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Pearce BC-1 Rebuild Project

Discussion in 'Amps and Cabs [BG]' started by PaulJSmith, Nov 13, 2018.

  1. The backstory ...
    After I divorced my first wife in 1990, I bought a Pearce BC-1 w/Billy Sheehan mod and a Pearce 210 cabinet. The cabinet was used strictly for the distortion channel. I questioned Dan Pearce about the use of Eden speakers in that cab, and he said, "Trust me. We are the bass distortion people after all. Just give it a try. If you don't like it, send it back and I'll put whatever you want in it." Turned out he was right. That cab worked great. I used that preamp and cabinet along with my old Wall-O-Crate (2 BE-410s and 2 BE-15s ... hey, I worked there and got them for cost) and eventually my SVT610HLF for many years and loved it. When I decided around '05 or '06 to stop carrying around a monster bass rig just for cover band gigs in bars, the rack went into storage in my basement. During the summer of 2013, I came home from work one day to find 28" of water in my basement from a storm drainage system backing up through a floor drain. The BC-1 was in an SKB rack case with some other unused rack gear, and that case was floating in the water ... oddly, with a box fan sitting atop it, still running. After I got the water pumped out and surveyed the damage, I found that I lost a lot of equipment that day. The Pearce 210 cabinet was one of many speaker cabinets I had amassed over the years that perished there. I opened the road case and found no standing water in it, so I closed it back up thinking the seal had worked.

    Fast forward 5-1/2 years to this past Sunday. I pulled that preamp from the rack, which has been sitting in a storage facility since I got remarried in 2013. I want to use it for a new recording project, and wanted to spend some time dialing in the sound. When I pulled it from the rack, I got a bad feeling about it's ability to come to life. Every fastener on the outside was badly corroded. When I got it home, I attempted to open it to take a peak at the condition inside. There are 13 screws holding the top on, and I gave them all a shot of Ballistol and let them sit awhile. 10 of the 13 came out rather easily, but three along the back stripped almost immediately. I was able to lift the lid just enough to see inside with a flashlight. The electronics looked good, but the hardware was rusty. I put the screws back in and decided to give it some fire. When I powered it up, the Power and Channel 2 LEDs did some flickering and went out, and the Limit LED came on. Not good. I took it into the studio and powered it up again while connected to an amp. Same thing with the LEDs, and there was a terrible hum at the output. OK, definitely not good.

    I opened it completely last night after drilling the heads off of the stripped screws. Again, the electronics looked OK, but the fasteners were clearly corroded. There is no evidence that there was ever water in there, but the dust being cleaned away near all the open chassis joints indicated that moist air was getting in at those points. Some multimeter probing confirmed that there are no decent ground connections to be found in the thing.

    I started to clean up the outside on Sunday, and yesterday decided to replace all of the internal fasteners and clean up all ground points on the chassis. I'll also have to clean all the connectors, and probably spray down the pots, even though they seem to turn smooth.

    For your viewing pleasure, here are some "before" pics.

    Pearce BC-1 1.JPG
    Pearce BC-1 2.JPG
    Pearce BC-1 3.JPG
    Pearce BC-1 4.JPG
    Pearce BC-1 5.JPG
    Pearce BC-1 6.JPG
    Pearce BC-1 7.JPG
    Pearce BC-1 8.JPG

    I'll post more pics when I get it cleaned up and (hopefully) working.
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Don't "spray down" the pots unless you want to further the already significant damage. A TINY bit of Caig DeOxit into the opening that the terminals exit from (which requires significant disassembly of the amp on that model) is the best way to approach this particular issue.

    BUT, you are likely going to need to use a scope and multi-meter to figure out where the signal is not correct and an understanding of the circuit to know why. Once you know why, you can think through the solution.

    Your preamp was exposed to VERY high humidity (possibly to the point of condensing) and I think you will find that a lot of time consuming work will be necessary to achieve reliability. Just the amount of corrosion on one of the regulator pass transistor leads is telling of what the preamp has gone through.

    (let me add that there might be some persuasive historical or sentimental reasons for restoring this piece properly, the story behind Pierce is both interesting and educational IMO)
    Last edited: Nov 13, 2018
  3. Thanks for your input, AH. A friend has generously offered to loan me a scope and tone generator for testing. I parted with my test equipment when I left the music electronics industry almost 15 years ago.

    I'm pretty sure the humidity was from some water getting into the sealed road case and staying in there while it was in a non-climate-controlled storage facility. Summers get hot here in the St. Louis area, and it sat there steaming itself for 5-1/2 years. Once I get the connections cleaned up and am sure I have power going where it's suppose to go, then I can start looking at any signal path issues.

    My reason for trying to restore it are kind of twofold:
    1) There is indeed a bit of sentimentality involved. I spent a lot of good years with this preamp, and there's a comfort factor there. It's always been very easy to get a great sound out of this thing. I've used it so much that at one point I had to replace the worn out switches in the footswitch.
    2) I already own it, and any minor expense to replace parts is easy enough. My alternatives are more costly; find another one of these hen's teeth somewhere (basically, wait for one to show up on eBay), or go the Line 6 Helix route.

    Honestly, I'm kind of leaning the Helix route. I have been for some time. Billy even tried to talk me into it earlier this year while discussing the Pearce sound. As he kept saying, "It's in there!" That one box could free up a good deal of space in my small home studio, for both bass and guitar. However, right before the holidays is not the best time to tell The Wife that I'm going to inject another $1000 into music gear, which at the moment is not paying for itself.

    So for now, I'm going to give this one last shot.
  4. BogeyBass


    Sep 14, 2010
    Get toothbrush start cleaning that puppy.

    Sounds like majority of the problems is corrosion. Unseat socket ic's and clean clean clean
    PaulJSmith likes this.
  5. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    It looks like you have a good set of bones to work with.

    The first thing that I'd do before powering it up again is to clean it. Remove all the rusted hardware and replace it. The Switchraft nuts and washers on the jacks are available from mouser.com. Other fastener hardware may be available from homedepot. Pay close attention to the chassis ground(s). You want them clean of rust and tight. Connectors should be clean. Then tackle the electronic issues.
    PaulJSmith likes this.
  6. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Make that someone elses toothbrush. :laugh:
    wave rider, BadExample and PaulJSmith like this.
  7. BadExample


    Jan 21, 2016
    That term makes me cringe and twitch a bit. Funny thing is, I don't know if that happens from understanding the the damage from chemicals, or if it's from my own exposure to chemicals.

    Hey bro. OP, on those fasteners, if they don't break free with little effort, get a mix of 50/50 acetone/ATF (or buy the real thing: Kroil, but it's expensive). Get just a tip of a tooth pick in the mixture and apply less than a drop, just enough so it wicks into the threads. Let it set for hours, then if it looks dry, repeat the process until it is moist with the mix. Fasteners should come out without stripping the heads or breakage. If they come out part way and seize, repeat. Less it more and don't get that !@#$ on anything but the threads. It will strip paint and melt plastic. If you have a few that get stripped heads or break, left handed drill bits are not just your friend, they are your BFF's.

    Rend Lake/Carbindale area? I've got oodles of cousins down there. In fact, you might be one.
  8. I know a lot of people seem to cringe at the mention of contact cleaners, but I've been using that stuff on dirty pots for over 35 years, and I've never had a bad experience with it. The WD-40 Specialist Contact Cleaner has been good to me.

    I'm further north in the St. Louis metro area. On a small farm outside of Trenton, to be more precise.
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Well good luck then. I have to deal with the damage from those magic cure all miracle products all the time and it costs more to properly service products that have been "hosed down" with that kind of crap.
  10. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    I think that it is telling when component manufacturers recommend using deoxit products for cleaning their pots.

    Solid State Logic sells mixers with lots of pots and switches, again they say to use deoxit products.

    Contact cleaners are often a solution of solvents that are intended to flush and dissolve organic deposits such as flux, greasee, nicotine, and airbourne pollutants such as smoke. They can be too harsh for pot conductive surfaces.
  11. If you didn't already know, and really want to make sure that thing is in tip-top condition, check out this guy...


    He's in my neck of the woods (I'm in Clermont, and commute to and from the Tampa area daily). While I haven't bought anything (other that to drool about getting some of his gear) or had repairs done by him, local legend says he's the "REAL DEAL".

    You may (at the least) try contacting him/them and see what he/they recommend.
    todd burns and PaulJSmith like this.
  12. Thanks for that link, basscapes. I seem to recall having stumbled across that site once before. The BS mod schematic might prove helpful.

    I sort of kept in touch with Dan Pearce over the years. He was always friendly and helpful when I had questions. He once directed me to a guy in the Buffalo area named George Alexander (I think) who was still doing work on Pearce equipment back about 20 years ago. Lost that contact many years ago, though, and I think he's no longer doing tech work anyway.

    When I was at St. Louis Music and George McKale was designing the Ampeg SVP-BSP, he used my BC-1 as a comparison of a factory unit vs Billy's modified G1 unit. He might have the schematics as well, but I haven't talked to him in several years either.
  13. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Ah, the good life!
    PaulJSmith likes this.

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