Pristine II restoration

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    • #365
      Nolafile
      Participant

      Greetings, I’m restoring a set of Pristine II’s and currently in the process of replacing the burnt resistors. Luckily it appears the wiring in the same area has survived. So it should be fairly straightforward installation of new resistors and perhaps replacement boards. This time around providing slight spacing between the resistors and the boards. Which should reduce the current drama. At this point I’m assuming the panels are still functional. So the question is what other weak areas should I be investigating while I’m in there? Perhaps the wiring connection points at the panels? I’m noticing discoloration on the back of the vented brilliance pots? I’d say chances are high that they are fouled internally from the pollutants created by the burning fiberboards. So I’m considering installing a resistor in place of them? Which I suspect would also be a sonic high frequency upgrade as well. So what would be the best size resistor to employ? Also does a detailed instructional exist on correctly connecting the bias taps? Anybody happen to have schematics or service data handy? These are serial 89 and I believe were produced in 2005.

      This is quickly becoming quite a project. But I suspect the results will be well worth the time invested. And many thanks in advance for any assistance.

      DD

    • #366
      yoshi
      Participant

      Hello DD:

      I have been fully updating my Pristine 2 this past year.

      1. Bypassed the tweeter pot with a 50 watt , 4R metal fin resistor( Mills 4R, MRC50 50 or 75 watt). Very cheap cost for a significant upgrade in HF presentation. $5.00 each…

      2. Factory installed Toroid 1: the Toroid 2 will not fit in your backlplate housing, and you may even have to put a spacer piece of wood to raise our the backplate housing up to accommodate the greater depth of the Toroid 1 transformer. I did with 3/4” thick strip.

      3. Replaced the bias supply module with the new regulated supply. This was installed my me. Roger will provide you all the parts, new bias control pot and wiring schematic. The new module will not fit in flat, so you must cut of one of the flanges ends and mount it on end for it to fit. 2 way tape, hot glue and a new small door hinge on the existing mounting screw works perfect to securely get it in. Has at least 30% more bias capability, and is voltage regulated.

      4. New bass-focused panels, mounted in the current pristine 2 frame. The pristines have 60 degree dispersion angle and you will need to provide Roger with the exact width of panels to have them specially made, due the wider panel than the current 545.
      They can be installed by you at home. The new panels take some time to break in, but are quite an upgrade, particularly the bass area. However, the original panel worked great for me for over 20 years. I had to turn up the old bias supply almost 100% to reach a full bias on the new bass focused panels. The new bass focused panels have a wider spacing of the grid wires, which Roger says enhances low frequency production. Consequently, I have found that the old bias modules a little under capacity for the bass focused panels.

      5. Clean the 3 banana plugs form the backplate to the panels and check the tension on the plugs for secure fit.

      6. I also had a panel arching repair before I purchased new bass focused panels. A repair is home doable if you have an issue there, with a degree of difficult and a lot of time. The Mylar is extremely delicate. If you have to wade into the panel for investigation, do not touch the mylar or even hard blow on it. You will pierce the Mylar with almost no tension on the membrane. I did… they will still work, but you will likely never be satisfied with a pierced panel membrane.

      7. If you do not the tip toes for these frames, get them. Big difference on this speaker.

      8. sallie home made backwave panels. firm rigid insulation panel,5’ H x 4” ( double up on 2”) thick, just placed behind the frame bas, angled parallel to the panel, centered, will improve acoustics and the front wave launch. I made a a stand with wood base, 2 dowls on the plate for rear support, and 2- 4 ‘ dowls mounted and glued vertical in the base, for panel support. works great and you can’t see them from the listening position.

      I would also suggest you figure out why the resistors blew and if there other electrical component issues in there.

      Good luck and keep us posted.

      Ken

      • #716
        Stphotog
        Participant

        Hey Ken cool write up…

        Hey where did u get a torroid for the pristine? Roger said the hot rod wont fit..

        I just replaced my caps today (only did the left so far. Even those i had to.put in a new spot.

        Also where did u get a plan for the diffuser?

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      • #718
        Stphotog
        Participant

        Hey Ken cool write up…

        Hey where did u get a torroid for the pristine? Roger said the hot rod wont fit..

        I just replaced my caps today (only did the left so far. Even those i had to.put in a new spot.

        Also where did u get a plan for the diffuser?

        Not sure if i posted this twice

    • #367
      John V
      Participant

      Hi,

      I’ve attached a wiring pictorial for you to peruse. The diagram may not match the wiring of your Pristines so I would suggest you contact the factory to obtain the correct one for your speakers.
      It would help if you posted a few pictures of your backplates to give us a better idea of what your describing.

      I’m unclear as to what you mean by “bias taps”. The bias level is set via a variable resistor. To set proper bias the shaft on the resistor is rotated clockwise to increase the bias to the point where the panel starts to crackle and then backed off to the point where the crackling just ceases.
      A number of people have replaced the brilliance control with a fixed value resistor by setting the brilliance to a level that gives a proper high frequency balance, measuring the resistors value and then replacing the control with the measured fixed value. I would use a 50W non inductive style resistor.

      Good Luck with your restoration, I hope the panels themselves are functional and in proper order.

      John

      • This reply was modified 11 months, 1 week ago by John V.
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    • #370
      yoshi
      Participant

      DD and John:

      I agree with John’s comments on tweeter value. I normally ran my brilliance control around 12:30 setting on my original Pristine 2. I measured the resistance at 3.9 ohms. The single resistor will sound much more open, so I slight round up to 4 ohms was perfect in my situation. I use all tubes for pre and power.

      Ken

    • #374
      Nolafile
      Participant

      Great info! Thanks to all. I seem to have improperly defined the EQ taps as bias. I apologise for any confusion. They indeed are transformer EQ taps. One row for the bass and another for the mid-range. And are ID’ed left to right as -3db 0db +3db. And are also color coded black white red. The previous owner only supplied one jumper per speaker. So I’m assuming I need to source another set to adjust both bass and mid on each.

      The overheated resistors in question are 7.5ohm 20w sand resistors. Which are tightly bundled 4 square and board mounted in each interface. For whatever reason the 2 mounted on the inside of the board seem to have run hotter than the outside facing pair. The 4 pretty well roasted the fiberglass and definitely compromised all solder joints in that area. After removing and sanding all 8 resistors ends. It now seems that only 2 of 8 are actually out of spec electrically. But all are pretty well roasted. All of which I suspect led to higher resistance solder joints along with higher required drive levels. And mucho heating. Unfortunately, I’m clueless as to what the previous owner employed for amps. But I suspect they were sizeable and humping.

      I’m definitely going to disconnect the brilliance pots. As I suspect the improvement in upper reproduction may be substantial. Plus I suspect the pots have seen better days and are polluted via the rear vents. Thanks so much for the great data on those resistors. I’ll get on the research and get them in the mail.

      I have pics which are no doubt worth thousands of words. But presently it seems due to handheld device issues. I’m incapable of uploading at this time. I’ll try later when the desktop is near.

      I’ll get the parts orders underway and let you know the progress. Hopefully the panels are still unburnt and in good shape. The socks are still tight so they should have only been externally exposed to microdust and humidity.

      Again many thanks for all of the assistance.

      DD

    • #375
      Nolafile
      Participant

      Well upon researching I just stumbled upon these modern Vishay TO-220 case style resistors. Interesting and high wattage. And I suspect lower overall Z. I wonder if the sonic results would be better than the aluminum cased milspec, or classic sand wirewound types. Being for the topend they might be the ticket.

      Any thoughts of ideas are most welcome. In fact if anyone knows what sonic differences exist between the classic sand type and the aluminum housed modern wirewounds? I’ve yet to experiment with these so I’m officially ignorant on the subject.

      Nevertheless check these Vishays out.

      Thanks,
      DD

      https://www.vishay.com/resistors-fixed/list/product-50050/

    • #376
      John V
      Participant

      How are you going to mount them as they need to be heatsinked to meet their power rating?
      Is this as a replacement for only the brilliance control or also the 8
      resistors on the input side of the Toroid?

      John

    • #377
      Nolafile
      Participant

      Hi John,

      I suspect that could be accomplished by attaching it to the backside of the existing pot. Which could be done with a high grade thermally conductive adhesive. Or even drilling the pot backplate for a 6 or 8/32. It definitely has the backside surface area. Or even attaching a standard TO-220 heatsink. I’ve inquired with the Vishay engineering team about audio signal usage. So we shall see what they have to say. They have to be way lower in L & C than the beefy circular wirewounds tracked by a carbon tooth. I was expecting around $30ish each. Looks like they are around for under $10.

      I did just take meter reading off the brilliance pots. And they are dirty with dropouts. But I suspect would survive a carbon tec flushing. So perhaps I’ll just flush them for now to get a closer bearing on where the happy setting is for this room.

      DD

    • #378
      Nolafile
      Participant

      Hi John,

      For the brilliance. Sorry I overlooked part of your question. I haven’t considered them for the other 8. But I guess it’s a possibility. So what can I expect to encounter under the bottom panel covers? They appear to be gun stapled on. I guess I should lay them over and closely inspect the terminations for corrosion to the panels themselves.

    • #379
      Nolafile
      Participant

      Hi John,

      I just had a look at the diagram you sent. Thanks a million. Very interesting and I wish there was a breakdown of the audio board. By looking at the pic. I’d say they doubled the number of resistors in order to eliminate this burning issue. I may make a board from perf fiberglass using military silver/teflon wire for the traces. The burnt boards are pretty smelly to say the least and have to go. Let me see if I can now post a few pics from the desktop.

      Many thanks again.
      DD

    • #381
      Nolafile
      Participant

      Sorry for the delay. Here are the pictures.

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    • #385
      Nolafile
      Participant

      Here is the last picture. Thanks for all of your help!

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    • #387
      John V
      Participant

      Looks like that is the earlier input circuit. There was a revision to increase the impedance of that circuit to make it easier for tube amplifiers to drive the speaker. At one time there was an upgrade kit which included a new circuit board.
      I would call the factory and speak to Connie to see what is currently available.

      John

    • #388
      Nolafile
      Participant

      Hi John,

      I kinda figured they most definitely released a revision. I think I’ll stick with the oem lower impedance. The revision doubles the amount of resistors to redistribute that damaging heat load. Increasing the overall inductance is likely counter productive to overall sound quality. So instead of the oem 3.75 ohm 40w 10% bundle. I’m going to try a single 4ohm 50w 5% ceramic spaced off on a homebrew breadboard. In theory that could be slightly lower in overall Z than the oem. Stepping up to 8 units is a large increase in inductance. I generally strive to keep parts counts to a minimum especially in signal paths.

      Perhaps it would reflect better with tube amps with the higher Z. But that depends on your output xformers. Most will drive the lower Z without complaint granted they may run a tad hotter. The overall plan here is to bi-amp with sealed passive subs. So the stats won’t even see anything below 50hz to begin with. Which should have the added benefit of unloading the panels of large excursions. And in this case it’s the higher frequencys where they dive down. Which leads to a few questions. On these brilliance pots, how much noticable change occurs from say 1 o’clock to wide open? That seems to be a range of around 4 ohms down to .4 on the pot. So the manual states they bottom out at 3 ohms Z. I’m assuming that is with the pot set to maximum? I wonder where it would bottom with 3 ohms added on the pot? I’m assuming around 4.5ohms minimal Z.

      Nevertheless I’ve got plenty to learn in the near future on operating these. And the manuals explaination of employing the EQ taps leaves plenty to be desired. At least it tells you one way how not to blow your amp. I can clearly see why they installed switches on the later models. As deciphering what little instructions lie in the manual is beyond normal human comprehension.

      The parts should be here soon within a week. And with a little luck they may live to sing again.

      DD

    • #389
      John V
      Participant

      AFAIK the brilliance control (L Pad) has a linear taper, but that said, the only way to know for sure is to measure it.
      As to mounting the resistor, why not just remove the brilliance control and mount your resistor to the backplate with a screw/washer passed through the controls mounting hole in the backplate? Add some thermal paste for heat transfer and away you go.

      John

    • #391
      Nolafile
      Participant

      Ken,

      Thanks for the detailed listing. After examining the diagram it makes more sense. So the toroid is standing on edge and causes you to have to elevate the outer housing. Interesting. At least for the time being I’m sticking with the oem. As I want to get aquatinted with the original sound prior to stepping forward.

      I also notice that the later design has added -6db selections for the EQ settings. Which seems odd and I guess is related to the new design producing higher potentials. So I’ll have to research it, but I wonder if this has increased the older 88db efficiency rating?

      I see you’ve cleaned these banana jacks before. Remarkably I haven’t noticed these yet. Are they located recessed in the HV box? I notice the drawing refers to BJ at the connections on the box. They must be well hidden. I’ll have to have a close look tonight.

      Thanks,
      DD

    • #429
      Nolafile
      Participant

      Good idea John. On the brilliance resistors I’m still debating ordering fancy Vishays. So far the engineering inquiry to them has not been followed up on. Half the input resistor order just arrived. The 50w resistors look pretty good. Idk how the original resistors were able to conduct the required input power with such small leads. These should definitely be a improvement. So this weekend the plan is to rework the backside of the EQ taps. Which at a minimum need to be dismantled, decarbonized and resoldered. Plus revarnish the side of the xformer laminations. Which burnt off causing minor light surface rusting. The input connections were also cooked loose and need a good polishing prior to reassembly. I may devise a point to point layout and discard the fiberglass input boards. As it all really need a bit more breathing room. After measurements on the larger replacement resistors. It looks like the input resistance will rise slightly from 7.5ish to 8.2ish ohms. And from 80 to 100 watt in rated wattage. Until recently I didn’t realize that these smaller panels require higher drive than the larger models. I normally run a 260wpc SS amp on my moderately inefficient mains. After this discovery I’m not sure if it is up to this task. But we shall see in a week or so. I think I may mount the interfaces on some filter stock 3/16″ or so off the bottom. And perhaps devise a topside vent. As I suspect a slight chimney flow wouldn’t hurt.

      DD

    • #440
      Nolafile
      Participant

      Hey Fellas!

      Well here are the latest updates. The input circuit boards have been replaced with a tidy point2point install. I made solid copper heatsink/supports for the new power resistors. Which corrected the oem layout issues and really opened those resistors up to breath. I decided to stick with the oem 7 conductor twisted solid copper input wire. But paralleled a small silver stranded conductor to them. A few hours ago I got them back together and hooked up.

      One requires about 1/3 on the bias pot to obtain crackling. The other only around 1/5 and develops crackling along with popping. After applying audio it seems the 1/5 bias unit has a bit lower output than the other. Plus perhaps some panel issues. As u see moderate drive I can hear distortions and can see what appears to be a few areas where the membrane appears to be loose. So instead of HOS tonight I’m retreating back to the shop to pull the sock for a close inspection.

      Wish me luck as it seems I’m gonna need it.

      Cheers,
      DD

    • #719
      yoshi
      Participant

      Hello:

      I sent the backplates to the factory for a Toroid 1 transformer installation. The new Toroid 2 will not fit in your backplate enclosure. Roger may still have the Toroid 1 in stock.

      Even with the Toroid 1 installed in the backplate, it would fit in the enclosure. I installed a 1/2” wooden square( 4 separate pieces, each one drilled to arrange with the housing mounting screws. This effectively raises the backplate to accommodate the deeper depth with the Toroid 1 transformer.

      Roger also did a minor parts upgrade to the crossover at a small cost while in there.

      I attached 2 pics on my backplates with the Toroid 1 and The new regulated bias supply I installed recently. You can see the height difference with the toroid 1 installed.

      With the new bias supply, you have to hack saw off one of the flanges(easy) and mount it on its side to fit in the small pristine backplate/ enclosure. I used a small cabinet bracket, screwed to the panel, 2 way tape and hot glue to mount it all together. This is only way it fits in.

      Good luck with your project!

      Ken

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    • #722
      Stphotog
      Participant

      did you hear a difference with the new Torroid?

    • #723
      Stphotog
      Participant

      Did you upgrade caps?
      I just did.
      Need to do the other side now.

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    • #727
      yoshi
      Participant

      Hi:

      No, I did not upgrade the caps.

      On the toroid1, I did a series of updates close to the time, so I can’t really comment on the sound upgrade with the Toroid 1. I had experienced progressive improvements in bass extension, image depth and treble extension with all the updates. I am certain this update contributed to the performance enhancement.

      If you have not replaced the tweeter pot with a fixed resistor(ie. 4 ohm, 50 watt, non inductive), do it. Best bang for the I buck.

      A new regulated bias supply also made a difference, for some reason. It has greater output, and is ac voltage fluctuation independent. But, to my mind, it was an upgrade in overall sound performance. More of everything, so to speak.

      I would appreciate so details from you on the what the new caps upgrade are and where you soldered the in. What improvement did you hear with this change?

      Ken

    • #731
      Stphotog
      Participant

      I just did the other side 😉

    • #732
      Stphotog
      Participant

      A new regulated bias supply also made a difference, for some reason. It has greater output, A new regulated bias supply also made a difference, for some reason. It has greater output, and is ac voltage fluctuation independent. But, to my mind, it was an upgrade in overall sound performance. More of everything, so to speak.

      Where did you get it?

    • #733
      Stphotog
      Participant

      I used Jansen Caps from Parts Connection (plus a coupling cap) and wired them in parallel. they do not fit on the board so I just hot glued them in place on the underside of the connection box (where red, yellow and black hook up)
      They sound good so far letting them burn in for hours before I do any critical listening.
      I also just added coupling caps to my FM 155 so I also did too many upgrades at the same time.
      I am interested in the torroidal and I will do the resister mod asap

    • #734
      Stphotog
      Participant

      this?

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    • #736
      Stphotog
      Participant

      or?

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    • #740
      yoshi
      Participant

      Stphotog:

      If you look at my photo, I am using what I think is your first photo. Frankly, there will be lots of options at parts connextion. I just unwired out the variable pot and hot glued on the new resistor on top of it and solder it in. Simple. Bang, open up the top end. After some time now, I have no motivation to change the 4 ohm value.

      Ken

    • #749
      Stphotog
      Participant

      So i spent an evening playing with Brillance found i liked it at 3 o’clock and measured the resistance at 1.6ohms
      Does that sound right?

    • #751
      chungjh
      Participant

      How did you measure the resistance?

    • #755
      yoshi
      Participant

      Chungjh has a good point. You should be measuring across the variable pot. My reaction is that 1.6 ohms seems low. If that’s the correct measured value, I would only say that a fixed resistor will sound cleaner and more open that the measured equivalent on the variable pot. For a small cost, I might suggest you buy a few values, 4 and 3 ohms( 50 watt, non conductive) and the 4 ohm a try. If you want more treble, then consider to go down to a 3 ohm and solder that value in place.

      Good luck, I do look forward to your
      Feedback on the treble sound change.

      Ken

    • #763
      Stphotog
      Participant

      I measured across the variable pot (I think I did that correctly. I will take a photo)

    • #788
      Stphotog
      Participant

      Here is how i measured

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    • #791
      yoshi
      Participant

      The test looks ok. Your call on inserting the resistor load. Again, my experience is that a new fixed resistor will sound more extended, and cleaner, than the pot, so you may not need to lower the R value down to less than 2 ohms to get your preferred HF extension. Not sure I would…

    • #800
      Stphotog
      Participant

      I am re covering the pristines. Any mods to the panel recommended?

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    • #803
      yoshi
      Participant

      Hello again:

      I am not aware of anything you could do on the uncovered panel.

      Could check if there is a copper diffusion ring on your set. I believe this a factory install. But, you should confirm whether you have it or not.

      I would remove all the stables before replacement fabric
      Of the fabric, to avoid tears when stretching it in place.

      Ken

    • #804
      Stphotog
      Participant

      What does the copper diffusion ring look like?

    • #805
      John V
      Participant

      The diffusion ring consists of copper foil that runs around the perimeter of the panel

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