Hawkesman Posted July 15, 2016 Posted July 15, 2016 I asked this question elsewhere and didn't get much response, so I thought I'd try you guys. The serial number dates it to September 1981. New battery, LED comes on, but no affect on sound when switched on. No hiss, no nothing, just sounds like the signal's going straight through as if it were switched off. There are no obvious loose wires or dry joints. I've re-soldered a few joints that looked potentially dodgy, but no luck. Has anyone encountered this before? Any ideas on what's wrong? Should I just bin it? Thanks. H.
capmaster Posted July 15, 2016 Posted July 15, 2016 Do the three controls have any effect on level or output noise?
Hawkesman Posted July 15, 2016 Author Posted July 15, 2016 Hi cap. No they don't. When I press the pedal the light comes on but there is absolutely no change in signal, no pop, hiss, and none of the knobs have any effect whatsoever. So it sounds exactly the same whether on or off. Cheers, H.
Dub-T-123 Posted July 15, 2016 Posted July 15, 2016 There's not enough info here for anyone to tell you exactly what's wrong. If it's passing your guitar signal then you know the buffer is working ok. There could be an issue with the flip flop circuit but the fact that the LED comes on indicates that it is working at least to some degree. If you can't fix it I may be interested in buying it if it doesn't get hacked up in the process. The DM-2 is a nice pedal though it would be great if you could get it working
Hawkesman Posted July 15, 2016 Author Posted July 15, 2016 Yeah - I appreciate that there's not much to go on. I've visually checked the board, pots and wiring, and there's nothing obviously awry with any of the components or connections. I've heard that these are really nice 'classic' pedals so I wanted to get it working just to try it out. Unfortunately it's missing its back plate, but if it worked then I know that replacements are available.
Dub-T-123 Posted July 15, 2016 Posted July 15, 2016 Yeah - I appreciate that there's not much to go on. I've visually checked the board, pots and wiring, and there's nothing obviously awry with any of the components or connections. I've heard that these are really nice 'classic' pedals so I wanted to get it working just to try it out. Unfortunately it's missing its back plate, but if it worked then I know that replacements are available. Yeah I have a working old Boss DM-2 and it's about as nice as a delay sounds without tape IMO but the max delay time isn't very long. It is possible that the trimpots are so badly out of adjustment that the delay chip isn't working. A lot of people try to adjust these for a longer delay time and can't get the pedal working properly again. That's how mine was when I bought it, though I was still getting echoes (just tons of aliasing)
Hawkesman Posted July 15, 2016 Author Posted July 15, 2016 Thanks Dub. Worth a try! There are 3 of them (as I'm sure you know) so do you know which pot does what, and which is the best to try first?
Dub-T-123 Posted July 16, 2016 Posted July 16, 2016 Thanks Dub. Worth a try! There are 3 of them (as I'm sure you know) so do you know which pot does what, and which is the best to try first? First question.. Since the backplate is missing, are all of the ICs still on the board? The delay chip in the DM-2 is the obsolete and very sought after Panasonic MN3005. It's not uncommon for people to remove this IC to repair or build another analog delay project. If that IC is missing, you won't be getting any echo. To adjust the trimpots properly you should really have an oscilloscope, frequency counter, and signal generator. This is why there are so many messed up DM-2s from guitarists randomly adjusting the trimpots until they can't get it working again. It is possible to adjust them by ear but not ideal. There is some good info here on adjusting the trimpots http://atomiumamps.tumblr.com/post/15659263080/boss-dm-2-adjustments
Hawkesman Posted July 16, 2016 Author Posted July 16, 2016 Yup - all still there. It's not a MN3005 though, but an MN3101. It's original I'm sure, as the soldering style and age colour matches the rest of the joints perfectly. The other 2 are an NE570N and a C4558C. I checked out the link you posted, but it's probably way beyond me as I don't have a scope. However I'll have a play around and see what happens. I doubt I can make it any worse than the dead duck it already is! Thanks.
Dub-T-123 Posted July 16, 2016 Posted July 16, 2016 Yup - all still there. It's not a MN3005 though, but an MN3101. It's original I'm sure, as the soldering style and age colour matches the rest of the joints perfectly. The other 2 are an NE570N and a C4558C. I checked out the link you posted, but it's probably way beyond me as I don't have a scope. However I'll have a play around and see what happens. I doubt I can make it any worse than the dead duck it already is! Thanks. The MN3101 is the clock, not the delay. The NE570N is the compander and the 4558 is buffering
Hawkesman Posted July 16, 2016 Author Posted July 16, 2016 These 3 are the only IC's on the board. The only thing that looks a bit like an IC is white and has 7 legs per side. No idea what it is. Everything else is caps, trim pots, resistors and diodes. Also some green two-legged things - I know not what they are!
Dub-T-123 Posted July 16, 2016 Posted July 16, 2016 These 3 are the only IC's on the board. The only thing that looks a bit like an IC is white and has 7 legs per side. No idea what it is. Everything else is caps, trim pots, resistors and diodes. Also some green two-legged things - I know not what they are! The thing with 7 legs per side sounds like the empty socket for the MN3005. It would be best not to touch the trimmers until you get an MN3005 to minimize the adjustment necessary at that point. Most of the MN3005 for sale online are fake and wont work. Unfortunately, to get the real one is relatively expensive This is a modern copy of the MN3005 that should work. I have bought a lot of parts from smallbear and they are at the top of their class. Do not try to buy a MN3005 from China. smallbear-electronics.mybigcommerce.com/mn3005-re-makes-xvive-audio/
Searcy Posted July 16, 2016 Posted July 16, 2016 It should look like this. http://www.ebay.com/itm/Xvive-Audio-MN3005-BBD-Analog-Delay-/331860686518?hash=item4d447036b6:g:9TAAAOSwDFNWE9Xq
Dub-T-123 Posted July 16, 2016 Posted July 16, 2016 If you use the xvive remakes in either link from me or Searcy you should be good to go. It's still not a good idea to try adjusting the trimmers by ear. The trimmer near the top of Searcy's pic is the bias. The one in the middle is the "cancel" which kinda affects the amount of repeats and helps to eliminate noise on the repeats. The bottom trimmer is the clock which is also interactive with the noise on the repeats. The MN3005 can't do much more than 300ms delay times without noise issues regardless of where the cancel trimmer is set. So those two pots are very interactive and need to be set somewhat precisely to get the most out of the pedal. You might not want to mess with the bias pot is kinda weird to adjust by ear. Probably touch it last You can get close tuning it by ear but it probably won't be "proper" specs
Hawkesman Posted July 16, 2016 Author Posted July 16, 2016 Searcy - Yup, mine is identical, except for the missing MN3005! Dub - Now you say that, I realise that I should have recognised it for the empty socket it is. Doh! Obvious really, but I guess I was thrown out by the fact that the other three IC's are hard soldered to the board. I wonder why they didn't do that with this one. It's almost like they were anticipating failures and therefore expected that regular replacement would be required. I haven't, and won't, touch the trimpots (not yet anyhow), and hopefully no-one else has either, and maybe they're still at the factory settings. However the guidance as to which one does what is really useful. I wonder why the the MN3005 was removed in the first place? Makes me wonder if the pedal was faulty in some other way which made the IC more valuable than the pedal itself. Thanks to both of you for all your help. I'll let you know how I get on. H.
Hawkesman Posted July 16, 2016 Author Posted July 16, 2016 I'm betteing you've got an easy fix there. Here's to hoping!
Hawkesman Posted January 24, 2017 Author Posted January 24, 2017 I'm betting you've got an easy fix there. You were right! I eventually got round to ordering the Xvive chip, and popped it in. The only other thing I needed to do before trying it out was to replace a 16k resistor which had broken. It worked fine, and everything seems to do what it should, and there's no background noise, at least not that I can hear. I have one last question though - the slowest repeat rate it'll do is roughly 3½ per second - this seems to be near the 300ms that Dub referred to earlier, so I'm assuming it's normal for this pedal (before I go and screw it all up by tinkering with the trimmers!) Thanks for all the help guys. H.
Dub-T-123 Posted January 24, 2017 Posted January 24, 2017 You were right! I eventually got round to ordering the Xvive chip, and popped it in. The only other thing I needed to do before trying it out was to replace a 16k resistor which had broken. It worked fine, and everything seems to do what it should, and there's no background noise, at least not that I can hear. I have one last question though - the slowest repeat rate it'll do is roughly 3½ per second - this seems to be near the 300ms that Dub referred to earlier, so I'm assuming it's normal for this pedal (before I go and screw it all up by tinkering with the trimmers!) Thanks for all the help guys. H. If you're getting clean repeats without noise issues and approx 300ms max delay time I would just leave the trimmers as-is personally. Nice job fixing the pedal. These are great delays, hope you enjoy it
Hawkesman Posted January 24, 2017 Author Posted January 24, 2017 If you're getting clean repeats without noise issues and approx 300ms max delay time I would just leave the trimmers as-is personally. Nice job fixing the pedal. These are great delays, hope you enjoy it Thanks Dub. I'll leave it alone, and start using it!
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