JLM AUDIO

Most small WBS modules have a simpler resistor and 2 x 18v power supply and need no modifying but the larger modules with the extra transistor stage need R118 removed and 2 x 18v zeners fitted to work direct of the 48v SMPS. http://www.jlmaudio.com/JLM%20Audio%20WBS%20power%20supply%20mod%20for%20r...

hi joe, just an update...i had another AC/DC board i bought for another project and decided to try it out with this toroidal. everything went smoothly dialing in 48v and 24v, so the PSU for my neve 1290 project appears to be all set. since the 4007s i pulled out of the old board were reading normal...

I put a new battery in the voltmeter, and it is reading the SMPS correctly. Good call, Joe. Sorry, I meant 33v zener :? My op amp pins now read: V+:37.3 1/2v:18.6 0v:0v out:4.3 -in:4.3 +in:18.6 Ok these voltages would be correct if you were using a 39v zener diode (+/-18v). And will be fine for the...

I recently built a BA4 for a API style (2622 input xfrm, 2520, and 2503 output xfrm) sound. I finished everything without the output iron and all the voltages were correct. All channels passed signal perfectly, sounded great Joe! :mrgreen: . Just the other day I got my ouput xfrmrs and something we...

I don't think it uses a pump charge, here's the schem : http://www.mentol.dk/diy/upload/DIY_9k_preamp.pdf Page 5. The power transformer is a 50 VA transformer. Yes it uses a pump charge with only small 100uF pump C3 & C4 and 220uF C5 storage caps. These do not allow for much current draw before the...

That should be able to handle it right? Using this power supply but with a 25-0-25 transformer and an LM7824 instead of 7818, and left out the 7918 as well OK does it use a pump charge circuit to get the 48v unreg rail? Schematic of the power supply is what I need see to work out why the 48v is sag...

Yea it's a heatsinked LM317 OK then what is the power supply circuit and secondary transformer winding voltages and VA or current as it doesn't sound like there is enough current from the transformer or high enough unreg input volts to the LM317 input to hold the current needed for the load. Also w...

Hey, I'm having some trouble with my FET DIs. Everything with the Go Betweens works fine, but when I add the FET DI I lose 6 volts on my 48V rail, and with a 4 channel pre I'm ending up around 28V or so, did I do something wrong? No just sounds like your 48v rail cannot handle the current load of t...

hey joe, thanks again! i tested just now and the fuse does indeed blow when the transformer is not connected to the AC/DC PCB. here is a picture of the label on the xformer...where should i look for the fuse rating? http://flic.kr/p/agD8gt i am using 1A fuses... http://search.digikey.com/scripts/Dk...

[quote="band_master"]thanks, joe! i put the cap back in C8 and changed the coupler setting to D. fired it up, set the positive probe to the 48v terminal and the black probe to the 0v terminal and blew the fuse again. here are some pics of the build...hopefully an obvious mistake on my part? First ch...

Short one: If i need a +25V and -25V can i modify the TREX to get this values (probably with another TIPxxx transistor). I need those +/-25V for WBS rack ... Thanks for any hints/infos. You can build a negative TREX or TREX2 by reversing all the caps and zener if fitted and use a PNP TIP126 instead...

hello Joe, i am building an ac/dc kit for a PSU to power 4 channels of a 1290 clone preamp. it seems i might be one of the first to use the v4 PCB boards for this project...the excellent assembly instructions provided by the designer of the 1290 PCBs references using the D coupler setting, while th...

I just realised that I had the impedance pot attached across #10K instead of RLoad. Doh! :lol: I've fixed that now and retested voltages again. Most voltages are ok except: #BD681 : 43.5v Bottom Right 470uF : 44.3v (looking from above) Bottom Left 470uF : 21.8v XFMR Yellow : 21.8v XFMR Blue : 21.8v...

baadc0de wrote:Thanks for the heads up. I can get the TI TL072ACP, I understand that's ok and within spec.

The regulators, as I see, will get me to +- 15V. Can I let IC3 work on +- 24V or must I always regulate that down?

Thanks

TL072 can only run on +/-18v max. So +/-15v is the ideal.

http://www.jensen-transformers.com/as/as083.pdf I see this "original schematic" says to use AD706 and seems to be using 15k as the resistor after the opamp. Maybe I could use OPA2604AP with +- 24V rails, the same as the discrete opamps will be using, so there should be no need for additional regula...