MXR Analog Delay

[michael_krell]

Mark, i was just thinking,

there is one thing that is bugging me.

when i was testing the IC's i found one + input on one of the 4558's that had a low bias voltage. the wierd thing is the signal is chained from another + input on another 4558. and one had a strong signal output, and the other one has nothing. I am wondering if maybe the op amp is shorting the signal or something.

i wanted to try and replace the opamp, but i dont want to "devintage" it if i dont have to.

[michael_krell]

Mark, i was just thinking,

there is one thing that is bugging me.

when i was testing the IC's i found one + input on one of the 4558's that had a low bias voltage. the wierd thing is the signal is chained from another + input on another 4558. and one had a strong signal output, and the other one has nothing. I am wondering if maybe the op amp is shorting the signal or something.

i wanted to try and replace the opamp, but i dont want to "devintage" it if i dont have to.

[Mark Hammer]

If your concern is about some hypothetical resale value, keep in mind that the difference between a vintage pedal that WORKS and one that doesn't work can be substantial.  If the removal of a chip and its replacement with another shifts the pedal from the one category to the other, then "vintagicity" be damned.  Besides, not being one of the original issues (that used a trio of cascaded SAD-1024's), you won't get rich off it anyways (well, not unless "rich" for you means selling a pint of your blood for $10).  Stick a socket in and replace with the "correct" chips as they become available.  I went through the same pangs of concern when it came time to re-cap my old Bassman.  As someone pointed out to me, I could always keep the original parts in a bag and make those part of the transfer of goods should I ever sell the thing.  I re-capped.

Your chief concern at this point is identifying the source of the problem without jeopardizing the state of the board (e.g., cracking traces, having traces lift, etc.) or any of the hard-to-replace components.

[Dan N]

Just for laughs, they are still selling the reworked boards over on ebay. $55 shipped and you get all the interesting clocking/filtering of the MXR, into a digital delay chip.

Kind of spendy if you just want the schematic.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=41415&item=3768382328

[michael_krell]

Ok so the forum has been down so i havent had a chance to post, but I do have one question.

Which IC is the compander? The ones that I see look like Flip Flops. I cant tell which one it is. There is one that has a label that is hard to read.

if someone can get me the number on it. I would appreciate it.

[Mark Hammer]

The compander chip will be an NE571 or NE570.  There will be identical-value electrolytic caps on pins 1 and 16.  Probably somewhere between 2u2 and 4u7.

[michael_krell]

i dont have any ne570's. i have other chips but no ne570's

[michael_krell]

these are the IC's (besides the opamps) that i have:

cd4013
cd4016
MC14001

Do i have a rare edition or something?

Also, i am not getting signal to most of the opamps.

There is one opamp at the input that has output and inpu signal, but the rest dont seem to have any input or output signal. And one has completely incorrect bias voltage. There is like .1 volt at the +. and almost 11 at the -. and the output is about the same as the -.

Maybe some of them arent being used as amplifier stages, but it seems to be theres a coupling cap problem or something.

i Really wish i had a schemo. I bought one from schem connection, but they have not contacted me or sent me anything. getting kind of worried about that.

[ISC]

Michael I have  the schematics in a Zip file  for the MXR Analog delay that uses a recticon 5101 chip, I can email it to you if you would like.
I also have a broken MXR Analog Delay with the same symptons as yours but mine has  the 3 SAD-1024 chips. I have been trying for a year to get a schematic without luck. If Mark Hammer reads this could  I  email you the schematics  to help Michael with his and get a copy of the one  that I need to get my pedal back to life.

Regards
Trevor

[Vsat]

Trevor,
I can email you the "three- SAD1024" MXR schematic, I have it here. Would like to see the R5101 schematic.
Regards, Mike

[Mark Hammer]

Michael I have  the schematics in a Zip file  for the MXR Analog delay that uses a recticon 5101 chip, I can email it to you if you would like.
I also have a broken MXR Analog Delay with the same symptons as yours but mine has  the 3 SAD-1024 chips. I have been trying for a year to get a schematic without luck. If Mark Hammer reads this could  I  email you the schematics  to help Michael with his and get a copy of the one  that I need to get my pedal back to life.

Regards
Trevor

I'd love to see the schematic for that issue (mhammer@marketbridge.ca).  If Mike/Vsat isn't too inundated with other things, though, I'd suggest seeking his input first before relying on mine.  I may write a lot more than him but my knowledge is absolutely dwarfed by his.

[puretube]

to be honest,
puretube
would like to see both schems, too...
:wink:
THX!

[ISC]

Mark/Puretube its on its way. Michael should have it as well.
Any problems let me know.

Regards
Trevor

[michael_krell]

Ok so i got the schematic, thanks again. And in about 3 seconds I seem to have diagnosed the problem. Looks like it is the first CD4016 chip. It is labeled A-6 on the schematic.

The signal goes through there and never reaches the next stage. So I already ordered some, because of mark's advice. So i will replace it and see what happens.

thanks, ill keep you updated.

[Vsat]

Mark,
Who'd you get the SAD1024 version of the schematic from a few years ago?    

And BTW congrats on your psychology consulting practice, you must be unbelievably busy doing this along with your daytime government job, and staying on top of Aron's at the same time. Wish I had that kind of energy.
Cheers, Mike

[puretube]

Mike, Trevor: thank You both, gentlemen!

[Mark Hammer]

Mark,
Who'd you get the SAD1024 version of the schematic from a few years ago?  

It was obviously a few years ago, but I do believe it was Sir Stephen Giles, 3rd Earl of Selsdon, who also may have bequeathed me the Ross Delay schem as well.  That guy is sitting on more unearthed info than you can shake a stick at.  He should e-bay the rights to sift through his attic after his death.  Of course, then we'd NEVER hear from him because with the size of the winning bid he be travelling even more than he does now.

And BTW congrats on your psychology consulting practice, you must be unbelievably busy doing this along with your daytime government job, and staying on top of Aron's at the same time. Wish I had that kind of energy.
Cheers, Mike

Well, I had to let the receptionist go.  Seems the 2 or 3 calls I was getting per year from Steve couldn't justify the overhead costs for my "practice". (I.E., lest anyone draw mistaken inferences, Steve WAS being tongue in cheek in his comments).  As for general busyness, there isn't a helluva lot going on at work.  I just switched directorates within my department, after returning from language training, and am waiting for something to do (a situation to be rectified in about 2hrs from now).  My output here should decrease soon enough.

[Paul Perry (Frostwave)]

[  I just switched directorates within my department, after returning from language training, and am waiting for something to do (a situation to be rectified in about 2hrs from now).  My output here should decrease soon enough.

There is somethig horribly wrong in a world that supports writers & poets & artists, but not stompbox builders! Let's lobby the canadian govt for a 'stompbox-led cultural renaissance'  

[Mark Hammer]

Not to worry, 90% of my participation here is aided and abetted by the tools placed at my disposal at work.  If I am able to send people schems or post them, it is through the benevolence of my employers.

[Maneco]

Could i please have a copy of those schematics?

Thanks!

maneco@gmail.com