AMZ FX ANALOG ALCHEMY GEOFX MEF ROG MEF DIY WIKI

Vintage MXR Flanger problem

Started by Govmnt_Lacky, September 07, 2011, 09:49:21 AM

Previous topic - Next topic
Print
Go Down Pages 1 2 3
User actions

Fender3D

#20
September 10, 2011, 12:44:06 PM Last Edit: September 10, 2011, 12:47:03 PM by Fender3D
There should be a slight increase of the wet signal 'cause the lower loss trough BBD... but I guess it wouldn't matter so much...
Bias is the same for both 512 stages, so no trimming...
A switch won't be harmful, even when shorted to ground (case/box)...

Come on, you're this close...  :icon_twisted:









DO IT
"NOT FLAMMABLE" is not a challenge

Govmnt_Lacky

#21
September 10, 2011, 12:59:01 PM
Quote from: Fender3D on September 10, 2011, 12:44:06 PM
There should be a slight increase of the wet signal 'cause the lower loss trough BBD...

I suppose a happy medium could be found without level trimming when switching between stages  ;D

Quote
Come on, you're this close...  :icon_twisted:


DO IT

Easy to say if it was 25+ years ago when SAD chips were somewhat plentiful and CHEAP! :icon_lol:

Another roadblock is that my madbean version is already boxed up TIGHT with no room for switches. I gotta figure something out with that:
1) A good switching diagram to switch out the jumper and cap
2) Someplace to squeeze in a switch  :icon_eek:

I think I have some DPDT miniature slide switches BUT, at first glance, I think this will require something with more than 2 poles.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

oldschoolanalog

#22
September 10, 2011, 01:22:11 PM
IIRC, you need to connect some pins of the unused 1/2 of the SAD to ground or power. Don't remember which goes where. Check out the datasheet.
BTW; 25+ years ago SAD1024's were plentiful; but at approx. $12-15 US in 1980's dollars; they hardly qualified as cheap...
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#23
September 10, 2011, 01:29:14 PM
Quote from: oldschoolanalog on September 10, 2011, 01:22:11 PM
IIRC, you need to connect some pins of the unused 1/2 of the SAD to ground or power.

Good Call  ;D

According to datasheet, ALL unused OUTPUTS should be connected to Vdd (Input power). Or, they should essentially be connected to Pin 7 of the SAD.

This complicates things a bit!  :-\
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#24
September 10, 2011, 01:35:37 PM Last Edit: September 10, 2011, 01:49:57 PM by Govmnt_Lacky
The way I look at it AND taking into account Dave's contribution....

This will take no less than a 3PDT switch with a few more off-board wires  :icon_eek:

Fortunately, madbean's board provides a jumper/access point to Pins 5 & 6 of the SAD so that can be run to a switch lug to go between normal and Vdd.

It is do-able for sure...... I just don't see it ALL happening in a 125B

1590BB is a definite possibility though  ;D

EDIT: NEVERMIND... Apparently ALL of the unused pins need to be tied to either Vdd or Ground. That is 5 pins in total. Too many for reasonable mechanical switching  :'(
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

jdub

#25
September 10, 2011, 01:56:15 PM
Man, I would be totally willing to try this, since I have a couple of half-functioning SADs, but I would have to do a new etch, repopulate, etc. which would take some time, plus I only have the shredaholic layout to work with.  Is there anywhere I can find the MadBean layout?  The link above didn't work for me. So Greg, if you're willing to wait a bit (probably not! ;D), I'm willing to guinea pig it for ya...
A boy has never wept nor dashed a thousand kim

Fender3D

#26
September 10, 2011, 02:17:40 PM
You have no unused pins on SAD, they're just NOT WORKING...
leaving all other parts ON the board, they will act as usual but with no signal.

@jdub
the link will work substituting 3 dots with the name of the other site...  :icon_wink:
"NOT FLAMMABLE" is not a challenge

jdub

#27
September 10, 2011, 02:22:10 PM
Oooooh, gotcha  :o
A boy has never wept nor dashed a thousand kim

Govmnt_Lacky

#28
September 10, 2011, 02:24:34 PM
Quote from: jdub on September 10, 2011, 01:56:15 PM
So Greg, if you're willing to wait a bit (probably not! ;D), I'm willing to guinea pig it for ya...

I am more than happy to wait  ;D

I already have 3 that are up and running so I can hold my breath for a while.  :icon_eek:

Let us know what you come up with.

Just remember also that the "changes" that fender3D recommended on the madbean board ASSUMES that your SAD chip has OUTPUT A broken (No output from Pins 5 & 6). If your chip had output B broken, then you will have to find another work-around.

Good Luck  ;D
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#29
September 10, 2011, 02:57:24 PM
Just checked in Madbean's PCB you will have to lift R32 or R33 (it's the same) too.  :icon_redface:

If you lift C6 (stock PCB) / C19 (MB PCB) and just 3 wires it's a simple 1 pole bypass, and no other lifting

"NOT FLAMMABLE" is not a challenge

jdub

#30
September 10, 2011, 02:59:55 PM
Aw crud- wasn't thinking. Both of my half-SADs have bad B-sides- the one you and I corresponded about, Greg, plus I have an SAD512, which is a 1024 with, of course, a non-functioning B-side  :-\.  Well, since both sides are pretty much the same, I might be able to jury-rig something (like a psuedo-daughterboard, just to see if ot works); otherwise, it's gonna entail modification of a layout, which is more time consuming. Sorry about that.  Lemme see what I can do.
A boy has never wept nor dashed a thousand kim

Govmnt_Lacky

#31
September 10, 2011, 03:10:03 PM Last Edit: September 10, 2011, 03:13:03 PM by Govmnt_Lacky
Quote from: Fender3D on September 10, 2011, 02:57:24 PM
Just checked in Madbean's PCB you will have to lift R32 or R33 (it's the same) too.  :icon_redface:

If you lift C6 (stock PCB) / C19 (MB PCB) and just 3 wires it's a simple 1 pole bypass, and no other lifting



I follow you Fender however, I am worried about this operation with a fully functioning SAD.

If you lift C6, that leave the OUTPUT on Pins 5 & 6 going to GND (via R10 and R11) and that is where the datasheet warning comes into play.

Will the GOOD chip react well if those outputs ARE NOT tied to Vdd when in the 512-stages position?

-AND- will it affect the operation of the outputs of the working channels on the 1/2 BAD chip?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Govmnt_Lacky

#32
September 10, 2011, 03:18:33 PM
Quote from: jdub on September 10, 2011, 02:59:55 PM
...plus I have an SAD512, which is a 1024 with, of course, a non-functioning B-side  :-\. 

???

I thought the 512s were 8 pin DIPs. SAD512s don't have 2 sides.
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#33
September 10, 2011, 03:32:45 PM Last Edit: September 10, 2011, 03:34:58 PM by Fender3D
Let's put it this way:
what if you were using a SAD in a stereo device with 1 section per channel (L/R), then shut off R channel?

SAD were used as delay line in older scopes to record waveforms... I recall an older Elektor project doing just this (it was "doable" it had 2 different separated clocks without heterodyning on the same device) and the claim "The sections may be used independently" must allow this operating setup  :icon_exclaim:

You're not "not using" those pins, you simply don't use the signal available there...
You will connect CMOS pins to Vcc or GND just to avoid autooscillations or signal bleeding, it won't broke anything not connecting unused pins (unless you touch them after sliding your feet over acrylic or wool  :icon_mrgreen: ), anyway they're connected somewhere actually..

@ jdub:
SAD512D were 8 pins, SAD512 were 16
"NOT FLAMMABLE" is not a challenge

jdub

#34
September 10, 2011, 03:43:02 PM
QuoteI thought the 512s were 8 pin DIPs. SAD512s don't have 2 sides.

Yeah, as F3D said, the SAD512Ds were the the 8 pin DIPs and are damn near impossible to find these days.  The SAD512 (no D) is a 512-stage BBD which, according to the datasheet, is identical to one half of a 1024, in a 16-pin package.  Datsheet also mentions that "in some instances" 1024s with a bad B-side may be used to make 512s.  I'm betting that there were a lot of those instances  ;)
A boy has never wept nor dashed a thousand kim

oldschoolanalog

#35
September 10, 2011, 03:45:50 PM
Mystery lounge. No tables, chairs or waiters here. In fact, we're all quite alone.

Govmnt_Lacky

#36
September 10, 2011, 03:46:53 PM Last Edit: September 10, 2011, 03:49:32 PM by Govmnt_Lacky
Consider me knowledgified!!  8)

Can anyone think of a good way to determine FOR SURE which side of a suspected SAD is broken? With a sig gen, oscope, etc?
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#37
September 10, 2011, 03:47:07 PM
Sorry I said jdub, but I meant Govmnt_Lacky  :icon_redface:

Quote from: jdub on September 10, 2011, 03:43:02 PM
Yeah, as F3D said, the SAD512Ds were the the 8 pin DIPs and are damn near impossible to find these days.  The SAD512 (no D) is a 512-stage BBD which, according to the datasheet, is identical to one half of a 1024, in a 16-pin package.  Datsheet also mentions that "in some instances" 1024s with a bad B-side may be used to make 512s.  I'm betting that there were a lot of those instances  ;)

Or maybe they were trying to mod an M117  :icon_mrgreen:
"NOT FLAMMABLE" is not a challenge

jdub

#38
September 10, 2011, 03:51:39 PM
lol  :D
A boy has never wept nor dashed a thousand kim

Govmnt_Lacky

#39
September 10, 2011, 03:57:49 PM
Does anyone else find it odd that it is always the same 4 or 5 people that talk about Flangers or modulation effects?

Fender3D, oldschoolanalog, jdub, Tomas, myself......

I wonder how many pages this post would be like if it was a Fuzz or a TS derivitive...  :icon_eek:

MODULATION ADDICTS UNITE!!!  :icon_lol:
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'
Print
Go Up Pages 1 2 3
User actions