Vintage Deluxe Memory Man Repair has me a bit stumped

[Govmnt_Lacky]

Have you tried looking here?

https://spreadsheets.google.com/ccc?key=0Ak9R7oW8W8MidHhCOHdKSkFTdGowdklDd2sza2VXMFE&hl=en&authkey=CJXI1aEF

You should be able to find the max current draw from Ron's spreadsheet.

I still recommend you get the transformer. There is a lot of things in that unit to draw a bunch of current. Transformer would set you back $6-8.

Did you try replacing the bridge rectifier? Did you bypass it? Your schematic above shows a bridge rectifier and that needs to be bypassed if you are injecting DC instead of an AC voltage.

Good Luck! 

[Scruffie]

As i've said, a transformer here is basically not an option, first off, it will cost more than $6-8 in the EU, second, i'd have to buy a voltage converter as well to to test it with as this is going back to a different country and source the correct socket from that country, massive pain and probably getting quite expensive with shipping etc so let's forget that one.

An -18V supply would come before that and be much simpler, which I have now convinced the guy to use if this wont work nicely but now it's a case of it's pulling voltage down even with enough current and that doesn't seem right to me. Current draw should be around the 30-40mA mark.

I've seen Ron's spreadsheet, it doesn't have the specific current draw but the supplies that EHX use are only 100mA which 2 parallel LT1054 should provide...

I have completely bypassed the entire original supply, I do know what i'm doing

I think something else might be up, which is why I brought up the caps... thinking about it's age, a re-cap is probably in order anyway with the tantalum's in there.

[Govmnt_Lacky]

...thinking about it's age, a re-cap is probably in order anyway with the tantalum's in there.

Agreed!

Good Luck 

[Scruffie]

So, it seems while it did need that recap and that helped quite a bit with the current drawing and also allowed the pedal to reach longer delay times (I think the LFO OpAmp filtering tantalum had gone bad as it also has a LOT more modulation on tap now too) it still wasn't quite enough to get it to run off 2 x LT1054 and it appears it actually requires 3 to get the job done! It appears the LT isn't as efficient at negative doubling as it is positive.

So it was just excess current draw causing the issue... and also it drawing too much current being an issue, so bit of both.

Gotta say though, man are these vintage EHX PCB pads weak, it was already in a state from who ever had hacked at it but trying to not pull the pads de-soldering the old caps was a nightmare! Got there without too many mishaps in the end though.

[Scruffie]

Revisiting this, I tried a steady 200mA 18V DC Supply, twice the mA the EHX DMM supply puts out...

Same damn problem! Replaced the minimum delay time resistor, the clock cap and delay pot, didn't fix it, we've both agreed before it cuts out it goes short enough (near enough reverb) so i'm just going to up the minimum delay time resistor but... whatever it is going wrong, I can't pin point.

Just to expand on the issue for a very small amount of rotation at the bottom of the delay pot, the clock seems to go wrong, there is a delay, that is overly distorted and twisting within that rotation, there is no pitch change like you'd normally get turning a delay knob until you get past the problem spot and the delay kicks back in properly. If the chorus is set deep enough you can even hear it swing back in to normal delay and back out.

But without a scope I officially give in, it works fine above that delay time and it's plenty low enough time for anything you'd want, in fact, i'm not even sure it should go lower.

[Govmnt_Lacky]

Might be a shot in the dark but....

Looking at the Small Clone circuit, it looks like they installed a silicon diode (1N914) between the minimum resistor and Pin 2 of the 4047. Might be worth a try.


Or, I might be out of my mind...... your choice 

[Scruffie]

Might be a shot in the dark but....

Looking at the Small Clone circuit, it looks like they installed a silicon diode (1N914) between the minimum resistor and Pin 2 of the 4047. Might be worth a try.


Or, I might be out of my mind...... your choice 

That's being used as a variable resistor, same as the 1N4002 in the Memory Man, which I have tried unhooked.

I'm going with gypsy curse.

[Govmnt_Lacky]

Replace minimum delay resistor (5K6?) with a trimmer. Set Delay pot to minimum and adjust trimmer to just where the problem JUST stops. Remove trimmer, measure, replace resistor with trimmer value. DONE! 

Good Luck bro! 

[Scruffie]

Replace minimum delay resistor (5K6?) with a trimmer. Set Delay pot to minimum and adjust trimmer to just where the problem JUST stops. Remove trimmer, measure, replace resistor with trimmer value. DONE! 

Good Luck bro! 

Exactly what i'll be doing as I said, it's just... weird!

[Govmnt_Lacky]

Dont know if you have looked at this already but....

Is that a 1N4041 Reference Regulator Diode next to the Chorus/Vibrato pot on the schematic? Could that be bad or causing issues? Am I reading that right? It looks like 4041 

Grabbing for straws here. 

[Scruffie]

Dont know if you have looked at this already but....

Is that a 1N4041 Reference Regulator Diode next to the Chorus/Vibrato pot on the schematic? Could that be bad or causing issues? Am I reading that right? It looks like 4041 

Grabbing for straws here. 

It's a 1N4001 working much like the diode in the small clone but I have unhooked both the 1nF caps that follow and connect to the clock, no go!

Unless it's died and is drawing too much current still... I can try replacing it, but it's not directly affecting issues.

[Govmnt_Lacky]

It's a 1N4001 working much like the diode in the small clone but I have unhooked both the 1nF caps that follow and connect to the clock, no go!

Unless it's died and is drawing too much current still... I can try replacing it, but it's not directly affecting issues.

OK. I guess you would know since you are working with the original PCB. It just looked funny to me looking at the schematic you posted. It looks like that diode has (2) cathode lines with a slash line going through it. Also, the second zero looks like a four.

Then again... I remember the troubles of going through the online Echoflanger schematic 

[Scruffie]

It's definitely a 1N4001 (although I can see it does look like a 041) it's the same on the RI Factory Schematic which is a lot clearer, I think it's drawn like that to show it's working as a variable capacitor to modulate the delay time.