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Topics - Rockhorst

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Open Discussion / Looking for help with an actual vintage EHX Memory Man
« on: February 10, 2019, 05:52:11 PM »
note: pictures of the unit attached.

Someone sent me an early EHX Memory Man hoping I can repair it. I'm a bit apprehensive to start working on it, so I hope someone with experience with these units can help me out a bit. It looks like there have been some modifications over the years, the transformer is dead and there's a loose wire coming from the boost switch. No clue if the delay chips are still good. Still looking for a verified schematic for this particular unit.

On the EHX forum I found that a replacement transformer for the DMM is the F-115X which Mouser carries. I'm going to compare some specs, but I expect it will work with the MM as well. I have a EHX 24V center positive wall wart, was wondering if I can use this to test the unit before buying the transformer.

Any other suggestions for testing the unit are very welcome.

Tech Help - Projects Page / Harbinger One - Rate LED not flashing
« on: December 22, 2018, 10:21:20 AM »
Two questions:

1) what's the benefit of the buffered rate LED circuit in the 2015 Harbinger compared to the old version? Is it to prevent ticking?

2) I subbed a BC560C for the 2N5087 in the rate LED circuit and the LED doesn't flash now. It does sometimes, but usually is just permanently on. Maybe I see a very faint flickering. Could this be due to the substitution? I looks to me like the 1uF cap may be charging up to quickly and the potential not going down anymore. Maybe subbing a smaller cap will fix it, but maybe there's other ideas?

Other than this, the build is working fine by the way :)

Open Discussion / Understanding Ring Modulators (Physics article)
« on: November 16, 2018, 02:04:24 AM »
I'm toying with the idea of making some pedal/effects based education kits to use in my physics class room. It's potentially a great way to get kids more involved in the subject of electricity and electrical systems (as VFE has also clearly demonstrated). Anyway, this week I received the latest issue of The Physics Teacher and one of this month's freely readable articles discusses ring modulators and specifically the Moogerfooger MF102. How cool is that :) Caveat: it doesn't discuss the actual electronics, but goes into how ring mods shift frequencies around.

Read it here
(there's also a downloadable PDF available on the same page)

Open Discussion / Desoldering station suggestions anyone?
« on: October 25, 2018, 05:01:16 PM »
I'm getting more and more tired of using braid and a sucker. I think my (repair) work would really benefit from a dedicated desoldering station. I'm guessing the heat stress on components would also be a lot less. These things seems to be quite expensive though (much more expensive than a reasonable soldering iron). Any suggestions, cheap (but good) stuff or expensive? Preferably something that is easy to get in Europe. What should I look out for? Features, things to consider for trough hole vs smd etc. I also use both leaded and lead free stuff. I have two separate irons for that, does one need to different suckers?

Open Discussion / Question for EMG connaisseurs
« on: October 09, 2018, 01:47:31 AM »
I've got a few Jackson Rhoads guitars with EMGs. One has just a single EMG 81 in the bridge and when I'm in a Swedish metal mood that works out just fine. I've also tried a spare 85 I had around in the bridge position (heard some good stuff about that) but didn't like that. Sometimes I do want to use the neck pickup but I've found that I also don't really like the 85 in that position. It's hard to describe. It's not actually muddy, but it feels like it. Sluggish, not enough attack. Something like that.

So the question is: anyone else here
1) like the 81
2) dislike the 85
3) got a good alternative from the EMG pickup line? (not looking for a complete wiring overhaul).

Open Discussion / NVD - or - that's what friends are for
« on: July 12, 2018, 03:51:06 AM »
So Björn, my Dutch-Swedish brother in metal, recorded a record last year with his band Graceless called Shadowlands. It's OSDM, so not too complicated, straight for the kill, zombie themed death metal. They got very favourable reviews from various magazines (average 8 out of 10). Anyway, I've been designing a distortion pedal for him since August (the Saturn V) for which the (for now) final version just got released. We've been tweaking his live rig over the past few months in the rehearsal space and it's a lot of fun seeing his live sound come together. It's the part I've always enjoyed the most: helping people sculpt their sound.

NVD: new vinyl day. Their record just got a vinyl release, see attached picture. Bottom right corner. How flippin' cool is that? Humbled and stoked at the same time. So the least I can do is give him a plug here as well, see above (not a lot of metal people here I believe, but hey).

Build Reports / Harbinger 2, sort of ;)
« on: February 26, 2018, 10:54:40 AM »
Sorry for the tongue-in-cheeck title Brian ;)

A client asked me to install his Dry Bell Vibe Machine into a Shin-Ei wah enclosure. The original pedal has a ludicrous amount of options (google the options manual to go insane). Now it also has that vintage mojo ;)

Open Discussion / NWD
« on: January 05, 2018, 08:34:58 AM »
New Workplace Day! There's a baby boy coming sometime in the middle of March, so we had to rethink the rooms in our house a bit. We decided to move the soldering room to the other side of the upstairs hall. Once we had installed a desk and stuff like that, it took the time between Christmas and New Year's to move everything.Why? Cuz I'm not the tidiest person in the universe. Luckily, my girlfriend loves sorting stuff. I ordered a few extra parts cabinets, explained the difference between resistor, capacitor and IC markings and we set to work. I've never before been this organized. Lighting is not ideal, but below is a guided tour in photos:

The new room is smaller and has a sloping ceiling, but actually, I now feel it's the better room because it has no weird corners and such like the other one. Behind those white panels at the far end, there's secret storage space.

On the left, there's storage (boxes boxes, parts parts, pedals pedals) and a place to populate PCBs

As I said: never been this organized before

Pedals and a DIY 18W combo amp hiding under the cover

On the far end on the right is a space to assemble pedals or take them apart, with appropriate tools nearby and containers to stash the parts so they don't get lost while working on the pedal.

Also shown here is my little test setup: a looper with She Sells Sanctuary played into it, a sort of break out box with aligator clips to hook up circuits, and a small practice amp. Behind that is a power supply. Simple, but this makes repair jobs and testing so much easier.

And finally, this is where the soldering should happen. I bought a second soldering iron. Instead of switching tips (and waiting for them to cool down) I now can just switch soldering irons when changing from leaded to lead free. I've switched to lead free for new projects permanently. It's actually working out pretty well. The parts bins contain switches and pots.

I've been assembling a 6u rack unit for 80s metal and hard rock toonz. The JMP-1 I bought second hand has some problems. It sometimes loses about 20dB of signal level. Not fully intermittent, but very annoying and unpredictable. So far I've concluded that the input jack could use a replacement (ordered it, it's an odd ball part, mirrored from the standard switched jacks). The tubes inside are still the original Marshall ones, so I'll replace those as well. That may solve all my problems. However, there's also a 3.2V Lion battery inside that maintains the presets in the memory and will need to be changed periodically. Here's the thing: I can't get the circuit board out (at least, not in one piece, I suspect) and can't find a service manual, step-by-step guide or whatever.

So, any JMP-1 users here with some experience with taking the unit apart and modding it? There's really very little on the net to be found.

Open Discussion / Ibanez WH10 tone suck
« on: October 31, 2017, 02:51:01 AM »
I'd like some input on this one from here if possible. I posted it over at DIYSB as well, seems to best fit the Open Discussion part of the forum. Take a look at this schematic if you can. Any clues why this sucks massive high end and volume in bypass? The pedal doesn't suck tone with another buffer in front of it and I'd like to understand why. I've removed those 2n2 caps and tried raising the input impedance by bumping the 510k to a 1M, but with little effect. My next bet would be to remove/or lower the 220R series resistors at the input, but I doubt that will do much. My thoughts are drifting more towards the input stage not being able to drive both the clean signal and the wah signal. It's being split in two/three and later mixed together when the effect is on.

The fix, in any case, is easy: put another buffer in the enclosure, either at the input or between clean and wah signal to separate the two. I'd just like to understand it a little bit better.

Open Discussion / NGD - Jackson RR24 1990
« on: October 28, 2017, 08:39:32 AM »
I've been hunting this guitar for years, finally found one in absolute mint condition for a steal! (600 euros, which is about $650 right mint condition I think this could fetch $1000 second hand). This is a Jackson Rhoads RR24 from 1990, one of the first to be produced in their Japanese factory. I'm really amazed that after 27 years, the wing tips are unscathed. This is now the oldest guitar in the collection (of 14) There was some gunk on the frets, but two light passes with 0000 steel wool reveiled frets about as shiny as they get. There's a weird design choice with the binding: there's binding along the full length of the neck and headstock, but it's black! So near invisible ::). I had a spare EMG pickup lying around, so I spray painted it yellow and popped it in to give it that extra touch :) I've got two more Rhoads models: a 2001 RR1 and a recent cheapo RRXMG. The build quality of this RR24 is miles above the RRXMG and very comparable to the RR1. I'd say they can almost rival each other in quality, the RR24 being a bit lighter, which is nice.

Enough talk! Picture time

Now, who will join me in developing silicon sleeves for pointy guitars and taking it to kickstarter hahaha? I'm gonna have a fit if I ever bump this thing into something, cracking the finish. That's the thing with these guitars. To me they are about the sexiest guitars in existence, but so so so fragile...

Build Reports / Nucleon Super Nova
« on: September 21, 2017, 11:54:28 AM »
Bit of a shameless plug, but I'm genuinely proud and surprised by this one. I took a Marshall Guv'nor and tweaked the circuit quite a bit. I changed the tonestack to a Baxandall with some clever mods to keep the outer bass and treble frequencies in check and altered the frequency response of the pre-clipping stage. I first made a big unit with a lot of switchable mods to experiment (I dislike breadboards as by the time I've changed a component I've already forgotten how the sound was) and last week finalized the prototype. I'm going to update the build document this weekend. If you want one, check this link ;) I'll give away one pcb for free to the first one to post the two metal songs referenced in the vid.

Big unit with mod boards

Final prototype in one of PPP's less succesful powdercoating experiments

And a video shot with a crappy iPad microphone. Going for a big metal sound here, but this thing can also sing the blues! Riding the volume knob is key to that.
Jackson Rhoads 1 with EMGs (metaaaaaal) into the supernova into a power amp (so no other preamp, the supernova is the pre). Sound quality is not the best, but it's enough to know that this thing can sing, scream and crush.
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Open Discussion / ICL7660 charge pump and filtering capacitors
« on: August 26, 2017, 06:18:06 PM »
I chanced upon this topic at EEVBlog a while back. Very interesting stuff and fun to see. The thing I took from it and applied to my personal builds is the following. If you use an extra power filtering cap parallel to an electrolytic, a film one is pretty much useless whereas  a MLCC type cap does quite a good job. I've not scoped anything myself but that's what the described experiments suggest to me. MLCC performs at least similar to film at this task and price is also nothing to stop you from using them. Thought that was worthwhile to share.

Edit: Reddesert below points out that I misread scale and that a film cap does seem to have some effect.

Tech Help - Projects Page / Kingslayer motorboat at high gain
« on: August 12, 2017, 03:05:41 AM »
I built a 2015 KingSlayer (so the current version) and it works until I crank up the gain to over the last 30 degrees or so of the turn. If I put it right on the edge, I have normal signal for a few seconds and then it craps out into a 'bop bop bop bop bop bop' tremolo/motorboat thing (at about 5 bops per second). I have to turn the gain way down (to about 40%) for it to get itself back together again. What you would call hysteresis. Level and tone controls have no effect on this, they just function as expected. So something craps out at high gain. I built one a while ago that worked fine, so I must've made a mistake somewhere, but I can't find it. Anyone a suggestion what/where to look?

Open Discussion / Good read if you want to understand JFETs
« on: June 21, 2017, 04:52:04 AM »
Accidentally found this on Google, haven't seen it mentioned before but it's very well written and will give you a practical working understanding of JFETs and their datasheets.

JFETs the new frontier

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