Hi all,
I'm trying to fix my Morley Wah/Volume model PWV and need some help.
This is the very first pedal i owned, bought it in 1993. It was stored for many years without use.
I opened it and made a visual inspection and clean it, all looking ok. But when i put a fresh 9V battery and test it there was no sound or only very little signal was passing on the wah setting.
I took some mesurements of the original TL071 and replace it with a new one. I also installed an IC socket and replaced all three electrolytic capacitors C3/C7/C8.
Power it up again and took mesurements with the freshly installed TL071. Inverting input and output of the TL071 now reading 5VDC, the original TL071 was giving 1.3VDC. i guess the original TL071 was faulty.
I plug in my guitar for testing, and so now there is some "clean" sound on the wah setting but no wah effect (i covered the LDRs with a piece of black tape while testing)
When i switch to volume mode, there is almost no sound and no volume change when i rock the pedal. Intensity does change a little when/if i remove the piece of black tape and let some light in.
When i short the LDR1, signal passes through.
So now I am suspecting the LDRs... i tried testing them "onboard", i get infinit resistance on my ohmmeter. Are the LDRs fried?
I trying to find some equivalent LDRs online but i can't find the same value.
Original LDRs are 400-850-L-ON and 150-250-L-ON.
Almost all LDRs i find are in the Kilo-ohm range, i could only find one LDR sold by Banzai music as a "morley replacement" but even this one is not in the correct range > 200-400 ohm.
Do you think i can replace the LDRs with the "Morley replacement" sold by Banzai music? it will work ok?
Thank you for your help.
Jonathan
Schematic attached for reference.
(https://i.postimg.cc/ZvHDXnnr/IMG-2818.jpg) (https://postimg.cc/ZvHDXnnr)
(https://i.postimg.cc/t7bR0c7T/IMG-2820.jpg) (https://postimg.cc/t7bR0c7T)
if I may ask... do the LEDs light up? if they do, then it's most likely the LDR.
If the LED is the one that's broken, replace the LEDs...
Wow fast response! :)
Yes the LEDs are lighting up correctly.
On the schematic one pair of LEDs is "Red diffused" (L1,L2) and the other pair seem standard RED LEDs.
You can see on the photo that LEDs L1 and L2 on the left side are more pink than red. but mabe this is normal since they are supposed to be "diffused" type? I first thought the pink color was a bit suspect when i first had a look until i read about the diffused type so mabe the pink color is normal.
So do you think the Morley replacement LDRs sold by Banzai music will work correclty even if they are not in the same range as the original?
Thank you Nathan!
If it would be possible, the only way to make sure the LDRs are fried it when we really see it at infinite resistance consistently (while rocking the pedal, for example)
Especially with this..
QuoteIntensity does change a little when/if i remove the piece of black tape and let some light in.
That means that at least 1 LDR works... i guess..
Could you try connecting your multimeter to each of the LDRs and try rocking the pedal? some alligator clips would help...
When you originally got it.. was it working?
The pedal was working perfectly when i bought it new in 1993, but it was stored and not used for almost 2 decades :icon_biggrin:
I did a new test feeding 1V RMS@440hz into the pedal.
Volume mode : almost no signal passing, no change in intensity when i rock the pedal. When i move the black tape on top of the LDRs there is a slight change in intensity but signal is always present (and very low) and does not disapear.
When i place aligator clips of my ohm meter across the legs of LDR1, it shorts the signal and sound now passes through the pedal at unity. I can read 3Mohm across LDR1 on my ohm meter but the wierd thing is i can only read when the range on the multimeter is at maximum (200Mohm range) if i switch to the 20Mohm range i read infinity, strange. Reading doesn't change when i rock the pedal.
Wah mode : the signal passes at unity but nothing happens when i rock the pedal. i can measure 50Mohm across LDR3 when the pedal is at maximum and about 160Mohm when the pedal is at minimum. but the reading keeps moving a lot on the multimeter.
This may have nothing to do with the pedal's current state but I am perplexed by the purpose of LED3. What is served by having an LED pointed at the back of an LDR? That's a headscratcher.
More relevant, I'm wondering if the issue may be the footswitch itself. The schematic shows that the footswitch enables/disables the LEDs, and engages L1 and L2 at once. If these remain "on" when you switch to wah, then LDR1/LDR2 would provide an always-on low-resistance path to ground, attenuating the input signal to the wah. A simple test would be to lift one end of R27, such that L1/L2 donot light up. You can also see if, with R27 left intact, they stay lit all the time, whether you're in wah or volume mode.
QuoteThis may have nothing to do with the pedal's current state but I am perplexed by the purpose of LED3. What is served by having an LED pointed at the back of an LDR? That's a headscratcher.
Mark, please correct me if I'm wrong, but from the schem it looks like a double sided LDR... if that even exists
more odder - the backface led operates on the volume circuit ldr, but switches on in wah mode.
You're correct in that the schematic shows an LED on both sides of the LDR, but look at the board and you can see that the leads of that photocell stick out the back, just like any normal unit.
Note that while photocells are most sensitive to light on their front, they are sensitive to light, albeit less so, from all sides. The world is full of lots of things that can seem opaque, but still let light through. Next time you measure an LDR's resistance, try measuring it covering the LDR with your finger, and then measure it with your finger on it, but under a table. Under the table, the "off" resistance will be much larger, because less of the ambient light is coming through your finger. Put the photocell "face" down on a table and hold it in place with a piece of masking tape. Now measure the resistance. It will be low-ish, because light permeates both the tape and the seemingly-opaque backside of the LDR. This is why vactrols are larger then you'd think they need to be. It takes a lot of black epoxy to keep the light out and allow them to reach their highest possible off-resistance.
The real mystery for me is why Morley felt the need to light up the LDR from both sides. Was this in an effort to push the LDR to its lowest possible "on" resistance?
Oh wait, I think I get it now....or maybe not. In volume mode, L3 is turned off, leaving only L1 to shine on LDR1, and LED2 to shine on LDR2, presumably in reciprocal fashion (i.e., the shutter blocks either LED1 or LED2, but not both at once), which would be required to produce volume changes. In wah mode, LED1 and LED2 are turned off, which would make LDR1 and LDR2 go high, and function like a large-value input terminating resistor. Is their combined dark resistance too high to provide a desirable tone from the wah? Maybe. In which case, lighting up LDR1 dimly from behind might result in a suitable LDR1+LDR2 resistance to ground.
IN any event, that simply dances around the logic of their use of front and back illumination, and doesn't really tackle why the pedal isn't working properly.
BUT, having said that, is the shutter itself aligned properly? I know it is misleading to judge from the single photo provided, but it looks like the shutter might be rubbing against, or even maybe blocked by, the PCB on the "lower" edge, where L2 and LDR2 are situated. I don't expect anything to be burnt out during 20 years of storage, but stuff CAN get jostled and repositioned, and as delightfully crackle-free as Morley's system is, the positioning of the shutter, light source, and photocells IS critical to their proper functioning.
I agree the back-side LED_LDR is very strange; but it is far too late to second-guess Morley on this. It worked that way in 1993 and unless the LDRs have been cracked and soaked in water I doubt they could be "burnt".
Measuring LDRs for basic function is trivial but you MUST control the light on them. With pedal power OFF and normal workbench lighting (don't strain your eyes) a plain ohm-meter across the LDR will read 500-5,000 Ohms. If you have a small bright flashlight, beaming the LDR should drop the Ohms even lower.
Now rig the bench for BLACK-out. Wait for midnight, kill the lights, the PC, and any nightlights. You probably need one SMALL light to set your probes and read your meter, but cover it as much as possible. Repeat the measurements. If the Ohms changes a lot then the LDRs aint dead.
The measured Ohms will be in parallel with the rest of the circuit. For LDR3 there is nothing else. LDR1 is shunted by the input jack so stick an open plug in it to break the switching.
(https://i.postimg.cc/HcwqFFYC/LDRs-metering-in-the-dark-42.gif) (https://postimg.cc/HcwqFFYC)
Not countering anything said, but it does like the original opamp got fried so maybe something catastophic has happened in its life? While musicians still use 1/4" jacks for speaker connections, could it have been plugged into the wrong place?
I wonder what the shutter is made of? Some plastics breakdown over time and it may not be as opaque as it was.
But as PRR just said, you have rule out stray light falling on the LDR.
QuoteIt was stored for many years without use.
I would bet it was the electros, not a bad opamp, causing the low voltage readings. LDRs can die for no apparent reason, but it would be strange if they all did.
I desolered all 3 LDRs and tested them:
LDR1_light=7Mohm_dark=infinity
LDR2_light=3.2Mohm_dark=infinity
LDR3_light=8Mohm_dark=infinity
All 3 LDRs vary with light but only in the Mega ohm range. When i put the face of the LDR against the table i read nearly 200 Mega ohms (max reading of my multimeter) when i cover the back of the LDR with a large black tape i read infinity on all three LDRs.
I guess i'm good to order some new ones... I will order the replacement part from Banzai.
Lets see if the new LDRs will fix the problem.
Many thanks to all for your help!
The LED on the back of LDR1 is strange indeed, the pink color LEDs L1 and L2 also caught my eye on first inspection, but all LEDs do light up, and the pink "red diffused" ones are indeed glowing a "red" light.
The LEDs, shutter holes and LRDs are all aligned correctly. The shutter seem to be made of very dense carton/paper material.
I will report back with the new LDRs installed
Thank you!
Quote from: isophase on October 05, 2020, 09:03:50 AM
I desolered all 3 LDRs and tested them:
LDR1_light=7Mohm_dark=infinity
LDR2_light=3.2Mohm_dark=infinity
LDR3_light=8Mohm_dark=infinity
If you are reading in the MegaOhms when any kind of light is being placed on the LDR then something is wrong with them. Even putting a small amount of light onto the LDR should result in them going down to 1 MegaOhm or below.
Replace all of the LDRs. It will cost you about $3 at most.
Hello,
I finally replaced the LDRs, problem fixed!
Thank you for your help!
So what happened to the original LDRs? I have the same Morley (mine is *only* 20 years old) but I ripped the guts out and used the shell for my own project. Like everything they've ever made, built like a tank. I remember thinking it sounded pretty damn crappy but it definitely worked, all the way up to a couple years ago. Where did you store it for those decades? In a non-climate controlled warehouse in Miami? In the shed behind your home in the Yukon? At the bottom of your pool? ;D
Every LDR I've seen that's gone bad is because the two wires going to the resistive element stop making good contact with said resistive element. This could be due to weather, corrosion, hairline cracks in the epoxy encapsulation, but it's usually right where the wire meets the resistive element.
Funny because I've always thought the Morley Wahs sounded best out of all the wah pedals. Maybe it's because the first time I heard a wah live was an old Tel-Ray Morley...
QuoteEvery LDR I've seen that's gone bad is because the two wires going to the resistive element stop making good contact with said resistive element. This could be due to weather, corrosion, hairline cracks in the epoxy encapsulation, but it's usually right where the wire meets the resistive element.
That makes a lot of sense to me, considering in my experience with audio gear, devices usually become faulty because of either age (electrolyte dries up, plastic or metal degradation, etc) or because of human user interfacing, in this case, the leads. I have a glitchy Mutron phaser on the bench (behind a couple other projects), I wonder how the LDRs are. I haven't had any problems with LDRs in my own builds, none of which are from the 1970s ;D
QuoteI've always thought the Morley Wahs sounded best out of all the wah pedals
At the time I played out of a Hot Rod Deluxe with a Strat, mostly "dirty clean". Maybe I didn't have my chain dialed in right. Or maybe it just sounded bad to my ears. Kind of whistle-y, like a tea kettle, and harsh, like there was a noisy 1kHz wash over everything. Anyway, I have a few "non-working" Morleys I've bought off eBay for 20 bucks, just for the shell. As opposed to cry babys, there's plenty of room for big PCBs and extra knobs!
Quote from: garcho on January 20, 2021, 11:19:16 AM
So what happened to the original LDRs? I have the same Morley (mine is *only* 20 years old) but I ripped the guts out and used the shell for my own project. Like everything they've ever made, built like a tank. I remember thinking it sounded pretty damn crappy but it definitely worked, all the way up to a couple years ago. Where did you store it for those decades? In a non-climate controlled warehouse in Miami? In the shed behind your home in the Yukon? At the bottom of your pool? ;D
The pedal was stored in a carton box with other pedals for many years without use. That box was moved quite a bit and was stored in a cellar for a couple of years at some point, so i guess humidity from the cellar helped with degradation..
The original LDR's had a very blackened surface compared to the new ones, so i guess they got oxydized ?
Thanks again to everyone for your help! very happy now with my recuscitated pedal! i'm using it mainly as an parallel feed on my pedalboard, its really perfect and absolutely noiseless.
i will have to post some photos of my new pedalboard with the new power supply, sounding really good! i am very happy and satisfied about it. 8)
Cheers
Very Cool you got is back to glory.
Humidity is a devil. We love gear in metal casings, but it's far worse in this respect than plastic. Even gear with plastic upper but a metal bottom plate can be damaged unless you store it the right way up.
Quote from: isophase on January 18, 2021, 03:38:07 AM
Hello,
I finally replaced the LDRs, problem fixed!
Thank you for your help!
I just picked up a PWV that is working only in wah mode. The switch and level pot seem fine, Led's all working...
Where LDR's did you get in the end - the ones from Banzai?
Sorry for very late reply!
I had bought some LDRs from banzai, but they took a long time to arrive. My local electronic shop had some LDRs with different range ratings but I bought them to try, and in the end it did fix the problem.
Did you fix your pedal?
No worries, and thanks for getting back to me.
TBH, I haven't looked at it yet - there's always other projects to finish! - but I hope to get onto this one now.
I've taken the two LDR's off and they're showing about 0.2M when lit; the drawings say "400-850 L on" - is that 400-850 Ohms? Seems a bit low, as most LDR's seem to show a few K when lit...
Incidentally, mine says Rev 3 10/28/92 and looks identical to yours with the exception that L1 and L2 in your image look pinkish, whereas on mine they're the same red/orange as the others - what revision/date is yours?
So, I replaced mine with some generic LDR's from eBay, trying a couple of different values, and whilst it's now working better than it was (in volume mode), it's still a little on the weak side compared to when it's switched to wah mode.
I would really like to know what values these LDR's are supposed to be: as the OP said, the PVW schematic says "400-850 L on", but this surely can't be in Ohms?
Even stranger the PVW II shcematic has LDR 2 as "0-300 L on"!
I've drawn the line at ordering the replacements from Banzai, as thanks to Brexit, I would now have to pay twice as much in postage as the value of the actual components.
I've also seen them advertised on a site in the U.S., but again, due to Brexit, they will now only deal in orders over a few hundred dollars...
https://www.morleyproducts.com/photocell-replacement-ldr/
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https://www.tubesandmore.com/products/photocell-morley-effects-pedals
I opened mine up and took measurements. They are all several megaohms in the rather-dark. With an LED flashlight shone through the cardboard slot as best as I could, LDR 1 and 2 are about 100 ohms, and LDR 3 is a bit over 200. LDR3's cutout is a bit smaller so that may explain the difference.
Wah mode measures toe down ~2.2k, toe up ~5M. Volume mode seems odd - couldn't really get a stable reading even though room was fairly dark and meter has 20M impedance. Toe up or down both LDR 1 and 2 read around 1.8k - 2.0k. Yes - pedal seems to work fine - it's on my pedal board first in line in volume mode and I don't notice any tone or volume loss. The resistances were constantly increasing by a few ohms a second the dropping down a bit every once in a while - I didn't wait longer than 10 or 20 seconds so it never fully settled.
I also noticed that the L1 and L2 LEDs for the volume are both quite a bit dimmer than L3 and the Wah's L4. And L3 - which is only on in wah mode - has no effect on LDR1.
So yes - "400-850" must mean ohms.
Thanks for your reply, and the links; unfortunately these are the guys that will only post an order to the UK if you're buying a couple of hundred dollars worth... :(
If anyone that side of the pond feels like buying a couple, putting them on eBay and letting me know, I'd be forever in your debt.
I guess it makes sense that the lit value should be as low as possible, looking at the circuit, but you just don't seem to be able to get generic LDR's that go that low - apart from those Morley replacements, it would seem.
OTOH, the OP said that he fixed his using some generic ones - wonder where he got them..?
Quote from: TheLoneRoger on July 28, 2021, 07:13:41 AM
Thanks for your reply, and the links; unfortunately these are the guys that will only post an order to the UK if you're buying a couple of hundred dollars worth... :(
If anyone that side of the pond feels like buying a couple, putting them on eBay and letting me know, I'd be forever in your debt.
I guess it makes sense that the lit value should be as low as possible, looking at the circuit, but you just don't seem to be able to get generic LDR's that go that low - apart from those Morley replacements, it would seem.
OTOH, the OP said that he fixed his using some generic ones - wonder where he got them..?
I misunderstood which side of the pond you were on. So why wouldn't you just buy from Banzai? Same part number: https://www.banzaimusic.com/morley-m79-211564-000.html
Or Warwick for a lot less money: https://shop.warwick.de/en/guitar-and-bass-effects/spare-parts-for-effects/21375/morley-spare-part-load-dependent-resistor?c=3855
I found these easily just by searching the part number M79-211564-000 - you might be able to find more.
Unfortunately, as we're no longer in the Single Market, shipping from the EU has gone up a bit (who knew?!):
price of parts: €2.86
postage & tax: €18.50! ::)
Good call on searching by part no. though - however, so far Googling for it in the UK only got me three hits; one genuine but out of stock, another some kind of weird search site and the other, a 404 from er, 'Prestige Dog Services'...! :P
I guess at the end of the day, it's a £90 pedal, so spending £20 to get it working again is acceptable - it just pisses me off at having to pay it, when the parts themselves are peanuts (I didn't vote for Brexit, in case you hadn't guessed!)
Quote from: TheLoneRoger on July 29, 2021, 07:41:46 AM
price of parts: €2.86
postage & tax: €18.50! ::)
I'm used to that kind of thing. Here in Canada, I haven't found any online dealers for pedal-specific parts so I end up ordering everything from south of the border which has a side benefit that using standard postal shipping avoids taxes and duties. Except for most electronic components which I almost always order from digikey.ca - that's actually in the USA but their CA$8 overnight FedEx shipping is cheaper than anywhere else and includes customs brokerage. Even for guitar parts in general, it ends up being cheaper to order from the USA most of the time. So I've just become used to factoring in $8-20 shipping as part of the cost and I avoid ordering just one or two items.