Dunlop MXR "Block Logo" Phase 90 Help

[soupbone]

I did the Eric Hansen "Block to Script Mod" To one of my dunlop mxr phase 90's.I took out C11 & C12,and lifted one leg of of R28 and put a spdt switch between the two modes.One problem i ran into i noitced was i could'nt get the speed to slow down that much at zero.I sent Erik an email,and he said to put C11 & C12 back in.They look like little yellow tantalum caps,but it doesn't appear that they are polarized?Does anybody know what kind of caps those are?(what kind,and they're value).

[soupbone]

I looked on Erik's page and C11 is a .01uf and C12 is a 680 pf.I'm not sure what kind of caps they are?(material)Dipped mylar?Anyone have any ideas what they could be?

[Fender3D]

Schematic link pls
You'll have an hard time looking for tantalum 680pF caps...
Anyway, if you found their values (.01uF and 680pF), then those caps have nothing to do with LFO speed...

[soupbone]

I called Dunlop today,and they said those 2 caps are mylar.They look like monolithic ceramic,but I'll take his word for it.If those 2 caps don't have anything to do with the speed,how i get the speed to slow down?I tried turning the trimpot(marked it with an ink pen)still didn't slow down

[Fender3D]

Dunlop answer may be vague 'cause there are many P90 revisions, each with small differences...
You should have 2 electros (15uF) connected in series (+ with +) they should be near one op-amp IC.
Increasing those caps you'll lower the LFO speed.
But my question is: "did your P90 work ok BEFORE the mod?" 'cause, should this be the case, you might have broken any trace, or injured any other component on PCB...

[soupbone]

I'm not sure.It was a friend of mine's pedal,and i did the mod without hooking it up first.I wen't and bought some 22uf El. caps today..Swap them out and see what happens.Thanks for the info Federico!

[Fender3D]

OOps 
I was looking at the wrong LFO...
there are so many P90 out there 
Anyway you should have 2 electros, one (usually 15uF) dealing with the LFO and another filtering Vbias.
Looking at the picture at Erik's corner there's a tantalum cap right above "C11": I bet it's our friend...
You can swap it with a "usual" aluminum electro.

[zombiwoof]

I just looked at Erik's Corner again, I hadn't been there for some time, and noticed his Phase 90 page no longer has the great pics of older Phase 90 boards and the info on them that he once had there.  That info was invaluable to me when I modded my older Dunlop Phase 90, which was identical to the vintage block Phase 90's (case-mounted jacks, pots, and switch, and the same board layout).  I wonder why he got rid of that stuff?.  Now he only has info for the newer Dunlops with the board-mounted pots, jacks and switch.

Al

[soupbone]

Cool!Thanks!

[soupbone]

Hey AL,I didn't the old pics Erik had on his site,Just the one he has on there know.I'm curious to what he had on there before.

[zombiwoof]

Hey AL,I didn't the old pics Erik had on his site,Just the one he has on there know.I'm curious to what he had on there before.

I think he has re-done his pages since I was last there.  He used to have a link on the Phase 90 page that sent you to pics and discussion of the various boards in the original Phase 90's (script, block, and the in-between variations).  I have an early Dunlop Phase 90, in the early Dunlop MXR pedals, they are made exactly like the last block versions of the originals, that is they have case-mounted jacks, switch, and pots, and the same boards with the through-hole components (I hear the latest Dunlop MXR's now have SMD components, and all jacks, pots, and switches are board-mounted).  Most of the info around for Phase 90 mods only talk about the recent Dunlop pedals, when I tried to mod my early one, I had a terrible time finding info on the position of the various components to be modded to put it to script specs, until I found that info on Erik's pages.  I sure wish he hadn't gotten rid of it, it really helped me at the time.  I may have printed the stuff out, but I'll have to search through all the printed stuff I have to find it, if I did print it at all.

It is possible that it was just a link to some other Phase 90 page, if so I hope someone can find it.

I don't know if Erik reads this forum, if he does I would suggest he put that info/link back in to the Phase 90 page.

Al

[vanhansen]

Hi.  When I redesigned the site, I decided to include only mods that I have done myself with my own research.  Granted, everyone has done the R28 mod but I also had done the switches and output buffer myself and wanted to share those along with with R28 mod.

That page comparing the older models was just a conglomeration of what was posted on this forum by another member.  With a little searching, all of that comparison info can be found here.

[zombiwoof]

Hi.  When I redesigned the site, I decided to include only mods that I have done myself with my own research.  Granted, everyone has done the R28 mod but I also had done the switches and output buffer myself and wanted to share those along with with R28 mod.

That page comparing the older models was just a conglomeration of what was posted on this forum by another member.  With a little searching, all of that comparison info can be found here.

As I said, that info about the older Phase 90 boards and the pics especially were invaluable to me when modding my early Dunlop Phase 90.  I couldn't find that info anywhere else, and I had searched this forum before finding it.  I really doubt I could find all of that stuff by searching here now, and I wish you hadn't deleted it.  But, it's your site, and I guess you can do whatever you want with it.

Thanks for the explanation, though.

Al

[vanhansen]

No problem.

I found the thread where it was all discussed.  Starts on the second page by cd.

http://www.diystompboxes.com/smfforum/index.php?topic=26093.0

[zombiwoof]

No problem.

I found the thread where it was all discussed.  Starts on the second page by cd.

http://www.diystompboxes.com/smfforum/index.php?topic=26093.0

Thanks for going to the trouble of finding that thread, I've bookmarked it.

However, I seem to recall that your page had more info than that, if I'm remembering correctly it graphically pointed out R28 and various other components, and had some text about the various revisions of the circuit.  But that thread does have some good info.

It's possible that the information about the original Phase 90's might be found on the net now somewhere, I haven't searched for a while, but at the time I was trying to mod mine, your page was the key to successfully doing the mod.  Many people don't know that the first versions of the MXR pedals that Dunlop put out were virtually identical to the last block logo originals, they had the same board layouts and separate switches, jacks, and pots, not the board-mounted stuff they are doing now.  Some people say that Dunlop actually had some leftover boards and parts from the old MXR company, but I don't know if that's true.  The Dunlop Phase 90 I have is based on the last original block logo circuit, so it has the circuit from that version including the feedback resistor that the original had.   I also have an early Dunlop DynaComp, and it has the same features.  They only made them like that for a while, then started changing them, having the switch, jacks, and pot board-mounted, and changing the layout to do that.  I think they are now using SMD components in the MXR pedals, but that's just something I read somewhere.

Thanks,
Al

[vanhansen]

Not really.  All that was said in that thread is what I had on that page.  Same images too. 

There is a good chance the Way Back Machine has an archive of my old site.