

[weiss]

No, not all the caps. Just the polarized electrolytics.

one module looks already recapped. guess that's the good one.
i removed the two big electrolytic caps (C121 and C122). Think that should be it.

thanks dmp!

 

[weiss]

Trying to find a possible replacement for C121 250uf/35v for over an hour now... but i can't find anything that matches the values and fits into the module.. do you know any resources? 25v won't be enough. it has to be 50v at least or 40.. (otherwise i already had something). 

not even on mouser..
https://eu.mouser.com/Passive-Components/Capacitors/_/N-5g7r?P=1z0wrj6Z1z0z819Z1y95jjtZ1yonltoZ1yzxn82Z1yojrdlZ1yykvdwZ1yzxbzbZ1yojrc7Z1yzvfkzZ1z0jf4bZ1z0x0wrZ1z0x3rsZ1yzvkyhZ1yzxdxw

 

[Bo Deadly]

If it's not for filtering audio (almost definitely not if it's electrolytic) then the size doesn't really matter that much. So 220u could be fine. Electrolytics  are usually overspecified to account for loss over time. Also a lot of times parameters of the part search interface are not selectable because they were not entered or sometimes they're just wrong. So if you're selecting dimensions and such, you might try looking at siblings of a similar part by going through the datasheets and just searching on part codes.

 

[[silent:arts]]

The value of C121 isn’t important.
Use 220uF or 330uF, doesn’t matter.
25V is fine.

 

[weiss]

If it's not for filtering audio (almost definitely not if it's electrolytic) then the size doesn't really matter that much. So 220u could be fine. Electrolytics  are usually overspecified to account for loss over time. Also a lot of times parameters of the part search interface are not selectable because they were not entered or sometimes they're just wrong. So if you're selecting dimensions and such, you might try looking at siblings of a similar part by going through the datasheets and just searching on part codes.

The value of C121 isn’t important.
Use 220uF or 330uF, doesn’t matter.
25V is fine.

oh thank you all for your help - really appreciate it!! 

 

[dmp]

one module looks already recapped. guess that's the good one.
i removed the two big electrolytic caps (C121 and C122). Think that should be it.

thanks dmp!

You've probably found the schematic, but if not, go to Kubarth's site and search for W695
With a quick look I see over 10 polarized caps on the schematic.
C121 is just on the DC supply to stabilize against power supply ripple. C122 is the output cap to the transformer to block DC from the windings. 
There are many other polarized caps blocking DC between amp stages. Old electrolytic caps can 'leak' current which throws of the design operation of the circuit. Like C209 (10uf), the output of the first amp stage, from the bias of the next opamps input (@ 12v).  I would replace all the caps on the schematic with a + on a side. I would NOT replace any of the non-polarized caps in the EQ sections.

 

[weiss]

Thank you. I'll do that.