SAD problem with a ross flanger i fear...

[pinkjimiphoton]

hi guys, gotta red ross flanger on fleabay in great shape for no money...30 bux shipped or so.
they said it passed signal, but no effect

(cue the audience going <siiiiiiiigh>)

so, i figured i'd open the dang thing up and see what's what.

i took some voltage readings, everything seems to be in the ballpark...modulating things are modulating, i can hear a faint clock in the background.

tried "laying of hands" and reseated the sad1024 chip. no dice. i'll get to voltages in a minute, but pretty sure it's the sad1024 chip that's toast.

no idea really how to check it other than to replace. i HAVE ONE. i've been saving it to build an mxr flanger, but this is almost the same thing from the research i've done so far.

i WILL post voltages...not gonna bother with the opamps, they're all 4558's, and all about right...there's a 20v transformer, and the reg is working it's magic..b+ is about 14.41v or so on the output of the regulator.

but...my question is...is it safe to plug the unused SAD chip in and see if i get flange, or can i damage it doing so? it's unused in the original blister pack still.

if it works, it would seem the next step would be to keep this thing, in which case if some of you brothers out there can guide my dumb newb ass thru it, i won't waste the sad1024, but hopefully convert it to a pair of MN3007's, of which i still have probably 10 or 12.

i'm gonna post this, then  come back with the voltages i wrote down in the other room... i'm a newb, but to me, they seem to be about reasonable, and not matching necessarily the kinda voltages i've seen others post with a dead sad chip...so i'm thinking it may be something else stopping the effected circuit from working.

i just don't wanna f it up doing something stupid. i'm sure it will need to be dialed in, as all the trimmers were pegged.

thanks for any and all help.

not sure which parts correspond to what yet on the mxr flanger, so i'll start with the sad and the clock... but i think everything is gonna be fine except the bbd, unfortunately.

i hope to be able to work up a vero daughterboard that will plug right into the existing socket...do you think that would be possible?

lotta questions...sorry!!

[Tony Forestiere]

http://www.diystompboxes.com/smfforum/index.php?topic=55292.0
Dork with the trimmers if they have been "dimed". I had the same issue with an 18v EHX EM and was able to get it back.
Luck!

[pinkjimiphoton]

 voltages...like i said, i won't post the OA's, they're all seemingly doing their thing...amplifying or modulating, etc..

sad1024
1   0.0
2   4.68
3   7.23
4   0.00
5   4.91
6   4.91
7  14.48
8   7.25

9   14.48
10  7.24
11  8.3 - 8.20 (modulating?)
12  8.4 - 8.21
13  0.0
14  7.24
15  4.82
16  0.00



the cd4013be

1  7.25
2  7.24
3  12.52
4  0
5  7.23
6  0
7  0

8  14.48
9  14.48
10  11.25
11  14.49
12  12.40 - 12.85 (modulating)
13  14.48
14  14.48

[pinkjimiphoton]

thanks tony for the help... i will play with the trimmers a little bit, but i am getting ZERO effected sound.
the voltages on the sad chip seem good, from what i can tell.. so i assume the bbd may have survived? i CAN hear - barely - what seems to be a slight "delay" sound on a couple of the pins..it's hard to really tell tho.
i'm gonna go try and mess with the trimmers a little bit.
i am getting ZERO hum.

wondering...do you think maybe one of the tants blew out somewhere between the output of the chip and the mixer stage or something?

i have a way steeper learning curve here than you may think.

[oldschoolanalog]

Audio probe it yet?

[pinkjimiphoton]

nope dave, not yet... i had a lesson that just left, and g's making chow. after everybody goes to bed, i'll break out the audio probe and see what's what.

i take it from the voltages *MAYBE* the sad chip survived?  i'm hoping that's what i'm reading into this?

seems to me, if i'm passing signal thru dry, it's gotta be a problem somewhere in the output or mixer stage of the wet signal. i gotta print up the data sheet too so i can look...this is way over my head, i'm afraid.

so i'm imagining i shouldn't sacrifice a virgin at the reticon altar yet? 

[Mark Hammer]

CMOS chips are "cheap like borscht".  Don't abandon hope for the BBD until you've verified that it's NOT the 4013.  Keep in mind that if the 4013 is fried, you ain't gettin no delay no how no way.  Should we assume that the modulation of the 4013 corresponds to the LFO rate?

Assuming, for the moment, that the Ross schematic corresponds at least 95% to the MXR 117 schematic, there should be 3 trimpots: a pair of 20k and a single 500k.  The 500k sets the clock range, one of the 20k (connected to BBD pins 11 and 12) sets the BBD output level, and the other 20k sets the input bias voltage.  For the moment, you can just dime the BBD output level trimpot, and set the 500k unit to its midpoint until you get the bias voltage right. 

Assuming that all the other things one might normally attend to in a dysfunctional pedal check out OK, like the stompswitch, the wiring of the jacks, continuity within the pots, etc., you would futz with the bias trimpot by setting Manual to minimum, depth and regen to max or near max, and the speed at about 2:00 (or as close close to 1-2hz as you can).  This would provide the most obvious in-your-face flange sound if you DO manage to hit a sweet spot on the bias trimpot.  Once you have that sweet spot roughly identified, you can back off the regen so that it does not smudge the sound so much, and allows you to aim the trimpot more precisely for audio quality, rather than just obvious delay.

Should wet signal be resurrected, and quality maximized, you will then want to aim for the overall delay range using that 500k trimpot.  For that, you may want to slow down the LFO to hear how it sweeps.  You may also want to futz with the manual control at this point, since one does not want the manual control and clock trim to work against each other.  Remember that the depth control works such that manual has the most impact on delay time when depth is at minimum, and has negligible impact on delay time when depth is at max.

[oldschoolanalog]

@jimi: +1 on everything Mark said. 
And... I will open up my properly functioning ROSS tomorrow and post some V's. Hope you have it sorted out by then. If not, you will have something as a reference.
Does your multi meter have a frequency counter function?

[pinkjimiphoton]

hi guys,

i understood some of what mark said dave,
i set the controls up as he suggested, and used my original readings to kinda tune it back in...or close.
no delay. but... i can hear clock and sweep, so i'm thinking it's gonna be a bad cap or something. i'm a mite too burnt to scree any schematics tonite,
tho i did print them out and start looking at it. it is indeed pretty close, the mxr is more adjustable i think.

with the sad chip up top, the 2nd 4558 from the right on the board has MUCH lower voltages than the other three,  but it's pretty premlinary of an assumption..
i've gotta go and actually match up which chips go where in the schematic, and i'm better off doing that stuff with a fresh set of eyes.

still betting it's somewhere between the output of the sad, and the mixer stage, probably that opamp. all the others are reading voltages around 14.5v at pin 8, that one's reading i think more like 4.5v or so.

i don't know what i'm doing, so yes, it's a 10,000 monkeys situation.

dave, yes, i do have a frequency counter on my meter.

also noticed slight discoloration on the socket for the sad , pins 12-15.. looks like it might have gotten hot.

tomorrow, i think i'll start by just replacing all the electros and see if that helps. next, the tants..
can i replace them with regular electros?

dave, if you can make out the values, i'd be indebted.. too small for me to see even with my glasses. glaucoma sucks.
so smoke lotsa funny vegetables to prevent it if so inclined.
just kidding. flux inhalation is all ya need.

it's like being an oracle, or something.


mark, i don't know really how to tell if the cd4012 is working, but the voltages seem to indicate it's doing something...unless i'm mistaking the changing voltages on the pins for the oscillators...but i thought the clock was the oscillator?

my brain hurts.
more tomorrow...thanks my brothers.

[Mark Hammer]

The pics I have seen online show both the SAD1024 and CD4013 in the Ross units soldered in place.

It's not Jimi's fault, obviously, but let this be a lesson to folks to spend a few extra pennies for the sockets.  Being able to pop either or both chips out and test them in a different pedal to confirm functionality can save LOTS of time and headaches in troubleshooting.

Of course, I can't really blame Ross either.  How could they know back in 1980-whatever that there'd come a time when it was easier to find the wreck of the Titanic than find another SAD1024?

[oldschoolanalog]

The Ross I have open and sitting in front of me as I type this has the 4013 soldered and the SAD1024 is in a socket.
I will take those V readings later. Now I have to go on a job interview. Bills to pay and all that other stuff. 

[pinkjimiphoton]

mark,
they all have just the sad chip socketed, at least the ones i've seen...i've owned 3-4 of these over the last 30 years or so, i never tend to keep them very long.
i have a pearl flanger that just blows these things away!! does the through zero point thing, too.

dave, this one has only the 1024 socketed. i will if necessary socket everything. but i really don't think it's the clock. i think it's either the bbd or a bad cap that's not passing audio.

good luck  break a leg at the interview today bro!

[digi2t]

Of course, I can't really blame Ross either.  How could they know back in 1980-whatever that there'd come a time when it was easier to find the wreck of the Titanic than find another SAD1024?

Eye popping story;

I recently repair a pedal for a gentleman down in the States. He asked if I could also clone said pedal, since the original is a rare collector, and he didn't want to gig with it. I said "OK". He then asks me if I could also create a clone of the the Mutron Flanger. He had one in the past, sold it, but missed it, and wouldn't mind having a clone. Not being familiar with it, I told him I would look into it. Checking out the circuit, and seeing the need for said SAD1024, I told him the dilemma concerning cost/availablity of said chip. He replies, "No problem. My buddy worked at Musitronics back in the day, and when they closed up shop, he gave me a tube of 25 of them. Just let me know if or when you're ready to build it, I'll send you what you need."



Of course, I did also advise him that the price that tube of chips could fetch, he can probably get himself a nice bevy of pedals.

Go figure.

BTW. I found a copy of the Mutron Flanger circuit, although the writing (values and such) was tough to read. Still, it was a hi-rez pic, so I blew it up to 3 feet to 5 feet size, which allows me to decipher pretty much all of the writing. Eventually, I'll get it cleaned up, and post it. That's one I wouldn't mind cloning.

[Mark Hammer]

 

Give me a sec while I try to get them back in their sockets.....there, better now.

The Mu-Tron Flanger is one of those exceedingly rare birds.....like SAD1024s.  I'd be very interested in the schematic once you have it deciphered, as I'm sure many would.  Of particular interst is the way in which the sweep range is defined, and the switchover from LFO to pedal control.  Interesting feature.

Speaking of which, I should probably ponder whether it is worthwhile to adapt the Anderton pedal-flanger circuit ( http://hammer.ampage.org/files/Anderflange1.PDF ) to something more available, like an MN3207 or similar.

[digi2t]

That's on my to-do list. I really need to get a bunch of work of my bench right now. I told the gentleman that IF I took it on, I wouldn't be able to tackle it before early next year.

I will do my best to clean up the schematic, and post it in the next few weeks.

It's a circuit that would fit nicely into the Hen's Tooth Cafe.

There's been some write up on it over at "you know where", including some posturing on replacing the SAD with and MN. Nothing concrete though, and ("out of my league here" alert) timing issues (?) with using a different chip? That's more up your alley Mark.

I just copy them. Analysis is still baby steps for me.

[pinkjimiphoton]

ok guys,
i bit the pickle.

yes, it's the sad chip. i broke down and in a fit of impulsivity, took the pristine brand new unused one out... . <cue the whole forum shrieking NO~~~!!!!!>

AND I STUFFED IT IN.

the new one, after a couple minutes tweaking, runs and flanges and delays and damn near phase shifts at some extreme settings... i swear i heard some of that yoyoyoyoyoy we all love so much.

but any signal going thru it is distorting no matter how i set the trimmers. turning the knobs generates crackle (not ok) so i'm assuming all new electros are in order, and i wanna replace all the tants, too. i don't have them.. and frankly, where i have room, i think i'd prefer the electros anyways. tants always seem to lead to probs for me, anyways.

so i'm gonna carefully take the new chip out, seal it back in it's package, and set out on the herculean task of figuring out how to adapt an mn3007 or two to the circuit.  i mean...dumb newb here... a 1024 bbd should be interchangeable i would imagine, right?

thinking daughterboard with any necessary components.  i know peeps have done this..

or should i just bite the bullet and use the 1024 in this thing? when dialed in right, pretty sure it'll be an amazing sounding flanger.

if i added a couple more trimmers, could i get all the functions in the mxr do you think?

obviously, if i install the 1024, it's a done deal, and i'm keeping it....so i have no issue modding the sucker. but i believe it's gonna be way the heck over my head.
i've compared the two chips data sheets, and the pinout is alot different, as is the function. i'm more than willing to try to do the work to reason it out, but some aspects i know i'm gonna get stuck on.

[pinkjimiphoton]

dumb newbe is learning. slightly.

it would seem to me, that the 1024 and 3007 are NOT gonna be able to be used.. the 1024 is two 512 bbd chips in one, the mn is one 1024 bbd.

so...this ain't gonna happen. guess the dream of building the mxr flanger is gonna go the way of the dodo byrd.

time to bite the bullet.

unless someone infinitely smarter (which could mean just barely to genius ) than me can figure out a way to do it.

i know folks have done it, or claimed to do it, but the visual evidence a newb like me would need doesn't seem to have survived.

[Tony Forestiere]

At least you know a 37 year old chip works

[oldschoolanalog]

With a small daughterboard you can easily build/repair either flanger w/the MN3007.  
Voltage readings coming soon.
And... you only need one 3007 for the job.

[Mark Hammer]

I'm confused.

Are you saying that installation of a NOS Reticon chip results in all the expected "tricks", except with unacceptable audio quality?

If I understood you correctly, then your problem lies outside the SAD1024.  I honestly can't think of a single instance in 30 years, whether in my own experience, or something someone else posted, where one of those chips could perform all the expected functions, but just do a crummy job at it.

Straighten me out here, bro.