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ARCHIVED FORUM -- April 2007 to March 2012
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This is the first Archived Forum which was active between 17th April 2007 and 1st March February 2012

 

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  • Re: Penta "Project Twins"

    Thanks for the warm welcome burantek! And thanks for the link to that thread...however, I think that project might be more fun to fabricate. Design parameters would be to blend with the Pentas, utilize the beolab 150 - modified with active crossover and combine both channels, trimmed with stainless, and probably a 10" driver. We'll see... Evan
    Posted to The Workbench (Forum) by egoh on 05-24-2011
  • Re: Penta "Project Twins"

    Fabricated new fuse board: Three fixed amps: re-capped, all new transistors, new trimmers, cleaned, and waiting for refinished plastic trim. WAIT! Three....they multiplied. Hehe :) Actually I found another blown amp on eBay and fixed it in case I needed a spare. I'm thinking of fabricating a "Penta" subwoofer and using the extra amp.
    Posted to The Workbench (Forum) by egoh on 05-23-2011
  • Re: Penta "Project Twins"

    Here are a few photos of the blown amps: Bulging caps: Fried transistors and melted resistor: Unsoldered from the excessive heat:
    Posted to The Workbench (Forum) by egoh on 05-23-2011
  • Re: Penta Bias Adjustment

    Sorry to talk out loud, but I figured it out and perhaps it may help someone else. 5 minutes is just about perfect (as mentioned before) to set the final bias. Obviously, set it as soon as you power up as to not fry the amp. Then let it stabilize which is just about 4-5 minutes and do your final adjustment.
    Posted to The Workbench (Forum) by egoh on 05-20-2011
  • Re: Penta Bias Adjustment

    I actually asked this in another thread but thought you guys might have some more insight. The manual says to set the bias to 30mV without load and while the amp is "cold." How cold do they mean? How many minutes after startup? At start, I'm at 22mV....rises to 27mV after 1 min., then 30mv after 2 min., 31mV at 3min. Thanks!
    Posted to The Workbench (Forum) by egoh on 05-19-2011
  • Re: Penta "Project Twins"

    OK, I made some progress during my lunch break from working. One amp is fully functional. I've also tested the displays and one works prefectly. The other one doesn't light up the yellow volume and source LEDs. It looks like IC4 was a victim of the heat from when the voltage regulator blew. I'm torn though - I like the look of the display
    Posted to The Workbench (Forum) by egoh on 05-19-2011
  • Re: Penta "Project Twins"

    Leslie, I'll definitely post up some more pictures soon. BTW, if anyone needs to repair the copper trim (bad chip or scratch), Testors Copper (#1151) is a pretty good match. It's available at most hobby stores in the USA. http://www.testors.com/products/136006 The amps are giving me a headache...too bad I need to finish them to stand these speakers
    Posted to The Workbench (Forum) by egoh on 05-18-2011
  • Re: Penta "Project Twins"

    Here is another quick update after the weekend. New stainless installed (protective white plastic hasn't been removed yet...in case you've ever wondered what white pentas would look like) and grills recovered.
    Posted to The Workbench (Forum) by egoh on 05-16-2011
  • Re: Penta "Project Twins"

    Thanks, but I still have a long way to go. I'm polishing scratches out of plastic and starting to re-skin the speakers today. The amps are pretty fried but I have most of the parts so I'm going to get to them as time allows. I don't have new potentiometers for the amps and I'm thinking it might be smart to change them out while everything
    Posted to The Workbench (Forum) by egoh on 05-14-2011
  • Re: Penta "Project Twins"

    OK guys, here is a quick update. The crossovers are finished. I don't recommend upgrading to polypropylene caps unless you like playing capacitor tetris. Everything fits and it sounds wonderful, but what a pain. Here is a picture of a stripped crossover: Rebuilding crossovers: Foam stripped: Re-foaming in progress: Fixing display boards: Naked Pentas
    Posted to The Workbench (Forum) by egoh on 05-13-2011
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