Author Topic: Yet another small stone  (Read 1738 times)

michael_krell

Yet another small stone
« on: October 03, 2004, 05:50:26 PM »
I have another small stone I am trying to get working here. The problem is definetly with the LFO. This is a new version of the pedal that you see all over the place. Not the Russian crap version. I am getting no output signal from the LFO. And yes I know its a current LFO. i take signal off of the 100ohm resistor and I get nothing. The IC has voltage. does anyone know what i should be looking for??

puretube

Yet another small stone
« Reply #1 on: October 04, 2004, 01:27:08 AM »
is the pot OK, and are the leads soldered correctly? (reflow...)

michael_krell

Yet another small stone
« Reply #2 on: October 04, 2004, 10:12:27 AM »
i will try all that and get back to ya

michael_krell

Yet another small stone
« Reply #3 on: October 04, 2004, 12:24:30 PM »
I reflowed all the sodler joints and checked the POT. no luck.

i dont think any of the wires are broken. its pretty new. im starting to think its probably the LFO IC.

Vsat

Yet another small stone
« Reply #4 on: October 04, 2004, 01:15:47 PM »
Don't know which LFO circuit or chip the reissue is using, but if the circuit is OTA-based, similar to the one in the "Issue J" it won't start oscillating unless the LFO is feeding something... perhaps the connection to the rest of the OTA's is broken (or shorted...)
Regards, Mike

michael_krell

Yet another small stone
« Reply #5 on: October 04, 2004, 05:36:14 PM »
is that because its a current oscillator??

Vsat

Yet another small stone
« Reply #6 on: October 04, 2004, 05:49:38 PM »
Yes, it's a current-mode oscillator. It senses the load current, and  oscillates between upper and lower current limits. Without a load, it will not oscillate properly.
Regards, Mike

michael_krell

....
« Reply #7 on: October 05, 2004, 10:57:59 AM »
I checked the traces to the 4 IC's and they are fine. I reflowed everything and I still have no LFO current activity. I am thinking that the IC is bad. Doe the LFO use the 33uF electrolytic cap for oscilation? if so coudl i swap it for one of slightly higher or lower value??

Vsat

Yet another small stone
« Reply #8 on: October 05, 2004, 11:30:16 AM »
Michael,
Yes, the 33 uF needs to be there ... but try anything convenient, say 10 uF to 47 uF for a test... it will run faster with 10 uF and slower with 47 uF. Is it an LM13600 or CA3094 (or LM324) that is used in the LFO?

michael_krell

Yet another small stone
« Reply #9 on: October 05, 2004, 12:10:34 PM »
Its the EH1048. which i think is the same as CA3094. ive bought it from small bear before so if its the IC i should have no problem getting it.

jimbob

Yet another small stone
« Reply #10 on: October 05, 2004, 12:18:58 PM »
One thing i find Very in common with newer EH effects that dont work are--the ic's are ussually fine as wellthe the components 99 percent of the time. Its ussually mechanical, or loose wire or something like that. My last few Eh repairs were Deluxe Mem Man and Micro Synth--both mechanical..

good look--seems the most obvious is the hardest to find.
"I think somebody should come up with a way to breed a very large shrimp. That way, you could ride him, then after you camped at night, you could eat him. How about it, science?"

Vsat

Yet another small stone
« Reply #11 on: October 05, 2004, 12:20:30 PM »
Yes, the EH1048 is the same as CA3094... mine was built using CA3094. Smallbear has them, I also have a good quantity on hand.

The two transistors are also essential for the LFO to work.
Mike